A-403 Gr WP 304 for design temp at -325 ¦F Impact Testing

[MEDK]

Piping Code B31.3.
Material for butt weld fittings ASTM A-403 Gr WP 304.
Impact Testing Requirement at -325 °F Design Temp.

From reviewing the piping code for this material, it appears that for EFW fittings, the base metal will be exempt from impact test requirements. However, the welds for an EFW fitting will require impact testing unless the weld procedure qualification welds can pass the impact requirements at the design temperature. If this is correct, the question has come up, how to confirm that the supplier of the fitting meets the design temperature requirements without specifying seamless fittings only? Currently our piping specifications allow both seamless and EFW butt weld fittings. Is there a way to check that the fittings used by a piping contractor will be suitable for the application?
A search of this forum did not indicate past posts for similar topics unless I missed them.
Thanks,
DK

 

[metengr]

MEDK;
No need for impact testing these fittings in accordance with ASME B31.3, paragraph 323.2.2. For ASTM A 403 fittings, the minimum service temperature is -425 deg F in Table A-1.

 

[MEDK]

metengr:
Thanks for the response. Have I misinterpreted the requirements for a welded (EFW) fitting per Table 323.2.2, A-4 (b) pertaining to the weld metal and HAZ? Also paragraph 323.2.2 (f) (1) and (2)?

One of the reasons for this question, is that a vessel fabricator has been agonizing over materials and welds for a stainless steel vessel design at -320 °F. This is an offshoot from their findings about the vessel design and also pertaining to connected pipe downcomers. I was always under the impression that 304 SS was suitable to -425 °F as you have stated. But the fabricator's findings in the pressure vessel code are almost identical to the B31.3 items listed above pertaining to base metal, weld metal, and HAZ.

Thanks again for your comments and any references to exclusions about impact testing similar items as the fittings.
DK

 

[metengr]

MEDK;
I took a little closer look at the entire section pertaining to 323.2.2 "Lower Temperature Limits, Listed Materials" in the 2004 Edition of B31.3.

I believe your statement regarding having to impact test welded fittings is a correct interpretation. Apparently, B31.3 is more restrictive on the use of welded austenitic stainless steel fittings versus seamless austenitic stainless steel fittings supplied under ASTM/ASME Specification A/SA 403. I really don’t see any other way around this issue because B31.3 has specific wording that their Code takes precedence over any conflicts with material specifications. Obviously for seamless austenitic stainless steel fittings, exceeding either the 0.1%C content or not having the material in a solution treated condition requires impact testing. However, with the fittings supplied as seamless under this specification, you are exempt from impact testing.

I also reviewed ASME SA 403 because this is the specification that I have handy at the moment. One good thing out of this is that the fittings are required to be clearly marked for the Grade WP or Grade CR, regarding the following;

S=seamless (exp WP304-S
W=welded, radiography or ultrasonic (exp WP304-W)
WX= welded, radiography
WU= welded, ultrasonic

 

[metengr]

MEDK;
One additional comment regarding the vessel. If this is an unfired pressure vessel, the impact testing exemptions would come from ASME Section VIII, Div 1. Refer to UHA-51 for information regarding impact testing of weld metal. This parallels B31.3 because of the concern with ferrite contents in austenitic stainless weld metal deposits. The base metal and HAZ's are exempt from impact testing at or above -320 deg F.

 

[MEDK]

metengr:
Thank you for taking the time to research and respond to this item. I appreciate the confirmation and will pass this on to the interested parties in our oganization and to the fabricator as well. I thought this was the correct interpretation, but with most codes there is always the footnote or buried information somewhere else in the code that can be overlooked.
Thanks again,
DK

 

[stanweld]

Checking of the welded fittings acceptability can be done by requiring the fitting manufacturer to submit its impact test qualified welding procedures for your review. If you are highly concerned, you may wish to audit the fitting manufacturer's welding activity. This can be done by incorporating these requirements in the Purchase Order.