ASME IX Multiple PQR PWHT Heat Inputs

[jrupert24]

I have a WPS supported by 2 PQRs that is going through 3rd party review (impacts required). There is a difference of opinion on the heat input allowed for the WPS. The governing codes are API6A and ASME IX. The production material is 1" thick. I've only posted a minimum amount of information that I think is relevant to this situation of heat input. All other variables are constant. The first PQR PWHT is 4 hours and the second PWHT is 8 hours. The first PQR is supporting the original weld and the second PQR is supporting if we need repairs. The heat input on the first PQR with 4 hours is 25KJ/in and the heat input on the second PQR with 8 hours PWHT is 35KJ/in. The WPS has to be supported by both PQRs per API 6A (based on the distinct PWHT times), however, 6A does not address or govern heat input. So we cannot simply remove the 4 hour PQR from the packet.

We are proposing to use the higher heat input of 35KJ/in on the WPS as we believe this meets the ASME rules for heat input based off the 8 hour cycle that covers any time less than 8 hours (all relevant mechanical properties according to ASME IX are met at 8 hours with the higher heat input)

Note that we would agree that if our PQR with 4 hour PWHT was 35 KJ/in and our 8 hour PWHT was 25 KJ/in, that we would need to limit to 25KJ/in.

Please give an opinion supported by sections or interpretations if possible. I have found a few that are relevant, but none specific to this situation. I feel this is relatively clear cut and the higher heat input would be acceptable, however, I am open to other interpretations. The 3rd party does not agree and requires the lower heat input.

 

[weldstan]

Per ASME IX, the only PQR requred is the second with the 8 hr PWHT. The first PQR is only required per API 6A and supercedes ASME IX. However, if API 6A specifies full conformance of each PQR to ASME IX, it is debatable as to whether the lower heat input value is required for the initial weld and the higher value is permitted for the repair weld.

I would have no problem using the higher value.

 

[DVWE]

I agree with weldstan, no issues with using the higher value, but I'm not your 3rd party either. I also agree that it's debatable which is the correct one to follow since API 6A has been invoked. It's for this reason that when I qualify a WPS with multiple PWHT cycles, it's worth leaving all other variables the same save for the PWHT time. Why create confusion?

Some important information is missing in your post, and therefore you can take the rest of my response with a grain of salt.

1. We don't know the welding process
2. We don't know the material

Both of these can change the answer to heat input significantly.

But consider this; 25KJ/in vs 35 KJ/in is almost spit in a bucket difference. It's up to you to determine if it's an argument worth having with your 3rd party. Sometimes it's just easier to give them what they want rather than try and prove them wrong. By comparison, most of my GMAW/FCAW/SMAW procedures are up in the 60-85 KJ/in range. GTAW some are as high as 50 KJ/in. If we're talking 80 vs 25....then ya, that's probably worth arguing just for production's sake.

The devil is in the details; she also wears prada.

 

[jrupert24]

Thanks for the comments. Believe me, I wasn't purposely shooting myself in the foot! Normally we do run a coupon with short and long but had an issue with the short and had to qualify separately later. Definitely not ideal but is what it is. Was much more complicated one than the usual qual with all sorts of restrictions boxing us into a very small target to hit, however, I only really included the details as they related to heat input since that is all he really is concerned with. His most recent comment is what supporting paragraph do I have from ASME IX that supports the heat input from the longer one overriding or trumping the heat input from the shorter one. This is basic ASME IX knowledge so I don't know how else to explain it. That is why I was looking for comments from a different perspective that maybe I am missing something. For me there is absolutely no issue here for the higher heat input.

Its SMAW, just difficult to get two different welders to run the same (or same welder for that matter!) which is why the short one ended up being lower heat input. Sometimes you have to deal with the cards you are given.

We can run with the lower heat input but wanted the higher just to be inclusive of some of the guys that typically run hotter. In the end, we will most likely bow to the 3rd party, but wanted to get some more perspective.

 

[DVWE]

Try this and see if your 3rd party bites.

QW-401.1, second paragraph. You have changed one or more supplementary essential variables in your 4 hour PQR - PWHT Time and Heat Input. You have requalified both with the 8 hour PQR.

For SMAW, QW-407.2 states that your fabrication PWHT and your repair PWHT can be combined with one coupon, which is your 8 hour.

Note that aggregate time usually includes provisions for one shop repair, and/or one future use by the client. Both of which may or may not be used.

The devil is in the details; she also wears prada.