pneumatic testing of fuel oil tank?

[vesselguy]

Hi,
I was just gogling the web for tank failure reports for use as a safety topic discussion when I came across an environmental and installation guideline by a government body in a country (I won't say which)that says "preferably, a fuel oil tank should be tested for leaks using a pneumatic test."

I would NEVER pneumatic test a tank nor a vessel, if it can be avoided. Is there something special with fuel oil that the tank that contains it is "preferably" pressure tested instead of hydro? I can't think any special reasons. Others may know more.

 

[gr2vessels]

vesselguy,
You are correct that the hydrostatic testing of a vessel or tank should be preferred over the pneumatic test. However, the small domestic oil fuel tank you mentioned for pneumatic leak test, could hardly qualify for dangerous test, since a party baloon would hold more pressure than the oil storage tank test pressure, if the test is conducted by professional tester/engineer. Also, i balieve that the pneumatic test mentioned in the document refers to any subsequent testing, after years of service (not the obvious manufacturer's code testing), when the owner is encouraged to test for any small leaks, before the leak would escalate in full size burst of the tank. I think the document is addressed to the average home owner in the middle of nowhere, not to the ASME/API design engineers.
Again, to you right, it doesn't seem to address the most sensitive issue, the level of compressed air pressure used for the test!!. Most of the domestic air compressors would blow a such tank to bits, if full pressure is applied on that tank (perhaps the indicative test pressure is being specified in a hidden part of the document or in another referenced document...). I also found this document a harsh punishment for the amateur installers/users of these oil tanks, since the amateur tester could easily hurt hiself or/and others, if only follows the instructions in that document...
cheers,
gr2vessels

 

[vesselguy]

gr2vessels,
Thanks for your reply. No, that document was written to people like us in the industry; not home owners. As for tank size; I don't know if it was refering to small tanks. I didn't think there is any thing special about fuel oil application that makes pneumatic test a better choice. I thought others might know something I didn't.

I can show you couple of photos that I'm using for my safety talk that shows what looks like an 12' dia x 20' tall API tank that got launched to the 3rd floor of a refinery in Brazil during an in-situ pneumatic test. Pneumatic testing of a tank, regardless of size, without due care on overpressure is a formula for disaster.

 

[gr2vessels]

http://www.esans.eca/pdf/oiltankinstall.pdf

This is the one document I mentioned, but this and the similar ones issued in Nova Scotia for heating oil and the like, are realy dangerous. The wording is also open to interpretation, eg.:

"All aboveground fuel oil tanks are to be installed bearing a visible label:
a) in accordance with the National Standard of Canada CAN 4-S602, latest edition, “Standard for Aboveground Steel Tanks for Fuel Oil and Lubricating Oil” as revised, amended or
substituted; or
b) in accordance with the National Standard of Canada ULC/ORD C80.1, latest edition, “Aboveground Non-Metallic Tanks for Fuel Oil” as revised, amended or substituted."

That is, once I have erected an old bucket, all what I need is a sticker to write these words on it, to comply with this document (not with the referenced codes!). It does not stipulate who can affix the label, so anyone can do it...

Obviously, there is no disagreement with regard to the code oil storage tanks and their testing. Safety first.
gr2vessels

 

[jhdjhdjhd]

Vesselguy,
Just wondering if you are aware of any industry safety guidelines or policies for performing pneumatic leak testing on tanks/vessels. I am particularly interested in what would be appropriate and safe practice for performing pneumatic leak testing on a small, non-ASME Code vessel like a water tank from a concrete mixer truck.
Thanks!

 

[eliebl]

Speaking of water tanks from Concrete Mixing Trucks...

http://www.absa.ca/IBIndex/IB05-002.pdf

Regards,
EJL

 

[MJCronin]

For factory made, production type fuel oil tanks, it is common to provide a 2-5 psig "air test" or air check"

From this site:

http://www.storage-tanks.com/html/steel.html

"The steel Horizontal Single-wall UL-142 tanks are primarily designed for storing flammable and combustible liquids and use a single sheet thickness of steel meeting ASTM specifications. ..... Flat-flanged heads, continuous exterior fillet welds on all joints, and a 5 psi factory air test and seam inspection ensure quality."

The state of NY seems to encourage pneumatic "checks" (tests) of fuel tanks, particularly when ownership has changed

(see page #9 of this document:

http://www.dec.ny.gov/docs/remediation_hudson_pdf/tbws2005.pdf

)

And New Jersey seems to allow/encourage the practice:

http://www.state.nj.us/dep/rpp/download/tanktest.pdf

(see page 5)

Its required by the USArmy ( page 23)

http://cbbs.spk.usace.army.mil/PDF/15176.pdf

Anybody...?

-MJC

 

[vesselguy]

jhdjhdjhd,

I did not see your question to me until just now, so sorry for the late response.

No, I do have nor have I seen any industrial standard for pneumatic testing of tanks. I have, however in the past, written a proceedure and scope work for pneumatic testing of a Reformer furnace P-91 tubing and connected piping. I would apply the same concerns to a vessel. the proceedure was accepted/approved by my local Boiler Authority. I can give you a basic summary as follows:

1. Never do a pneumatic testing unless there no alternatives.
2. Have a qualified professional engineer to calculate the test pressure and check membrane stresses. The PE shall also write a detail proceedure for the test and have the proceedure reviewed by applicable group, and with input from the Pneumatic Testing Contractor that will perform the test.
3. Determine the ductile to brittle transition temperature of the material you're testing. Specify that the skin temperature must be at least 10°C above this temp. If necessary, like testing during winter, provide hording with heat supply by blown in hot air. Preheat the test medium (air or N2) if necessary, again the point is you must ensure the metal skin temp is above the brittle transition temp.
4. Calculate the equaivalent TNT explosive energy and include that in your report and proceedure. Determine the safe distance radius and specify that all personel to not be within this distance during testing.
5. Specify your ramp up proceedure. Tape up all flange joints. Poke a pin hole in the tape at flange join.
6. Ramp up with 25% test pressure to perform visual leak testing at the pin holes. You can use a soapy water solution to detect leak. Slowly pressurized to 50% of the test pressure at test temperature and then increased in increments of 10% until the test pressure is reached. When leaks are identified the pressure shall be reduced before flange bolts shall be torqued up to stop the leak. Where the leak cannot be stopped inspection for evidence of other problems shall be carried out; this may require depressurizing and stripping.
7. Best way to present the pressure ramp up is to show in on a diagram or graph. A picture is worth a thousand words.
8. HAZOP the hell out of the entire line/equipment.
9. Specify isolation blind locations isolate test pressure to only the equipment/piping you want to test.
10. Specify a walk through proceedure so nothing is missed before a test. I specified a double walk through.
11. Specify the test be done on a day where most plant people are away, if that is possible. If not, get Manager to limit personel access to the area for the duration of the test. Idea is to limit the number of people you kill.
12. Present the plan and proceedure to your local boilers branch for acceptance.
13. Do the test. Make sure you're away on vacation that day or leave the proejct before that.

Hope this helps.

 

[vesselguy]

jhdjhdjhd,
I forgot the most important part.

Specify pressure monitoring method and provide pressure relief valve on the equipment or air inlet line.

 

[jrjones]

For standards used to perform air tests on vessels that consider stored energy, etc., there is a decent document developed by NASA. I will try to find the document and attach it in a follow up post.
It was used to show management at the refinery that used to work at that air testing (~250 psig) of a reformer furnace was effectively insane! The NASA doc tries to estimate the "blast" zone which should be cleared during the air test. It was very large and impractical.

Anyway, will have a look for the pdf.

Cheers
jrjones