Hydro testing branch spool against run pipe external 1

[gA2002]

Hi everyone!

Has anyone did hydro-testing of branch spool welded to the run pipe with weld-o-let, before cutting the hole from the main pipe?
Let me explain further:
1) 3" weld-o-let to be welded to a 10" run pipe.
2) Weld neck flange is welded to the weld-o-let. A valve will be fitted to the flange.
3) Before cutting the hole on the run pipe, hydro test will be conducted.
The piping is designed as per ASME B31.3.

Any help on the calculation for the external pressure allowable for the run pipe?
Will the external pressure applied on the 3" nominal bore area cause buckling on the 10" pipe?

Your sharing of similar experience is appreciated.

 

[XL83NL]

Why do you want to hydro the pipe before making the hole for the olet? Is the placement of the weldolet an alteration, repair or anything of that kind?
Why do you want to know the external pressure? See 304.1.3 of B31.3 for calc of the external pressure. It refers you to ASME VIII-1.
It may buckle the pipe if the external pressure on the 10" pipe, at the point of the 3" olet, is greater than the MAEWP at calculated for THAT PART only.

 

[SNORGY]

I have done this before and with 3" on 10" it shouldn't be an issue.

 

[gA2002]

@SNORGY - Thanks for the inch of confidence!

@XL83NL - Thanks for the thought. To hydro test before cutting of hole is to test the olet welding. No way of hydro testing with the main pipe. I am safe external pressure in order not to collapse the main pipe area enclosed by the olet. 304.1.3 refers to straight pipe under external pressure, we are not subjecting the entire main pipe into external pressure, that's why I am considering this clause not applicable.

After posting the thread, I come across with a similar post that you might get interested as well -

http://www.eng-tips.com/viewthread.cfm?qid=218840

 

[XL83NL]

I didnt knew that this was a Code requirement in terms of hydrotesting the olet-weld... ?

 

[gA2002]

@XL83NL: the olet is part of the new spool, complying to B31.1, so it needs to be hydro tested as well.

 

[XL83NL]

Thanks for clearing that up, now it makes sense.