Pneumatic Test 5

[St sh]

There is a Tower that has been make from SA-516 70 with diameter 5700 and length 15 m.(MAWP=12 bar)
I have a question about pneumatic test.according to ASME CODE UG-100 we can do pneumatic test in lieu of hydro static.
but we have never done pneumatic test at our shop.
Please help me if there are points about pneumatic test and its dangerous?!

 

[DekDee]

No problem at all.
Just make sure you and your family are in a different town when you do the test.

 

[LittleInch]

This has been discussed a lot. Search for pneumatic test and things like this turn up.

http://www.eng-tips.com/viewthread.cfm?qid=348164

That is one big vessel to do an air test on at 12 bar. The consequence of failure would be very extensive and I would struggle to see how anyone would permit this to occur. Doing it in a quarry with no one within 100m might be acceptable....

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

 

[mk3223]

Based on the risk management, by considering the failure likelihood and severity, the hydro testing is better than the pneumatic testing. IMO, your shop have used a right procedure for the testing. You can google online and see many failure events associated with the pneumatic testing.

 

[zdas04]

I am always the advocate for pneumatic tests in this forum, not this time. The gas that can participate in an explosive decompression must be less than 25 mS from the failure at sonic velocity. That says that the energy from any gas within about 10 m from a failure would make the explosion bigger. There are a lot of failure points in this vessel that the entire volume would add energy to the explosion. That works out to a big explosion risk that really isn't justified. The hydrostatic head of the full vessel is about 1.5 bar. If you are testing to 150% of MAWP then you can set your test gauge at the bottom which will leave the top at nearly 140% of MAWP. Do the hydro.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[St sh]

Thanks for your all response.

 

[LittleInch]

The only thing you might be able to do is a very low pressure test ( say 10psi) to check for leaks, bubbles etc round welds and flanges. Or add some helium or other gas you can "sniff"

full scale air test to > 12 bar? Nope.

What are going to do next?

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

 

[St sh]

Dear LittleInch(Petroleum)

Thank you for your nice guidance.I told our CEO that we could not use Pneumatic test but he insisted on this matter.I wanted to investigate about Pneumatic test and found major reference.now we are going to test with water like before.

 

[DSB123]

Setareh sh, if your CEO insists on a pneumatic test then ask him to conduct the test. Sit him on the top of the vessel with the air filling valve located within arms length. Then you and your work colleagues should vacate the facilities and make sure you are around 1 mile away. Call the CEO on the phone and tell him to open the air filling valve to fill the vessel to the 12 bar test pressure.

 

[St sh]

Dear DSB123
This is an good point......

 

[DekDee]

Years ago when I was on the tools I spent a bit of time on Alumina Refineries.
Caustic everywhere.
We would cut in to a pipe that was supposedly isolated and hot caustic was shooting everywhere.
We were contractors and we quickly lost confidence in the plant operators as to what was isolated and what was not.
New MD came on the plant, heard what was going on and demanded his area managers take responsibility, climb the scaffold and sit beside the fitter / welder whilst they cut into the pipe.
Never had any problems after that !!!

 

[GD2]

Shetareh Sh,
I will calculate the TNT bomb in terms of lb/kg the test will generate and the safe distance required to perform the test over the weekend.You can then present the bomb to your CEO to convince him out of the pneumatic test.
This is somewhat weird. People ask for hydro instead of pneumatic test and here is a reverse case.
My understanding is that the tower is fabricated in your shop, there is no internals installed and the tower will be tested horizontal on the floor. My main concern is the refractory. It becomes extremely difficult to dry refractory after hydro test. What's the service?
Give some more details.

Ganga D. Deka, P. Eng
Canada

 

[LittleInch]

DSB,

your comment reminded me of one of the key points in the film Dr Strangelove....

See attached.

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

 

[Gator]

I don't see where refractory is mentioned in any of OP's posts.

 

[GD2]

Setareh sh,
Whats the design temperature and service of the tower?

Ganga D. Deka, P. Eng
Canada

 

[GD2]

Satareh sh,

Here is my calc for the pneumatic test with Air/Nitrogen:

Test Pressure: 1320 kPa
Minuimum Safe Distance required between all personnel and tested equipment: 114 metre
Stored Energy: 186 Kg of TNT.

To pneumatic test this size of test, you will need:
1. A Test plan approved by senior management
2. If air, must be oil free
3. 114 meter radius for safe distance. Possibly, you will plan to do the test in a weekend.

Assumptions:
1. The 114 meter of safe distance is calculated based on - if a failure occurs, only glass will break of the nearby building. There will be no biological or any other structural damage.
2. The calculation is valid only upto the tower design temperature of 38C (100F). If the design temp is higher, the test pressure, the stored energy and the minimum safe distance will increase and requires recalculation.

Try to walk out your CEO out of the pneumatic test by giving him the numbers.

Hope this helps.





Ganga D. Deka, P. Eng
Canada

 

[DSB123]

GD2,
Test Pressure quoted by OP is 12 Bar = 1200 kPa NOT 1320 kPa. If you got the basic number wrong I don't think we can trust your other figures either!!!

 

[DekDee]

DSB123,
You shouldn't be so quick to criticise.
12 bar is noted by OP as MAWP - not test pressure.

"There is a Tower that has been make from SA-516 70 with diameter 5700 and length 15 m.(MAWP=12 bar)"

Please correct me if I am wrong but 1200 kpa x 1.1 will be pretty close to 1320 kpa

 

[DSB123]

Well Spotted DekDee - so sharp you might cut yourself!!!

 

[Compositepro]

Using lbs. of TNT as an energy unit is rather meaningless, and is merely intended to scare people who do not know better. The gas tank of a truck contains about as much energy and does not cause much concern. A flying bullet, in comparison, contains virtually zero energy, yet is of far greater concern. It is all in the details, which are completely obfuscated with the TNT comparison.