Inquiries and interpretations for NACE MR0175/ISO 15156

Inquiries and interpretations for NACE MR0175/ISO 15156 (Updated April 16, 2007) Foreword NACE Standard MR0175, “Metals for Sulfide Stress Cracking and Stress Corrosion Cracking Resistance in Sour Oilfield Environments,” was revised and reorganized over a seven-year period, resulting in the publication of the 2003 edition in February 2003. Because the changes were extensive, the ISO 15156 Maintenance Panel formed to maintain this widely used standard, which was combined with ISO 15156 (based on MR0175) in December 2003, has received many questions regarding the requirements and revisions. Following are the inquiries and responses provided thus far by the Maintenance Panel. Users of NACE MR0175/ISO 15156, “Petroleum and natural gas industries—Materials for use in H2S-containing environments in oil and gas production,” who have questions are encouraged to review these to determine whether your question may have been answered. Replies to some inquiries have yet to be formulated and this information will be updated periodically as more replies become available. The inquiries and responses are listed in the order of the sections of NACE MR0175/ISO 15156-1, -2, and -3 to which they refer. Notes: To allow cross reference, the references to NACE MR0175-2003 in the original questions and answers have been retained. Additional comments have been added to the original answers, for example, when work on an amendment proposal to address a problem is in hand. New additions to the compendium since the last edition are shown in a green font. References have been introduced to ISO Technical Corrigenda where amendment proposals have led to approved changes to parts of NACE MR0175/ISO 15156. These Technical Corrigenda shall be read in combination with the document of which they now form a part. Copies of the Technical Corrigenda can be found at www.iso.org/iso15156maintenance . These responses represent a consensus of the members of the ISO 15156 Maintenance Panel and should not be construed to reflect the opinions of NACE International, its officers, directors, or members. General Scope of NACE MR0175/ISO 15156 QUESTION: 2 Some of the materials we produce are in thicknesses or diameters that fall outside the scope of MR0175. We request clarification or guidance as to how hardness testing requirements that fall outside the scope of MR0175 should be addressed. (MP INQUIRY #2003-05) ANSWER: The Maintenance Panel cannot provide interpretations that are outside the scope of MR0175. QUESTION: MR0175 is obviously written for guidance in meeting the H2S corrosion problem. Where does NACE address chloride corrosion cracking, particularly in pipe and tube materials? We are seeing more and more customer specs calling for special materials. What is the NACE opinion on best pipe/tube materials for defeating chloride corrosion cracking? (MP INQUIRY #2003-24 Q2) ANSWER: Please refer to Section 1 of NACE Standard MR0175-2003 and also to ISO 15156 Part 1 for the scope of the documents for which cracking mechanisms are considered in H2S service. QUESTION: The "Changes to NACE Standard MR0175-2003" document states the following: "MR0175 is not expected to be technically changed before it is combined with ISO 15156. ISO 15156 is in a different format, with most information provided in tables, so it will not look the same, but it will be technically equivalent." Although this statement says that the two standards will be technically equivalent, their respective sections on applicability show the following deviations: a) NACE MR0175 has a generic rule (1.4.1.1) of a H2S partial pressure above 0.0003 MPa abs, whereas NACE MR0175/ISO 15156 has no such rule. b) NACE MR0175 has a generic exception rule (1.4.2.1) of a total pressure less than 0.45 MPa abs, whereas, within NACE MR0175/ISO 15156, this is only applicable to "Flow-lines, gathering lines, field facilities and field processing plants" and "Water-handling equipment." (I assume that you are aware that MR0175/ISO 15156 Part 1 (2001) mentions 4.3 bar whereas Parts 2 and 3 (2003) mention 0.45 MPa abs). c) NACE MR0175 has a generic exception rule (1.4.2.2) for multiphase systems under certain conditions, whereas NACE MR0175/ISO 15156 has no such rule. Can you please clarify? (MP INQUIRY #2005-05) ANSWER: Response to Questions 1, 2a, and 3. Your interpretations of the NACE MR0175/ISO 15156 are correct. In all cases the decisions to accept differences between NACE MR0175-2003 and NACE MR0175/ISO 15156 were only taken after discussions in the ISO/TC 67/WG 7 committee charged with the preparation of the three parts of the standard. 3 Response to Question 2b. The difference between 0.45 MPa and 4.3 bar was recognized and has been corrected in a Technical Corrigendum for ISO 15156-1, Reference 2. Address for requests for interpretations QUESTION: Is a NACE office available in Italy or in other European countries? (MP INQUIRY #2003-26 Q5) ANSWER: All inquiries should be transmitted to the ISO Maintenance Panel through Linda Goldberg at NACE Headquarters in Houston, Texas. The Maintenance Panel has international membership. A membership roster is attached. NACE MR0175/ISO 15156-1 General QUESTION: With reference to Paragraph 1.10.2: Equipment manufactured with UNS N04400 and operating before the issuing of the last MR0175 edition may be replaced today with equipment manufactured with the same material, if the equipment design and environmental conditions have not been changed? If a conformity declaration to MR0175 is required for the new equipment, which edition must be declared (2003 or previous)? (MP INQUIRY #2003-26 Q2) QUESTION: For new wells and/or petroleum plants designed according to MR0175 before its last edition, but manufactured after the last edition was issued, may materials considered by the design but not listed in the new standard edition be used? If a conformity declaration to MR0175 is required for the equipment of the new well/plant, which edition must be declared (2003 or previous)? (MP INQUIRY #2003-26 Q3) QUESTION: May materials not listed in the last edition of MR0175, which have successfully passed test requirements of TM0177 and/or have demonstrated adequacy for service performances, have your declaration of conformity and be certified by the manufacturer "in conformity with NACE MR0175-2003"? (MP INQUIRY #2003-26 Q4) ANSWERS 2, 3, 4: NACE and ISO support the latest editions of their documents. We cannot comment on conformity declarations. Please see ISO 15156 for requirements to document materials performance outside the current limits. This documentation may be through laboratory data or from field experience. Clause 1, Table 1 The revised version of this Table is given in Reference 1. 4 Clause 3 QUESTION: I need your help with the definition of CRAs in Part 3 of MR0175/ISO 15156. The "corrosion-resistant alloys" is very general and does not specify whether or not the definition includes the Fe-based alloys or not. More than that, the term CRA is used together with "other alloys" making it even more confusing. (MP INQUIRY #2004-12) ANSWER: NACE MR0175/ISO 15156-1, Paragraph 3.6 contains a definition of "corrosionresistant alloy" (CRA). It reads: "alloy intended to be resistant to general and localized corrosion of oilfield environments that are corrosive to carbon steel." This is taken from EFC 17. "Other Alloys" are those not covered by the definitions of carbon steel or CRA. For example, copper is not considered resistant to general corrosion but is considered in NACE MR0175/ISO 15156-3. QUESTION: Could you please confirm that NACE MR0175/ISO 15156:1: 2001, Paragraph 3.3 contains errors in some copies of the document and should read: 3.3 carbon steel alloy of carbon and iron containing up to 2% carbon and up to 1.65% manganese and residual quantities of other elements, except those intentionally added in specific quantities for de-oxidation (usually silicon and/or aluminum) NOTE: Carbon steels used in the petroleum industry usually contain less than 0.8% carbon. (MP INQUIRY #2005-11) ANSWER: Yes. Clause 5 and Clause 8 QUESTION: Paragraph 1.8.3.3.1 of the 2003 edition allows "interpolation" between data presented in the tables. If these data are plotted on semi-logarithmic graph paper such that the ordinate is temperature and abscissa H2S partial pressure, much of the data plots as curves rather than straight lines making "interpolation" problematic lacking the polynomial ex-pression for the curves obtained by a curve-fitting, mathematical routine. Since graphical data are easier to use than the discrete, Cartesian coordinates, I suggest that NACE give the data in the various tables in graphical form, along with the respective polynomial ex-pressions for the resulting curves that enable the user to calculate pH2S for any given temperature. (MP INQUIRY #2003-13 Q6) 5 ANSWER: Since the data are limited it is not appropriate to attempt interpolation in all cases. Interpolation can only be valid for cases in which all environmental and metallurgical limits, other than those for which a particular interpolation is being carried out, are identical. The solution for this problem chosen in NACE MR0175/ISO 15156-1, Clause 5, is as follows: "Qualification, with respect to a particular mode of failure, for use in defined service conditions, also qualifies a material for use under other service conditions that are equal to or less severe in all respects than the conditions for which qualification was carried out. QUESTION: In Paragraph 1.8.3.3.1 it is mentioned that interpolation between H2S levels and temperature is acceptable. When applying this to Table 3 (as an example) what will be the maximum partial H2S pressure at 140°C, where an interpolation is required between 2.8 MPa and unlimited? Does this mean that below 149°C there is no limit to the maximum partial H2S pressure? (MP INQUIRY #2003-19 Q1b) ANSWER: ISO 15156, Clause 5, states: "Qualification, with respect to a particular mode of failure, for use in defined service conditions, also qualifies a material for use under other service conditions that are equal to or less severe in all respects than the conditions for which qualification was carried out." In this case, for the precipitationhardenable nickel-based alloys addressed in Table 3, this automatically qualifies the material for use at temperatures below 149°C and below 2.8 MPa H2S partial pressure. Qualification of a material for application under specific conditions that are more severe than those listed in ISO 15156/NACE MR0175 is allowed. Qualification on the basis of laboratory testing or field experience is required to comply with the (ISO) standard. The equipment user is responsible for ensuring a material is properly qualified. Clause 6 QUESTION: My customer has some swab tanks that were manufactured in 1953; they are made of rolled 1/2-inch plate A283C; the tank is 84 in. in diameter and is rated for 100-psi service. The question is given the following conditions does this tank meet NACE MR0175? According to Section A2.1.6 the requirement that all rolled or deformed material must be stress relieved and have a hardness of 22 HRC max. The problem is we cannot or have no documentation as it relates to the heat treat of the plate post welding. yet when tested the material meets the A283C requirements and the hardness are in the 120-127 HB. Ultrasonic testing as part of a corrosion survey on the tank was performed and all was in order. Engineering approval was granted on the status of the vessel as a pressure vessel under the ABSA (Alberta Boilers Safety Association). This tank is 52 years old, is in excellent condition, and the customer wants to have more current documents on the tank as it relates to its status as an ABSA pressure vessel and it's NACE MR0175. With all this information can a determination be made that this material in its current state is suitable as a material that qualifies as a NACE MR0175/ISO 15156- 6 compliant material? Using the long life, performance, and the mechanical data gathered can this determination be made? If so, can this criteria be used to establish a basis for performing future work on this exact style of tank? (MP INQUIRY #2005-31) ANSWER The ISO 15156 Maintenance Panel cannot advise on the suitability of this tank for use in sour service. It is the responsibility of the equipment user to assess the suitability of the material and to ensure compliance with NACE MR0175/ISO 15156. Consideration of the following could contribute to any evaluation of suitability you undertake:- For some equipment NACE MR0175/ISO 15156-2, Table 1 allows the equipment user to categorize equipment as a "Permitted exclusion" where the operating pressure does not exceed 0.45 Mpa (65 psi). NACE MR0175/ISO 15156-1, Clause 6 and in particular 6.2 d) offer some guidance on the fitness for purpose evaluation of materials in existing equipment. Clause 7 QUESTION: Base Material In accordance to NACE MR0175/ISO 15156, Part 1, Item 7, 3rd paragraph, "no additional laboratory testing of pre-qualified materials selected in these ways is required." In accordance to NACE MR0175/ISO 15156, Part 2, Item B1, letter "a," "Some carbon and low alloy steels described or listed in A.2 might not pass some of laboratory . . ." In our understanding, NACE Standards TM0177 and TM0284 are used to qualify new materials that are not previously included in NACE MR0175. If we are using materials previously included in NACE MR0175, it is not necessary to test them according to NACE TM0177 and TM0284. We would like you to confirm if our interpretation below is correct and if not give us the correct interpretation. (MP INQUIRY #2005-08Q1) ANSWER: See response posted under ISO 15156-2, B.1 below. Clause 8 8.2 QUESTION: 7 • Paragraph 1.10.2 states, “The user may replace materials in kind for existing wells or for new wells within a given field if the design basis for the equipment has not changed.” Does this statement include valves or valve components that are used within wells? (MP INQUIRY #2003-12 Q1) ANSWER: Yes, this paragraph does apply to valves and valve components used within the wells. QUESTION: When materials in an existing field are replaced, what criteria should be used? Paragraph 8.2 of ISO 15156-1 provides some criteria for qualification, but it is not clear what approach should be used for materials that have been in use with no problems, but documentation does not exist. (MP INQUIRY #2003-41) ANSWER: NACE MR0175/ISO 15156-1 Paragraphs 6.2, 8.1, 8.2, and 9.0 provide a complete description of the documentation required for two years’ successful field service. These paragraphs replace Paragraphs 1.10.1 and 1.10.2 in the 2003 edition of NACE MR0175. There has been no change in intent. These paragraphs in the 2003 edition required that “The user shall verify that the environmental conditions of the field have not changed.” Documentation has always been required. QUESTION: I need some clarifications on the clause 8.2 of the MR0175/ISO 15156-1 (Qualification based upon field experience). “A material may be qualified by documented field experience”--”the duration of the documented field experience shall be at least two years. . . “ What kind of documentation is expected? We need to know exactly what to ask from the end user. Is a letter describing the conditions for which the material qualified for the past two years enough? (MP INQUIRY #2004-05 Q1) ANSWER: NACE MR0175/ISO 15156-1 2003, Paragraphs 6.2, 8.1, 8.2, and 9.0 provide a complete description of the documentation required for two years’ successful field service. These paragraphs replace Paragraphs 1.10.1 and 1.10.2 in the 2003 edition of NACE MR0175. There has been no change in intent. These paragraphs in the 2003 edition required that “The user shall verify that the environmental conditions of the field have not changed.” Documentation has always been required. QUESTION: What do we (the equipment manufacturer) do with this documentation? Does it have to be filed with NACE? If yes, is this our responsibility? (MP INQUIRY #2004-05 Q2) ANSWER: a) The equipment user is responsible for the preparation of the required documentation (see NACE MR0175/ISO 15156-1, Clause 9, Paragraph 1 to support 8 the use of a material in a plant on the basis of field experience. It would also be in the equipment user’s interest to keep copies of this documentation in their records in case they are challenged to prove they are responsible operators. The equipment manufacturer can choose to retain a copy for future reference. b) The equipment user may feel that they would wish to make the decision to file the information with NACE given that this would involve their actual field conditions rather than laboratory test conditions. c) It is not the responsibility of the equipment manufacturer to file information with NACE, unless they choose to. This may be the case because the equipment manufacturer has made the effort to compile a non-proprietary database that they believe supports the use of alloys for their equipment under the conditions documented by the process in Question One. QUESTION: If filing with NACE is not required, do we have to verify the claims or can we just provide the materials as requested by the end user? (MP INQUIRY #2004-05 Q3) ANSWER: The manufacturer can provide this information to a user, but it is the user’s responsibility to determine the operating conditions and select the appropriate materials. It is the manufacturer’s responsibility to meet the metallurgical requirements of the appropriate alloys in NACE MR0175/ISO 15156-2003. QUESTION: In the pre-December 2003 MR0175, Paragraph 1.10 (The Effect of Changing Requirements in MR0175 on Existing Equipment) spelled out how to handle materials that MR0175 made changes to. Where is such a statement or treatment in the December 2003 MR0175/ISO 15156? If it was left out, is there a way of handling those changes? (MP INQUIRY #2005-10) ANSWER: There is no such statement in NACE MR0175/ISO 15156. By convention, a new version of an ISO standard is not applied retrospectively to equipment built to the previous version of the standard (in this case NACE MR0175:2003 or earlier) valid at the time of equipment construction. New requirements in the latest version may be applied retrospectively by an equipment user or mandated for retrospective application by a regulatory authority. ISO 15156-1, 8.2 and the responses to inquiries on Clause 8 in Document 02. Inquiries and Answers at the Web site . . . www.iso.org/iso15156maintenance . . . offer further guidance on how such changes might be handled. 9 NACE MR0175/ISO 15156-2 Clause 1, Table 1 The revised version of this Table is given in Reference 2. Clause 3 3.1, 3.16 and 3.2.3 For the use of ASTM E10, ASTM E18 and ASTM E92 as alternatives to ISO 6506-1, ISO 6508-1 and ISO 6507-1 respectively see Reference 2 3.14 QUESTION: Definition of pressure-containing parts on page 7. “Those parts whose failure to function as intended would result in a release of retained fluid to the atmosphere. Examples are valve bodies, bonnets, and stems.” Are stems always defined as pressure-containing parts, regardless of features that by design keep the stem intact? Example #1: Internal entry stems for ball valves that have a shoulder that rests against the body around the stem bore. Example #2: Shafts for butterfly valves that have a retaining ring holding the shaft inside the valve. (MP INQUIRY #2003-12 Q2) ANSWER: NACE Standard MR0175 cannot interpret design issues. The Maintenance Panel may only refer you to the definition of pressure-containing parts in Section 2 and the use of this definition with restrictions in Section 9. Clause 7 7.1.2, A.2.2.3.3, Table A.2, and Table A.3 QUESTION: Sub-clause 7.1.2 says SSC Resistant Steels for partial pressures equal to or above 0.3 kPa (0.05 psi) can be selected using A.2. a) If criteria, like temperature, hardness are met, do we assume that for all partial pressures above 0.05 psi the suggested SSC-resistant materials could be used? E.g., SSC-resistant materials mentioned in Table A.2 and Table A.3. b) What are the acceptable pH and Cl- limits? c) Does A.2.2.3.3 cover L80 type 1? 10 d) For low-alloy steels described in Section A.2 of this standard, what are the cases where injection of corrosion inhibitors are required, both for downhole casings/tubing and surface pipelines? (MP INQUIRY #2005-14) ANSWER: a) This is correct. b) No limits of pH and Cl- have been formally defined for carbon and low-alloy steels. Any combinations of chloride concentration and in situ pH occurring in production environments are considered acceptable. Metal loss corrosion, which can be influenced by both pH and chlorides, is not the subject of the standard. c) No, this grade is covered in Paragraphs A.2.2.3.1 and A.2.2.3.4. d) NACE MR0175/ISO 15156 does not cover the use of corrosion inhibitors. The use of any kind of corrosion inhibitor is not considered to allow any relaxation of the requirements for cracking resistance of materials in sour service. 7.2.1.2, Fig.1 QUESTION: There is the sentence in the note 1 of Figure 1 in ISO 15156-2: "The discontinuities in the figure below 0.3 kPa (0.05 psi) and above 1 MPa (150 psi) partial pressure H2S reflect uncertainty with respect to the measurement of H2S partial pressure (low H2S) and steels performance outside these limits (both lower and higher H2S)." I understand the above sentence, and if I will use the carbon steel and low-alloy steel in the sour service above 1 MPa (150 psi) of partial pressure of H2S, what can I do? Should I require a special laboratory test imitating the H2S partial pressure and pH in the service for SSC of the carbon steel and low-alloy steel? Which solution can I use in the special laboratory test? NACE TM0177 A solution or the imitating solution in the service? (MP INQUIRY #2005-17) ANSWER: The following response must be seen in the context of NACE MR0175/ISO 15156-2, Clause 7. 1. NACE MR0175/ISO 15156-2, Fig. 1 is a schematic definition of Regions of environmental severity with respect to SSC of carbon and low alloy steels. As mentioned in Paragraph 7.2.1.4, qualification for the use of a material not listed in Annex A for use in one or more of the Regions of Fig. 1 is always dependent on reported field experience or laboratory testing. There is little documented evidence that describes the SSC resistance of carbon and low alloy steels in H2S-containing environments outside the H2S limits of Fig. 1. The Note quoted reflects this. 2. The equipment user must decide whether the listing of a steel in Annex A serves as an adequate guide for its behavior in H2S-containing field environments that might 11 be more severe with respect to SSC than those represented by the SSC testing methods normally used; see Annex B.1a). For qualification for a specific application all the test conditions must be at least as severe, with respect to the potential mode of failure, as those expected to occur in field service. 7.3.2 QUESTION: Does the MR0175/ISO 15156-2, 7.3.2 also apply to low-alloy martensitic steels such as CA6NM which is in fact considered a CRA (MR0175/ISO 15156-3)? (MP INQUIRY #2004-18 Q2) ANSWER: No, it does not. Please see ISO 15156-3, 6.2.1 and ISO 15156-3, A.6.2, Table A18. 7.3.3 QUESTION: Seal welding of vent holes on saddle plates welded to pipe. We have provided vent holes on saddle plates in accordance with ASME B31.3. We have used these saddle plates at support locations as a protective shield to pipe. Now we would like to close the vent hole by seal welding after completion of saddle welding with pipe and carrying out PWHT. Permanent closing of vent hole is required to avoid corrosion in offshore conditions. Service is crude oil with H2S, i.e., NACE MR0175 is applicable. Kindly advise us about the acceptance of seal welding for these service conditions. (MP INQUIRY #2005-21) ANSWER: The ISO 15156 Maintenance Panel cannot provide guidance on the acceptability of seal welding in this application. It is the responsibility of the equipment user to decide whether NACE MR0175/ISO 15156-2 (the latest edition of this NACE standard) is applicable to these seal welds. The applicability of this standard is described in Clause 1, Scope. If this standard is considered applicable then the seal welds must comply with the requirements of NACE MR0175/ISO 15156-2, 7.3.3 or NACE MR0175/ISO 15156-3, 6.2.2. 7.3.3.2 QUESTION: Is it acceptable to use HV 500g (microhardness) testing for NACE applications for WPS qualification? I understand that Paragraph 7.3.3.2 of NACE MR0175/ISO 15156 Part 2 says that hardness testing shall normally be carried out using HV 10kg or HV 5kg, which is our usual practice. 12 FYI, the hardness testing was done with HV 500g on CSA Z245.1 Grade 359 pipe material. (MP INQUIRY #2006-08) ANSWER: Yes, subject to the agreement of the equipment user. Please see NACE MR0175/ISO 15156-2, Para. 7.3.3.2. 7.3.3.2 and 7.3.3.3 The revised texts for these sub-clauses are included in Reference 2. 7.3.3.3 QUESTION: Per 7.3.3.3 as modified in NACE / ISO 15156-2:2003/Cor.1:2005(E), "Using the Vickers or Rockwell 15N measurement methods, hardness impressions 2, 6, and 10 should be entirely within the heat-affected zone and located as close as possible to, but no more than 1mm from, the fusion boundary between the weld overlay and HAZ." Is a correct interpretation that when welding dissimilar metals such as corrosion resistant overlays on low alloy steels, the phrase, "as close as possible to, but no more than 1mm from, the fusion boundary" means that the indentation should be no less than 3x the mean diagonal length of the indentation from the fusion boundary as is required for adjacent indentations in ISO 6507-1:1998? Note: ISO 6507-1:1998 is referenced by NACE / ISO 15156-2:2003 in the first paragraph of Section 7.3.3.2 (Hardness testing methods for welding procedure qualification). (MP INQUIRY #2006-01Q2) ANSWER: The ISO 15156 Maintenance Panel cannot provide an interpretation of the ISO 6507- 1:1998 in relation to the minimum distance of hardness indentations from the boundary between the base metal and the overlay weld. As stated in ISO 15156-2, 7.3.3.2 and ISO 15156-3, 6.2.2.2.2 hardness measurements can also be carried out using a smaller indentation load, for example HV5 rather than HV10, and in many cases this will allow compliance with the requirements of ISO 15156-2, Fig. 6. It is important to recognize that there will be a gradient in HAZ hardness in any case, and thus measurements too far from the fusion boundary could be un-conservative. In all cases it is the task of the equipment user (and hence the supplier) to ensure that the hardness values measured are the most representative possible of the cracking resistance of the welded material in any sour service it is expected to experience. 7.3.3.4 13 QUESTION: About welds, in accordance with NACE MR0175/ISO 15156, Part 2, Item 7.3.3.4, "hardness acceptance criteria for welds," "weld hardness acceptance criteria for steels selected using option 1 (see 7.1) shall be as specified in A.2.1.4. Alternative weld hardness acceptance criteria may be established from successful SSC testing of welded samples. SSC testing shall be in accordance with Annex B." So, in our understanding, if our welding procedure qualifications (WPSs) are qualified in accordance with NACE MR0175/ISO 15156, Part 2, Item A.2.1.4, it is not necessary to test them according to TM0177. We would like you to confirm whether our interpretation below is correct and if not give us the correct interpretation. (MP INQUIRY #2005-08Q2) ANSWER: Your interpretation is correct. QUESTION: NACE MR0175 and NACE TM0177--WELDS On the other hand, if we make the test in accordance with NACE TM0177 in our WPSs that are previously qualified to conform to NACE MR0175, what kind of results will we have? Will we have a necessary or redundant results? (MP INQUIRY #2005-08Q3) ANSWER: A manufacturer may choose to qualify a welding procedure specification in accordance with ANNEX B. Testing welds acceptable in accordance with A.2.1.4 is an optional activity chosen by the manufacturer to confirm resistance to cracking. This is not necessarily a redundant result depending on the anticipated service conditions and the selected test environment, the results could be used -to confirm that the hardness control specified in A.2.1.4 is adequate to prevent sulfide stress cracking -or to define alternative weld hardness control requirements that will not lead to sulfide stress cracking when the requirements of A.2.1.4 are not met. Clause 8 QUESTION: We are trying to interpret the NACE requirements for pressure vessel plate material. The NACE standard leaves the option of HIC testing with the client, as it appears. In accordance with the standard, the condition in which the HIC testing becomes mandatory should be based on some criteria other than H2S partial pressure. We would appreciate it if you can guide in giving the other conditions if sulfur and phosphorous content are controlled in accordance with NACE. Does HIC become 14 mandatory due to non-uniformity of sulfur and phosphorous in the material due to steelmaking process even if the limit of these elements are maintained? Are there other reasons such as chloride environment? (MP INQUIRY #2005-04) ANSWER: The statements in ISO 15156-2, 8 "Evaluation of carbon and low-alloy steels for their resistance to HIC/SWC" are based on the extensive experience of the experts who drew up the requirements of the standard. They serve as a warning to the equipment user that damage to products from some flat-rolled carbon steel types due to HIC has been common and the risk of attack must be considered when selecting such materials for sour service. (See ISO 15156-1, 3.19 for definition of sour service in this context.) They also provide some indications of the types of flat-rolled carbon steel likely to give satisfactory resistance to HIC. The overall aim of ISO 15156-2, Clause 8, is to ensure that materials that give satisfactory HIC performance in sour service can be selected. It is not the intention of this Clause to provide detailed information that can lead to the qualification, without testing, of HIC-resistant steels. If, in accordance with NACE MR0175/ISO 15156:2, Clause A.2.2.2, Paragraph 3, the HIC resistance of flat-rolled plate is uncertain then the equipment user can elect to carry out HIC testing, possibly for use in an application-specific environment. Testing in accordance with Annex B.5 is proposed as a means of qualifying the material to ISO 15156-2. Testing is not necessary if the equipment user can document that he has evaluated the risk of HIC failure of his equipment and considers the risk acceptable. QUESTION: According to NACE MR0175/ISO 15156, Part 2, Paragraph 8, HIC test is not mandatory for carbon steel SMLS pipe. But what about maximum sulfur content? Do we have to apply maximum sulfur content requirement to carbon steel regardless of HIC test? (MP INQUIRY #2005-15) ANSWER: There are no requirements for the control of the chemistry of any elements to prevent HIC in NACE MR0175/ISO 15156. Some guidance concerning acceptable sulfur levels is given in Section 8 of NACE MR0175/ISO 15156 Part 2. For seamless products, testing can also be performed according to Table B.3 if deemed necessary. QUESTIONS: It appears that ISO 15156-2 is ambiguous in defining the acceptance criteria for HIC testing. Section B.5 and Table B.3 refer to NACE TM0284. This TM prescribes CLR, CTR, and CSR results to be reported for each of the three sections taken from a specimen and also as the average per specimen. 15 Q1. Could you please confirm that the intention of Section B.5 and Table B.3 is that the requirements of NACE TM0284 for the evaluation of test specimens should be followed and that CLR, CTR, and CSR should be calculated and reported for each section and the average for each test specimen. Table B.3 does not specify if the criteria apply to the single section numbers or to the averages per specimen or to the averages over a series of specimens. The last of these was suggested recently to us, for qualification purposes, by a materials manufacturer. ISO 3183-3 (the successor to API 5L) uses the same CLR, CTR, and CSR values as criteria as ISO 15156 but in addition it mentions that averages per specimen should be measured against the acceptance criteria (not single section numbers). I think it is common practice to apply this approach. If one decides that the acceptance criteria are to be applied to single sections, I do not believe that using, in addition, the same criteria for the average per specimen yields any useful additional information (because it is less restrictive), but it does no harm either. If, however, one decides that the acceptance criteria are to be applied only to the average per specimen, I am of the opinion that an additional condition should be imposed for single section results or for single crack lengths, for instance, no single crack length should exceed 5 mm, as part of the overall acceptance requirements. Q2. Are the acceptance criteria intended to apply to the test results of both single section and the average per specimen? Q3. Is the intention that, in coming to a qualification the CLR, CTR, and CSR values be calculated by averaging the results for a series of specimens? Q4. If they are intended to apply to only the average per specimen, what additional requirements should be placed on the results of single section results? ANSWERS: A1. Yes. A2. The referenced standard, NACE TM0284, Paragraph 8.4, requires the (calculation and) reporting of test results for each of three sections and the average for each test specimen. The application of the acceptance criteria to single section and/or the average for a specimen is subject to agreement between equipment user and the manufacturer. A3. See Answer A.2 above, the referenced standard NACE TM0284 makes no mention of calculating results by averaging the results for a series of test specimens. A4. The Maintenance Panel is unable to comment on issues that would involve an extension of the requirements of the standard. Any materials purchaser is free to add requirements beyond those required or made optional by the standard. 16 Any amendment proposal to extend the requirements for single section test results must be submitted in accordance with the requirements outlined in:- 01. Introduction to ISO 15156 maintenance activities (Annex C) of the Web site www.iso.org/iso15156maintenance. Annex A A.2.1.2 and A.2.1.3 QUESTION: Paragraph A.2.1.2 on page 17 still shows hot-rolled yet Paragraph A.2.1.3 states that ASTM A 234 grade WPB is an acceptable material. My question is as follows: --Does NACE MR0175/ISO 15156-2 allow the use of material ASTM A 234 grade WPB with a heat treatment as shown in ASTM A 234/A 234M-02 Section 7 Heat treatment, subsection 7.2.1, although this type of forming and cooling in still air is not listed in Paragraph A.2.1.2 of the NACE standard? --Does the term “hot rolled” referred to in Paragraph A.2.1.2 only apply to sheet or plate material and as such cannot be applied to the forming of butt weld fittings? (MP INQUIRY #2004-06) ANSWER: Answer 1: The first paragraph of ISO 15156-2, A.2.1.3 is not intended to imply that the requirements of A.2.1.2 also apply to A.2.1.3. ASTM A 234 Grades WPB and WPC are acceptable subject to a hardness limit of 197 HBW. The Maintenance Panel will consider an amendment to A.2.1.3 to make this clearer. Answer 2: Yes, “hot rolled,” in the view of the Maintenance Panel, does not apply to the forming of butt weld fittings. QUESTION: Often my company is asked by customers to certify our forgings to NACE MR0175. It is my understanding from them that our competition (including imports), certifies to MR0175 without normalizing and consequently we are pressured to do the same. We have three presses, two are fed by gas-fired furnaces, and one is with induction heaters. The gas heat forgings are typically heated to 2,300 to 2,350°F and forged on a 900T or 3500T open die press in a tooling pot, then still air cooled to ambient. The forgings heated by induction are heated to similar temperatures but only a portion of a bar and the flange end is forged close to shape, then air cooled in still air. Customers can order these forgings in the "as forged" or "normalized" condition per SA105. My question is do we have to normalize the forgings coming from either forging process in order to certify to NACE MR0175? The problem is interpretation 17 of NACE MR0175/ISO 15156-2:2003(E), page 17, Annex A, Paragraph A.2.1.2. The heat-treated condition "hot-rolled" is not clearly understood and competitors with similar processes interpret that if the entire raw material piece prior to forge, let's call it a mult, is taken to 2,300 to 2,350°F prior to forge that this satisfies the "hot-rolled" definition. We have contended that our products need to be subsequently followed with a normalizing cycle after being fully cooled to ambient in order to be certified to NACE and that neither of the forging processes listed above satisfies the definition of "hotrolled" process. (MP INQUIRY #2005-25) ANSWER: Hot-forged material does not meet the intent of NACE MR0175/ISO 15156-2, A.2.1.2a). An exception to this statement is given in A.2.1.3a). Other hot-forged materials would have to be treated according to one of the five other heat-treatment conditions described in Paragraph A.2.1.2 to comply with this standard. Please note: We acknowledge that Paragraph 1 of A.2.1.3 is poorly worded. The intent of this paragraph is to allow forgings according to ASTM A 105 to be used, subject to A.2.1.3a) free of the restrictions stated in A.2.1.2. As a consequence, ASTM A 105 material is acceptable in the "as-forged" condition not because it is equivalent to a "hot rolled" condition in A.2.1.2, but because it is a permitted exception in A.2.1.3.a. A.2.1.3, and Table A.3 QUESTION: We require a determination on the acceptability of products manufactured out of materials meeting ASTM A 234 Gr WPB, ASTM A 420 Gr WPL6, ASTM A 350 Gr LF2, and API 5CT J55, K55, N80, and L80 materials. Alberta Oil Tool manufactures Swage Nipples and Bull Plugs primarily for use in the oil and gas industry. Swage Nipples and Bull Plugs are manufactured from line pipe, tubing, and casing. Line pipe swage nipples and bull plugs are manufactured with materials that meet the requirements of the following specifications: ASTM A 234/ASME SA 234 Gr. WPB ASTM A 350/ASME SA 350 Gr. LF2 ASTM A 420/ASME SA 420 Gr. WPL6 Tubing and casing swage nipples and bull plugs available in materials meeting API 5CT Grades J55, K55, N80, and L80. Our initial determination is that these products fall into the scope of Section 11. Paragraph 11.5, Pipe Fittings, states that fittings meeting the requirements of ASTM 18 A 234 Grade WPB and ASTM A 105 are acceptable. However, we can find no criteria for pipe fittings that are to be used in low-temperature service applications. In comparison to ASTM A 350 Gr. LF 2 (a low-temperature specification), ASTM A 105 is congruent and therefore we determined that fittings manufactured to ASTM A 350 Gr. LF2 are acceptable under NACE MR0275-2003. Table D2, Acceptable API and ASTM Specifications for Tubular Goods, lists API 5CT Grades J55, K55, and L80 as acceptable materials for tubing and casing, as well as ASTM A 106 Gr. B and ASTM A 333 Gr. 6 materials for pipe. This table lists many of the materials in question. ASTM A 106, GR. B material is used to manufacture fittings that comply with ASTM A 234 Gr. B material is used to manufacture fittings that comply with ASTM A 234 Gr. WPB, while ASTM A 333 Gr. 6 material is used to manufacture ASTM A 420 Gr. WPB, while ASTM A 333 Gr. 6 material is used to manufacture ASTM A 420 Gr. WPL6 fittings. As NACE Standard MR0175-2003 does not clearly identify all the acceptable materials in one location, our interpretation of the entire standard is that all of the swage nipples and bull plugs that we manufacture are acceptable, and meet the requirements of NACE MR0275-2003. Is this interpretation correct? Please have our findings confirmed by answering the following questions. Please provide reasons for any products that do not comply with NACE MR0175-2003. 1. Are fittings meeting ASTM A 234/ASME SA 234 Grade WPB acceptable for use under the scope of NACE MR0175-2003? 2. Are fittings meeting ASTM A 420/ASME SA 420 Grade WPL6 acceptable for use under the scope of NACE MR0175-2003? 3. Are fittings meeting ASTM A 350/ASME SA 350 Grade LF2 acceptable for use under the scope of NACE MR0175-2003? 4. Are fittings manufactured from API 5CT Grade J55 material acceptable for use u under the scope of NACE MR0175-2003? 5. Are fittings manufactured from API 5CT Grade K55 material acceptable for use under the scope of NACE MR0175-2003? 6. Are fittings manufactured from API 5CT Grade N80 material acceptable for use under the scope of NACE MR0175-2003? 7. Are fittings manufactured from API 5CT Grade L80 material acceptable for use under the scope of NACE MR0175-2003? (MP INQUIRY #2004-03) ANSWER: API grades in Table A.3 of NACE MR0175/ISO 15156-2 are acceptable as downhole tubular goods under the environmental temperatures if they meet the respective API requirements in NACE MR0175/ISO 15156-2. Only if Swage nipples and bull plugs are downhole tubular goods are API 5CT Grades J55, K55, N80, and L80 acceptable. Also see notes below. #1. This must meet the requirements of A.2 and of hardness control as specified in A.2.1.3. #2. This must meet the requirements of A.2. 19 #3. This must meet the requirements of A.2. #4. The material manufactured to API J55 applies only to downhhole tubular goods. #5. The material manufactured to API K55 applies only to downhole tubular goods. #6. The material manufactured to API N80 applies only to downhole tubular goods. #7. The material manufactured to API L80 applies only to downhole tubular goods. A.2.1.4 QUESTION: Per A.2.1.4 as modified in NACE/ISO 15156-2:2003/Cor.1:2005(E), "Tubular products with an SMYS not exceeding 360 MPa (52ksi) and listed in Table A.2 are acceptable in the as-welded condition. For these products, hardness testing of welding procedures may be waived if agreed by the equipment user". Is a correct interpretation that all hardness testing is being waived for tubular products with an SMYS not exceeding 52 ksi in the as-welded condition if as agreed by the equipment user? (MP INQUIRY #2006-01Q1) ANSWER: No, tubular products listed in Table A.2 with an SMYS not exceeding 360 MPa (52 ksi) are acceptable in the as welded condition. For these products hardness testing OF WELDING PROCEDURES may be waived if agreed by the equipment user. A.2.1.4 and Table A.1 The revised versions of A.2.1.4 and Table A.1 are included in Reference 2. A.2.1.4 and A.2.1.5 QUESTION: We have weld overlays (Inconel 625 filler metal with SAW process) applied to lowalloy ferritic steel valves (ASME/ASTM A 352 Gr LCC). The steel valve is used on wet gas wellhead production platform with operating temperatures at 93°C, operating pressure of 145 bar with vapor fraction of H2S (177 kg-mol/h) and CO2 (877 kgmol/ h). Hardness tests were performed on the as-welded condition. The results achieved were well below the 250 HV criteria of Table A.1 of NACE MR0175/ISO 15156-2 first edition. Since the hardness results complied with the requirements of Table A.1 of NACE MR0175/ISO 15156-2, we believe and understand that the valve does not require postweld heat treatment after the weld overlay. Having met the hardness criteria after overlay we believe that we met the requirements of the following paragraphs of NACE MR0175/ISO 15156-2 first edition: -Paragraph A.2.1.5 -Paragraph A.2.1.4 Question: Is our interpretation of Paragraphs A.2.1.5 and A.2.1.4 of NACE MR0175/ISO 15156-2 correct based on the above-stated specific application and conditions and that the valves overlayed with Inconel 625 consumables do not require postweld heat treatment? (MP INQUIRY #2004-11) ANSWER: 20 Paragraph A.2.1.4 states (in the third sentence): “As welded carbon steels, carbon manganese steels, and low-alloy steels that comply with the hardness requirements of Table A.1 do not require postweld heat treatment.” Paragraph A.2.1.5 states: “Overlays applied by thermal processes such as welding . . . are acceptable if they comply with one of the following: (a) The heattreated condition of the substrate is unchanged, i.e., it does not exceed the lower critical temperature during application of the overlay. (b) The maximum hardness and final heat-treated condition of the base metal substrate comply with A.2.1.2 and, in the case of welded overlays, A.2.1.4. Therefore, your interpretation is correct. Provided your weld procedure qualification complies with the hardness requirements in A.2.1.4 and A.2.1.5, no postweld heat treatment is required. A.2.1.5 b) The revised text for this sub-clause is included in Reference 2. A.2.2.1, A.2.2.2 and A.2.2.3 QUESTION: We need a clarification on MR0175/ISO 15156 Part 2:2003, Annex A. We are a manufacturer of temporary pipe work, flowlines, etc., for sour gas service in well testing and process use in a surface application. As such we believe Paragraphs A.2.1 through A.2.4 and Table A.1 with a hardness limit of 22 HRC are applicable in these circumstances. However, pipe suppliers in this region tell us that 26 HRC is acceptable in such applications. I believe the 26 HRC limit is only applicable to material used in a downhole application as in Paragraph A.2.2.3, etc. (i.e., not a surface application) and that this is in error in terms of our usage. (MP INQUIRY #2005-23) ANSWER: ISO 15156-2, A.2.2.1 indicates that carbon and low alloy steels for use in any product form must comply with the requirements of A.2.1 which include the hardness requirement of maximum 22 HRC for the parent material. Exceptions to this rule are named specifically in other paragraphs of Annex A. Welds in such materials shall comply with the requirements of A.2.1.4 that also refers to Table A.1 that sets hardness requirements for welds. Please note that ISO 15156-2 Technical Corrigendum 1 includes revised versions of A.2.1.4 and Table A.1. Sub-clause A.2.2.2 provides examples of materials that can comply with A.2.1, including some examples of tubular products in Table A.2. Sub-clause A.2.2.3 addresses downhole components only. 21 The standard allows materials, such as AISI 4130, to be qualified at higher hardness than 22 HRC for possible use as pipe in sour service by laboratory testing in accordance with Annex B and Table B.1 or on the basis of field experience as described in ISO 15156-1, 8.2. Welds must be shown to comply with the requirements of Paragraph 7.3.3.4. A.2.2.2 and A.2.2.3 QUESTION: In reference to Table D2, Acceptable Specifications for Tubular Goods, in the left column titled “For All Temperatures,” why is Pipe a separate category from Tubing and Casing? In the API 5CT specification (see Paragraph 1.1), as well as the NACE MR0175-2003 standard, “casing” is identical to “pipe” (see Sections 10 and 2, Tubular Components). (MP INQUIRY #2003-24 Q1) ANSWER : Casing and tubing are generally but not always intended for the completion of oil and gas wells. These materials are referred to and specified in API Spec. 5CT. Pipe may have many intended uses and is referred to and specified in API Spec. 5L and other industry standards. A.2.2.4 QUESTION: Are the bolting materials and nuts specified in Paragraphs 6.2.1.2 and 6.2.1.3, respectively, the only acceptable materials in compliance with MR0175-2003 for Exposed Bolting? (MP INQUIRY #2003-22 Q1) ANSWER: Bolting materials may be chosen in accordance with Sections 3 and 4 as described in MR0175-2003, Paragraph 6.2.1.1. QUESTION: Does Paragraph 6.2.1.1 allow other nuts and bolting materials besides the ones listed in Paragraphs 6.2.1.2 and 6.2.1.3? (MP INQUIRY #2003-22 Q2) ANSWER: Yes, in accordance with NACE Standard MR0175-2003 Sections 3 and 4. QUESTION: Are the following ASTM bolting materials and nuts acceptable for exposed bolting in accordance with Paragraph 6.2 of MR0175-2003? (ASTM A 193, carbide solution treated, GR B8R, B8RA, B8, B8M; A 194, carbide solution treated, Gr 8R, 8RA; A 320, carbide solution treated, Gr B8, B8M) (MP INQUIRY #2003-22 Q3) ANSWER: The manufacturer is responsible for the effects of carbide solution treatment on the material properties. 22 QUESTION: SUBJECT: Paragraph 6.2.1.1 of NACE MR0175-2003 Standard QUESTION: It is not clear whether or not the word "restrictions" as used in Paragraph 6.2.1.1 of NACE MR0175-2003 includes any environmental restrictions for bolting and nuts exposed to sour gas environments. Are bolting and nuts, which are manufactured from wrought austenitic stainless steel materials in accordance with the applicable paragraph in Section 4 of NACE MR0175-2003, acceptable for use in exposed sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature, and free elemental sulfur? QUESTION: Is the answer to the above question in agreement with ISO 15156? (MP INQUIRY #2003-39) ANSWER: Paragraph 6.2.1.1 requires materials to meet the requirements of Sections 3 and 4 as applicable to the base material. This paragraph does not specify just "metallurgical requirements." If the bolting is non-exposed in accordance with Paragraph 6.3.1, then the environmental requirements are not necessary. QUESTION: Does NACE MR0175/ISO 15156-2, Paragraph A.2.2.4 apply to Gr. 660 flange bolting materials or only to carbon and low alloy steel bolting materials in Part 2? (MP INQUIRY #2005-09Q1) ANSWER: Paragraph A.2.2.4 only applies to materials in Part 2. See also response to MP Inquiry #2005-09Q2 posted under ISO 15156-3, Table A.26. QUESTION: This query is about specifications of external bolting material in NACE MR0175/ISO 15156. In MR0175-2003, Section 6, Paragraph 6.2.1, all external bolting on sour systems that is denied direct atmospheric exposure, due to insulation or flange protectors, is considered to be in sour service because of the chance of exposure to H2S leaks. This seems to be in contradiction with Paragraph 1.4/Appendix A, where a minimum total pressure of 0.45 MPa (4.5 bara) is given as a minimum pressure level for sulfide stress cracking in gas. External bolting is normally at a lower pressure than that. On the other hand, external bolting may be considered potentially wet, which would lower the limit to a partial pressure of 0.0003 MPa H2S. In NACE MR0175/ISO 15156 Part 2, this specification is maintained for C-steel bolting but it is not extended to CRA bolting in Part 3. I have two questions about this guideline: How should I interpret the ambiguity/exception that exists in regard to minimum pressure level around external bolting? What is the current position of CRA external bolting on sour systems? 23 Is Class 2 bolting accepted or shall it be Class 1? (MP INQUIRY #2006-09) ANSWER: The ambiguity you describe does not exist in NACE MR0175/ISO 15156. As shown in Table 1 of all parts of the standard, no gas systems, whatever their total pressure, are included in the "Permitted exclusions" listed in Column 2. The equipment user is responsible for the selection of materials suitable for the intended service. The requirements of NACE MR0175/ISO 15156-2, A.2.2.4 apply only to carbon and low-alloy steels. NACE MR0175/ISO 15156-3 does not address the selection of materials external to the production environment. A.2.3.2.2 QUESTION: The title of Paragraph A.2.3.2.2 in NACE MR0175/ISO 15156-2 is “Shear rams.” This section allows the use of rams made from quenched and tempered, Cr-Mo, lowalloy steels up to a maximum hardness of 26 HRC provided the composition and heat treatment are carefully controlled and supporting SSC testing is performed. The text of this section does not limit these provisions to just shear rams; however, the section title would imply that only shear rams are covered by its provisions. This apparent shear ram restriction was not in previous revisions to NACE MR0175 (see 12.4.3 in NACE MR0175-2003 for example). It is important to ram manufacturers as well as end users that all Cr-Mo, low-alloy steel rams, not just shear rams, be allowed up to 26 HRC to ensure maximum hang-off capacity and for anti-extrusion purposes. Do the provisions of A.2.3.2.2 apply only to shear rams or can they be applied to other types of rams as well? (MP INQUIRY #2004-16) ANSWER: The requirements for Cr-Mo, low-alloy steel rams in A.2.3.2.2 in NACE MR0175/ISO 15156-2 are not intended to be restricted to shear rams only, but may be applied to other types of rams as well. This is consistent with all previous revisions of MR0175. A.2.4.1 and Table A.5 QUESTION: In NACE MR0175/ISO 15156 Part 2, Paragraph A.2.4, ductile iron ASTM A 536 is listed in Table A.5 as acceptable materials for drillable packer components for sour service. However, it is not mentioned in Paragraph A.2.4.1. Can we use this material for pressure-containing parts, i.e., valve stems? (MP INQUIRY #2004-20) 24 ANSWER: No, ductile iron ASTM A 536 is not listed in A.2.4.1 and may not be used for pressure-containing parts. A.2.4.3 QUESTION: I have a query regarding material suitability on a recent enquiry to supply a nodular iron screw compressor. NACE Standard MR0175 accepts ferritic ductile iron to ASTM A 395. My question is if our existing in-house standard of ASTM A 536 Grade 60/40/18 will comply as a direct alternative. On the face of it tensile strength, elongation are similar at 415N/mm2 and 18%! (MP INQUIRY #2005-27) ANSWER: The ISO Maintenance Panel cannot advise on materials selection issues. The role of the Maintenance Panel is solely to ensure that NACE MR0175/ISO 15156 (the current edition of NACE MR0175) is clear in its stated requirements and is kept upto- date. Should you wish, the procedure to propose an amendment to the standard to include ASTM A 536 Grade 60/40/18 is described in "01. Introduction to ISO 15156 Maintenance Activities" on the Web site www.iso.org/iso15156maintenance. Annex B B.1 QUESTION: Base Material In accordance to NACE MR0175/ISO 15156, Part 1, Item 7, 3rd paragraph, "no additional laboratory testing of pre-qualified materials selected in these ways is required." In accordance to NACE MR0175/ISO 15156, Part 2, Item B1, letter "a," "Some carbon and low alloy steels described or listed in A.2 might not pass some of laboratory . . ." In our understanding, NACE Standards TM0177 and TM0284 are used to qualify new materials that are not previously included in NACE MR0175. If we are using materials previously included in NACE MR0175, it is not necessary to test them according to NACE TM0177 and TM0284. We would like you to confirm if our interpretation below is correct and if not give us the correct interpretation. 25 (MP INQUIRY #2005-08Q1) ANSWER: NACE MR0175-2003 and its earlier editions only aimed to specify materials in relation to their resistance to SSC, SCC, and GHSC. They did not specify materials in relation to their resistance to SOHIC, SZC, HIC, or SWC. For carbon and low alloy steels, their resistance to SSC is referred to in ISO 15156- 1, Clause 7, Para. 1 and in ISO 15156-2, Annex A.2 and Annex B.1 a). Many materials included in NACE MR0175-2003 and its earlier editions were allowed by these documents on the basis of the general rules of acceptance now given in ISO 15156-2, Annex B.1 a). ISO 15156-2, Annex A.2, Para. 2 explains that carbon and low alloy steels complying with Annex A.2.1 " . . . might not resist SOHIC, SZC, HIC, or SWC without the specification of additional requirements." Hence, you may apply ISO 15156-1, 7 in relation to SSC of carbon and low alloy steels, but more testing may be required to evaluate carbon and low alloy steels for their resistance to HIC/SWC and other forms of H2S cracking. These requirements are addressed in ISO 15156-2, 7.2.2, 8, and in Annexes B.4 and B.5. No additional testing is required, but testing and weld qualification is recommended for cases in which HIC and SOHIC are considered a risk. Table B.1 QUESTION: We have some questions about some particular points concerning the SSC (NACE Standard TM0177) and HIC (NACE Standard TM0284) tests and the requirements of NACE MR0175/ISO 15156-2003. Our understandings are: SSC tests shall be performed in accordance with NACE Standard TM0177. The solution shall be Solution A given in TM0177 in accordance with requirements given in Table B.1 of NACE MR0175/ISO 15156-Part 2. The duration of the test shall be 720 h in accordance with Paragraph 8.6.7 of TM0177. Test method used shall be in accordance with guideline given in Table B.1 of NACE MNR0175/ISO 15156-Part 2, for severe sour service, i.e., Region 3. UT (Method A) appears to be more adapted to test raw plate and FPB (Method B) to reveal susceptibility to SOHIC and/or SZC that occur at welds, then this latest test appears to be more adapted to test welds. Our questions are: 1) What would you recommend for SSC test methods (refer to TM0177: Method A, B, C, or D) for: -Raw plates -Weld (to qualify a welding procedure)? 26 In addition, we would like to know which method--A or B--is more contraingnant. (MP INQUIRY #2005-26Q1) ANSWER: The ISO 15156 Maintenance Panel cannot make recommendations with respect to the test method to be used in particular circumstances; however, ISO 15156-2 Table B.1, Footnote (b) provides some guidance. The test method must be acceptable to the equipment user. Table B.3 QUESTION: For HIC test, NACE MR0175/ISO 15156-2:2003 Table B.3 is not clear regarding the acceptance criteria to be taken into account. We usually understood that "CLR, CTR, CSR" to be taken into account is the average of the values measured from one test specimen as defined in NACE Standard TM0284, Paragraph 4.2.1. What is your position? (MP INQUIRY #2005-26Q2) ANSWER: ISO 15156-2, B.5, Paragraph 3 makes clear that where no requirement is given NACE TM0284 shall be followed. Annex C QUESTION: NACE MR0175/ISO 15156, Part 2, Annex C, Section C.1 states that "The partial pressure of H2S may be calculated by multiplying the system total pressure by the mole fraction of H2S in the gas." Does the word "may" permit other methods, such as incorporating the effects of non-ideal gas behavior, to calculate partial pressure for determining material selection? (MP INQUIRY #2004-08) ANSWER: Yes. Please note: Annex C as a whole is "informative" rather than "normative" and is therefore not mandatory. 27 NACE MR0175/ISO 15156-3 General QUESTION: I need your help with the definition of CRAs in Part 3 of MR0175/ISO 15156. The "corrosion-resistant alloys" is very general and does not specify whether or not the definition includes the Fe-based alloys or not. More than that, the term CRA is used together with "other alloys" making it even more confusing. (MP INQUIRY #2004-12) ANSWER: NACE MR0175/ISO 15156-1, Paragraph 3.6 contains a definition of "corrosionresistant alloy" (CRA). It reads: "alloy intended to be resistant to general and localized corrosion of oilfield environments that are corrosive to carbon steel." This is taken from EFC 17. "Other Alloys" are those not covered by the definitions of carbon steel or CRA. For example, copper is not considered resistant to general corrosion but is considered in NACE MR0175/ISO 15156-3. QUESTION: Please see the answer included in this compendium under NACE MR0175/ISO 15156-2, A.2.2.4. (MP INQUIRY #2006-09) Contents The revision of the contents list to highlight "Table A.1 Guide to the use of the materials selection tables of Annex A" is included in Reference 3 Clause 1, Table 1 The revised version of this Table is given in Reference 3 Clause 3 QUESTION: Paragraph 9.2.4.1 Pressure Containing Components--What is the definition of bonnets? What about drain plugs? (MP INQUIRY #2003-27 Q1) ANSWER: Unfortunately, as you have noted, there are no NACE definitions for the terms you have listed. Therefore, they are open to your interpretation. Clause 6 6.2.1 QUESTION: 28 Our company has understood that NACE Standard MR0175 required the maximum specified hardness for austenitic stainless steels be satisfied at any location on bar stock (e.g., at locations considered significant by the user). Since cold-finished bars frequently have surface hardness values above the maximum specified in MR0175, we have declined to certify these products as compliant to the specification. We appear to be in the minority, or perhaps the only stainless bar producer that interprets the standard in this way. We routinely find competitors' cold-finished stainless bar in the marketplace certified to MR0175 based on a mid-radius hardness even though the surface hardness is above the maximum permitted in the standard. We realize this is a long-standing issue, but would like to clarify the hardness requirements of the MR0175 standard. We understand the logic in requiring the material meet a hardness maximum at any location (e.g., surface) in order to provide a predictable level of stress corrosion cracking resistance. Yet the standard does not clearly state, for example, that meeting surface hardness is a requirement. Please clarify the hardness requirements of MR0175 to allow all stainless bar producers to provide a uniform product to this standard. (MP INQUIRY #2003-06) ANSWER: NACE cannot provide assistance in specifying where to take hardness impressions and readings for this alloy or for any other alloy. This is because NACE Standard MR0175-2003 is not a quality assurance document. It is the responsibility of the alloy supplier to meet the hardness requirements and metallurgical requirements of the austenitic stainless steels in Paragraph 4.2. 6.2.2 QUESTION: We have some 316 stainless steel housings with a large through bore machined. Inadvertently this bore was machined oversize. We would like to flame spray build up the surface with 316 or 316L stainless material and remachine to size. As we understand the standard, 316 and 316L stainless are both included in a lengthy list of materials accepted for direct exposure to sour gas. As we intend to apply stainless to stainless for the purpose of remachining to dimension and not as a corrosion-inhibiting coating, would this process be acceptable and compliant with the NACE Standard MR0175/ISO 15156? (MP INQUIRY #2005-01) ANSWER: See response posted under ISO 15156-3, A.1.5.1 below. QUESTION: Seal welding of vent holes on saddle plates welded to pipe. We have provided vent holes on saddle plates in accordance with ASME B31.3. We have used these saddle plates at support locations as a protective shield to pipe. Now we would like to close the vent hole by seal welding after completion of saddle welding with pipe and carrying out PWHT. Permanent closing of vent hole is required to avoid corrosion in offshore conditions. Service is crude oil with H2S, i.e., NACE MR0175 is applicable. Kindly advise us about the acceptance of seal welding for these service conditions. 29 (MP INQUIRY #2005-21) ANSWER: See answer given to this inquiry under ISO 15156-2, 7.3.3. 6.2.2.2.2 QUESTION: Per A.6.3 as modified in NACE / ISO 15156-3:2003/Cor.2:2005(E), "The hardness of the HAZ after welding shall not exceed the maximum hardness allowed for the base metal, and the hardness of the weld metal shall not exceed the maximum hardness limit of the respective alloy used for the welding consumable." Per Table A.23 note (b) as modified in NACE/ISO 15156-3:2003/Cor.2:2005(E), "Low-carbon, Martensitic stainless steels either cast J91540 (CA6NM) or wrought S42400 or S41500 (F6NM) shall have 23 HRC maximum hardness..." Per 6.2.2.2.2 as modified in NACE / ISO 15156-3:2003/Cor.2:2005(E), "Hardness testing for welding procedure qualification shall be carried out using Vickers HV 10 or HV 5 methods in accordance with ISO 6507-1 or the Rockwell 15N method in accordance with ISO 6508-1. The use of other methods shall require explicit user approval." However, neither a Vickers nor Rockwell 15N acceptance criteria is specified for Martensitic Stainless Steels. Furthermore, ASTM E140 does not provide a hardness conversion for Martensitic Stainless Steels. Thus, there is neither a Vickers nor Rockwell 15N acceptance criteria. Is a correct interpretation that the acceptable hardness test method for qualification of Martensitic Stainless Steels is the Rockwell C Method, regardless of the applied stress, and without the need for explicit user approval? (MP INQUIRY #2006-01Q3) ANSWER: No, ISO 15156-3, 6.2.1, Para. 2 states "The conversion of hardness readings to and from other scales is material dependent; the user may establish the required conversion tables". 6.2.2.2.2 and 6.2.2.2.3 The revised texts for these sub-clauses are included in Reference 3. Annex A A.1.3 QUESTION: If I want to ballot a new alloy to be used in the acceptable environments described in Table A.32 of NACE MR0175/ISO 15156, which environmental test conditions should be used to qualify for “Any combination of hydrogen sulfide, chloride 30 concentration, and pH” at 135°C (275°F) with elemental sulfur? The same question applies to Table A.34. (MP INQUIRY #2004-09, Q1) QUESTION: In general, for the tables listed in Annex A of NACE MR0175/ISO 15156, what should the environmental test conditions be to qualify a new alloy where the “Remarks” in the respective tables state “Any combinations of temperature, partial pressure H2S, chloride concentration, and pH”? (MP INQUIRY #2004-09, Q2) ANSWER: NACE MR0175/ISO 15156 reflects the content of the 2003 edition of NACE Standard MR0175. The wording “Any combination of temperature, pH . . . Is acceptable” in various tables of NACE MR0175/ISO 15156-3 indicates that previous (early) editions of NACE documents had no environmental limits set for the alloys mentioned. The alloys were not tested to procedures laid out in later editions of NACE Standard MR0175 but instead “grandfathered” into the standard (i.e., they were added to the various early editions by common consent and common experience of good performance). No formal environmental limits were established and listed. The process for the addition of an alloy to later editions of MR0175 included laboratory testing under defined environmental conditions, which resulted in the environmental limitations for the alloy as listed in NACE MR0175/ISO 15156. This process will continue to be used for future additions of alloys to NACE MR0175/ISO 15156. Any proposal for additions/changes to NACE MR0175/ISO 15156 will be subject to a ballot/approval process. See also ISO 15156-1, 6 and ISO 15156-3, 6. A.1.5.1 QUESTION: We have some 316 stainless steel housings with a large through bore machined. Inadvertently this bore was machined oversize. We would like to flame spray build up the surface with 316 or 316L stainless material and remachine to size. As we understand the standard, 316 and 316L stainless are both included in a lengthy list of materials accepted for direct exposure to sour gas. As we intend to apply stainless to stainless for the purpose of remachining to dimension and not as a corrosion-inhibiting coating, would this process be acceptable and compliant with the NACE Standard MR0175/ISO 15156? (MP INQUIRY #2005-01) ANSWER 1.0 Flame spraying as a coating for corrosion resistance over a base material that is resistant to sulfide stress cracking is acceptable within the requirements of NACE MR0175/ISO15156 Part 2 Paragraph A.2.1.5 when applied over carbon steels and of Part 3 Paragraph A.1.5.1. In the case of your inquiry, the 316 or 316L base 31 materials are acceptable coating substrates if they conform to the metallurgical requirements of Part 3 Table A.2 and are used within the environmental restrictions of this table for any equipment. 2.0 If this application of flame spray is for the replacement of material that will be load bearing of tensile stresses, then the inquiry is not currently addressed by NACE MR0175/ISO15156. NACE/ISO have not been balloted with data to demonstrate that the 316 SS or 316L SS deposited flame spray coating has the same cracking resistance as the materials referenced in Part 3 Table A.2, which are assumed to be in the cast or wrought conditions. A.1.6 GENERAL REMARKS: The following remarks are prompted by questions related to Table A.2 (See also Reference 3), Table A.18, and Table A.23. Note: The revised version of Table A.2 is included in Reference 3. As indicated in ISO 15156-3, A.1.6, the Tables of Annex A fall into two groups: those for the selection of materials for "Any equipment or component" and a second group for specific named equipment or components when other, less restrictive environmental and metallurgical limits may be applied as an alternative. The scopes and contents of the Tables of ISO 15156-3, Annex A are not interdependent. (MP INQUIRY #2004-23) A.1.6, Table A.1 The revised version of Table A.1 is included in Reference 3 QUESTION: Do Paragraphs 9.2 and 9.5 both apply to choke valves? Additionally, choke valves are also used in applications where they are not directly mounted on the Christmas tree (i.e., manifolds, heaters, separators, etc.); can we still consider the choke valve to fall under Paragraph 9.2 for these applications? (MP INQUIRY #2003-02 Q1) ANSWER: Please see attached ISO 15156-3 Table A.1, which will provide the interpretation of NACE MR0175 Paragraphs 9.2, 9.3, and 9.5. NACE will be adopting ISO 15156 in 2003 as a technically equivalent document. QUESTION: Paragraph 9.2—Wellheads and Christmas trees. Does this paragraph include the valve bodies that are on the Christmas trees as well as other valve bodies exposed to H2S? In other words, which paragraph in Section 9 refers to the valve body? (MP INQUIRY #2003-04) ANSWER: 32 See attached ISO 15156-3 Table A.1, which will provide the interpretation of NACE MR0175 Paragraph 9.3. NACE will be adopting ISO 15156 in 2003 as a technically equivalent document. Please see ISO 15156 Part 1 for guidance as to how to use field experience or laboratory data to qualify a material for H2S service. QUESTION: Paragraph 11.4 of the standard, which is titled "Compressors and Pumps," appears to not address many significant applications for pumps. None of the material classes addressed in Paragraphs 11.4.2, 11.4.3, 11.4.4, 11.4.5, 11.4.6, or 11.4.7 speak to applications in pumps in sour service. Is this intentional? It would appear that the limitations applied to compressors would be also applicable to pumps. (MP INQUIRY #2003-20 Q2) ANSWER: It is intentional that the paragraphs you have cited apply only to compressors. The Paragraphs 11.4.2 and 11.4.3 come from the previous 2002 edition. The other paragraphs were added as a result of the balloting process for the 2003 edition. A.1.6 Table A.1 (Row “Any equipment or component”) QUESTION: Are the bolting materials and nuts specified in Paragraphs 6.2.1.2 and 6.2.1.3, respectively, the only acceptable materials in compliance with MR0175-2003 for Exposed Bolting? (MP INQUIRY #2003-22 Q1) ANSWER: Bolting materials may be chosen in accordance with Sections 3 and 4 as described in MR0175-2003, Paragraph 6.2.1.1. QUESTION: Does Paragraph 6.2.1.1 allow other nuts and bolting materials besides the ones listed in Paragraphs 6.2.1.2 and 6.2.1.3? (MP INQUIRY #2003-22 Q2) ANSWER: Yes, in accordance with NACE Standard MR0175-2003 Sections 3 and 4. ISO 15156-3, Table A.1 (Row “Any equipment or component”) lists the tables which may be used to select bolting materials. A.2.1 and A.2.2, Table A.2 QUESTION: With the former MR0175-2000 the material 316L (bar and pipe material) and CF8M (casting material) was allowed for use for NACE applications. With the new revision (MR0175-2003) the 316L does not fulfill the new allowed limits of the chemical components any more and the allowed temperature range to use CF8M is drastically reduced (so that it has nearly no meaning anymore for the NACE applications). According to our experiences these two materials have been very common for applications that require the "NACE conformity." 33 Now we are very interested in the reasons why these two materials are (nearly) not possible with the new specification any more. --Do you know what have been the reasons to change the limits of the allowed alloys and the allowed maximum temperature in this way? --Have there been serious problems with these materials in NACE applications in the past? (MP INQUIRY #2003-30) ANSWER: 1. We are not aware of having restricted the general composition of 316 SS beyond that of an industry consensus that was reviewed during the balloting process for the 2003 edition. It is important to emphasize that the chemical compositions for any alloy category in the 2003 edition are those of the alloys as delivered and not from the specifications. 316L SS is within the range as specified in Paragraph 4.2.1 of MR0175-2003 and is acceptable. 2. The austenitic stainless steels were restricted because of industry and lab failures. Please see the attached documentation. Upon the final ballot, there was a single negative that was not withdrawn. This negative suggested making the restrictions on 316 SS even more restrictive. You may choose for a future addendum to propose new limits based on the documentation described in NACE MR0175/ISO 15156. This documentation may be either laboratory data or successful field experience. A.2.2, Table A.2 The version of Table A.2 included in Reference 3 provides new guidance on the environmental limits of temperature, H2S, chlorides, pH and sulfur for austenitic stainless steels in sour service. QUESTION: Paragraph 4.2—Austenitic Steels (say 316 SS). One of the acceptance limits for these materials is a maximum H2S partial pressure of 15 psia at a maximum of 140°F when no chlorides are present. Can I assume that I can still use a material from this category at a higher temperature than 140°F if the partial pressure of H2S is lower than 15 psia? (MP INQUIRY #2003-04 Q1) REVISED ANSWER 2005-09-01: See Reference 3 QUESTION: In the past we have used 300 series SS pipes and valves in sour service. We are not sure of the implications and use of SS in sour service according to NACE Standard MR0175-2003. Could you please advise whether 300 series SS (304/316, etc.) can be used at lower H2S partial pressures for temperatures above 60°C (140°F)? (MP INQUIRY #2003-08) REVISED ANSWER 2005-09-01: See revised version of Table A.2 included in Reference 3 34 Please see ISO 15156 Part 1 for guidance as to how to use field experience or laboratory data to qualify a material for H2S service. QUESTION: Paragraph 4.2.2 is new. Would you let us know which interpretation applies? 1. Paragraph 4.2.2 is intended to place a limit on acceptable H2S content under the conditions stated, i.e., when temperature does not exceed 60°C, when no elemental sulfur is present, but without restriction on chlorides. 2. Paragraph 4.2.2 places a maximum temperature limit of 60°C on the use of austenitic stainless steel under any conditions in which MR0175 applies, for example, at 0.1 psia H2S partial pressure with no chlorides present. (MP INQUIRY #2003-23 Q1) REVISED ANSWER 2005-09-01: See revised version of Table A.2 included in Reference 3 QUESTION: In addition, please clarify the reason for the 60°C limit in Paragraph 4.2.2: We have noted that a limit of 60°C is commonly cited with respect to chloride stress corrosion for austenitic SST in other publications, and that chloride is mentioned in Paragraph 4.2.2. Are we correct in assuming, therefore, that the 60°C limit in Paragraph 4.2.2 is based on chloride stress corrosion concerns above 60°C when chloride concentrations above 50 mg/L are present rather than H2S corrosion concerns? That is, the first sentence of Paragraph 4.2.2 does not have a limit on chlorides but does have a temperature limit, whereas the second sentence limits chlorides but does not have a temperature limit. (MP INQUIRY #2003-23 Q2) REVISED ANSWER 2005-09-01: See revised version of Table A.2 included in Reference 3 See Paragraph 1.1 in NACE Standard MR0175-2003 for the scope of MR0175. The environmental restrictions in Paragraph 4.2.2 were established to provide resistance to sulfide stress cracking (SSC) and/or stress corrosion cracking (SCC) in austenitic stainless steels. QUESTION: AISI 316: Technical justification of the temperature limitation to 60°C. (MP INQUIRY #2003-27 Q5) REVISED ANSWER 2005-09-01: See revised version of Table A.2 included in Reference 3 The austenitic stainless steels were restricted because of industry and lab failures. Please see the attached documentation. Upon the final ballot, there was a single negative that was not withdrawn. This negative suggested making the restrictions on 316 SS even more restrictive. QUESTION: 35 SUBJECT: Paragraph 6.2.1.1 of NACE MR0175-2003 Standard QUESTION: It is not clear whether or not the word "restrictions" as used in Paragraph 6.2.1.1 of NACE MR0175-2003 includes any environmental restrictions for bolting and nuts exposed to sour gas environments. Are bolting and nuts, which are manufactured from wrought austenitic stainless steel materials in accordance with the applicable paragraph in Section 4 of NACE MR0175-2003, acceptable for use in exposed sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature, and free elemental sulfur? QUESTION: Is the answer to the above question in agreement with ISO 15156? (MP INQUIRY #2003-39) ANSWER: Paragraph 6.2.1.1 requires materials to meet the requirements of Sections 3 and 4 as applicable to the base material. This paragraph does not specify just "metallurgical requirements." If the bolting is non-exposed in accordance with Paragraph 6.3.1, then the environmental requirements are not necessary. QUESTION: NACE MR0175/ISO 15156-Part 3: From Table A.2 it seems that AISI 316/316L SS can no longer be used whenever the process temperature is above 60°C even if chlorides are totally absent from the environment. As this could have an enormous impact on the material selection for oil and gas processing plants, I would like to have a confirmation of the above. (MP INQUIRY #2004-17) REVISED ANSWER 2005-09-01: See revised version of Table A.2 included in Reference 3 QUESTION: We are now in the detailed engineering design phase of a sour gas refinery, and we have implemented NACE MR0175/ISO 15156 for design purposes. NaCl (sodium chloride) will come to the refinery through three-phase flow pipeline from offshore, after liquid separation in slug catcher; then the sour gas will go to gas treatment units for further processing. Table A.2 refers to chloride content in aqueous solution as mg/L; my question is in sour gas treatment units in which we use austenitic stainless steel, what are the criteria for the limitation of application of austenitic stainless steel? My idea is we have to comply with the first row of Table A.2. There is no means to identify the chloride content in the gas stream. (MP INQUIRY #2004-21) REVISED ANSWER 2005-09-01: It is assumed in Table A.2 that this is a mixed-phase environment with both a gas phase and a liquid phase. This is always true throughout the document. The operator is responsible for determining the service conditions, including chloride content (see ISO 15156-1, 6.1) and the ISO Maintenance Panel cannot provide advice. As mentioned in ISO 15156-3, A.1.3, Paragraph 2: “The tables show the application limits with respect to temperature, pH2S, Cl, pH, S. These limits apply collectively.” See also revised version of Table A.2 included in Reference 3 36 However, if, as an equipment user, you feel that ISO 15156-3, Table A.2 does not address your expected field conditions you have the freedom to test materials under alternative environmental limits and to use the outcome of successful tests to justify the use of a material outside the limits set in the standard. (See ISO 15156-3, 6.1, Para. 5.) QUESTION: Would you let me know whether our interpretation is correct? NACE MR0175/ISO 15156-3:2003 Para. A.2.2 states environment limits for austenitic stainless steel. According to Para. A.2.2, austenitic stainless steel (304/316 SS) is applicable with max. H2S partial pressure of 15 psi at a max. temperature of 140°F and UNS S20910 for valve stem is applicable without environmental limit. Austenitic stainless steel (304/316 SS) is applicable to valve stem material at a max. H2S partial pressure of 15 psi and a max. temperature of 140°F. Over a temperature of 140°F, UNS S20910 is applicable material to valve stem. (MP INQUIRY #2004-23 Q1) REVISED ANSWER 2005-09-01: See revised version of Table A.2 included in Reference 3 "Any equipment or component" includes valve stems, pins, and shafts. Table A.3 allows the use of UNS S20910 without environmental restrictions for "valve stems, pins, and shafts" but not for other equipment. See also "General Remarks" under ISO 15156-3, A.1.6 of this "Inquiries and interpretations" document. QUESTION: I have a technical query related to the latest edition of MR0175/ISO 15156 and the use of 316 stainless steel for sour service application. This latest edition of the standard imposes new restrictions on the use of 316 SS in environments operating above 60°C. My question is can 316 SS be used above 60°C for non-stressed vessel internals or for items such as thermowells located into sour lines or vessels? I ask this because I note that the standard need not be applied to parts loaded in compression (Part 2, Table 1). The implication may be that parts have to be stressed for SCC to be an issue. As a similar situation to vessel internals and thermowells, please could you advise on the use of 316 stainless steel for valve internals in a sour application, operating above 60°C. Of particular interest is the use of solid 316 SS balls for ball valves. (MP INQUIRY #2005-03) ANSWER: 1.0 The scope of NACE MR0175/ISO 15156 Part 3, Paragraph 1, Sentence 1 defines the applicability of the standard. The standard need not be applied for equipment not covered by this sentence. In addition, in Table 1, parts loaded in compression are included among those considered to be "permitted exclusions." SCC requires a tensile stress (applied and/or residual) to occur. There is no 37 provision for any of the alloys in the standard for a threshold tensile stress below which failure cannot occur. 2.0 The Maintenance Panel cannot analyze the design of equipment. It is up to the manufacturer and equipment user to agree whether or not the scope or any of the listed exclusions in Table 1 apply for a given design. A.2.2 including Table A.2 QUESTION: Paragraphs 4.2 and 4.2.1 refer to all CRAs being used in contact with well fluids but do not necessarily include instrument or control tubing (Bourdon tubes) being used in pressure indicators as listed in Paragraph 8.4.4.1. Currently this means that 316 stainless steel alloys (L, Ti, etc.) containing those elements are not ruled out from their being used in gauges where the well fluid wetted parts are not exposed to fluids that do not exceed: 4.2.2 The maximum acceptable H2S partial pressure shall be 100 kPa abs (15 psia) at a maximum temperature of 60°C (140°F), with no restrictions on chlorides, and no elemental sulfur. If the chloride content is less than 50 mg/L, the H2S partial pressure shall be less than 150 kPa abs (50 psia). Each application is subject to the specific environmental conditions to the equipment supplier, particularly if the equipment will be used in sour service. Under the above stated conditions, do gauges that are made with 316 SS alloy steels comply with NACE Standard MR0175-2003? (MP INQUIRY #2003-18) REVISED ANSWER 2005-09-01: You have correctly cited Paragraph 4.2 of MR0175 for the general use of austenitic stainless steels. It is the manufacturer's responsibility to determine whether the 316 SS meets the metallurgical requirements of this paragraph, including the requirement that the alloy will be "free of cold work . . . " --There is no exclusion for Type 316 stainless steel from the metallurgical or the environmental requirements of Paragraph 4.2 in Paragraph 8.4.2 of MR0175-2003. --NACE will adopt in 2003 the ISO 15156 document as being technically equivalent to MR0175. At this time there will be only a joint standard, NACE MR0175/ISO 15156. The NACE MR0175 2003 edition will cease to exist. See revised version of Table A.2 included in Reference 3. Table A.2 Revised version (see Reference 3) QUESTION: I would like to have advice regarding the addenda with particular focus on Reference 3. 38 Q1. According to Table A.2 of NACE MR0175/ISO 15156-3-2003/Cor. 2-2005 (E), an environmental limit for austenitic stainless steel was added under the title of "Any equipment or components in oil and gas processing and injection facilities after separation." Fluid from the oil wells is processed in the gathering center, which usually consists of flow lines, separators, desalter, storage tanks and gas processing facilities. 1. What does the "separation" facility mean? Is "separation" the facility downstream from the separator in the gathering center? 2. In case that environmental condition of a stream after separation is maximum chloride content above 50 mg/L and max H2S partial pressure below 15 psia, is the austenitic stainless steel acceptable for use? 3. If not, is there any technical reason for different environmental limits defined for the facilities before and after separation? (MP INQUIRY #2005-30Q1) ANSWER Q1.1) The subsection you refer to was introduced to correspond to a category of equipment that was familiar to users of NACE MR0175:2003 and had been omitted in NACE MR0175/ISO 15156-3. The environmental limits upstream and downstream of separation are identical. Q1.2) Yes, if the temperature is less than 60°C. Q1.3) No, see answer Q1.1) Q2. According to NACE MR0175/ISO 15156-3-2003/Cor. 2-2005 (E), environmental limits for some materials. Please advise when NACE MR0175/ISO 15156 would be accordingly revised. (MP INQUIRY #2005-30Q2) ANSWER Q2 This is addressed under the topic "FAQs" on the ISO 15156 Maintenance Web site at www.iso.org/iso15156maintenance. A.2.2, Table A.3 QUESTION: Paragraph 4.3.1 for UNS S20910 allows this material to be used in sulfur-free environments when the maximum H2S partial pressure is 15 psia to 150°F in the annealed or hot-rolled (hot/cold-worked) condition at 35 HRC maximum hardness. Paragraph 9.4.1 for UNS S20910 allows this material to be used for valve shafts, stems, and pins at a maximum hardness level of 35 HRC in the cold-worked 39 condition, provided this cold working is preceded by a solution-anneal heat treatment. Does this mean that I can use UNS S20910 for valve stems in the cold-worked condition (preceded by a solution-anneal heat treatment) at 35 HRC max with no environmental restrictions? (MP INQUIRY #2003-12 Q3) ANSWER: There are no environmental restrictions for UNS S20910 permitted at the higher hardness of 35 HRC in Paragraph 9.4.1 for the applications defined in Paragraph 9.4. Please see the attached Table A.3 from ISO 15156, which provides the correct interpretation of this paragraph. NACE will be adopting ISO 15156 in 2003 as a technically equivalent document. QUESTION We have a client that wishes us to use UNS S17400 double age-hardened stainless steel for the valve stem on some 4.1/16-in. 5k gate valves (basically because we have some in redundant stock and can deliver far quicker than the nickel alloy version of stem we currently use). He does, however, want the valves to comply with API 6A material class DD and the latest version of NACE MR0175. Where there is slight ambiguity is with the use of UNS S17400 for valves and choke components (excluding bodies and bonnets) with an allowable partial pressure of 0.5 psi (ref. Table A.27). Is it correct to assume that this additionally excludes valve stems because these are specifically dealt with in Table A.3, or can valve stems be used manufactured from UNS S17400 (in the required treated condition), as they are a valve component, with an allowable partial pressure of 0.5 psi in accordance with Table A.27? (MP INQUIRY #2006-07) Answer: No, Table A.3 does not preclude the selection of other materials for valve stems. Please see Table A.1. In general, materials for equipment or components may be chosen from Tables for "Any equipment or component" or from Tables for specific named equipment or components when other, less restrictive environmental and metallurgical limits may be applied as an alternative. For the specific example of UNS S17400 valve stems, they may be selected using Table A.27 subject to the environmental and metallurgical limits of this Table. A.2.2, Table A.2, Table A.3, and Table A.6 Note: The revised version of Table A.2 is included in Reference 3. QUESTION: SUBJECT: Paragraph 9.4 of NACE MR0175-2003 Standard 40 QUESTION: Are shafts, stems, and pins used in valves, unloaders, and other devices, when manufactured from austenitic stainless steel materials in accordance with Section 4 of NACE MR0175-2003, acceptable for use in sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature and free elemental sulfur? QUESTION: If the answer to the former question is no, what are the specific environmental limits? (MP INQUIRY #2003-36) ANSWER: 1) For stainless steels, the environmental limits of Paragraph 4.2 apply (as opposed to compressors where in Paragraph 11.4.7 there are no restrictions). (2) For individual alloy UNS S20910 there are no environmental restrictions if cold work and hardness are set within the restrictions of Paragraph 9.4.1 in Table A.3 of NACE MR0175/ISO 15156-3. Since in Paragraph 9.4.1 of MR0175-2003 there are no environmental restrictions, then the environmental restrictions of Paragraph 4.3.1 do not apply for shafts, stems, and pins. QUESTION: SUBJECT: Paragraph 9.4 of NACE MR0175-2003 Standard QUESTION: Are shafts, stems, and pins manufactured from austenitic stainless steels in accordance with and meet the hardness and heat-treat requirements of Section 4 of MR0175-2003 acceptable for use in sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature and free elemental sulfur? QUESTION: Is the answer to the above question in agreement with ISO 15156? (MP INQUIRY #2003-37) ANSWER: (1) For stainless steels, the environmental limits of Paragraph 4.2 apply (as opposed to compressors where in Paragraph 11.4.7 there are no restrictions). (2) For individual alloy UNS S20910 there are no environmental restrictions if cold work and hardness are set within the restrictions of Paragraph 9.4.1 in Table A.3 of ISO 15156-3. Since in Paragraph 9.4.1 of MR0175-2003 there are no environmental restrictions, then the environmental restrictions of Paragraph 4.3.1 do not apply for shafts, stems, and pins. A.2.2, Table A.2 and Table A.6 Note: The revised version of Table A.2 is included in Reference 3. QUESTION: SUBJECT: Paragraph 9.3 of NACE MR0175-2003 Standard The packaging content of large skid-mounted gas compressors applied in the oil and gas, gas processing, and process industries generally include several valves varied in type, such as relief valves, ball valves, globe valves, plug valves, gate valves, butterfly valves, and check valves installed on scrubbers, in process gas piping, and in off-skid mounted header systems and sometimes contain chokes in higher pressure scrubber drain systems. Are the body and bonnet components of valves, when manufactured from austenitic stainless steel materials in accordance with Section 4 of NACE MR0175-2003, acceptable for use in sour environments with no 41 environmental limits with respect to chloride content, partial pressure of H2S, temperature, and free elemental sulfur. (MP INQUIRY #2003-35 Q1) ANSWER: The latest editions of API Standard 618 for Reciprocating compressors and API Standard 617 for Axial and Centrifugal compressors define the scope of equipment associated with the compressor environment including accessories, instrumentation and piping systems. It is the user’s responsibility to determine whether the equipment mentioned in your inquiry is directly associated with the compressor and experiences the same service environment as inferred for compressors in NACE MR0175/ISO 15156-2003 Table A.6. QUESTION: If the answer to the former question is no, what are the specific environmental limits? (MP INQUIRY #2003-35 Q2) REVISED ANSWER 2005-09-01: a) The austenitic stainless steels when used outside the compressor environment are subject to the environmental restrictions in NACE MR0175/ISO 15156-2003 Table A.2. See revised version of Table A.2 included in Reference 3 b) The austenitic stainless steels were restricted because of industry and lab failures. QUESTION: Are the non-pressure-containing components of valves, when manufactured from austenitic stainless steel materials in accordance with Section 4 of NACE MR0175-2003, acceptable for use in sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature, and free elemental sulfur? (MP INQUIRY #2003-35 Q3) ANSWER: a.) The user must determine if individual components or parts of equipment must meet the requirements of NACE MR0175/ISO 15156-2003. b) NACE MR0175-2003 provided guidance for this applicability of the standard in Paragraph 1.3. This paragraph stated that “This standard applies to all components where failure by SSC or SCC would (1) prevent the equipment from being restored to an operating condition while continuing to contain pressure, (2) compromise the integrity of the system, and/or (3) prevent the basic function of the equipment from occurring.” These guidelines can be applied within NACE MR0175/ ISO 15156- 2003. QUESTION: If the answer to the former question is no, what are the specific environmental limits? (MP INQUIRY #2003-35 Q4) ANSWER: The austenitic stainless steels when used outside of the compressor environment are subject to the environmental restrictions in NACE MR0175/ISO 15156-2003 Table A.2. 42 Note: The revised version of Table A.2 is included in Reference 3. QUESTION: Are the answers to all of the above questions in agreement with ISO 15156? (MP INQUIRY #2003-35 Q5) ANSWER: Yes. QUESTIONS: I have an application where I am supplying a pipeline from a gas compressor to a turbine generator. The pipe is 10 in. in diameter and contains natural gas with H2S. The H2S concentration is 250 ppm by volume. The gas is pressurized to 475 psi @152°F. I would like to know what table from Annex A this pipe would fall under. The material I would like to use is 304L SS, which satisfies the requirements in A.2. I would appreciate any guidance you can provide with this subject. (MP INQUIRY #2004-02) ANSWERS: 1a) NACE MR0175/ISO 15156-3:2003 Table A.6 provides environmental and materials limits for austenitic stainless steels used in compressors. NACE MR0175/ISO 15156-3:2003 Table A.2 applies to austenitic stainless steels used for any equipment or components. Note: The revised version of Table A.2 is included in Reference 3. b) The limits on austenitic stainless steels in NACE MR0175/ISO 15156-3:2003 Table A.6 (when compared to those of NACE MR0175/ISO 15156-3:2003 Table A.2) are based upon industry experience with these alloys in compressors. c) The latest editions of API Standard 618 for Reciprocating compressors and API Standard 617 for Axial and Centrifugal compressors define the scope of equipment associated with the compressor environment including accessories, instrumentation, and piping systems. d) It is the user’s responsibility to determine if the pipe mentioned in your inquiry is directly associated with the compressor and experiences the same service environment as inferred for compressors in NACE MR0175/ISO 15156-3:2003 Table A.6. e) The Maintenance Panel cannot review individually designed equipment and pressure stations to make this interpretation. 2a) The manufacturer and user may consider documenting previous experience with pipelines in accordance with NACE MR0175/ISO 15156-1:2001 Paragraphs 8.2 and 9.0. b) NACE MR0175/ISO 15156-1:2001 provides minimal requirements for these issues and the user is ultimately responsible for ensuring the alloy in final fabricated form has adequate resistance to the types of cracking listed in the Scope 1.0 of NACE MR0175/ISO 15156-1:2001. 43 3. The ISO Maintenance Panel cannot comment on the suitability of using the 304L SS materials compared to alternative alloys. QUESTION: I am requesting a clarification of intent for comments included in Tables A.2 and A.6 in Annex A of the 2003 edition. In both of these tables there is a statement "these materials shall also -- -- be in the solution-annealed and quenched . . . . condition." It is my interpretation that this was a requirement for the base material and was not intended for a fabricated part, e.g., a welded compressor housing. We have to complete some fabrications and believe the required heat treatment will cause cracking and distortion of the part--however, a part must meet the requirements of MR0175/ISO 15156. (MP INQUIRY #2006-10) ANSWER: You are correct. NACE MR0175/ISO 15156-3, Tables A.2 and A.6 apply to base materials only. The requirements for welding are given in NACE MR0175/ISO 15156-3, A.2.3, "Welding of austentitic stainless steels of this materials group." A.2.2, Table A.6 The revised version of Table A.6 is included in Reference 3 QUESTION: SUBJECT: Paragraph 11.4.7 of NACE MR0175-2003 Standard QUESTION: It is not clear whether or not the word "restrictions" as used in paragraph 11.4.7 of NACE MR0175-2003 includes any environmental restrictions. Does Paragraph 11.4.7 provide an exemption to all of the environmental restrictions or limits detailed in Paragraph 4.2.2 in cases in which an austenitic stainless steel material has been selected for use in compressors in sour environments? QUESTION: If the answer to the former question is no, are all of the environmental restrictions detailed in Paragraph 4.2.2 of NACE MR0175-2003 included in the word "restrictions" as used in Paragraph 11.4.7? (MP INQUIRY #2003-33) ANSWER: NACE MR0175/ISO 15156 provides a clear interpretation in Table A.6 that only the metallurgical limits in Paragraphs 4.2 and 4.2.1 apply. Environmental restrictions do not apply. No data have been submitted to verify resistance to cracking in the presence of elemental sulfur. QUESTION: As a manufacturer of reciprocating compressors, we supply machines for compressing sour gas sometimes with a H2S partial pressure up to 10 bar. Before NACE Standard MR0175-2003 came into force, compressor components like valves, 44 valve cages as well as packing cups were manufactured out of austenitic stainless steel to prevent corrosion. The 2003 edition of MR0175 now contains many restrictions regarding the use of austenitic SS, limiting the H2S partial pressure and temperature to very low values (see page 9, item 4.2.2). Under these circumstances (max. temperature 60°C) these materials are not any more applicable for the compression part. On the contrary, the use of austenitic SS (UNS S31635/1.4571) acc. EN ISO 15156- 3:2003 is allowed--presumed the required heat treatment has been carried out (see page 19, Table A.6). In order to avoid surface corrosion we furthermore intend to use austenitic SS. But by doing so we are contradicting the NACE standard requirements--the standard that is mostly quoted by our customers. We ask for clarification on your part. (MP INQUIRY #2005-19) ANSWER: For your information ISO 15156-1, ISO 15156-2, and ISO 15156-3 (and their EN versions) all have NACE versions with identical technical content; they are: NACE MR0175/ISO 15156-1, NACE MR0175/ISO 15156-2, and NACE MR0175/ISO 15156-3 These NACE/ISO documents replace all earlier versions of NACE MR0175 including NACE MR0175-2003. In addition, there have been a number of inquiries on NACE MR0175/ISO 15156-3, Table A.6 since this standard was published; the answers provided by the ISO 15156 Maintenance Panel are included in the document titled "02. Inquiries and Answers" available on the ISO 15156 Maintenance Web site at www.iso.org/iso15156maintenance These answers provide clarification of the intent of Table A.6. A.2.2, Table A.2 and A.2.3 Note: The revised version of Table A.2 is included in Reference 3. QUESTION: The way I read Paragraph 4.2, austenitic stainless steels meeting Paragraph 4.2.1 must be solution-annealed and quenched or annealed and thermally stabilized with a maximum hardness of 22 HRC. (1) Am I correct in assuming these materials must be annealed regardless of hardness? (2) If a construction started with materials in this condition, would it be necessary to anneal again following a welding operation? (MP INQUIRY #2004-04) ANSWER: You are correct that materials must meet the requirements of MR0175-2003, Paragraph 4.2 regardless of their hardness. Please see Paragraph 5.3.3 for 45 requirements for welding the austenitic stainless steels. Paragraph 5.3.3 does not specifically require an anneal after welding to meet the requirements of 5.3.3. The requirements for austenitic stainless steels are now presented in Table A.2, NACE MR0175/ISO 15156; you are correct that the materials must meet the treatment conditions regardless of their hardness (maximum 22 HRC). Please see NACE MR0175/ISO 15156 A.2.3 for requirements for welding austenitic stainless steels. A.2.3 QUESTION: My stainless steel sheet material qualifies to Section A.2. I am forming this sheet into tubes and (longitudinally) welding the formed tube without filler metals using an automatic arc welding process (ASTM 249/ASTM 269). After welding the tube is fully annealed per ASTM. My hardness values are all below 22 HRC as required. A. Is my welded and annealed tubing bound to the welding requirements of A.2.3 and 6.2.2? B. After annealing, if I now butt weld two ends of the tubing above using the orbital weld (no filler metal) process (no additional anneal), am I now bound to A.2.3 and 6.2.2? (MP INQUIRY #2004-19 Q2) ANSWER: A. Yes, this is still a weld even if it was made without filler materials. B. Yes. QUESTION: In Section of Part 3: Table A.2 (austenitic stainless steel) states: "These materials shall also -be in the solution-annealed and quenched, or annealed and thermally stabilized heat-treatment condition, -be free of cold work intended to enhance their mechanical properties, and -have a maximum hardness of 22 HRC." Whereas for welding in Section A.2.3 it is stated that: "The hardness of the HAZ after welding shall not exceed the maximum hardness allowed for the base metal, and the hardness of the weld metal shall not exceed the maximum hardness limit of the respective alloy used for the welding consumable." I addition Section 6.2.2.2.2 states that "Hardness testing for welding procedure qualification shall be carried out using Vickers HV 10 or HV 5 methods in accordance with ISO 6507-1 or the Rockwell 15N method in accordance with ISO 6508-1. The use of other methods shall require explicit user approval." Q1. Please clarify how the requirement for 22 HRC is interpreted in light of this, i.e., what Vickers (HV 10 or HV 5) or Rockwell (15N) value should be used as a maximum for weld HAZ and weld metal? 46 On an associated point, for solid-solution nickel-based alloys (Section A.4) and duplex stainless steels (Section A.7) there are no hardness requirements for materials in the solution-annealed condition (with the exception of one HIP duplex stainless steel alloy). The relevant sections (A.4.3 and A.7.3) on welding state: "The hardness of the HAZ after welding shall not exceed the maximum hardness allowed for the base metal, and the hardness of the weld metal shall not exceed the maximum hardness limit of the respective alloy used for the welding consumable". Q2. Please confirm that the interpretation that NACE MR0175/ISO 15156 therefore places no hardness restrictions for welds in these materials is correct. (MP INQUIRY #2005-13) ANSWER: (1) NACE MR0175/ISO 15156 provides no guidance for hardness conversion from the Vickers to the Rockwell scales for the austenitic stainless steels, which is then left to an agreement between the manufacturer and the equipment user possibly based on conversion tables made using empirical data; see ISO 15156-3, 6.2.1, Paragraph 2. (2) There are no hardness limits for the HAZ of welds of corrosion-resistant alloys when there are no hardness limits in the tables or the text of the document for the base materials. For the weld metal, any hardness limit depends on any hardness limit set for the alloy used as consumable. For matching consumables for solid-solution nickelbased alloys (Section A.4) and duplex stainless steels (Section A.7) there are no hardness limits for weld metal. A.3 and A.4 QUESTION: In several paragraphs of both NACE MR0175 and ISO 15156 it is stated that materials (e.g., austenitic SS) are acceptable if they are free of cold work intended to enhance their mechanical properties or is stated "in the annealed or solutionannealed condition only" (e.g., Ni-based only). Question: Is there a limit to what is considered cold work, e.g., 5%, or is any cold work whatsoever included? (MP INQUIRY #2003-28 Q1) ANSWER: NACE MR0175/ISO 15156-3 does not prohibit all cold work of the austenitic stainless steels; it prohibits cold work intended to enhance mechanical properties. A limit for the percentage of cold work is not provided. QUESTION: In order to decrease the danger of low stress creep we slightly overstress superaustenitic SS and Ni-based alloy valve bodies during hydrotesting. This overstressing causes a "cold deformation" of 0.2-0.5%. We do not use the cold deformation in order to enhance the mechanical properties! 47 Is this practice allowed under the rules of NACE MR0175/ISO 15156 ? (MP INQUIRY #2003-28 Q2) ANSWER: Hydrotesting the austenitic stainless steels to the appropriate industry or design code is acceptable. A.3.2, Table A.8 The revised version of Table A.8 is included in Reference 3. QUESTION: We have requirement of 6Mo valves for one of our ongoing projects wherein we need to use A 351 CK3MCuN (J 93254) body material. With reference to Table A -8 of NACE MR0175/ISO 15156 - 2003 Environmental and materials limits for highly alloyed austenitic steels used for any equipment or components ) we have following clarification: Table A - 8 lists the above material J 93254 (ASTM A 351 CK3MCuN) can be used for any combinations of temperature, pH2S, chloride concentration and in situ pH occurring in production environments are acceptable. We understand that forging grade equivalent of above J 93254 which is UNS 31254 will also be qualified under these conditions. Please confirm /clarify the whether forging grade equivalent of J 93254 which is UNS 31254 will also be qualified? (MP INQUIRY #2006-12) Answer:- Table A.8 is the subject of an amendment proposal that has been accepted by the ISO 15156 Maintenance Panel, by NACE TG 299 (ISO 15156 Oversight Committee) and by ISO TC67 WG7 and will now go forward for publication. The revision involves limits being placed upon the application of UNS J93254. Publication of this document can be expected within the coming year. A.3.2, Table A.8 and Table A.9 QUESTION: We have a question regarding the meaning of a sentence in Paragraph 4.4 in MR0175-2003. This same sentence is repeated in Paragraph 10.2.1. The paragraph states: Highly alloyed austenitic stainless steels in this category are those with Ni% + 2 Mo% >30 and 2% Mo minimum. A1. Does the statement mean that there are essentially two groups in this category? Such that . . . 48 One qualifying group consists of materials that contain N% + 2 Mo% >30 Another qualifying group consists of any austenitic stainless steel with 2% Mo minimum (such as 316, 317). A2. Or does the statement mean that there must be a minimum of 2% Mo in the Ni% + 2 Mo% >30 requirement? Since the environmental restrictions in Paragraph 4.4 are the same as in 4.2 (where most austenitics are acceptable), I assume #A1 is the correct interpretation since this would allow for inclusion of 316 and 317. (MP INQUIRY #2003-15) ANSWER: Your answer A2 is correct. The chemistry requirements are additive. QUESTION: NACE Standard MR0175-2003 has two different highly alloyed austenitic SS families, one (Paragraph 4.4) with Ni% + 2 Mo% >30 (and Mo>=2%) and one (Paragraph 4.5) with PREN >40. Both have two different ranges for temperature, partial H2S partial pressure, and maximum chloride content. Which environmental limits have to be used for materials applicable for both categories like UNS S31254? (MP INQUIRY #2003-19 Q1a) ANSWER: If UNS S31254 has a PREN >40, then the less restrictive environmental limits in Paragraph 4.5 apply. QUESTION: Paragraph 4.4 in MR0175 identifies "Highly Alloyed Austenitic Stainless Steels with Ni% + Mo>30 and 2% Mo minimum" as a category. Is it intended by the standard writers that the two conditions be both present? In other words, is it Ni% + Mo>30 with 2% Mo minimum? Or is the 2% Mo minimum another defined material group in the category? I believe it to be the former as I am not aware of highly alloyed austenitic stainless steels only defined by the term "2% Mo minimum." (MP INQUIRY #2003-20 Q1) ANSWER: Paragraph 4.4 in NACE Standard MR0175 is a single alloy category defined by the additive requirements of Ni% + Mo% >30 and 2% Mo. Both requirements for chemistry must be met. A.4 QUESTION: Alloys 400 (N04400), 600 (N06600), and 800 (N08800) were previously listed in MR0175-94 as acceptable to 35 HRC. The newest revision does not list either 600 or 800 and now appears to place equipment restrictions on alloy 400 (Table A.16). None of these alloys appear to qualify by chemistry under A.4 Solid Solution Nickel Based Alloys (Table A.12, p. 21). A. Does 600 qualify anywhere in NACE MR0175/ISO 15156? B. Does 800 qualify anywhere in NACE MR0175/ISO 15156? Can 800 be qualified under A.2.1 Austenitic Stainless Steels? Some publications refer to 800 as a 49 stainless steel and others as a nickel alloy. ASTM lists it as an Ni-Fe-Cr alloy as did MR0175-94. C. I assume 400 is restricted to only the equipment and conditions listed in Table A.16? (MP INQUIRY #2004-19 Q1) REVISED ANSWER 2005-09-01: A. Alloys UNS N06600 and N08800 were inadvertently left out of the document. Unfortunately after 6-plus years of balloting, no one noticed this. The Maintenance Panel will be grateful if you would submit a ballot item for their inclusion in the set of addenda now being prepared for 2005. This ballot should take the form illustrated in “01. Introduction to ISO 15156 Maintenance Activities” Annex C. This document is available at www.iso.org/iso15156maintenance. B. See answer A. C. No, it is included in the revised version of Table A.13, that is included in Reference 3, that allows less restricted use. QUESTION: Are "contained" electrical tubular heating elements manufactured from solutionannealed or annealed UNS N08800 tube (sheath material) acceptable for applications under Paragraph A.4.1 (MR0175/ISO 15156-3)? By "contained" we mean that the heating elements are in a bundle totally enclosed inside a pipe body, shell, or tank. (MP INQUIRY #2005-06) ANSWER: 1.0 The solution-annealed or annealed material UNS N08800 does not match any of the materials groups mentioned in NACE MR0175/ISO 15156:3, A.4.1 and Table A.12. Please see also the previous interpretation (2004-19Q1) provided in response to a similar question to the ISO Maintenance Panel and listed under "Inquiries and Answers" for NACE MR0175/ISO 15156-3, A.4 at http://www.iso.org/iso15156maintenance. 2.0 Please note the ISO 15156 Maintenance Panel is unable to comment on questions related to design. In addition, any decision concerning the applicability of the standard is the responsibility of the equipment user. Please refer to the Scope of NACE MR0175/ISO 15156-3 on page 1 for the applicability of the standard. A.4.1, Table A.12 QUESTION: Paragraph 10.5.1.1 (NACE MR0175/ISO 15156-3, Sub-clause A.4, Table A.12)) requires a minimum Ni content of 29.5%, but solution-annealed and cold-worked alloy UNS N08535 (Alloy 2535, classified as a "nonferrous alloy" in MR0175-2002) only contains 29.0% Ni (minimum). Does this mean that Alloy 2535 must be restricted to environments described by Paragraph 10.2.1.1 of MR0175-2003 (NACE MR0175/ISO 15156-3, Sub-clause A.2, Table A.9) that are the same as for austenitic stainless steels like 316? (MP INQUIRY #2003-13 Q1) 50 ANSWER: You are correct; without further restrictions on their chemical compositions, materials to the specification UNS N08535 can only be guaranteed to match the Category requirements of "Austenitic stainless steel" (Covered in NACE MR0175-2003 as Paragraph 4.2 (NACE MR0175/ISO 15156-3, Sub-clause A.2)) or of "Highly alloyed stainless steel" (Covered in NACE MR0175-2003 as Paragraph 4.4 (NACE MR0175/ISO 15156-3, Sub-clause A.3)). Use in accordance with either of these two sub-clauses does require adherence to the relevant environmental limits. Use in accordance with Paragraph 10.2.1.1 (NACE MR0175/ISO 15156-3, Subclause A.2, Table A.9), while applying the same environmental limits, does accept cold-worked material with a maximum hardness of 35 HRC. However, if the chemical composition of heats of UNS N08535 is specified to a minimum nickel concentration of 29.5%, i.e., higher than the minimum stated Ni content of 29%, the alloy qualifies as a material of Type 4c as defined in NACE MR0175/ISO 15156-3, Table A.12 and is acceptable for use in accordance with the requirements of NACE MR0175/ISO 15156-3, Table A.14, Rows 2-6. These rows include the provisions of NACE MR0175-2003, Table 5. QUESTION: Alloy G-3 (UNS N06985, classified as a "Nonferrous alloy" in MR0175-2002), a 6% Mo, solution-annealed and cold-worked alloy, may contain as little as 35.9% Ni. Does this mean that its environmental limits are given in Table 5 of MR0175-2003 instead of Table 6 (NACE MR0175/ISO 15156-3, Sub-clause A.2, Table A.12)? (MP INQUIRY #2003-13 Q2a) ANSWER: Yes, you are correct. However, for NACE MR0175/ISO 15156, if the chemical composition is specified to a minimum nickel + cobalt concentration of 45% the alloy qualifies as a material of Type 4d and can be used in accordance with the requirements of NACE MR0175/ISO 15156-3, Sub-clause A.4, Table A.14, Rows 2- 8. These rows include the provisions of NACE MR0175-2003, Table 6. QUESTION: Question: Is annealed UNS N06625, Grade 1, per ASTM B443, B444, or B446 (also commonly referenced as stabilized or stabilize annealed) acceptable as a material under Paragraph 4.11.1 of MR0175-2003? Discussion: It clearly was acceptable in the previous version of MR0175; however, Grade 1 material is NOT solution annealed, as appears to be required by Paragraph 4.11.1. Solution-annealed material requires annealing at a temperature above 2,000°F and is identified as Grade 2. This condition is typically reserved for service temperatures in excess of 1,100°F. (MP INQUIRY #2003-40) ANSWER: Please see the definition of solution anneal in NACE MR0175 Section 2. This Maintenance Panel cannot interpret ASTM specifications. However, please note that 51 UNS N06625 is considered in NACE MR0175/ISO 15156 Table A.12 as an alloy that may be used in the solution-annealed or annealed metallurgical condition. A.4.1, Table A.12 and sub-clause A.4.2, Table A.13 QUESTION: Paragraph 4.11 of NACE Standard MR0175-2003 does not stipulate a minimum cobalt content. Do solid-solution nickel-based alloy wrought materials complying with either of the two chemical composition alternatives detailed in Paragraph 4.11.1, but with zero percent cobalt, qualify for no environmental limits with respect to partial pressures of H2S in accordance with Paragraph 4.11.2? (MP INQUIRY #2003-25) ANSWER: There are no environmental limits with respect to partial pressures of H2S or elemental sulfur as stated in NACE Standard MR0175-2003 Paragraph 4.11.2 for solid-solution nickel-based alloys defined as a category in Paragraph 4.11. There is no individual requirement for the minimum content of Co alone in Paragraph 4.11. Chemistry requirements for Co are expressed only for the sum of nickel and cobalt. QUESTION: We manufacture a fluid-handling product machined from UNS N06600 in the coldworked condition with a hardness less than 35 HRC. We have certified that this product meets MR0175 based on Paragraph 4.1.4.1 of MR0175-2002. a) It appears this material is not included in MR0275-2003. Is it acceptable to certify that this material meets MR0175-2003 based on the listing in previous versions? b) If not, is it acceptable to continue to certify meeting MR0175-2002? (MP INQUIRY #2003-10 Q2) ANSWER: The MP cannot provide interpretations involving the certification of equipment. We can only interpret the current edition of MR0175. The MP will investigate the history of this alloy in NACE MR0175 and may make an amendment proposal to re-include it. QUESTION: Old (2002) Paragraph 4.1.5.1 UNS N06625 HRC >35 New (2003) Paragraph 4.11 and A13: N06625 solution-annealed only: Technical justification? (MP INQUIRY #2003-27 Q2) ANSWER: The consensus during the balloting process for the 2003 edition was that no hardness limit was required for solution-annealed material. Alloy manufacturers did not object to the change. A.4.1 and A.4.2, Table A.16 QUESTION: We believe that Alloy 400, UNS N04400, should be included in both the latest version of MR0175 and the imminent ISO 15156 standard. As outlined in the foreword of MR0175-2003, “Many of the guidelines and specific requirements in this standard are based on field experience with the materials listed . . . “ 52 We propose that Alloy 400, UNS N04400, be added to Section 8, Special Components, Paragraph 8.4.2, Diaphragms, Pressure-Measuring Devices, and Pressure Seals. (MP INQUIRY #2003-07) REVISED ANSWER 2005-09-01: The revised version of Table A.13 is included in Reference 3. QUESTION: In what paragraph are the requirements for wrought bar in nickel-copper alloy (i.e., UNS N04400 and N04405)? In the 2002 version, these materials were covered in Paragraph 4.1.1. (MP INQUIRY #2003-09 Q1) ANSWER: These alloys, UNS N04400 and N04405, are no longer in the standard except in Paragraphs 10.6.2.2 and 10.7.3. QUESTION: We manufacture a fluid-handling product machined from UNS N04400 and N04405 in the cold-worked condition with a hardness less than 35 HRC. We have certified that this product meets MR0175 based on Paragraph 4.1.1.1 of MR0175-2002. a) May we continue to certify that this product meets MR0175-2003, since this material is mentioned in Paragraph 10.6.2.2? b) Is it acceptable to continue to certify meeting MR0175-2002? (MP INQUIRY #2003-10 Q1) ANSWER: The MP cannot provide interpretations involving the certification of equipment. We can only interpret the current edition of MR0175. Paragraph 10.6.2.2 states that UNS N04400 and N04405 may be used for gas lift equipment. QUESTION: What are the reasons for the exclusion of nickel-copper alloys, e.g., UNS N04400, from the materials listed in Section 4? (MP INQUIRY #2003-26 Q1) ANSWER: The wrought nickel-copper alloys were removed from the general section of NACE Standard MR0175 because of concerns from field failures of UNS N05500. It was expected that as a result of ballots over the 6-plus years of drafts that the 2003 edition of MR0175 would include the reinsertion of UNS alloys N04400 and UNS N04405 into the appropriate equipment sections. This has not been the case. There has not been a single ballot for including these alloys. However, the ISO Maintenance Panel has agreed to put forward for ballot to the ISO Oversight Committee and ISO WG 7 a proposal to include these two alloys into the Instrumentation and Control Devices Paragraph 8.4. If the ballot passes, the alloys will be included in a 2004 addendum to ISO 15156/NACE MR0175-2004 in the table currently numbered A.16. QUESTION: NACE Standard MR0175-96, Section 4, includes Paragraph 4.1.1 titled Nickel- Copper Alloys specifically listing UNS N04400 (K-Monel), UNS N04405, and 53 N05500. These CRA metals have been omitted from MR0175-2003 except for brief mention under Section 10 for specific equipment not related to our business. We are a manufacturer of process gauges, some of which are for use in sour gas environments. These metals (especially N04400) have always been used in our (and other manufacturers') gauges for pressure-containing parts having direct exposure to sour gas. Have these materials been omitted for a reason or are they still acceptable? (MP INQUIRY #2003-29) ANSWER: MR0175 was revised based on several years of balloting and input from NACE TG 081 members. Several alloys were eliminated from the general section of the document because members were concerned that these alloys were being used without appropriate restrictions to the environment. There were no ballots, or comments on ballots during this process, to insert Monel alloys back into the document in the section on gauges. The MR0175 document will within this year become ISO 15516/MR0175. At this time, ISO/NACE will begin to accept ballots for revisions. Attached is the standard format for balloting. Prior to or in lieu of balloting, Section 16 may be used............. Also, please note that in Paragraph 1.10.2, “The user may replace materials in kind for existing wells or for new wells within a given field if the design basis for the equipment has not changed.” This Paragraph allows customers to purchase materials that have provided satisfactory performance in the past, even if the materials are not listed in the current 2003 edition. QUESTION: We manufacture instrumentation and in particular, BOURDON TUBE-type pressure gauges. Due to the manufacturing process, 316 SS tube exceeds the hardness limit in NACE MR0175. The alternative has always been to supply “MONEL” UNS N04400 to comply with NACE MR0175. Paragraph 8.4 would previously have referenced N04400 in Section 4, thus meeting the requirements. We note N04400 is referenced in Section 10 only, specific to downhole equipment. We are holders of your standard NACE MR0175-2003. We have a particular query regarding UNS N04400. The 2003 edition of the standard does not contain in Section 4 (CRAs) a section for nickel-copper alloys (NACE MR0175—ALL PREVIOUS ISSUES), and as UNS N04400 does not fall within the stated parameters within Section 4, can you please clarify: Is UNS N04400 no longer within the scope of MR0175-2003 section 4, or will an amendment be issued to re-include it in Section 4? (MP INQUIRY #2003-31) REVISED ANSWER 2005-09-01: The wrought nickel-copper alloys were removed from the general section of NACE Standard MR0175 because of concerns from field failures of UNS N05500. There were no ballots for the drafts of MR0175-2003 to reinsert UNS N04400 and UNS N04405 into the appropriate equipment sections. The ISO Maintenance Panel has agreed to put forward for ballot to the ISO Oversight Committee and ISO WG 7 a proposal to include these two alloys in the Instrumentation and Control Devices Paragraph 8.4. If the ballot passes, the alloys will be included in a 2004 addendum to NACE MR0175/ISO 15156. The revised version of Table A.13 that addresses any equipment or component is included in Reference 3. 54 A.4.2 QUESTION: According to NACE Standard MR0175-2003, 625 material, as a solid-solution nickelbased alloy, is acceptable only in the solution-annealed condition. This constitutes a major change with respect to previous editions, in which 625 material was accepted up to 35 HRC regardless of the delivery condition. The annealed condition is considered the most suitable condition by most of our customers and we are not aware of problems or failures with material 625 used in this condition for NACE applications. Unless a real problem exists in using annealed 625, we would like to understand whether: • The definition of solution annealing given in NACE Standard MR0175-2003 has to be interpreted to exclude 625 material in the annealed condition; or • For 625 material, annealing performed in a given temperature range (to be suitably defined, even more narrow than the range from 1,600 to 1,900°F) can be considered a solution-annealing heat treatment as defined in Section 2. (MP INQUIRY #2003-11) ANSWER: Tables A.12, A.13, and A.14 in ISO 15156 provide answers to your requests for interpretations. NACE will be adopting ISO 15156 in 2003 as a technically equivalent document. The nickel-based alloys may be used in the annealed or solution-annealed condition within the requirements of these ISO tables. Please also refer to the definition of “solution-annealed” in Section 2 of NACE Standard MR0175. This definition does not prescribe the temperature for the solution-annealing heat treatment. A.4.2, Table A.12 QUESTION: Question on Alloy 31 (UNS N08031) The typical chemical composition of this alloy is: Fe bal, Ni 31, Cr 27, Mo 6.5, Cu 1.2, N 0.20. Based on the individual heat chemistry, the alloy could be either a nickel-based alloy (nickel being the highest element) or high-performance stainless steel in which iron is the highest element. NACE MR0175-2002: *Alloy 31 appears in Section 4: Nonferrous Metals. *4.1.3 Nickel-Iron-Molybdenum Alloys Paragraph 4.1.3.14 (provides allowed use and the table of balloted data). NACE MR0175-2003: The nonferrous section is no longer present in this version. *Section 4 is now entitled “Corrosion-Resistant Alloys (CRAs)--All Other Alloys Not Defined As Carbon and Low-Alloy Steels and Cast Irons in Section 3” 55 *Section 4.11 Solid-Solution Nickel-Based Alloys (Category) appears to be the section in which Alloy 31 fits the category of 4.11.1: 19.0% Cr min., 29.5% Ni + Co min., and 2.5% Mo min. No specific mention of alloy 31 is made in this section. *The balloted table of data for alloy 31 appears in Appendix C: Ballot Submittal Data, Table C7. It appears that name of this alloy UNS N08031 (alloy 31) began to disappear in this version. I fully understand that this document NACE MR0175-2003 is no longer valid and now has been replaced by NACE MR0175/ISO 15156 First Edition, Part 3. NACE MR0175/ISO 15156 First Edition, 2003-12-15, Part 3 (Comments and Questions) It appears that alloy 31 (UNS N08031) should appear in Section A.4 Solid-solution nickel-based alloys. It would further appear that alloy 31 (UNS N08031) fits the materials type 4c described in Table A.12 as: 19.5% Cr min., 29.5% Ni + Co min., and 2.5% Mo min. Is this the material type/grouping that alloy 31 (UNS N08031) should be grouped with? Table D.4 lists various alloys included in the Section A.4 Solid-solution nickel-based alloys. Alloy 28 (Alloy 28 in reality is not a nickel-based alloy) and 32 are listed in this table. No mention is made of alloy 31 in this table or within the document. Could 32 be a typo error and should be 31?? It appears that alloy 31 (UNS N08031) has completely disappeared from this version. I would appreciate clarification on this point. Alloy 31 (UNS N08031) should be listed in this NACE MR0175/ISO 15156-3 First Edition, 2003-12-15, Part 3 document. If this is an error, how do we get it corrected and if this is not an error how do we get alloy 31 in this document? (MP INQUIRY #2004-15) ANSWER: Alloy 31 as you describe it fits in Type 4c as defined in NACE MR0175/ISO 15156-3, Table A.12. Alloys that comply with the requirements of Table A.12 for solid-solution nickel-based alloys are not individually listed in NACE MR0175/ISO 15156-3, Annex A. The document makes use of alloy types in order to avoid the listing of all possible examples of such alloys. Similarly, NACE MR0175/ISO 15156-3, Table D.3, as noted in its title, does not attempt to provide an exhaustive list of alloys that can meet the requirements of these types of alloys. Please note it is not a requirement of NACE MR0175/ISO 15156 that an alloy be individually listed to meet the requirements of the document. 56 If a solid-solution nickel-based alloy, as defined in NACE MR0175/ISO 15156-3, Table A.12, is used within the environmental and metallurgical limits defined in Table A.13 or Table A.14 it meets the requirements of the standard. QUESTION: I have a query regarding UNS No 08825 pipe material in hot finished annealed delivery condition as availability of ASTM B 423(UNS No 08825) material in cold finished annealed condition is scarce but it is generally available in hot finished delivery condition above 8" size. Therefore my query goes as follows: "NACE MR 0175/ISO 15156-3:2003(E) does not list UNS No. N08825 in hot finished annealed condition in Table A.12, A.13 and A.14. Table A.12 breaks down Solid solution nickel-based alloys into Type-4a, 4b, 4c and 4d depending on Cr, Ni+Co, Mo and Mo+W mass fraction and metallurgical condition. Now my question is whether ASTM B 423 (UNS N08825) pipe in hot finished annealed delivery condition for 8" and 10" pipe shall be acceptable for piping because for type 4a and 4b metallurgical condition does states the requirement of cold-worked or hot worked". (MP INQUIRY #2006-15) ANSWER: The alloy UNS N08825 in the annealed condition falls under the materials Type 4a in Tables A.12, A.13. The term "annealed" refers to the final stage of the heat treatment of the material or component that determines its metallurgical condition in the service environment. A.4.2, Table A.14 The revised version of Table A.14 is included in Reference 3. QUESTION: Table 4 (for precipitation-hardenable, 6Mo alloys) (NACE MR0175/ISO 15156-3, Sub-clause A.9.2, Table A.33) permits elemental sulfur in the environment at 450°F, but not at 425°F, yet again at 400°F. Where does the user discover whether sulfur is or is not acceptable for applications between these temperatures? This is odd enough, but Table 6 (for 6 Mo, precipitation-hardenable 6 Mo alloys) (NACE MR0175/ISO 15156-3, Sub-clause A.4.2, Table A.14) does allow sulfur at 425°F. Are the precipitation-hardenable versions of these alloys more resistant to cracking than their solution-annealed and cold-worked analogs? (MP INQUIRY #2003-13 Q3) ANSWER: In response to your questions 3 and 4a): The data used in NACE MR0175-2003 and NACE MR0175/ISO 15156-3 represent the limits of successful laboratory tests reported to NACE so far. In some cases the available data cannot be used to answer the questions you pose. QUESTION: (a) Table 6 (NACE MR0175/ISO 15156-3, Sub-clause A.4.2, Table A.14) permits sulfur at 300°F in any H2S partial pressure, but not at 425°F. Where, if anywhere, between 425°F and 300°F are alloys in this category sulfur-resistant? If an oilcompany client has a well with bottom-hole temperature of 350°F with produced 57 brine that contains sulfur, will an alloy like 2550 (UNS N06975) be sufficiently resistant, or (b) must C-276 (UNS N10276) be deployed? (MP INQUIRY #2003-13 Q4) ANSWER (a) In some cases the comparisons you make are not strictly valid because the data sets for the materials considered vary in the H2S limits, in the temperature limits, and in the metallurgical limits that are imposed. It is thought that the limits given are conservative and further testing could demonstrate that the true limits are less restrictive than those shown; see also the answer to MP Inquiry #2003-13 Q6 under ISO 15156-1 Clause 5. ANSWER: (b) UNS N10276 would be acceptable. QUESTION: Could you please confirm that the kPa units of the H2S column of ISO 15156-3, Table A.14 are incorrect and that the units should be MPa not kPa? (MP INQUIRY #2004-07) REVISED ANSWER 2005-09-01: The revised version of Table A.14 is included in Reference 3. QUESTION: NACE MR0175/ISO 15156-3: We make bellows for use in Safety Relief Valves. We use all nickel alloy materials but we are particularly concerned with Inconel 625/Inconel 625LCF. In previous editions of the NACE standard, the material hardness value for UNS N06625 is clearly stated as being acceptable to 35 HRC maximum, but in the above-referenced latest edition we are finding it difficult to trace this requirement and keep our records and practices updated. Would you please confirm the hardness requirements stated in the above-referenced latest edition and also reference relevant paragraphs and tables. We buy the strip material in the solution-annealed condition, but there is a certain amount of work hardening that takes place during the bellows forming process. (MP INQUIRY #2004-10) REVISED ANSWER 2005-09-01: The individual hardness limit of 35 HRC max. for cold-worked alloy UNS N06625 has been dropped in NACE MR0175/ISO 15156-2003. Please see Table A.14 for hardness and yield strength limits achieved by cold work for nickel-based alloys. The revised version of Table A.14 is included in Reference 3. A.4.2, Table A.16 QUESTION: Does Monel in the annealed condition in accordance with ASTM B 127 and Monel in the as-cast condition in accordance with ASTM A 494 M-35-2 and M-30C meet NACE Standard MR0175-2003? (MP INQUIRY #2003-14) ANSWER: 58 (Response from Transition Team) As a sub-paragraph to 4.11, Paragraph 4.11.1 is a constraint. Therefore, Monels do not apply since they are not alloyed with chromium or molybdenum. UNS N04400 appears in MR0175 in Paragraphs 10.6.2.2 and 10.7.3; the use must fit an application described in one of these two paragraphs in order to be directly acceptable. Otherwise, please note Paragraph 1.8.4, which directs the reader to the options of balloting the material and/or application for inclusion into MR0175 or using the material for application-specific cases without balloting. A.4.3 See A.2.3, MP inquiry #2005-13 QUESTION: This question relates to NACE MR0175/ISO 15156 Part 3, Appendix A, Paragraph A.4.3. Is the hardness testing survey required as part of the welding procedure qualification for solution heat-treated nickel-based alloys welded with solid-solution nickel-based weld metal? In accordance with A.4.3 there are no hardness requirements. A.4.3 Welding solid-solution nickel-based alloys of this materials group. The requirements for the cracking-resistance properties of welds shall apply (see 6.2.2). The hardness of the HAZ after welding shall not exceed the maximum hardness allowed for the base metal, and the hardness of the weld metal shall not exceed the maximum hardness limit of the respective alloy used for the welding consumable. There are no hardness requirements for welding solid-solution nickel-based alloys with solid-solution nickel-based weld metal. Is the hardness testing survey required as part of the welding procedure qualification for solid solution nickel-based alloys (as addressed in NACE MR0175/ISO 15156-3, A.4) welded with solid-solution nickel-based weld metal? (MP INQUIRY #2006-06) ANSWER No. A.6.2, Table A.18 QUESTION: We need clarification of Paragraph 4.8.2—Low-Carbon Martensitic Stainless Steels. In the 2002 edition this was Paragraph 3.7.2.1. The 2002 edition allowed wrought material meeting the chemistry requirements of ASTM A 487 CA6NM. The 2003 edition appears not to allow these F6NM wrought materials (UNS S41500), just S42400, which is not the same thing. Please advise whether this material is acceptable. (MP INQUIRY #2003-17) REVISED ANSWER 2005-09-01: The revised version of Table A.18 is included in Reference 3. 59 QUESTION: My inquiry concerns CA6NM: In the old MR0175-2002 this material is discussed in Paragraph 3.7.2.1. In this paragraph there is a note (12) stating that the hardness correlation in ASTM E 140 doesn’t apply to CA6NM and that for this material the maximum permissible value (in Brinell) is 255 BHN. In the new MR0175/ISO 15156, this statement is no longer used. There is, however, a paragraph in Paragraph 7.3.2 of MR01756/ISO 15156-2 which stipulates that users can establish hardness correlations for individual materials. Please see below: For ferritic steels EFC Publication 16 shows graphs for the conversion of hardness readings, from Vickers (HV) to Rockwell (HRC) and from Vickers (HV) to Brinell (HBW), derived from the tables of ASTM E 140 and BS 860. Other conversion tables also exist. Users may establish correlations for individual materials. Finally the questions: Is CA6NM acceptable per MR0175/ISO 15156 at a hardness of max 255 BHN which has been (empirically) determined to be the equivalent of 23 HRC (but which on the ASTM E 140 scale corresponds to about 25 HRC)? (MP INQUIRY #2004-18 Q1) ANSWER: The prescribed hardness limit of 23 HRC for CA6NM in Table A.18 in NACE MR0175/ISO 15156-3 utilizes the Rockwell C scale as the basis for acceptance. Conversions to other hardness scales are no longer included in the standard. Other hardness scales may still be used provided a correlation can be shown between the scale used and the prescribed Rockwell C scale for the particular material being tested. As stated in Paragraph 6.2.1 of NACE MR0175/ISO 15156-3, conversion between hardness scales is material-dependent. The ISO Maintenance Panel cannot make this conversion for you. The user may establish the required conversion tables. QUESTION: My question is about SS 431 (wnr 1.4057/S43100) which is a martensitic stainless steel. In Part 3 of the documentation, according to A.6 Martensitic (stainless) steels (identified as individual alloys) and Table A.18. Environmental and materials limits for martensitic stainless steels used for any equipment or components. As the alloy SS 431 (wnr 1.4057/S43100) is not mentioned, does that mean that it cannot be used according to NACE or can we use it as long as the hardness of the material is max. 22 HRC? Do we need to apply any special attention to the heat treatments, as shown in Table A.18? (MP INQUIRY #2005-29) ANSWER: Alloy UNS S43100 is not at present qualified to the requirements of NACE MR0175/ISO 15156 for inclusion in Table A.18. 60 A proposal to amend Table A.18 may be submitted and must contain supporting evidence from field experience or laboratory testing. With the agreement of the equipment user, the alloy may be qualified for specific applications and may then be used without listing in the standard. Requirements/procedures for qualification are given in NACE MR0175/ISO 15156-1, Clause 8, NACE MR0175/ISO 15156-3, Annex B and in "01. Introduction to ISO 15156 maintenance activities" at www.iso.org/iso15156maintenance. QUESTION: I have a question regarding NACE MR0175/ISO 15156-3:2003. On Table A.18, the heat treatment requirements for CA6NM and F6NM are listed. Is this the only approved heat treatment? If we follow this heat treatment initially, are other heat treatments allowed as long as they do not exceed the original? We're trying to find out if a supplemental stress relieve is acceptable to try and lower the material hardness. (MP INQUIRY #2006-19) ANSWER: Only the heat treatments listed are currently acceptable. Other heat treatments may be qualified in accordance with the requirements of NACE MR0175/ISO 15156-3 Annex B. A.6.2, Table A.18 and Table A.23 QUESTION: Inconsistency between Table A.18 and A.23 of Para. A.6.2 in NACE MR0175/ISO 15156-3:2003. Table A.18 allows martensitic stainless steels for any equipment or component, but Table A.23 excludes casing and tubing hanger and valve stems. What is the meaning of any equipment or component? Does any equipment or component from Table A.18 exclude casing and tubing hangers and valve stems? (MP INQUIRY 2004-23 Q2) ANSWER: No, ISO 15156-3, Tables A.18 and A.23 set different H2S limits for the same selection of martensitic stainless steels. The other environmental limits are the same. Table A.18 addresses the use of the materials under the environmental limits of this table. "Any equipment or component" included wellhead and tree components and valve and choke components, and casing and tubing hangers and valve stems. Table A.23 allows the use of the same selection of materials for wellhead and tree components and valve and choke components under a less restrictive set of environmental conditions but excludes casing and tubing hangers and valve stems under these less restrictive conditions. Please see Table 1 of NACE MR0175/ISO15156-3 for the list of equipment covered by this standard and also "General Remarks" under ISO 15156-3, A.1.6 of this "Inquiries and interpretations" document. 61 A.6.2, Table A.19 The revised version of Table A.19 is included in Reference 3. QUESTION: Is the maximum hardness limit for ISO 11960 L-80 Type 13 Cr tubing used as a downhole tubular component, packer, and other subsurface equipment in accordance with NACE MR0175/ISO 15156 the maximum hardness as specified in the latest edition of ISO 11960? Note: ISO 11960 is also designated as API 5CT. Note: ISO 11960 currently specifies 23 HRC as the maximum hardness for L-80 Type 13 Cr tubing. Discussion: NACE MR0175/ISO 15156-3, Table A.19 lists ISO 11960 L-80 Type 13 Cr and two other materials as begin acceptable for "downhole tubular components, packers, and other subsurface equipment." There are notes in this table that specify the maximum hardness limits of the other two materials, individually. However, there is no note to specify the maximum hardness limit of ISO 11960 L-80 Type 13 Cr tubing. This seems to indicate that ISO 11960 becomes the controlling document for L-80 Type 13 Cr, and therefore the maximum hardness for ISO 11960 L-80 13 Cr tubing is currently 23 HRC as specified in Table C.6 and Table E.6 of ISO 11960. (MP INQUIRY 2006-03) ANSWER: Your interpretation is correct. As a general rule during the preparation of ISO 15156, the unnecessary repetition of information provided in cited sources was avoided. A.6.2, Table A.19, A.20 and A.21 QUESTION: I need to clarify a confusion about NACE MR0175/ISO 15156-3:2003 (E). Why are tubing and subsurface equipment in Tables A.19 and A.20, respectively, treated as two separate categories? Tubing itself is subsurface equipment so why is it treated separately? Moreover, K90941 as mentioned in Table A.20 is recommended for subsurface equipment under any H2S partial pressure but not for tubing, exposed to the same condition; why? L-80 type 13 Cr is more crackingresistant material than K90941; still it is not recommended for subsurface equipment apart from tubing; why? We are in a process of developing a sour gas field and purchased a copy of this standard to be a guideline for material selection. We need answers to these 62 questions so we can select the most appropriate material for downhole casing/tubing. (MP INQUIRY #2005-22) ANSWER: NACE MR0175/ISO 15156-3 reflects the contents of NACE MR0175-2003 and earlier editions of this NACE standard. These contents in turn reflect the experience of the oil industry and its experts in the use of materials in sour service over many years. The separation of materials into Tables A.19, A.20, and A.21 allowed convenient grouping of the data available and is the same as the grouping in the previous NACE standard. In some cases the differences you identify reflect the availability of different product forms manufactured from the different materials. As indicated in the title of Table A.19, ISO 11960 L80 type 13Cr is acceptable for other subsurface equipment (other than tubing) providing the material fully meets the applicable material requirements of ISO 11960 L80 type 13Cr. Additionally as indicated in the title and notes of Table A.21, 420 (modified) having the chemical composition of ISO 11960 L80 type 13Cr is acceptable for packers and subsurface equipment. In all cases the data presented reflect successful laboratory testing of an alloy or successful field experience with the alloy used in the product form listed. For martensitic alloys not listed in Tables A.19, A.20 and A.21 qualification of the alloy for use in accordance with ISO 15156-3 can be carried out in accordance Annex B. Please note: A revised version of ISO 15156-3, Table A.19 is included in ISO 15156-3 Technical Corrigendum 2 that was published September 1, 2005. A.6.2, Table A.22 The revised version of Table A.22 is included in Reference 3. A.6.2, Table A.23 The revised version of Table A.23 is included in Reference 3. A.6.3 The revised version of the text of A.6.3 is included in Reference 3. A.7.2, Table A.24 The revised version of Table A.24 is included in Reference 3. QUESTION: 63 In the 2002 version of MR0175, the maximum hardness requirement for duplex UNS S32550 was covered in Paragraph 3.9.1. This same material is now covered in Paragraph 4.9 of the 2003 version of this standard, but the hardness requirement seems to be missing. Has the hardness requirement been dropped for this material, or is the hardness assumed to be acceptable as long as the material has been solution annealed and liquid quenched? (MP INQUIRY #2003-09 Q2) ANSWER: This is correct. There is no hardness requirement for the duplex stainless steels covered in Paragraph 4.9.1. QUESTION: What is the foundation for limiting forged and cast UNS S31803 (Paragraph 4.9.3) to a maximum partial H2S pressure and temperature while the hot isostatic pressureproduced equivalent (Paragraph 4.9.4) is only limited to maximum hardness? (MP INQUIRY #2003-19 Q2) ANSWER: Paragraph 4.9.4 should have been 4.9.3.1, having the same environmental limits as Paragraph 4.9.3, and this error has been corrected in an interpretation and in Table A.24 of ISO 15156. Paragraph 4.9.4 was intended to provide metallurgical requirements only for the HIP alloy. QUESTION: Zeron 100: Old (2002): Paragraph 3.9.6/3.9.7: pH2S <0.2 bar (20 kPa) and 120 pH2S <1>5.6 New (2003) Paragraphs 4.10 and A24: pH2S <0.2 bar (20 kPa) only: What is the technical justification for this change? (MP INQUIRY #2003-27 Q3) ANSWER: The restrictions for duplex stainless steels was a consensus of the original drafting team based on their review of the literature. There was no negative on the final ballot for the 2003 edition. A.7.3 See A.2.3, MP inquiry #2005-13. QUESTION: The question is in regard to Appendix A.7 of NACE MR0175 / ISO 15156-3:2003(E). In A.7.3 third paragraph, it requires that "the microstructure ... shall have grain boundaries with no continuous precipitates." Is there any guidance as to what continuous means? For example, does it mean continuous throughout the microstructure? Our laboratory has reported suspected continuous precipitates "at some locations". (MP INQUIRY #2005-18) ANSWER: 64 There is no definition of "continuous precipitates" in the standard. An acceptance criterion or other quantitative limit shall be agreed between the manufacturer/supplier and the equipment user. As noted in the WARNING above ISO 15156-3, Scope, it is the equipment user's responsibility to select the CRAs and other alloys suitable for the intended service. This responsibility includes the selection of specific quality requirements when none are given by the standard. QUESTION: ISO 15156-3, A.7.3--Regarding metallographic examination of the microstructure: a) Do closely spaced spheroidal precipitates such as grain boundary carbides constitute continuous precipitates? b) At what spacing would closely spaced spheroidal precipitates be considered continuous? c) Are the quantification of precipitates (intermetallic phases, nitrides, carbides) to be evaluated as a volume fraction relative to the bulk sample? d) In cases where only grain boundary precipitates are observed, is the quantification to be made as a volume fraction relative to the bulk sample or as a lineal fraction relative to grain boundary length? e) In the absence of intermetallic phases and nitrides, does 1 vol.% represent the maximum allowable carbide precipitate content? f) What is a suitable recommended practice or standard by which to perform this quantification? (MP INQUIRY #2005-28) ANSWER: a), b), e) For NACE MR0175/ISO 15156-3, A.7.3 it is the responsibility of the equipment user and the manufacturer to set the quantitative standard they wish to follow when this goes beyond the guidance given. c), d), f) It is the responsibility of the equipment user and the manufacturer to agree on the method and acceptance criteria for the measurement of precipitates. QUESTION: Can you please answer the following queries or pass to committee. These queries relate to welding of 22% Cr duplex/25% Cr duplex Annex A7, of MR0175/ISO 15156- 3, A.7.3 (2nd para) "The hardness of the HAZ after welding shall not exceed the maximum hardness allowed for the basemetal," When applied to ASTM A790 UNS 32760 (see attachment) only a Brinell hardness is given 270 BHN (28 HRC equiv.). This is a reduction of 6 HRC from the 34 HRC allowance in NACE MR0175:2000. If no HRC limit is given in the material specification do we assume no maximum HRC hardness limit or use the Brinell hardness specified (28 HRC equiv.). Alternatively do we revert to the referenced NACE MR0175 [14] and assume 34 HRC. (MP INQUIRY #2006-02) 65 ANSWER The ISO 15156 Maintenance Panel can only provide a response to the inquiry in the context of NACE MR0175/ISO 15156-3 and cannot give interpretations based upon earlier editions of NACE MR0175. The texts that form the lower parts of Table A.24 " Environmental and materials limits for duplex stainless steels used for any equipment or component" and Table A.25 " Environmental and materials limits for duplex stainless steels used as downhole tubular components and as packers and other subsurface equipment " provide information on the metallurgical requirements, such as heat treatment and hardness etc., which must be met by duplex stainless steels in sour service. In most cases Table A.24 does not define a maximum acceptable base material hardness. As indicated in the first paragraph, last sentence of Clause 1 "Scope", alloys must also meet the requirements of the appropriate design codes, standards or regulations such as, for the example quoted, ASTM A790 UNS S32760. For this alloy, the use of Brinell 270, as maximum base metal hardness in the interpretation of A.7.3, is correct. (The equivalent Vickers/Rockwell 15N hardness for use in welding procedure qualification can be determined in accordance with ISO 15156-3, 6.2.1, Para. 2.) Where the material manufacturing specification does not define a hardness limit but the alloy base metal does comply with the requirements of one of the Tables, it is the responsibility of the equipment user and the manufacturer to agree on any hardness limit used for welding procedure qualification. Please note, for Table A.25 the maximum hardness of 36 HRC refers to the maximum hardness of any solution annealed, liquid-quenched and cold-worked alloy base metal that qualifies for use in sour service. A.8, Table A.26 QUESTION: What grade of stainless steel meeting NACE requirements can be used for a tubing hanger when the pH is <3.5? My interpretation based on understanding Paragraph 9.2 of NACE MR0175 and Section A.8 of ISO 15156 is that only UNS S66286 is acceptable. Could you please confirm my statement or correct it? (MP INQUIRY #2004-13) ANSWER: UNS S66286 is the only precipitation-hardenable stainless steel that is acceptable for tubing hangers in environments with pH <3.5. The martensitic stainless steels are also not acceptable for environments with pH <3.5. QUESTION: Table A.26 limits the precipitation-hardened austenitic steel UNS S66286 to 150°F and 15 psi H2S when chlorides are present. a) Can this material be used at higher temperature if no chlorides are present? 66 (MP INQUIRY #2005-02 Qa) ANSWER: No, it may not. The table states that the temperature restriction is for "Any combinations of chlorides . . . " Neither ISO 15156-3 nor its predecessor NACE MR0175-2003 defines the expected performance of UNS S66286 in environments containing no chlorides. b) Is this material included in the current ballot for austenitic steels which (apparently) would allow their use at a higher temperature if no chlorides are present? (MP INQUIRY #2005-02 Qb) ANSWER: No, it is not. The current ballot is for materials currently covered in Table A.2, which represent materials free of cold work to enhance their properties and with hardnesses of 22 HRC maximum. c) Would the MP consider adding an unrestricted clause for the use of this material for valve stems, pins, and shafts (similar to Table A.3 for UNS S20910)? This material would perform much better as a valve stem in H2S environment than the cold-worked Nitronic 50. (MP INQUIRY #2005-02 Qc) ANSWER: The IMP would accept a ballot item with the proper documented laboratory data and/or field experience to expand the acceptable environmental limitations for the alloy. The procedure for the submission of a ballot item is described in the document "01. Introduction to ISO 15156 Maintenance Activities," which can be found at http://www.iso.org/ISO15156Maintenance. QUESTION: Does NACE MR0175/ISO 15156-3 Table A.26 apply to Gr. 660 material used in subsea bolting applications external to the production wellbore environment when indirectly heated above 150°F? (MP INQUIRY #2005-09Q2) ANSWER: Table A.26 does not apply to Grade 660 material used in subsea bolting applications external to the production wellbore environment. A.8.2, Tables A.27 QUESTION: Reference: NACE MR0175/ISO 15156-3 Table A.27--Environmental and materials limits for martensitic precipitation-hardened stainless steels used for wellhead and christmas tree components (excluding bodies and bonnets), valves and chokes (excluding bodies and bonnets) and packers and other subsurface equipment API 6A makes a distinction between hangers and body components. NACE MR0175/ISO 15156 doesn't define either. This has led to some confusion regarding 67 whether or not UNS S17400 material may be used as hangers in a sour environment. Q1. Does the exclusion of wellhead "bodies and bonnets" in Table A.27 also mean that hangers are excluded? Q2. Are hangers considered "subsurface equipment" in the context of Table A.27? Q3. Does Table A.27 prohibit the use of UNS S17400 material for hangers in sour service? (MP INQUIRY #2005-12) ANSWERS: A1. No, it does not. A2. In the context of Table A.27, hangers are more commonly considered to be covered by the term "wellhead and christmas tree components." A3. No, it does not provided the environmental limits and metallurgical requirements of Table A.27 are followed. See also response to MP Inquiry #2007-07 posted under ISO 15156-3, Table A.3. A.8.2, Tables A.27 and A.28 QUESTION: If both Paragraphs 9.2 and 9.5 are applicable, as we believe they are, can we select which paragraph we follow when they cover the same component or materials? Does Paragraph 9.4 apply to choke valves? (MP INQUIRY #2003-02 Q2) ANSWER: Choke non-pressure-containing parts made of alloy UNS S17400 have no environmental restrictions in accordance with Paragraph 9.5.2, while there is a limit of 0.5 psi H2S for pressure-containing parts in Paragraph 9.2.4.1. QUESTION: Paragraphs 9.2.4.1 and 9.5.2. Why is it that UNS S17400 can be used for pressurecontaining wellhead and Christmas tree components (Paragraph 9.2.4.1) but not for pressure-containing valve components (Paragraph 9.5.2)? (MP INQUIRY #2003-12 Q4) ANSWER: Paragraph 9.5.2 allows UNS S17400 to be used with no environmental restrictions. Therefore, the alloy is not allowed for pressure-containing components in valves. In comparison, Paragraph 9.2.4 has environmental restrictions and will therefore allow the use of S17400 for parts other than bodies and bonnets. A.8.2, Tables A.27, A.28 and A.30 QUESTION: 17-4 pH: Old (2002): Paragraph 3.8.1. Only requirement: HRC 33 68 New (2003): Paragraph 9.2.4.1 and A27: pH2S <0.034 bar: Technical justification? (MP INQUIRY #2003-27 Q4) ANSWER: The 17-4 pH SS alloy was restricted because of industry failures. Please see the attached documentation. There was no negative on the final ballot. A.8.2, Table A.28 QUESTION: Can you provide clarification on Paragraph 9.5.7: “UNS S17400 …. has been used in service tool applications at the surface when stressed at less than 60% of its minimum specified yield strength under working conditions.” Paragraph 9.5 is concerned with Internal Components for Valves, Pressure Regulators, and Level Controllers. What exactly do service tool applications encompass? (MP INQUIRY #2003-32) ANSWER: This paragraph is intended to apply to components that are temporarily installed at the surface as part of routine well servicing. For example, components of wireline valves used during a wireline job are considered as service tools. A.8.2, Table A.30 QUESTION: SUBJECT: Paragraph 11.4.5 of NACE MR0175-2003 Standard QUESTION: Are wrought UNS S17400 and S15500 martensitic precipitationhardenable stainless steels that meet the hardness and heat-treat requirements of Paragraph 11.4.5 of NACE MR0175-2003 acceptable for use in compressors in sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature, and free elemental sulfur? QUESTION: If the answer to the former question is no, what are the specific environmental limits? (MP INQUIRY #2003-34) ANSWER: Yes, they are acceptable with no environmental limits in accordance with NACE MR0175/ISO 15156 Table A.30. No data have been submitted to verify resistance to cracking in the presence of elemental sulfur. QUESTION: SUBJECT: Paragraphs 11.4.4 and 11.4.6 of NACE MR0175-2003 QUESTION: Are the martensitic stainless steels that are listed in Paragraphs 11.4.4 and 11.4.6 of NACE MR1075-2003 and meet the hardness and heat-treat requirements specified in their respective paragraphs acceptable for use in compressors in sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature, and free elemental sulfur? QUESTION: If the answer to the former question is no, what are the specific environmental limits? QUESTION: Are the answers to the above questions in agreement with ISO 15156? (MP INQUIRY #2003-38) ANSWER: 69 Yes, they are acceptable with no environmental limits in accordance with ISO 15156 Table A.30. No data have been submitted to verify resistance to cracking in the presence of elemental sulfur. A.9.2, Table A.31 The revised version of Table A.31 is included in Reference 3. QUESTION: The precipitation-hardenable version of G-3 has no environmental limits per Paragraph 4.15.6 of the 2003 edition. "Conventional wisdom" has it that a solutionannealed and cold-worked nickel-based alloy is more resistant to environmental cracking than its precipitation-hardenable clone. (MP INQUIRY #2003-13 Q2b) ANSWER: Materials used in accordance with Paragraph 4.15.6 are subject to the environmental limits stated in Paragraph 4.15, i.e., the limits of Table 2. These limits are restated in NACE MR0175/ISO 15156-3, Table A.31, Rows 2-5 for material UNS N07048. A.9.2, Table A.32 QUESTION: I think that the (Cartesian) coordinates in Table 3 (NACE MR0175/ISO 15156-3, Sub-clause A.9.2, Table A.32) {T 390°F, pH2S 360 psi} may have come from data supplied by me to NACE from my office files for recommendations made to oil companies for Alloy 925 (UNS N09935). If so, I have no confirmation that the oil companies ever deployed equipment made from Alloy 925 in these environments. I recommend that NACE remove these data from Table 3, replacing them with test data from Battelle showing cracking resistance at 450°F, pH2S 400 psi in 15% Cl and also a second set of coordinates at 425°F, pH2S 300 psi in the presence of elemental sulfur (Hibner). (MP INQUIRY #2003-13 Q5) ANSWER: A technical change such as that suggested can only be made following a ballot process involving the ISO 15156 Maintenance Panel and the Oversight Committee (NACE TG 299) on behalf of ISO/TC 67/WG 7. Ballot proposal forms can be obtained from Linda.Goldberg@nace.org. QUESTION: Our question relates to ISO 15156-3, Table A.32: How should the table be interpreted in terms of the maximum allowable temperature for applications with less than 30 psi partial pressure of H2S? For example, in its current layout the table prohibits the use of UNS N07718 at temperatures higher than 450°F at any H2S pressure below 30 psi. (MP INQUIRY #2005-20) ANSWER: ISO 15156-3, Table A.32 does not qualify UNS N07718 for use at higher temperatures than 450°F. 70 The limits on temperature, H2S, Cl-, pH, and sulfur defined in some of the tables of ISO 15156-3, Annex A apply collectively and reflect the knowledge available, usually from laboratory tests, at the time the standard was published. There were no data available related to the use of UNS N07718 at any temperature higher than 450°F. ISO 15156 allows the qualification and use of materials, to an equipment user's requirements, outside the limits stated in the tables. (See ISO 15156-3, Figure B.1, Column 2.) A qualification to define an alternative temperature limit for UNS N07718 for a partial pressure of H2S less than 30 psi must be carried out in accordance with ISO 15156- 3, Annex B. A.9.2, Table A.33 The revised version of Table A.33 is included in Reference 3. QUESTION: Table 4 (for precipitation-hardenable, 6Mo alloys) (NACE MR0175/ISO 15156-3, Sub-clause A.9.2, Table A.33) permits elemental sulfur in the environment at 450°F, but not at 425°F, yet again at 400°F. Where does the user discover whether sulfur is or is not acceptable for applications between these temperatures? This is odd enough, but Table 6 (NACE MR0175/ISO 15156-3, Sub-clause A.4.2, Table A.14) (for 6 Mo, precipitation-hardenable 6 Mo alloys) does allow sulfur at 425°F. Are the precipitation-hardenable versions of these alloys more resistant to cracking than their solution-annealed and cold-worked analogs? (MP INQUIRY #2003-13 Q3) ANSWER: In response to your questions 3 and 4a): The data used in NACE MR0175-2003 and NACE MR0175/ISO 15156-3 represent the limits of successful laboratory tests reported to NACE so far. In some cases the available data cannot be used to answer the questions you pose. (MP INQUIRY #2003-13 Q4a is addressed under heading NACE MR0175/ISO 15156-3, Table A.14) A.12 QUESTION: Because UNS C72900 and C96900 are copper alloys, are they, by definition, covered by Section 4 of NACE Standard MR0175, which basically states copper alloys are suitable for use without restriction other than as noted in the footnote, which informs the user that such materials may exhibit accelerated general weightloss corrosion in some sour environments? (MP INQUIRY #2003-21) ANSWER: The UNS C72900 and UNS C96900 copper alloys are included in NACE Standard MR0175 Paragraph 4.20. A.13.1 71 QUESTION: Paragraph 1.5.1 of NACE Standard MR0175-2003 states that “SCC may be controlled by any or all of three measures: (1) using the materials and processes described in this standard; (2) controlling the environment; or (3) isolating the components from the sour environment.” My client has an application in which Inconel 625 weld metal is overlay welded onto a martensitic steel component. The martensitic steel component base material and heat-affected zones are isolated from the fluids by the Inconel 625; all wetted surfaces are Inconel 625. My client’s customer believes the base material must be stress relieved in accordance with Paragraph 5.2.1, which states: “Overlays applied to carbon and low-alloy steel or to martensitic stainless steels by thermal processes such as welding, silver brazing, or spray metallizing systems are acceptable for use in sour environments, provided the substrate does not exceed the lower critical temperature during application. In those cases in which the lower critical temperature is exceeded, the component must be heat treated or thermally stress relieved in accordance with procedures that have been shown to return the base metal to the base metal hardness as specified in this standard.” We believe that Paragraph 5.2.1 does not apply since the base metal is isolated from the sour environment with Inconel 625, which is acceptable to 35 HRC. (MP INQUIRY #2003-16) REVISED ANSWER 2005-09-01: The requirements of NACE MR0175-2003 are provided in Paras 5.2 and 5.3. The requirements of NACE MR0175/ISO 15156 are provided in ISO 15156-3, Sub-clause A.13.1. The revised version of the text of A.13.1 is included in Reference 3. A.13.2 A.13.2.2 QUESTIONS: (1) Subject: Equivalency of the technical content of both MR0175-2003 and MR0175/ISO 15156 in relation to the use of Stellite 6 cladding. Question: In NACE MR0175-2003 cobalt-based alloys (e.g., Stellite 6) are acceptable for hardfacing applications (Section 5, Paragraph 5.2.5). In NACE MR0175/ISO 15156, Paragraph A.13.2.2 states "the cracking resistance of alloys specifically designed to provide hard-facing is not specified in this part of NACE MR0175/ISO 15156." Is there perhaps another part of this specification that we may have overseen? (2) Subject: Solid Stellite 6 Castings. Question: Are solid Stellite 6 castings are permitted for wear-resistant parts in valves under the MR0175/ISO 15156 regime? (MP INQUIRY #2004-01) REVISED ANSWER 2005-09-01: 72 There has been no change of technical intent between previous editions of NACE MR0175 and NACE MR0175/ISO 15156. For ISO documents, that something is not listed as approved is not a sign that it may not be used; it becomes the equipment user's responsibility to use it or not. This contrasts to the approach in earlier editions of NACE MR0175 when not being listed was a bar to use. Nevertheless, the Maintenance Panel accepts that the intent of A.13.2.1 and A.13.2.2 should be made clearer and is processing a ballot to achieve this. The revised versions of the texts that clarify the intents of A.13.1 and A.13.2 are included in Reference 3. Annex D General QUESTION: We believe that the inclusion of some alloy trade names in the second columns of ISO 15156-3, Annex D Tables D.1-D.12 is in conflict with the NACE policy on the use of trade names in standards. Could the Maintenance Panel please propose steps to resolve this policy problem? (MP INQUIRY #2004-22) REVISED ANSWER 2005-02-15: This issue is resolved by the publication of ISO 15156-3:2003/Cor.1:2005(E) 2005- 02-15, see Reference 4. QUESTION: It is our understanding of NACE MR0175/ISO 15156 that provided ASTM A 995 Grade 4A (UNS J92205) 22 Cr duplex stainless steel complies with the materiallimits of Table A24 of Annex A, it can be selected for use in H2S-containing environments provided the environmental limits given in Table A24 are not exceeded. (MP INQUIRY #2006-04Q1) ANSWER: Your understanding is correct. Q2 It does not ALSO have to be listed in Annex D Table D7, which we believe is for information only and lists only SOME duplex stainless steels. (MP INQUIRY #2006-04Q2) ANSWER: You are correct. Table D.2 QUESTION: 73 Could you please confirm that the information given for alloy UNS N08367 in NACE MR0175/ISO 15156-3, Table D2 is incorrect and should be that shown below for the elements affected? S maximum should be 0,03 N range should be 0,18 to 0,25 Cu range should be 0,00 to 0,75 FPREN should be 42 to 49 Ni + 2 Mo should be 35,5 to39,5 (MP INQUIRY #2005-24) ANSWER: Yes. 74 References: 1. Petroleum and natural gas industries — Materials for use in H2S-containing environments in oil and gas production — Part 1: General principles for selection of cracking –resistant materials TECHNICAL CORRIGENDUM 1 (2005-09-01) 2. Petroleum and natural gas industries — Materials for use in H2S-containing environments in oil and gas production — Part 2: Cracking-resistant carbon and low alloy steels, and the use of cast irons TECHNICAL CORRIGENDUM 1 (2005-09-01) 3. Petroleum and natural gas industries — Materials for use in H2S-containing environments in oil and gas production — Part 3: Cracking-resistant CRAs (corrosion-resistant alloys) and other alloys: TECHNICAL CORRIGENDUM 2 (2005-09-01) 4. Petroleum and natural gas industries — Materials for use in H2S-containing environments in oil and gas production — Part 3: Cracking-resistant CRAs (corrosion-resistant alloys) and other alloys: TECHNICAL CORRIGENDUM 1 (2005-02-15) All are available via www.iso.org/iso15156maintenance