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pWPS Question

pWPS Question

Hello all,
I am fairly new to procedure writing and am still fumbling my way through the interpretation aspects of things. Currently, I am reviewing a customer who had an inspector kick back one of our procedures that was written to D1.1:2015. One of the markups was the fact that we listed multiple electrode diameters for the pWPS. Based off of pWPS Essential Variables in 3.7, item #7, I interpret that as a change outside of what we decide to list on the procedure requires re qualification. The inspector is saying we need a separate WPS for each diameter. Same thing with base metals. On the pWPS we list that AWS Group I and/or II may be used, and the inspector is saying we need to be specific with Spec and Type and Grade based off of 3.7, item #3. I interpret this the same way as I am interpreting filler metals.


Thanks in advanced!

RE: pWPS Question

The question is: pWPS - preliminary WPS or prequalified WPS?

If you are speaking of a preliminary WPS, you are giving the welder directions for welding up a test assembly used to qualify the WPS. The welded assembly is then tested to demonstrate it meet the minimum mechanical properties required by the applicable code.

If you are speaking of a prequalified WPS, then all the conditions of Clause 3 must be met. The prequalified WPS can cover multiple base metals, multiple weld types, multiple joint types, and/or multiple electrodes and electrode diameters.

Best regards - Al

RE: pWPS Question

Hey Al,
Thanks for the quick reply. I am speaking of a prequalified WPS per Clause 3. When you say "Multiple Joint Types", are you saying that I can write one WPS to cover B-U2 and B-U2a This has also been a questions i've had in mind.

-Justin Lambert

RE: pWPS Question

Unless the customer has included a restriction in the project specification, the contractor can have a single WPS that includes multiple base metal specifications and multiple joint details. As you asked in your inquiry; "can you include all the base metal in Group I or Group II, or Group III, etc.?". The answer is "yes" provided a matching filler metal is used. Likewise, any of the prequalified joint details, both grooves, fillets, plug, and slot welds can be welded with a single WPS.

Having said that, I would not recommend that approach for many situations. One must remember the primary intent of the WPS is to provide direction to the welder so that a code compliant weld with the required mechanical properties can be deposited. There are several approaches that can be taken. A separate WPS can be written for each joint type, electrode classification, electrode diameter, and each welding position. The binder of WPSs would become unwieldy very quickly to say the least. That approach makes sense if there are a very limited number of joint details to be welded and only one electrode classification is involved.

The approach I use for several of my clients that are "job shops" is to develop a single WPS that references several annexes. One annex for the multitude of base metal specifications covered, another for the joint details (this annex includes sketches of the specific joint details with tolerances), and another annex that covers acceptance criteria. The welder then has the basic WPS for the general information, i.e., welding process, shielding gas (if required), welding parameters, etc. For a specific joint detail, the welder looks in the appropriate annex referenced by the WPS. Likewise, for specific information regarding the base metal specifications, thickness limitations, product form, preheat, etc. another annex is referenced by the WPS.

I include the electrode classifications and the appropriate electrode diameters and the appropriate ranges for the welding parameters. However, unless more than one electrode classification is used on a single joint, I limit the WPS to one electrode classification, but that is my preference, not a code limitation. Only the electrode classifications listed by the WPS can be used.

A WPS used for general fabrication is not necessarily the same as one used for a complex repair projects. Again, one must keep in mind the purpose of the WPS and who is expected to use it. An engineer reviewing the WPS is looking for code compliance. The welder is looking for useful information that will tell him how the weld is to be made. The information needed by the engineer is not necessarily the same as what is needed by the welder.

The trick to writing a good WPS is to make sure it doesn't become so all inclusive it becomes to cumbersome and confusing to follow. It is a balancing act that is learned by experience.

Best regards - Al

RE: pWPS Question

Excellent explanation Al.
Many times I have seen an impressive WPS folder sitting in the Quality Managers office that is designed to impress clients / customers but on closer inspection has very little of any actual benefit to the welder (unless they have a university degree)

I have a perfect example in front of me at the moment.
In the notes of the WPS this is listed.
"With an increase in the CEV of 0.01% the preheat shall be increased by 10 degrees celcius as per Table 1"

How many welders actually know what the Carbon Equivalent Value even means ?
How many welders carry a calculator or know the formula to recalculate the CEV ?

It is information that is put on a WPS to impress the person reviewing the WPS but is of absolutely no assistance to the welder,

RE: pWPS Question

Thank you very much for the great feedback and explanation. I really appreciate the time and effort you put into your post, it means alot. As I am young, and eager to learn, clarifications like this will help me in the future. After today I was a bit unsure of myself. I previously thought it was an inspector who marked up the procedure, but it was actually and engineer. I spoke to the engineer today to try and sway him on the interpretation of essential variables for pre-qualified procedures, but it did not work. He insisted that you could not have multiple electrode diameters, base metal groupings, or joint configurations on the same procedure because they are listed as "essential". Unfortunately, the company will now have to spend more money for us to write these procedures to his liking, when in actuality the procedures they have in place would suffice.

Its great to have this knowledge for future projects and encounters. Again, thanks a million!

-Justin Lambert

RE: pWPS Question

My good friend DekDee makes a valid point that is often overlooked. Base metals are typically grouped together to reduce the number of WPSs that need to be qualified by testing or prequalified. The intent is to reduce the number of WPSs needed. So, the base metals are grouped by M number (AWS B2.1), P numbers (A Section IX) or S numbers (NAVSEA TP248/278). Individuals developing the WPS may be tempted to list the base metals on the WPS as "All P1" or "All M1". This is fine if the welder understands what the base metal groupings mean. Unfortunately, few welders have formal training in "code speak", thus "All P1" means very little if anything to the welder. That is the reason I refer the welder to an annex. The annex lists all the "P1" or "M1" by material specification, product form, and other useful information the welder can relate to. Pipe, plate, and structural shapes are marked with the ASTM/ASME/Military specification, etc., but rarely, if ever, are they marked with the P number or M number. Thus the WPS listing "All P1" is nearly meaningless to the welder that is suppose to be using it.

In a production facility, where a few products are produced with a few typical joint details and where a single electrode classification is used, a WPS listing the particular joint detail and the particular electrode classification makes sense because it can provide the level of detail needed by the welder and simplifies the use of the WPS. I frequently use that approach for manufacturing facilities with a limited number of products. It is the job shop that is welding many one of a kind or limited production runs that can best utilize a "general WPS". Each particulars of the facility must be considered when developing a WPS.

The information provided must be useful to the welder. One must understand the technical competence of the individual that is tasked with using the WPS, i.e., the welder. "Code speak" can confuse the welder with limited training or understanding of codes. That point can be easily overlooked by the "technocrat" tasked with developing a WPS that meets the technical requirements of the applicable code.

DekDee mentioned few welders understand "carbon equivalency". Few welders understand "heat input" or the importance of controlling heat input or when it is applicable unless they are provided with appropriate training. This is where accolades are due by those that formulated Navy welding standards. Welders qualified to the requirements of NAVSEA TP 248 are required to pass "workmanship" training where the welder are taught the technical aspects of meeting the welding requirements of the applicable fabrication standards. I have been providing training courses for my clients for twenty plus years and the results are very impressive. The amount of rework and rejection rates plummet after the training because the welders have a better understanding of why the code requirements are imposed. Welders that understand why a requirement is imposed is less likely to take shortcuts or attempt to circumvent the requirements. The welder training also includes a review of the "quality" requirements so they are know what is required. Time is also spent explaining how to use the WPSs. Welders need to understand what information is provided by the WPS and how to apply that information.

Best regards - Al

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