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Welded Pipe Patches
2

Welded Pipe Patches

Welded Pipe Patches

(OP)
We receive "requests for temporary approval" from various ships who weld pipe patches on various piping systems with through-wall leaks.  We disposition each request on a case by case basis.  We do not know of any industry standard for pipe patch geometry, weld joint design (I am referring to simple lap patch), or special NDT requirements.  Does anyone know if such a standard exists?  We would like to provide the fleet with some info on how to properly affix such welded patches before they come to us with requests to approve patches that are too small, incorrect geometry, improperly NDT'd, etc.

RE: Welded Pipe Patches

When working for a manufacturer of piping components we at times made standard forms and instructions regarding pressure vessel components based on calculations. This allowed the "designers" to proceed with a design. The engineer responsible signed off on the design to verify the table was used properly.

This method allowed some "standard" work processes with people not capable of code certification, but still had the engineer in the loop. We only did these standards where we had a large amount of repeat usage.

I wonder if you could not use such an internal standard to streamline your work process while maintaining the oversite necessary to assure any thing out of the ordinary did not escape engineering oversite.

RE: Welded Pipe Patches

Well we do intend to create an internal standard for temporary emergent repairs. The purpose of my inquiry was to determine if similar standards currently exist in industry, so that we could determine what the best current recommended practices are.  If any other readers are interested, I have identified two API publications through the help of DonLeffingwellPE and Mr. John Quigley at the ASME site:  ANSI/API RP 1107 - Pipeline Maintenance Welding and ANSI/AP 570 - Insp, Repair, Alteration and ReRating of In-Service Piping Systems.  We are in the process of procuring these publications.

RE: Welded Pipe Patches

Sorry I missed part of the intended thrust of your question. I have used the standards above in analysis of systems, but they do not provide a detailed proscription like what you asked for. The standards are in my view are necessary to consider when determining whether a particular repair should be undertaken.

When doing such repair designs in the past I have relied on ASME Section VIII Div. I and Div. II. The API standards allow you to evoke Div. II rules. This allows more flexibility and experience judgement in the design by the engineer. All this leads in my experience to more options not less and thus less specifics not more.

RE: Welded Pipe Patches

go with the api 570. We have use it as the basis When we develop our own standard/policy/procedure for the inspection and repair of process piping.
Note that Plidco has some clamps available for quick fix. The thing u really wanted to do is to ensure u have enough meat on your exisitng pipeline before doing the weld - should not be less than 5 mm minimum to prevent burnthrough.
The other reference u may want to consider is the AWS Welding Tech Sereis "Pipeline Welding and Inspection"

RE: Welded Pipe Patches

(OP)
Thanks for the help Ralph.  You're right; we almost always do a UT of existing pipe wall to ensure adequate thickness prior to repair welding.  I'd seen the AWS Pipeline Welding & Inspection a while back - I'll look at it again.
Thanks for posting,
Nelson

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