Drilling after hydrotest B31.3 1

[coolniks37]

Hi all,

I am designing a gas header for a ground flare. Applicable code of design is B31.3 & hydrotest will need to be conducted.
Is there an option in B31.3 to hydrotest the header in undrilled condition and later after hydrotest drill the distribution holes?
Thanks in advance!

 

[LittleInch]

Well its going to be difficult to hydrotest a pipe which has a lot of holes in it....

One option might just be to flange the end, test against the blank flange then bolt on a short section which has all the holes in it?

Bit isn't this supposed to eb a proper burner / flare piping? It's going to get rather hot.

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

 

[coolniks37]

Thank you @LittleInch for your response.

I am actually designing the section with all holes.

Is it possible to get an exception to hydrotest, as the section is open to atmosphere as per 345.1.d ?

 

[LittleInch]

Relief lines / vents are often designed as "atmospheric pressure" which if there is no valve or means of blockage, then a hydrotest is not required.

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

 

[coolniks37]

Thanks again!
Though it is open, wouldnt it be subjected to gas pressure during operation.
Again, in B31.3 when code says about hydrotest has to be carried out to check tightness - whether it is for checking leakage of joints or integrity of the wall ?

 

[LittleInch]

Yes, but so long as it is not > 15 psi or you can't make use of the exemption in para 345.1 d)

"(d) Unless specified in the engineering design, lines open to the atmosphere, such as vents or drains downstream of the last shutoff valve, need not be leak tested."

Now whether you can call your thing a "vent" is the key.

A hydro test on the rest of the pipping is required for tightness, which included joints and pipe and fitting integrity.

Still very difficult to do with lots of holes in the pipe

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

 

[coolniks37]

Exactly. My design pressure is around 20psi, and actual operating might be less than that.

Is there an option to hydrotest header in undrilled condition, and later drill on site.
If some welding is needed at site, can it be done at site without PWHT & hydro?

 

[SnTMan]

Sure not my area of expewertise (if any) but parsing para 345.1 d)

"(d) Unless specified in the engineering design, lines open to the atmosphere, such as vents or drains - downstream of the last shutoff valve, need not be leak tested."

1) Is leak teting specified?
2) Is the line open to atmosphere?
3) Such as: only as two of any number of examples
4) Is it downstreanm of the shutoff?

1) Yes - Test
2) No - Test
3) No bearing on test / no test
4) No - Test

This may be a topic best settled by agreement among the parties; Fabricator, Client / Owner, Authorized Inspector, etc.

Regards,

Mike


The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[LittleInch]

There's no option as this is rather an odd situation, but first look to the design intent and operation and see if it needs to be hydrotested at all.

If it is then yes, that sounds like a good compromise. - Test then drill some holes.

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

 

[coolniks37]

Thanks SnTMan, and LittleInch for your replies.
Could you point me to ASME B31.3 clause which lists activities that can be carried out post hydro?

 

[SnTMan]

coolniks37. sorry I have no knowledge whatsoever of the piping codes.

There is a piping forum you might find helpful: forum378

Best of luck

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[kremenco]

I don't know whether this would help depending on the configuration of the holes.
You can try welding threadolets/ threaded coupling to the header and hydrotest. Then remove the plugs after hydrotest.
Regards

 

[mk3223]

Again, in B31.3 when code says about hydrotest has to be carried out to check tightness - whether it is for checking leakage of joints or integrity of the wall ?

- Why needs to check the tightness of the pipe with holes?
- Are the joints on the open pipe to be tested for the leakage, or the piping section before it? Can they isolated for hydro?

 

[DekDee]

Why would you need to hydrotest ?
After you drill distribution holes there is no requirement for "leak tightness" as there is no way you can have any pressure build-up - exactly the same as a vent or drain.
Critical one to consider in 345.1 (d) Unless specified in the engineering design,.......
You are the designer - over to you.

 

[r6155]

Welding is not allowed after hydrostatic pressure test.

Regards

 

[DekDee]

Could you point me to ASME B31.3 clause which lists activities that can be carried out post hydro?

345.2.6 Repairs or Additions After Leak Testing. If
repairs or additions are made following the leak test,
the affected piping shall be retested, except that for
minor repairs or additions the owner may waive retest
requirements when precautionary measures are taken
to assure sound construction.