Question:
A new carbon/low alloy steel installation is to be built to handle wet gas, from a nearby field, that contains H2S at a level below that traditionally described as sour with respect to sulfide stress cracking (SSC) (0.05 psi H2S). A group of project engineers are doubtful about the need for sour service materials and is concerned about their cost. You are a project engineer and have input to the group decision. What is your input, according to the standard?
a. Explain the types of cracking H2S can cause even at levels below the threshold for SSC, the possible consequences of cracking, and how costs can be minimized.
b. Accept the engineers' approach to select non-sour materials for the plant, and recommend assessing the risks to personnel and the surrounding area.
c. Emphasize that H2S-resistant materials are required by the standard even less than 0.05 psi H2S.
d. Recommend that H2S-resistant materials be used, with a view, nevertheless, toward minimizing the costs.
Answer: C
Normally, no special precautions are required for the selection of steels for use under these conditions, nevertheless, highly susceptible steels can crack.
Nevertheless, a number of factors, as follows, that can affect a steel's performance in this region should be
considered.
— Steels that are highly susceptible to SSC and HSC can crack.
— Steel's physical and metallurgical properties affect its inherent resistance to SSC and HSC; see Clause 6.
— Very high-strength steels can suffer HSC in aqueous environments without H2S. Above about 965 MPa
(140 ksi) yield strength, attention should be given to steel composition and processing to ensure that
these steels do not exhibit SSC or HSC in region 0 environments.
— Stress concentrations increase the risk of cracking.
A new carbon/low alloy steel installation is to be built to handle wet gas, from a nearby field, that contains H2S at a level below that traditionally described as sour with respect to sulfide stress cracking (SSC) (0.05 psi H2S). A group of project engineers are doubtful about the need for sour service materials and is concerned about their cost. You are a project engineer and have input to the group decision. What is your input, according to the standard?
a. Explain the types of cracking H2S can cause even at levels below the threshold for SSC, the possible consequences of cracking, and how costs can be minimized.
b. Accept the engineers' approach to select non-sour materials for the plant, and recommend assessing the risks to personnel and the surrounding area.
c. Emphasize that H2S-resistant materials are required by the standard even less than 0.05 psi H2S.
d. Recommend that H2S-resistant materials be used, with a view, nevertheless, toward minimizing the costs.
Answer: C
Normally, no special precautions are required for the selection of steels for use under these conditions, nevertheless, highly susceptible steels can crack.
Nevertheless, a number of factors, as follows, that can affect a steel's performance in this region should be
considered.
— Steels that are highly susceptible to SSC and HSC can crack.
— Steel's physical and metallurgical properties affect its inherent resistance to SSC and HSC; see Clause 6.
— Very high-strength steels can suffer HSC in aqueous environments without H2S. Above about 965 MPa
(140 ksi) yield strength, attention should be given to steel composition and processing to ensure that
these steels do not exhibit SSC or HSC in region 0 environments.
— Stress concentrations increase the risk of cracking.
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