Vessel hydrotesting

[sree60]

Hi Members
We have a situation where the Stainless steel pressure vessel having internals and built to ASME Sec VIII div 1.
is required to be hydrotested ( test pressure -12 bar)with all the internals fitted. is there any precaution which needs to be taken apart from proper bolting of internals?
Are internals normally designed to take hydrotest loads?
Thanks in advance
sree60

 

[vesselfab]

bolt in internals, trays and such, are not normally installed before testing.

If internals can stop bleeding of air off, can make a hydrotest hard to carry out.

what kind of internals??

 

[rneill]

I don't know that hydrotest loads would have much impact since the internals would be exposed to pressure on all sides as opposed to one side only. Kind of like dropping them into the ocean, since they are surrounded by the pressure, I wouldn't think that there would be a large force to damage them but it would depend on the specific configuration.

 

[davefitz]

All of the normal precautionms for hydrotest are required, including assurance that the metal temp is above the brittle transition temp or min standard test temp. Shop hydotest failures in the winter months are not unheard of.

hydrotest with internals is a good "proof test" as there could be some reactions at the attachment points of internals , espescially if teh internals span the full diameter of the vessel, and proof that pre-existing weld cracks will not fail during service would be provided by such a test.

 

[jte]

If by "proper bolting" you mean snug, but not tight, then that's probably ok. Consider something like a bed or tray support beam which will not expand with applied pressure. The shell will get a bit larger - on the order of 0.2% strain. Doesn't seem like much, but for a 5m diameter vessel that equates to 10mm diametrical growth. A tightly bolted beam could restrain the shell's expansion a bit and cause some high localized loads. Normally these components would be installed a bit loose to allow for thermal expansion; if this is the case then there is no concern for this issue for a hydrotest.

jt

 

[JTRY]

I am aware of successful hydotest on packed and trayed towers with internals in the field. Such internals are not exposed to a differential pressure .

 

[doct9960]

sree60,

What type of internals? After hydrotest, do you have access to dry out the water in the vessel and on all the internals?

 

[unclesyd]

We have tested numerous SS pressure vessels with the internal in place with no problems.

Not mentioned in the above post is the importance of using low chloride water for testing. I don't know the current line of thinking is but our requirements were less than 20 ppm Chloride..

 

[sree60]

Hi All

Thanks for the generous inputs

The vessel is a flare KO drum ( dia 6 meters)and we have inlet vane diffusers as internals. We do have CFD report
( computational fluid dynamic )However we are checking with vessel internal designers to confirm if the internals are designed to take hydrostatic test loads .
The vessel expansion during hydrotest , requirement of water to be drained and dried, are valid points to be considered. Chloride content in water is meeting the requirements.

Sree 60

 

[JohnGP]

The CFD report would cover operational issues, not hydrotest. As has been highlighted above, the internals should not be subjected to differential pressure so not a problem. Inlet vane diffusers shouldn't affect shell loadings during hydrotest either. Some years ago I saw some separators tested - these had inlet diffusers, substantial rings for packing support, and other stiffening elements (pipes that went laterally though the vessel) - and they survived the hydrotest.

Cheers,
John