ASME External Presssure Test

[Karloss12]

ASME VIII Div1 makes no mention of external pressure testing of pressure vessels.

Does anyone have any advise here? Is this a use your common sense situation?

I am designing an off shore vessel that needs to operate at 200 metres of depth.

ASME specifically specifies 1.3P for internal pressure and for multiple compartments but nothing for full external pressure of a vessel.

Our biggest problem is we're having trouble finding a 3rd party inspector who is willing to climb inside during the test to conduct the check for leaks.

 

[SNORGY]

See ASME Section VIII Division 1, UG-28 & UG-29; along with ASME Section II Part D Sub-Part 3.

The methodology is sensible and pretty straightforward and surprisingly user-friendly, not characteristic of other sections of the Code.

Failing that, apply Timoshenko's formula for elastic collapse of cylinders (or Haagsma's Equation for full plastic yielding) and divide by 3. The former of those two is the approach used by L.C. Peng in his book.


Regards,

SNORGY.

 

[SNORGY]

However, I should have read your OP carefully because you did say *testing* to that external pressure. Short of putting the vessel being designed inside a bigger one and then pressurizing the bigger one, I don't see a practical way of doing it. I would just do the design calculations.

Here is one website link I found...



Regards,

SNORGY.

 

[trottiey]

You might want to refer to ASME PVHO-1.

Stress is a biological mechanism that improves strength at the expense of thought. It is counter-productive to solving technological problems.

 

[bcguy]

Karloss12

For your information, the 2011 Addenda of ASME Section VIII Div.1 will include a change in UG-99(f) to allow for vacuum testing in lieu of hydrostatic testing for vessels in vacuum service only (MAWP <= 0 psi)

Action covers vessels that cannot be internally pressure tested because of design/operational issues.

I think a Code case has or will be implemented for early use.

 

[Kiwi2671]

karloss12,
Please excuse my ignorance but why would you externally pressure test the vessel ?.
Submarine pipelines are hydrostatically tested every day with no problems.
Surely you will achieve (hopefully) exactly the same results (no leaks) whether it is internally or externally pressurised,
Regards,
Kiwi

 

[cloa]

Would an API code be more relevant?

 

[Karloss12]

Thanks for your comments.

It is for the Diving industry. PVHO-1 does have a procedure for manned submersibles. I am trying to find a procedure or guidelines for general vessels for unmanned rovers etc.

 

[OSIRIS7]

The hydrotest is NOT a leaktest, it is a STRENGTH test, so please do NOT insert inspectors inside when doing such a strength test.;-)

200mtrs is 20 bars of external pressure. I would recommend to do a strength test acc. ASME regulations at 1.3x design pressure. How you do it? I think you need a bigger tank.... Or you could sink it to a depth of 260mtrs. If it does not collapse, nor any dammages are done to the vessels, it should be ok. A leak test does seam a bit odd to me. If it MUST be done do it with internal air pressure and bubble test. When you are sinking to great depth all closures fitted to open outwards will be pressed even harder on the gasket.