Double bevel on vertical seam

[Syahar1975]

Dear experts,

We have a shell plate 23 mm thick Group IV as per API 650.

The vertical joint detail is double bevel. By mistake we have cut to single bevel.

The tank designer suggest to raise a concession request to the client since double bevel on 23 mm plate is a project specification.

As per the approved WPS this vertical to be welded by EGW (electro gas welded) process.

I propose to make a test plate (1 ft long) with the same thickness and material group. Start welding till complete on bevel side. Grinding and make a bevel on the opposite site as per the approved drawing and complete welding on this side. Do visual, RT and other mechanical tests.

If the result is OK then we will apply the same thing on the shell plate i.e. complete welding on bevel side and make bevel on the opposite side then complete welding on this side.

Any comments or other suggestion ?

 

[JStephen]

You may get excessive weld distortion (peaking) with your solution (which may be the reasoning behind the specification requirement.)

 

[valleytank]

It isn't really thick enough to warrant a double-v prep from the start. In my opinion keep the single-v, deposit your root and hot pass, go back inside and backgouge the square edge back to your original root and dress it up to the same V prep angle. VT/MT back gouged/ground surface. Deposit internal side root watching heat. You can manipulate and stagger your passes to keep a good eye on distortion.

Follow up with FINAL MT on Cap both sides, any temporary attachments, and spot RT.

 

[Oscarvs]

Syahar1975,

Because the EGW process will be used, only one pass is required for vertical welding.
I think the extra work proposed is not necessary, because for 23 mm thickness single-V-bevel could be used. I have seen that double-V-bevel is normally recommended by EGW equipment manufacturers for plates over 1 inch thickness.
I suggest you ask for a concession to his client.