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FluidicTech (Mechanical) (OP)
9 Dec 08 19:33
I need to qualify a welding procedure in accordance with Section IX, with the supplementary essential variables for Charpy impact testing as required by ASME B31.3.  

The base material is 304 SS, with production material thickness ranging from 0.500" to 1.000" in thickness. This is for cryogenic service and impact testing of the weld and HAZ will be performed at -320 F. I intend to use a GTAW and SAW process combination on a 1/2" thick test coupon for procedure qualification.

I have the following problems:

1) Per QW-403.6 and QW-451 of Section IX, the qualified thickness range using a 1/2" plate will be 0.500" to 1.000".  However, per Table 323.3.1 of ASME B31.3 (falling under column A for "Requiring Impact Tests Only on Welds") the qualified thickness would be 0.250" to 0.750".  It seems that in order to meet both codes, 2 procedure qualifications would have to be performed.  (And, it seems for someone requiring even more range qualified, the amount of PQR's would continually grow because of the way the two codes overlap in qualified thickness)  

2) I recently attended a Section IX course where the instructor stated that impact tests for multiple processes should include a sample from each process.  At the time I took this to mean that one set of charpies should be taken from one process, and another set of charpies should be taken from the other process, etc.  Or, it now occurs to me that I suppose it could be taken that a single set of charpies should include both processes in the same specimen.  The fault I see with the second interpretation is that if there were 3 processes it would not be possible to include all of the processes in one specimen.  The problem I have with taking 2 sets of charpies, one set from each process, is that I am told by the lab performing the testing that even if I split the two processes evenly across the 1/2" test plate, they would have difficulty in machining a full size set from each process (given the amount of material).

Please contribute any thoughts concerning these two issues, point out any oversights, alternate ideas, or proposals on the best way to qualify the WPS.  Thanks.
GRoberts (Materials)
9 Dec 08 20:51
I don't have any B31 codes handy, so I can't comment on that, but as for taking the samples, you are almost on the right track. One specimen can have two processes represented and be OK per Section IX.  Technically, the same could be said for 3 processes, but it is hard to do from a physical standpoint since the CVN specimen is only so big.  So it looks like you will need to take at least 2 sets from the weld.  With a 1/2" plate, you can only get one full size CVN sample per "slab" of weld.  Typically welds test are cut into a series of approximately 1/2" thick "slabs" (for bends and charpies- with approx 1/8" of machine stock) and about 1" wide for tensiles.  So you just need one "slab" per CVN test.  Take some CVNs from the cap, and some from the root, and it will guarantee to cover all processes in a 1/2" thick plate.  Make sure your test plate is long enough.
weldtek (Materials)
10 Dec 08 11:59
Fluidtech,
I've reviewed B31.3 and concur that the impact test requirements in B31.3 and ASME Sec IX do not match.  Obviously you want to qualify your WPS per B31.3 to avoid the need for production impacts and unfortunately it appears to me that in your case, more than one test will be necessary if you want your WPS to meet both Codes, for the range of 1/2" - 1".  On the other hand if you don't need to qualify impacts to Sec IX, why not run one plate on 3/4" thick material.  
 
pipewelder1999 (Industrial)
11 Dec 08 9:36
One thought I have is to perform the PQR on the material as listed . Then write one WPS for B31.3 using the ranges allowed for by B31.3. If you are using some type of program that uses Sec IX rules only for generating the documents, you should be able to turn off the code rules.

Then create a WPS within the rules of Sex IX only. If you then need the Sec IX WPS to have a lower min T then do another coupon with the same parameters on 1/4" material and do impacts only. Then combine both PQR's for one WPS. Thet will not eliminate the fact that the codes do not match but will get your min T down for Sec IX only.  

Or just add a note on the WPS that indicates one MIN T for B31.3 work and another for any other codes of construction.



Here are some interpretations that may be helpful or informative.

B31-85-031 Thickness Range for 31.3
IX-04-04  Combining PQRS


 

Gerald Austin
Iuka, Mississippi
http://www.weldingdata.com

Ballbearing1 (Petroleum)
10 Feb 09 0:49
Hello guys,
Just a bit confused as to why you need to have the lower ASME IX thickness.
ASME IX states the impact tests shall be made when required by other sections.
Therefore if B31.3 gives a range of T/2 to T + 1/4" that is what you will work to when fabricating B31.3 pipework.
Is there anything wrong with having the three base metal ranges listed on the one WPS or as an attachment?
(1) Base metal thickness range without impacts ASME IX
(2) Base metal thickness range with impacts  ASME IX
(3) Base metal thickness range with impacts B31.3

Regards,
BB

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