ASTM A312 / B31.3 Weld Joint Strength Reduction Factor " W"???

[just73gray]

We are designing our piping to B31.3 - 2008 and have had an issue come up with the Weld Joint Strength Reduction Factor "W". Our piping is 347H with a design temperature of 1150F and is built to ASTM A312. Section 6, of A312, MANUFACTURING - 6.1.3 states that "welded (WLD) pipe shall be made using an automatic welding process with no addition of filler metal during the welding process." However, Section 15, of A312, Repair by Welding - 15.2 "Welds repairs of the weld seam shall not exceed 20% of the seam length." Now, if we have 10ft of pipe and 20% needs to be repaired then 2ft of the weld seam may be repaired with filler metal. This now leads to the question regarding the Weld Joint Strength Reduction Factor "W". Table 302.3.5 in B31.3 - 2008 says that for Autogenous welds in Austenitic stainless grades 3XX that W = 1.0
Can I still still take credit for the W = 1.0, since the pipe is now made with 2ft of filler metal? I am trying to clarify how B31.3 might interpret A312 Sec. 15 for weld repairs and the Weld Joint Strength Reduction Factor. Or see if B31.3 would allow for a certain percentage of the pipe to be repaired with filler metal and still have W=1.0? I have checked and there are currently no deviations for B31.3 regarding this issue.

 

[ColonelSanders83]

Let me start by stating that I am not an expert with the material you using.

That being said this is a very specific question with a lack of clarity and detail on the exact situation that you have. In my opinion this is a perfect situation to go through the code interpretaions and see if something has been previously addressed by the code comitee.

http://cstools.asme.org/csconnect/CommitteePages.cfm?Committee=N10020400&Action=17904

If that comes up empty a request for interpretation is justified unless some of the other more experienced forum members can point to some rock solid justification.

Just my two cents worth

A question properly stated is a problem half solved.

Always remember, free advice is worth exactly what you pay for it!

 

[metengr]

First off, I reviewed ASME/ASTM A 312. Please go back and re-review this specification.

1. Regarding weld repairs - piping that is weld repaired must be uniquely identified as having been repaired along with the type of filler metal on the certificate of tests.

2. Weld repairs can only be performed on pipe 6" NPS and greater diameter and 0.200" wall and greater.

3. Welding process is limited to GTAW.

4. Weld repairs of the weld seam shall not exceed 20% of the seam length.

Review of ASME B31.3 2006 Edition, Table 302.3.4 Longitudinal Weld Joint Quality Factor

For fusion welded pipe, single or double bevel, with or without filler metal, as long as radiographic examination is performed (100%) your long seam weld joint quality factor remains at 1.0.

 

[metengr]

Sorry, I just realized your post was for the weld joint strength reduction factor in the 2008 edition versus the 2006 Edition of ASME B31.3.

I just reviewed Table 302.3.5 in the 2008 Edition of ASME B31.3 and there are applicable notes. The weld joint strength reduction factors on the line for autogenous welds only applies to welds with no filler metal, period

My interpretation is this, if you have purchased pipe to SA 312 and there were repairs made using filler metal this is known on the test certificate, and you cannot take credit for using the weld joint strength reduction factor for autogenous welds. The next line down applies for welded austenitic stainless steel pipe with filler metal.

 

[just73gray]

Further Clarification:
The lines in question will be 347H 12", 10", & 8" lines all schedule 40s, at a temperature of 1150F. They are used for our process gas in a Steam Methane Reformer. B31.3-2008, for straight pipe under internal pressure, Section 304.1.2 - Equation (3a), now includes a WELD STRENGTH REDUCTION FACTOR "W", which is used because at eleveated temperatures, the long-term strength of weld joints can can lower than the long-term strength of the base material. These values are now found on Table 302.3.5 in B31.3-2008, this table wasn't available in B31.3-2006. This is different than the Longitudinal Weld Joint Quality Factor found on Table 302.3.4. I have already determined that the Quality Factor "E" is 1.0, but need help in deteriming whether the WELD STRENGTH REDUCTION FACTOR "W" is still 1.0. As previously stated above in my first thread.

 

[just73gray]

Thank you. I appreciate the help. Another possible scenario. B31.3-2008 Section 302.3.5(f)(1)Unlisted Weld Strength Reduction Factors, states that other values than those which are listed in table 302.3.5 for "W" maybe used per the following criteria. Creep test data maybe used to determine the weld joint strength reduction factor. If the mill maufacturing the 347H, does have to make a repair and use filler metal. If the filler metal used passes the 1000hrs. rupture test and proves that has the same creep strength as the base metal. Could I take credit for the Weld Joint Strength Reduction Factor equaling 1.0?

 

[metengr]

just73gray;
The short answer is this;

IF weld repairs were performed using filler metal, the autogenous weld line in Table 302.3.5 does not apply. So for weld repaired pipe repaired with filler metal the weld joint strength reduction factor of 0.82 at 1150 deg F applies.