RE: [MW:19115] RE: 19056] -40F (-40C) impact qualification of 1-1/4Cr 1/2Mo (P4)

Mr.  Bathula,

Please see this link ( http://www.scribd.com/doc/117612021/SA-387--) downloadable presentation from Arcelor on SA 387 Gr 11 steel, stating the the various pros and cons.  This material has limitations with respect to  allowable lowest operating temperature,  typically toughness guarantee from the mills  :-(54/47J) limited to –18°C / 0°F. 

 

API 934E requirement  for hydro treating services (improved metallurgy):-

 

• The minimum CVN impact values shall be 40 ft-lbs (54 Joules) average of three specimens at 0˚F (-18˚C) and 20 ft-lbs (27 Joules) minimum for a single specimen at 0˚F (-18˚C).  By and large the  safe  temperature limit    for this grade is  minus 18-20 Deg  C with the high levels of impact.

 

Typically ASME Sec-VIII, DIV-1 accepted impacts values are lower than API recommended limits, ref:-FIG. UG-84.1. Hence  without API requirement if the steel satisfies ASME requirements @ -40Deg F , it may  be acceptable, though the margins allowed for passing impact tests following welding and  fabrication would be very little.

 

ASME-FFS /API-579  addresses the "Brittle Fracture "are specified below.  As defined the CET may be lower than the MAT  (for the Low Alloy Steels in  Russian Environments) , e.g -45 Deg C or below.  Use of LAS at such subzero temperature   may be permitted, provided:-

• the design validation finds this steel is safe to use even under the conditions which accelerate  the brittle fracture (see below)
• steel is not drastically loaded at such sub zero temperature.  
• or subjected to the conditions below (API-579), which could accelerate the brittle failures.

As  you know refinery and petrochemical piping are very well insulated to contain the heat and  this may  allow the exposure  to -45 DegC.  If bare (non-insulated) metal is exposed to -45 Deg C for prolonged period notch toughness could be an issue, otherwise as deemed safe by design such pipes could be safe to work @ -45 DegC(with insulation). However Minimum notch toughness values following fabrication as per the design code has to be met in BM,HAZ and WM.

 

Thanks

 

Pradip Goswami, P.Eng,IWE

Welding & Metallurgical Specialist

Ontario, Canada

pgoswami@quickclic.net

pgoswami@sympatico.ca

 

 

API-579/ASME FFS, Requirements on Brittle Fractures are as stated below:-

3.1.2 A brittle fracture assessment may be required as part of the assessment procedure  when there's need for a brittle fracture assessment as listed below:-

a) A change in process operating conditions, including startup, shutdown and upset conditions, that increase the possibility of low metal temperatures.

b) A process hazards review indicates that process temperatures, including those during start up, shutdown and upset conditions, could be lower than anticipated in the original design.

c) The equipment item is rerated using a lower design margin.

d) A minimum temperature is needed for a hydro test.

e) The equipment is expected to be exposed to a general primary membrane tensile stress greater than 55MPa (8 ksi) at or near ambient temperature and either of the following is true:

•  The equipment has a wall thickness equal to or greater than 50 mm (2 in.)
• The equipment has been subjected to conditions that may cause embrittlement.

3.1.3 The Critical Exposure Temperature (CET ) as used in this Part is defined as the lowest (coldest) metal temperature derived from either the operating or atmospheric conditions at the maximum credible coincident combination of pressure and supplemental loads that result in primary stresses greater than 55 MPa (8 ksi).

Note that operating conditions include startup, shutdown, upset and standby conditions. The CET may be a single temperature at the maximum credible coincident combination of pressure and primary supplemental loads if that is also the lowest (coldest) metal temperature for all other combinations of pressure and primary supplemental loads. If lower (colder) temperatures at lower pressures and supplemental loads  are credible, the CET should be defined by an envelope of temperatures and pressures..

3.1.4 The Minimum Allowable Temperature (MAT ) is the lowest (coldest) permissible metal temperature for a given material and thickness based on its resistance to brittle fracture. It may be a single temperature, or an envelope of allowable operating temperatures as a function of pressure. The MAT is derived from mechanical design information, materials specifications, and/or materials data using the guidance in this Part

 

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From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Raghuram Bathula
Sent: Thursday, October 24, 2013 3:10 AM
To: Materials-Welding
Subject: Re: [MW:19065] RE: 19056] -40F (-40C) impact qualification of 1-1/4Cr 1/2Mo (P4)

Dear Mr Goswami

do you have encountered any such case (where atm temp are very low),  few of the Russian region projects where amb temp is colder than -45 °C. LAS being primarly used for high temp service. 

On 24 October 2013 07:36, pgoswami <pgoswami@quickclic.net> wrote:

John,

 

To the best of my knowledge , very few mills would commit impact @ -40F (-40C) for this grade of steel unless there's a very specific requirement and the necessary technical query.  It's very difficult to meet  such requirement with a consistency.  Same applies for welding consumable  also. 

 

API -934C/E (if applicable) enforces temper embrittlement factors, however the impact is never called for at such low temperature.

 

I would say ask few good mills, what's best achievable for this steels and then go from there.

 

Best Regards.

 

Pradip Goswami, P.Eng,IWE

Welding & Metallurgical Specialist

Ontario, Canada

pgoswami@quickclic.net

pgoswami@sympatico.ca

 

 

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From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of jhenning@deltak.com
Sent: Wednesday, October 23, 2013 4:57 PM
To: materials-welding@googlegroups.com
Subject: [MW:19056] -40F (-40C) impact qualification of 1-1/4Cr 1/2Mo (P4)

I have a customer requiring -40F (-40C) impact qualification for 1-1/4Cr 1/2Mo material (ASME Sc IX).  Design and fabrication is required to be in accordance with ASME Sc. VIII, Division 1.  Weld thickness is approximately 1-3/4 in. (45mm).  It is anticipated that only SAW and SMAW will be required.  While I have a number of procedures qualified at -20F (-29C) it would appear that they are approaching the DBTT for the weld metal and HAZ in most instances.  I would like to know if anyone has qualified 1-1/4Cr 1/2Mo to -40 and what special measures were taken to achieve it;  i.e special filler metal requirements or specific filler metal employed, special weld techniques or parameter restrictions, etc.  Materials are SA-387 Grade 11 Class 2 and SA-182 F11 Class 2.

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