Patch Welding on A335 P22 Pipe 1

[ak1965]

We have a A335 P22 Header (16" & 21.44 mm thick) at the outlet of a double pipe heat exchnager. The Header is horizontal & has 12 nos. pipe connections at the inlet on bottom side of pipe & 01 outlet pipe connection from the middle of header on the top side of header. This equipment was designed as per ASME sect. VIII Div.1 & requires PWHT, if any welding is done on the header. Temperature in the header is approx 450 Deg C & pressure is 2 kg.cm.2/. Service is hydrocarbons.

This header receives hot process gases (hydrocarbons) with high velocity that impinge at 12 locations on Inner surface on the top portion of header. Over a period of time, 4 to 5 mm erosion has taken place at the location of impingement which is beyond corrosion allowance.

We wish to weld additional patch plates of same material (i.e. A335 P22)at all 12 locations, on the affected portion on the top side of header from outside.

1. Would it be the right approach to prevent failure of eroded part by providing a patch plate?


2. PWHT shall be required or not?

3. Can we follow ASME B31.3 instead of ASME sect VIII div. 1 that allows us to weld a patch plate with austenitic filler wire to avoid PWHT?


Please give yr expert opinion.

 

[DSB123]

Stay with the original Design Code!!!!

 

[metengr]

ak1965;
Just to make sure we understand one another, in my mind a patch plate is where a plate is fillet welded to the pressure boundary. If this is what you are referring to versus a flush patch plate (which is full penetration welded and is permitted by the NBIC), a patch plate is prohibited by the NBIC for repairs of pressure retaining components, and I absolutely agree.

In your situation where you have wastage along the ID surface of a header, you can use the flush patch concept except apply a stainless steel (309) or Inconel inlay to a P22 flush patch and use a full penetration weld. This would require PWHT and follow the code of construction NDT requirements. This is doable but costly.
Another is to cut one end of the header and use a long reach automatic welding machine to locally build-up the header ID surface using Inconel or stainless steel (like an inlay) to increase erosion resistance at the 12 locations along the ID surface. You can selectively PWHT from the OD surface at the 12 locations.
The last option I can think of is to evaluate the rate of erosion at the 12 locations and if they fall below minimum wall thickness you can re-visit the flush patch concept above or replace the header.

 

[stanweld]

If possible per the Jurisdiction, use API 510 for guidance.

 

[ak1965]

metengr,

Thanks for the useful information...!

To me, a patch plate means an external patch plate that is fillet welded onto the header to prevent a gas leak, if the header fails due to loss of thickness beyond corrosion allowance. patch plate would prevent a leak.

The idea of flush plate is well understood & can be considered, you mentioned that a inlay is needed(or I understnd it a buttering layer with incone)... please confrim as which part should be inlayed, the existing parent bevel edges or the bevel edges of new P22 plate that is to be flush welded with flush welding.

 

[metengr]

ak1965;
The inlay I was suggesting was to be applied only along one surface (the ID portion) to increase erosion resistance. The actual installation of the flush patch plate (with ID inlay) should be with matching filler metal to the existing header base material.

 

[ak1965]

metengr

Point well taken...! overlay on flush patch plate ID side..!

Since we are using same paterial so no need to overlay on bevel edges on flush plate or the parent of existing pipe...!

 

[Guest102023]

I vote for the internal weld overlay, probably with austenitic filler metal. PWHT is not optional.

A patch on the outside is a non-starter.

ak1965, I don't understand the intent of your last comment.

 

[ak1965]

brimstoner,

Resubmitting metengr thought & my understanding to it!


1. Cut a window in the header, covering the eroded portion of header. An overlay or inlay (for me both are same) with inconel wire on flush plate ID side before welding it with existing header.Inlay is fro improving erosion resistance in future.

2. Do a full penetration weld of flush plate to the header using a matching filler wire.

3. PWHT as per code.

 

[metengr]

Yes, correct.