Subsea valves with welding end 1

[salmon2]

I am in process of writing subsea valve Spec with welding ends for manifold fabrication. So there probably are two contractors involved: valve manufacturer and manifold fabricator. Then how should I specify the FAT test in the valve Spec (no blind flange can be used for testing given the welding ends)? What is the typical work-around? The valve is pretty much specified along with 6A/17D. Thanks a lot.

 

[LittleInch]

It is relatively rare for a WE valve to be specified without a pup piece welded on during the valve manufacture. This is to avoid any heat issues with pipe welding onto the completed valve affecting the valve internals / seals etc and also another weld procedure due to the different properties of the valve (the purchaser normally suppplies a length of pipe the same as you are going to use for your manifold). Also if the weld fails NDT or needs to be cut out for any reaons, you're not doing this onto the valve itself and running out of metal.

With pup piece, you just make them longer than you need, weld a flange on, test it, cut the flange off and away you go. You then cut the pup piece to size.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[pennpiper]

LittleInch,
I do not think this statement is quite true based on the available evidence.
[It is relatively rare for a WE valve to be specified without a pup piece welded on during the valve manufacture]
It is also not consistent with my experience over the years I was still doing piping.
If you look at this web site >

http://bonneyforge.com/resources/CSV.pdf<

and scroll down to page 11 thru 14 you will see that all the gate valves come in Raised Face, RTJ Face and Butt Weld Ends all with the same end-to-end dimensions(L, L1 & L2) per valve size/rating. There is no indication that an extra Pup was added on.

prognosis: Lead or Lag

 

[salmon2]

Excellent! Littleinch, that has answered my concern perfectly.

 

[LittleInch]

Pennpiper,

The dimensions of the valve are fixed, I agree, but as noted above by the OP, if you don't add a pup piece as part of YOUR data sheet / spec, then it becomes very difficult / impossible to test and, in reality, very difficult to actually install without risk of damage of seats (especially if these are soft seated) and issues about how to cut out or repair the weld if it fails NDT.

In addition, each valve then needs it's own WPS and test because it is a new material whereas if you supply the pipe pup that issue just goes away and becomes a valve supplier issue, not yours.

The only other possible way to test WE valves is to place them between seals and apply large forces to seal the ends whilst you test, similar to pipe mill pipe tests.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[salmon2]

Ok, littleinch, that is another way, thank you again. But the hydro test at pipe mill is usually low pressure, not the maop, I think. My specific case is 15ksi for fat, which is very high to me for a pressed seal method.

 

[LittleInch]

FYI, Pipe hydro test at the mill is commonly 90% SMYS, but only for about 10 seconds. 15,000 psi is a pretty meaty valve Ok - you would probably end up bending the valve to get a seal on that. I'm a little surprised that your piping / mechanical engineer didn't indicate pup pieces, but glad to be of assistence.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way