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Up Topic Welding Industry / Inspection & Qualification / Is melt through on a PJP rejectable?
- - By DeanS Date 11-26-2005 14:24
We have been receiving customer complaints regarding weld melt through on some of our products on PJP weldments.

The original implementation of borescoping product was to detect chips and FOD that may impair the products performance we produce. As time has passed, this ability to borescope the back side of welds has creped into the expectations of the weld inspection process. There is no customer specification that addresses borescoping or weld inspection with a borescope.

Trying to reference weld quality acceptance on the back side of weldments with a Borescope, there appears to be ambiguity in the customer specification requirements on melt through on partial joint penetration, (PJP) welds. The visual inspection requirements from the customer specifications we use, allows weld reinforcement and internal protrusion to limits based on material thickness. However; whether this applies to a PJP is not clear.

It is my understanding that Visual Weld Inspection is normally done on the “As Welded” side of a weld. In The Guide for the Visual Inspection of Welds (AWS B1.11:2000) the following is stated: “Melt through is a visible root reinforcement produced in a joint welded from one side and Melt through is generally acceptable unless it results in excessive root reinforcement.”

From the design point of view, the amount of backing supplied by the welded components may provide as little as .030 backing for a .500 bevel groove weld utilizing the manual GTAW Process in 304 Stainless Steel. This presents difficult welding scenario where “0” melt through is difficult to expect in a production environment given the obstructions. Components are being rejected for as little as .030 melt through protrusions that do not impede fit, form or function on piping inside diameters between 1 ½ and 2”.

The potential for “over inspecting” is real and is as reprehensible as “under inspecting”. This results in the disruption in the flow of product and additional rework costs, and worse of all; misunderstanding between customer and supplier.

Can anyone shed light on whether weld reinforcement is or is not an acceptable attribute to the back side of a PJP weld joint and how I should address this?

DeanS
Parent - - By vonash (**) Date 11-27-2005 04:07
Sorry, visual inspection of the weld root area using borescopes and other testing equipment is common practice.
Melt-thru is not acceptable because fit-up of butt welds requires backing per your PQR/WPS. This requirement is to prevent melting-through the root. Fusion of weld metal to steel backing is critical; melt-thru represents non-fusion.
Best regards,
Vonash
Parent - - By GRoberts (***) Date 11-30-2005 20:30
Vonash,
Your reply puzzles me a little. Is there something I'm missing here as far as the WPS/PQR requiring backing. I don't see anything in the post referencing backing. This would be unusual for PJP welds, as the base metal usually acts as backing for these welds. Also, burn-through on backing material would be considered to demonstrate excessive penetration, not lack of fusion.

DeanS,
The key question to any inspection interpretation question is - which specification being used to reject the part? You mentioned you were working to a customer's specification. If your customer is rejecting the part, they should be able to show you in black and white from their specification why the part is rejectable. Ask for chapter and verse. The amount of inspection you are experiencing is common for some industries and unusual for others. However, no customer should reject parts that meet thier specification in any industry or additional compensation should be required. Is there any way to get your customer to put their requirements in writing so that everyone is playing the same game, and you know what you are required to meet?
Parent - By DeanS Date 12-03-2005 14:04
Yes, GRoberts This is a customer spec. and no one has been able to apply paragraph or table where melt through is or is not allowed. There is acceptance criteria that allows "Weld Reinforcement and protrusions" within limits defined by material thickness however this table does not define whether this is applicable to PJP's or CJP's. In my opinion, all is fair when criteria and limits are specified but without clear definition, then subjectivity presents these issues. It is difficult to get changes to prints and specifications due to the size and dynamics of our customer and a major fault is that this specification is a "General Weld Spec.", far too broad for all applications this spec. may be applied to. With that said; I don't believe the allowance of intermittant .060 melt through protrusions on these PJP's would affect any flow dynamics or create stress risers that would promote failure in service. Engineers I have spoken to agree with this and given the ambiguity of criteria and limits, I as an inspector need to make a disposition so based on the available information supplied by the customer and by standard practices, (visual inspection is normally done on the deposited face of a weld on a single sided weld unless otherwise specified). I feel I am adhering to the intent of the inspection requirements by allowing "protrusions" to their limits as stated in one of the acceptance tables. This is why my position has been similar to your comment, " Show me where this is not allowed".
Parent - - By Bill M (***) Date 11-30-2005 17:31
I am not really clear about your current joint configuration. Is a backing surface created by a machined joint configuration tube to tube fit, or is it a simple open root with a .030" land that has some melt thru?

What fabrication code applies here? I am not sure if your condition is accceptable or not. Obviously is the melt thru is excessive and a nodule has the potential to break off...

I am not sure if this idea is applicable or economical to your application, ..but have you considered any stainless consumable insert or a stainless backing ring to eliminate the melt thru? A backing ring might eliminate some joint machining configurations. For typical backing rings: www.robvon.com
Parent - By DeanS Date 12-03-2005 14:17
The backing material is actually integral with the pipe where the OD of a 2" Dia. Sch 40 pipe has been turned down leaving about a .030 wall thickness. This is being inserted into the surface of the component in a machined port- I really consider this more of a socket joint arrangement. There is a bevel groove also machined above the reduced backing diameter to provide for groove welding to the diameter of the pipe and a fillet required on top of that. The fabrication code referenced is ASME PB&V but the acceptance criteria for visual inspection is provided in the customer spec.
Parent - - By NEQA (**) Date 12-02-2005 18:20
DeanS - when you say "...we have been receiving customer complaints...", does that mean you are receiving the same complaint over and over again from the same customer, or are you receiving the same complaint from several different customers? If the later (and I suspect it is), why not just accomodate your customers before they decide to take their business elsewhere next time?

As the Owner of a large NE utility, we have complained to our Contractor on this identical issue. Our inspector would not accept melt through on PJP welds - so, I understand where your customers are
coming from.

Yes, the danger of "over inspecting" is just as bad as "under inspecting". Seems to me, when the Contract document is unclear or unambigious, something can be worked out between Owner and client - for this particular assignment. From my point of view, it is the client's responsibility to read and understand ALL contract requirements BEFORE you begin the work.

Just a thought from the "customers" point of view.





Parent - - By DeanS Date 12-03-2005 14:39
Customer satisfaction is paramount in all successful business. Good, communication is key to this. I have found that industrial specifications vary widely as to thoroughnes and even with the best specifications, interpretation by the reader can vary. So when a contractor is given a set of documents to work to by a client and criteria given; if certain aspects of those details that are within that criteria are not addressed then I would think it understandable that the contractor would consider those unaddressed details equally unimportant. Unfortunately, communication on such details as you mention begins after a descrepency is found. I am curious to know if your inspection criteria addressed melt through on PJP welds?

Parent - By vonash (**) Date 12-19-2005 20:52
Sorry guys,
I stand by my earlier post.
Vonash
Up Topic Welding Industry / Inspection & Qualification / Is melt through on a PJP rejectable?

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