Hi,

I am involved in a project where we are making a vertical pressure vessel 36.5 meters in height and 4.1 meters in damater. Transportation troubles with such a size restricts us to fabricate the vessel in two halves for final joining to be done at site. Also the location where the vessel shall be joined is having a Bolting bar (internal attachment) across the joint extending to both sides (ofcourse this bolting bar shall also be welded on site after the vessel is joined at seperation).

To assess the leak proofness this vessel shall also be hydrotested at site in two parts and a local hydrotest is planned for site. Is such local hydrotest allowed by the Code? and since there would be a bolting bar welded inside, the only option I am left with is to weld a coil (half pipe) on the outside of the vessel and then pressure test the same. So the list of questions are -

1. Is it allowed to locally hydrotest a vertical vessel like this?
2. If yes, can a vessel designed for internal pressure be pressure tested applying external pressure to assess leak-proofness of a local joint?
3. Can anyone suggest a better way out?

Regards

Shashank Jain
New Delhi, India

ps: I would have attached a schematic sketch of the whole arrangement but there is no option to do so here, so request you visualise the arrangement with a half pipe bent in circular form welded around the cir-seam weld or the site joint and then pressure being applied in that half pipe.

The vessel can be Hydrotested in horizontal posistion . Pressure at the top of the vessel in horizontal position should be 1.3 x Design Pressure.

Why this can not be done ?

With regards
Rathnam

The vessel shall be pressure tested on completion of all fabrication activities. No chance.
You may h.test separate part, but this would not be the Code hydrotatic test.
It is allowed to perform air pressure test per UG-100 at the pressure per shall be at least equal to 1.1 times the maximum allowable working pressure34 multiplied by the lowest stress ratio (LSR) for the materials of which the vessel is constructed. Mind requirements of UW-50.
If the h.test in two parts has been done, shouldn't be so dangerous to test with air.
Mauro

Hi, many thanks for your prompt response...

1. Firstly this query stands corrected in that the preliminary hydrotest is being done at shop (I incorrectly mentioned it "at site") and subsequent so called "local hydrotest" is being planned at site.

2. Secondly for below quoted text - is it the test of complete vessel that you are talk about or test after making some local arrangements? like coil welding as I indicated above?



3. Would really appreciate if you try clarify query no. 2 above.

I do not understand what you mean, but, I repeat: Vessel on completion shall be hydro or pnumatic tested. Any partial pressure test is not a Code pressure test.
Mauro

Quote: Any partial pressure test is not a Code pressure test.
Unquote:
The requirements of UG-99 are only satisfied if you perform hydro test after all the fabrication activities (costmetic grinding and weld end preperation may be performed after test). So local test is not a Code required test.

_________________
Thanks & Regards,
Nasir
Welding Engineer
DESCON Engineering Limited.
Lahore, Pakistan.
Mobile # 0092-336-4145402

The question is not clear to me .I presume the question is whether any additional test may be done or not ?

Code expects Hydro Test or Pneumatic Test in lieu of Hydro Test for acceptance.Any additional test is neither required nor prohibited by Code .

The weld may be tested by any NDE method such as RT or UT or PT .Helium Leak Test may also be used .