Pneumatic test of atmospheric vessel

[ElCidCampeador]

Hello, I have a horizontal vessel O.D.=2,5m Lg.=4m Thk.5mm material carbon steel.
Design/operating pressure=atm, fluid=oil.
My client wants to check leakage with a pneumatic test. What pressure test do you suggest to adopt?

There is no construction code, it's only good construction pratice and hydrotest is not accepted. What do you say? Thanks

 

[SnTMan]

ElCidCampeador, some guesswork on my part here: Vessel has flat heads and is designed for Zero gage pressure.

If so, I'd expect you could apply a pressure equal to the vessel static head. I suppose you'd bubble test?

Alternately, you could perform an analysis to arrive at a higher pressure, or perhaps perform a helium test at a low pressure.

Regards,

Mike

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

 

[chicopee]

what type of heads do you have on that tank?

 

[LittleInch]

Your design pressure is atmospheric, but you want to do a pressure test?

hydrotest is not accepted? Why?

If you air test this you will need such a low pressure ( inches water column) you might not find any leaks.

You could try a helium test? e.g.

https://www.tqc.co.uk/our-services/leak-testing/helium/sniffing/

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

 

[ElCidCampeador]

Heads=elliptical
Medium test=air
Water not accepted

My opinion is to test @ minimum pressure (I don't want any kind of problems)...what about 1 barg?

Regards

 

[LittleInch]

Only if you want to destroy your vessel or kill someone.

What part of "This thing is not designed to hold pressure" don't you understand?

At 2.5m diameter the force on the end heads is 50 tonnes at 1 bar. It's 5mm thick.

No one here can stop you doing what you want, but this has a very high probability of going horribly wrong. IMHO.

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

 

[david339933]

3 - 5psi max. (bubble)

 

[ElCidCampeador]

Could you please someone explain me very briefly what are the risks of a 1 bar hydrostatic test vs 1 bar pneumatic test, for this specific vessel? Thanks

 

[SnTMan]

Stored energy

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

 

[ElCidCampeador]

Stored energy

This is ok, I understand that damage for an explosion due to wrong pneumatic test pressure could be much more high than hydrotest one...but in my case I calculated minimum thickness acc. to ASME VIII Div.1 (only to check) choosing pressure design equal to 1 bar and minim thickness required is something like 1mm...5mm>1mm so why do I have to be worried about?

 

[LittleInch]

Sudden catastrophic failure.

Hydro you might get wet.

Pneumatic you might get a dished end flying at you.

But any test on a vessel "designed" for atm pressure above atm pressure has risks of failure. Your statement "there is no construction code" doesn't fill me with delight either.

But you seem pretty determined to do this so I'm going to wait for your next post saying you've done it and it's all ok. Maybe it will, but it doesn't make it a good or technically correct idea.

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

 

[SnTMan]

ElCidCampeador, I read your OP as though no calculations had been done, and you were looking for "educated guesses".

...you could perform an analysis to arrive at a higher pressure...

If you have done the calculations and are confident of the results, then by all means, go ahead. From that standpoint, no difference between hydro and pneumatic pressure.

Regards,

Mike

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

 

[r6155]

1) The maximum pneumatic pressure is 25% of the design pressure. So the air pressure is 1 psi
2) Customer approved design calculations and written procedure for this test
3) Only if welding procedures and welders are qualified.
4) I suggest that the Client witness the test.

@ ElCidCampeador : you are some confused
Did you do any inspections or NDEs during manufacturing?

Regards

 

[SnTMan]

r6155, "1) The maximum pneumatic pressure is 25% of the design pressure."

Where you getting that?

I think your requirements are more than needed to leak test a smallish vessel at a low pressure.

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

 

[r6155]

@ SnTMan
See ASME V
T-1044 PRESSURE/VACUUM (PRESSURE LIMITS)
Unless specified in the applicable Mandatory Appendix
of this Article or by the referencing Code Section, components
that are to be pressure-leak tested shall not be
tested at a pressure exceeding 25% of the Design
Pressure.

Regards

 

[SnTMan]

OK I suppose, but it would be justified to say ASME V need not be applied to this non-Code oil tank.

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

 

[r6155]

SnTMan
I only answer your question. Do you have any alternative?

Regards

 

[SnTMan]

Yes, thank you, I am not familiar with ASME V.

I think if ElCidCampeador has confidence in his calculations he should leak-test this tank at any pressure up to the value used in the calculations. I think he should involve the client or not as suits the relationship.

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

 

[DriveMeNuts]

Establish a pneumatic test pressure and conduct that test safely (without any personnel standing next to the tank).
Then drop the pressure to half and conduct the leak test.

 

[r6155]

a) @ DriveMeNuts
You are some confused. Leak test is not similar to hydrostatic pressure test. Leak test is not to check the structural integrity. Please take a look on ASME V.

b)I insist with my post 7 Jul 21 17:53 3) Only if welding procedures and welders are qualified.

c)Instead of doing the pneumatic pressure leak test it is the vacuum box test. But this test requires the box to accommodate circumferential welds and nozzle welds. Risk-free with the Vacuum Box test

Regards