Multiple Process WPS

[MathGuy]

Does Section IX or D1.1 prevent the combining of multiple PQRs, one with PWHT and another without, from qualifying a WPS. A reference paragraph would be greatly appreciated.

 

[rneill]

You might want to look at ASME IX Clause QW-200.2 thru QW-200.4. These address the issue of combining PQRs and WPSs though I'm not sure if they talk about this specific issue.

 

[DVWE]

I'm curious why you would want to combine them? Would it not just be simpler to have two separate WPSs?

At initial thought, I don't think this would be possible as PWHT is an essential variable.

 

[bpv66]

QW-200.2 (f) allows a single WPS to cover several essential variable changes as long as a supporting PQR exists for each essential.

This is a very common practice, especially with the larger contractors/companies that have dozens of WPS's.

 

[DVWE]

QW-200.2 (f) allows a single WPS to cover several essential variable changes as long as a supporting PQR exists for each essential.

Sure. I understand that, but for PWHT? Seems to me something like that would only convolute things rather than make them simpler by combining them....but that's just me.

 

[stanweld]

Many manufacturers write a WPS defining PWHT and no PWHT conditions supported by PQRs with and without PWHT. This does not confuse the welder who is not responsible for conducting PWHT. There may be confusion regarding when additional preheating is required (due to thickness or other considerations)but the WPS can be written to effectively instruct the welder in this regard.

Our company policy is much more specific so as not to confuse those responsible for PWHT and assuring appropriate preheat and interpass temp. control.

 

[vesselfab]

we run the same procedure with and without PWHT, but, give each wps & pqr a separate identifier name.

not dozens, but hundreds of weld procedures.

 

[DVWE]

Whatever works best for the shop. Here, our guys are trained to do both welding and PWHT (not to mention all other activities such as bending and forming too).

 

[vesselfab]

i guess i should have answered the original question.

combining wps s is fine as long as PWHT with PWHT

Non PWHT with Non PWHT

you can not mix essential variables like PWHT

 

[GenB]

DVWE (Petroleum), it is is common practice of wps'es combination,
you are probably confusing it with PQR's which you have to have one for every process.
i know shops who do PQR's combinations as well but it is a more complicated matter,
I think the ASME does not like the practice so during audits, i stay away from the practice.
genblr

 

[DVWE]

GenB,

Actually, I'm not, but thanks for caring

 

[Mr168]

Vesselfab: What is your basis for saying that segregating PWHT from non PWHT is a code requirement, i.e. the two cannot be combined on a single WPS? QW-200.4(b) permits the combination of different sets of essential variables as long as they are appropriately applied and the limitations of QW-451 are met. It's very common for multiple PQR's to support a single WPS either permitting or not requiring PWHT based on the exemption criteria of the applicable code.

It may not be the most simplistic or straight forward means of conveying PWHT (or other) requirements, but it is not prohibited.

 

[vesselfab]

huh

I always thought that the tensile test and bends had to be in the final heat treated condition.

 

[DVWE]

It's very common for multiple PQR's to support a single WPS either permitting or not requiring PWHT

Can someone please give me a good example of why you would want to do this? For example, maybe a vessel in which some sections require it and some don't?

Everyone keeps saying how common it is, but to me, a better use of combining multiple PQRs into a single WPS would be a qualified range of thicknesses, or similar F-Nos. PWHT? Sure, you can but why?

 

[GRoberts]

It is not uncommon to have one WPS with PQRs for the PWHT condition and the as-welded condition. I think most fabricators do it for convenience. You don't have to worry about getting different welding procedures used in the wrong place if they are combined. Also, if you use the same WPS for both conditions, and you have no-PWHT welds that are later changed to PWHT welds due to repairs or something like that- no big deal as the WPS with both supporting PQRs cover the weld either way.

Vesselfab- the tensile tests and bend test do have to be in the final heat treated condition. So if you have one PQR with tensile tests and bend tests in the PWHT condition, and one PQR with tensile tests and bend tests in the as-welded condition, there is no reason they cannot support the same WPS.

 

[DVWE]

GRoberts,

I don't mean to play devil's advocate too heavily, but the "what if" scenarios could be played all day. I would like to know of some real life examples from someone who actually does this, why, and how it simplifies things. If it's such commonplace, that shouldn't be asking for too much, should it. Has anyone in this post personally done it?

My shop represents "most fabricators" and of the 100+ WPSs which I am responsible for, I can't think of any off the top of my head which we have done this. A reputable pressure vessel shop should have a weld plan or weld map in place detailing which WPSs and respective NDE apply to the applicable joints on any particular vessel. If a mistake is made, or a change is made, it is easier to revise the document with the appropriate WPS and subsequent NCR if required.

 

[rneill]

DVWE, I typically represent end users who are having vessels fabricated and I know I've had a few discussions with fabricators who have wanted to combine WPSs and PQRs in completing weld joints and I'm usually not a fan of this. To try and get around the issue for vessels in severe sour service where I think it is potentially a bit of a risk, I now right in any specs I issue that there needs to be a single WPS and single PQR supporting each weld joint.

I have had quite a bit of pushback on this.

 

[vesselfab]

yes, we like many other fabricators have identical wps/pqrs in as welded condition and in pwht condition. we assign completely different wps numbers to pwht wps to differentiate between pwht/as welded condition

BUT, I think the original poster was talking using two different pqr one in as welded and one in pwht condition to make one weld.

to me this is just wrong. essential variables are essential

 

[DVWE]

BUT, I think the original poster was talking using two different pqr one in as welded and one in pwht condition to make one weld.

Vesselfab, I don't think that's what he was asking.

 

[DVWE]

I typically represent end users who are having vessels fabricated and I know I've had a few discussions with fabricators who have wanted to combine WPSs and PQRs in completing weld joints and I'm usually not a fan of this.

rneill,

What about two PQRs, one with PWHT, and one without, into a single WPS?

Correct me if I'm wrong, but I believe you are talking about something like using GTAW, SMAW, and SAW all in the same weld joint.