Pressure testing a Petrol tank

Can anyone tell me how a petrol tank would be pressure tested to identify leaks, and is it something that can be done on a DIY basis?

Thanks

Peter

I have tested (and found leaks ) on the T100 tank. I cut the valve section from an old inner tube, tied a knot in one end and tie wrapped the other round the filler cap. With fuel taps fitted and closed, I connected the the valve to an electric pump with the pressure set to its lowest limit. It doesn't need much air pressure in there and you can totally destroy your tank - take it easy! With the pump running, I painted along the seams with a strong soapy water mixture. The bubbles show the leaks.

The hard bit was trying to plug the leaks!

David

I tested a tank that I built by using a bicycle tire pump. Get the necessary fitting to thread an ordinary tube type valve stem into one of the fuel tap bungs. These are available at low cost as they are a standard item fitted to a well water pressure tank. Put a plug in the other tap bung unless you are certain that that fuel tap shuts off totally. Plugging up the filler neck requires some imagination. I used a solid plug cut out of a piece of 2" thick wood, the cut done with a hole saw. I stretched a ballon over the bung so that it would easily seal when tapped lightly into the filler neck.

You do not want more than about 2 lbs air pressure max, even a pound will do. Do not use an air compressor supply and tire inflater, this method destroys tanks instantly. A friend spent $6,000 having a very rare fuel tank taken apart, pounds of lead filler removed, much body work done, put back together, resoldered, gold leafed and painted.
He then blew the tank up with a tire inflator, looking for a leak which turned out to be in the petcock, not the tank!
He is now up to $10,000 after sending the tank to the Ross Thompson sheet metal hospital (beautiful work) and yet another gold leaf/ high end paint job.
I found that twenty strokes of the bike pump gave about 1.5 lbs. Pressure, however yours may differ. The only way to be sure is to fit an accurate low pressure gauge into one or other bung. Even with the bike pump it is fairly easy to destroy a tank. I have another friend who built his own al. tank then destroyed it while checking for leaks with a bike pump. He pumped the tank up to 15 psi, much too high.

Once the air was in, I immersed my tank in water, same as is done to find a leak in an inner tube.
If you think you know the general area for the leak, as an alternative to submersing the tank (best) you can make up a small dish of soapy water and brush it on the suspect area(s) . This, plus pressure leakdown tests, is how gas fitters check for leaks.

Glen

Saw a tank that had been 'pressurised' from a compressor, supposedly at very low pressure.
Had spread out and opened its wings out flat, like a butterfly !!! Ooops.

That bicycle pump sounds like a good idea....

Guys. Great advice and ideas! I get the message "take it easy"

You can seal up the top with a plumber's hole plug from McMaster-Carr. One way to test a tank without worrying too much is just to seal up the tank and submerge it in the bathtub with hot water. The water will warm the air in the tank creating some positive pressure and any leaks will be seen as bubbles in the tub. (Wait til your wife leaves to avoid the questions.)

batrider said:

You can seal up the top with a plumber's hole plug from McMaster-Carr. One way to test a tank without worrying too much is just to seal up the tank and submerge it in the bathtub with hot water. The water will warm the air in the tank creating some positive pressure and any leaks will be seen as bubbles in the tub. (Wait til your wife leaves to avoid the questions.)

Click to expand...

Hey, thats clever, well apart from having to use the bathtub

What is a plumbers hole plug? I'm in the UK. Is it one of the low pressure test plugs shown on the McMaster site?

Old Bloke said:

Can anyone tell me how a petrol tank would be pressure tested to identify leaks, and is it something that can be done on a DIY basis

Click to expand...

IIRC the proof testing rule here in Germany is 0.3bar (1.3bara) for 1/2 hour submerged under water at room temperature or somethink like this. No big deal.


Tim

Old Bloke said:

batrider said:

You can seal up the top with a plumber's hole plug from McMaster-Carr. One way to test a tank without worrying too much is just to seal up the tank and submerge it in the bathtub with hot water. The water will warm the air in the tank creating some positive pressure and any leaks will be seen as bubbles in the tub. (Wait til your wife leaves to avoid the questions.)

Click to expand...

Hey, thats clever, well apart from having to use the bathtub

What is a plumbers hole plug? I'm in the UK. Is it one of the low pressure test plugs shown on the McMaster site?

Click to expand...

The low pressure test plug should work fine. The one I bought was the long stem version with bypass. I threaded in a valve stem on the bypass to pressurize the tank (and monitor the pressure) but found it really wasn't necessary. When I tried using a bicycle pump to pressurize it the tank was fine but it shot the plug out from the filler neck and it hit my living room ceiling with some force and a big bang. (and that sucker was heavy cast iron!) I knew enough not to pump it up like crazy but even at <3-4 lbs it really went off. That alone convinced me that this shit is trickier than it seems and to stop right there.

I used the dunk method also, but with a big Rubbermaid tub. It was key to finding a leak along the pinchweld.

On my T120 tank I put the petcocks in, put a big stopper in the gas filler and hooked up an old airbrush compressor to one of the petcocks. I closed one petcock and opened the one that was attached to the air brush compressor, put the tank in water and plugged in the compressor. Then bubbles were easy to see.

If you have a flip gas cap a piece of garbage bag between the lid and tank may seal it. You want to keep the pressure around 1 psi. An aquarium pump may work too.

Dave