Localized Hydrotest using external jacket to check final Field Weld Joint 1

[ashaykadam]

Hi,

We are having few oversized equipment (Height more than 40 m) where due to logistic constraints many vendor's are proposing that they will fabricate the equipment in shop, perform Hydrotest, cut in two pieces, transport them to site, carry out final weld joint at site and perform Localized Hydrotest using external jacket to check final Field Weld Joint.

ASME Sec. VIII Div. 1 does not provide any such guidelines where Localized Hydrotest using external jacket is allowed to check final Field Weld Joint.

Can anybody provide me information whether this procedure of Hydrotest proposed by vendor is acceptable?
If yes, then on what grounds we can accept this w.r.t. ASME Sec. VIII Div. 1 requirements?
If No, then what can be the alternative to carry out Hydrotest of final Field Weld Joint?

Thanks.
Have a nice day!

Ashay Kadam
Sr. Manager
Mechanical Department
thyssenkrupp Industrial Solutions (India) Private Limited (Formerly Uhde India Private Limited)

 

[DSB123]

You seem to be the engineering Company responsible - so really it is up to you to determine if this is acceptable to you - your Company - the owner and the Insurers!!!

 

[marty007]

I have heard of this done is a couple of cases, but there is nothing specific in the code that explicitly allows the practice. It would certainly have to be discussed with the AI that would be overseeing the work.

My first question would be, why can't they hydrotest the complete vessel on-site? (weight? internals that can't get wet? ...?)

The other route I've seen would be:
[ul]
[li]Shop fabricate entire vessel and hydrotest[/li]
[li]Stamp vessel and apply ASME nameplate[/li]
[li]Cut vessel in two pieces and ship to site[/li]
[li]Re-weld shell together, but now the work is being done as a repair under NBIC Part 3[/li]
[li]NBIC Part 3 for hydrotests states that the complete vessel should be hydrotested, unless it is not practical (I don't remember the exact wording), and full RT of the repair welds can be used in lieu of the hydrotest. You would need a very good reason though...[/li]
[li]Repair is documented on an R-form[/li]
[/ul]

 

[racookpe1978]

How could they verify the structural weld strength of a joint under operational pressure from the inside by applying an external pressure from the external jacket wrapped around the PV?

 

[r6155]

1) Transport in two sections
2) Final weld in site
3) Hydrotest in horizontal position.

Regards
r6155

 

[PMCap]

why not a pneumatic test??

 

[DSB123]

PMCap,
Too much energy in a pneumatic test. The exclusion distance would be excessive and the consequences of a failure under test - don't want to go there!!!!

 

[GenB]

I see no fix on this one. After certain size the shells shall be overlapped then you can't just cut n half and reweld. Have it finished at the job site and Hydrotest as required and then sleep well at night.

General Blr. CA,USA

 

[MikeHalloran]

You also need to check the collapse pressure of the proposed field joint under external pressure, as if it were a submarine.

Especially if the shell is large relative to its thickness, the collapse pressure may surprise you.
The collapse event certainly will; hell of a bang.




Mike Halloran
Pembroke Pines, FL, USA

 

[Steve.sw90]

Providing break flange to the equipment is also a considerable option.

 

[PMCap]

For repairs/alterations in the field - the National Board Inspection Code (NBIC) allows for this type inspection. It is addressed in a NBIC Interpretation 01-15

 

[SJmetallurgist]

I don't know why i am not able to find an input I was expecting from so many people who have posted above. Actually such field hydro-test technique is quite common in practice.
There is no harm in doing a field hydro-test using limpet coil, i.e., a half pipe welded inside the vessel on the field weld. It is safe as well.

Of-course there needs to be a proper method statement from your manufacturer, which should cover the method of welding the coil to the vessel. If PWHT is there, then needs to be PWHTed as well. Proper NDE after removal of coil, etc.
Requires some mind-work but safe and sound practice it is.

As far as acceptance based on code is concerned. Do apppreciate that code doesnt specify about shop or field hydrotest. neither does it restrict any field/local hydrotest. your apprehension is a consequence of lack of exposure/experience in such techniques.

 

[mk3223]

There are all good recommendations above tried to resolve the construction issue. Instead of accepting the vendor proposal, the owner may want to have a full field hydrates after the vessel erected in place. It's a new construction project, and one should make sure the equipment is a brand new as it's paid for.

 

[ashaykadam]

Thanks All...

Ashay Kadam
Mechanical Engineer
India.

 

[MrPDes]

Check the shop hydrotest to get the test pressure to say 1.4×MAWP.

Then make the strake where the vessel is cut in half thicker so the site Pneumatic test provides no more risk than the risk while applying MAWP to the vessel.

This solution is about reducing risk to less than what would be experienced during operation.

 

[LittleInch]

SJM - I think the key to your answer is a half shell welded INSIDE. The Op was talking about testing from the OUTSIDE hence the comments. I agree your idea looks like a good solution, but is far from simple, which is what I think the vendors were trying to do.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.