Pressure testing integral fiberglass diesel tanks

No, not really but ask the same question about three PSI (I lost a friend to an oil filter cannister on a tugboat because he pressurised to two PSI to drain quickly and forgot to take off pressure before removing the lid. You know this can happen. That is why you tailored your question to 1 PSI. You are snide and fairly sharp - but not sharp enuf) What you want is someone to do your homework for you and tell you that you didn't screw up in building your tank. I've done your homework for you and you will get a passing grade - but will you have learned anything? No. No, because you are but another troll in a long line or came here hoping to have someone tell you that 1.5 is great for FRP. It is not, as you learned in the very first response.

 

this is typical, some dont want to hear, some do not wish to learn either
We have two diff topics going here, one boiler hydro testing, HP the other fuel tank testing Lo press, nobody argues abt hydro testing of boilers but that was not the question
You can say all you want, , and the guy does not even say thanks for input

 

Thanks Mark775 for the link to CFR183, which I had already read, but the version I had was text only and was apparently incomplete. It is the information on page 7/8 of this version and on page 92.

As for the "test with water" camp, I would refer them to the test procedure page 89 "fill the tank with air or inert gas to the pressure...) This is section 183.580(a)

No intention to do destructive testing on my part. Now that I have the precise procedure I was seeking, having failed to find it previously, but having gotten awful close, other than having found an incomplete version of the appropriate document, I am now set. Thanks again for the URL.

And so much for water testing and internet opinions.

 

I am glad you researched that, here is another link
http://www.nmsc.gov.au/documents/fuel tank.pdf
In fact all class societys use this method, can you imagine filling a 20000 tonne tank with water to test it
Some people are not informed and are just guessing, you have found this out, good luck with your tanks 2-3 psi will show the minunetest leaks, mark the tube with a felt tip and watch it , leave it overnight, because once you have put fuel into anything made other than steel; it is too late to fix a leak
here is a SA guv dwg

http://www.dtei.sa.gov.au/marine/su...ressure_Testing_of_Pontoons_or_Fuel_Tanks.pdf
there is no need to calibrate or be that accurarate all you are doing is looking for a pressure drop

http://www.iflyez.com/manometer.shtml

 

The difference is that water is incompressible, the pressure is built up by compressing tiny air pockets trapped in the system or by forced hydraulic expansion of the envelope. Air is a gas and follows the Gas Laws, P X V / T = k.

The other difference, as I mentioned earlier is that air will show a leak through a pinhole that would need to be seven or eight times bigger to show a leak using water.

Leak-testing, not hydro-static testing, of completed hydrocarbon systems is done using a nitrogen/helium mixed gas. The molecules of helium are so small that they will escape through gaps that will not let any other gases through. The potential leak area is taped up and a suctiuon probe inserted. This is fed to a spectrometer that gives a ppm reading for any helium found. It is quite normal to find helium coming through even the tightest joints. As long as it is below a certain threshold the joint is good for hydrocarbons.

 

Having the correct procedure does not change the fact that your tank was showing signs of deforming at 1.5psi. You have to ascertain if your tank needs reinforcement or if you are reading correctly, or are getting a proper reading, at your gauge.

I would test the gauge against a manometer before I would risk putting any air in the tank again. If your gauge is correct, then reinforce your tank before proceding. Only calibrated gauges should be used on pressure testing as, even at such low pressures, damage and injury can result.

 

sometimes when pressing up metal tanks the top will go Boing!! As for GRP, How do you know when the tank will just burst? At lo pressure, 1.5 psi as you say, , standing clear, I can not see what it could do, , split? shatter, , ??
Admittedly sticky stuff is not in my language)

 

I agree that it is a low pressure, but in his opening post he said it was "well domed" at 1.5 psi. It is a fairly large tank, 95 Gals, so it may need supported or reinforced in some way to keep its shape. If the wall/top measures 50" X 20", then at 3psi this tank's adjacent sides are being subjected to forces totalling 3000 pounds, so yes it could split or shatter.

My other concern is that he may be misreading or using a defective gauge, a good reason why a manometer should always be used for this kind of testing.

 

Testing tank

I agree with Whoosh. When we were building boats in a Lloyds Certified yard, we were filling up the tanks with water through a hose connected to the filler inlet, all vents plugged off. Requirement was we fill up with up the level (head) we will be operating. Sometices, the added added hose pipe goes up vertically to 20 feet. We use blue dye for leak test.

For air test on integral tank (can't remember which rule) we pressure test it to 1.5 psi then hold it for several minutes and see if the pressure holds. If it doesn't, the tank has a leak. If it domes, then there is not enough stiffness. Strong maybe but not stiff.

Also the tanks has to be subdivided as a rule. The divisions adds to the stiffness.

Rx

 

Like 1 pound of lead and 1 pound of cotton? It is the same unless someone argues about the use of troy and avordupois system.

Rx

 

THE USCG on Subchapter T (passenger service) allows a simple hose filled above the tank to create water pressure.

The head (PSI ) from each foot of water is well known .

I seem to remember 11ft is 5psi , but its been too many years.

But the system does work.
\
FF

 

No, it is not the same. The test medium can sometimes be of critical importance. Read my previous post, six above you, I think.

 

You're about right with your pressure/head conversion. If you can remember back to your schooldays, standard barometric pressure was 30" Hg, or 14.7 psi, or 33 ft of water head. I just found a table here, View attachment FeetHeadofWatertoPSI[1].pdf

 

They must have to test polyethylene fuel tanks to the same pressures as others. It's hard to imagine one of them not expanding and doming.

It's informative and humorous to watch Mark775 call Petedd a dink, stupid, ignorant and ungrateful and then his own link backs up Petedd 100%.

 

It is the mark of an educated mind to be able to entertain a thought without accepting it."
--Aristotle

In other words... different opinions are always welcome, vituperation on the other hand is evidence of a lack of valid positions.

Back to working on the tank...