Tank testing question
 

Hi Everyone,

Testing my first tank. I'm using the balloon method. I was having a hard time getting the balloon sealed properly so I used a piece of 3/8 tubing over the vent tube fitting with hose clamp and then zip-tied the balloon on. After some pieces of electrical tape, it seemed to not be leaking anymore.

I did the kids bubbles test twice with no signs of leakage. The balloon deflates over a period of 3-4 hours but never fully deflates, it just has a light pressure on it. If I squeeze it, it deflates and then goes back to the same size.

Anyone else experience this? I just want to make sure I'm sealed so I can build on.

Thanks for the input!

It takes very little temperature change for the balloon to change in size over time, both directions. I pulled my tanks out of a shaded hangar onto the sunny ramp and my balloons filled up fast! The balloon method is kind of rough but if you did the soap bubble test along all seams you should be good.
Most leaks I see are slow seeps over time. Very difficult to test for those unless you fill them with fuel and let them sit over time. I wouldn't recommend it due to the obvious hassle and hazards. If it was me,I would consider them ready for use.

I didn't like the balloon test as all of them leak on their own through their skin, some faster than others and make it tough to get a good sense of leak vs no leak. I recently went to the store and bought a length of clear tubing and made a manometer and the tanks both held pressure for a week each then I disconnected the tubing. 100% sure now of no leaks.

Thanks. I did the test in the late morning knowing the garage would warm more as it got later. So while expecting to see it inflate further as it warmed it was the opposite.

Much better and easier to just take a long section of clear vinyl tubing and make a manometer. Make a "U" shape hanging down and put some water in the tube. Inflate the tank just enough to push the water down about a foot as compared to the other side of the U. You will see the water level go up and down with the temperature and barometric changes, but unless the levels on both ends of the tubing go to the same level (ie, a leak) then you can be sure your tanks are OK.

Well, sounds like a trip to ACE is in order so I can sleep easy.

Thanks everyone!

All the balloon is supposed to do is hold pressure while you do the soap test. The soap test, properly done, will identify any leaks.

Allen, The balloon is just a good way to hold some pressure and not risk damaging the tanks. There are several tank pressure test documents from Vans,
See: http://www.vansairforce.com/communit...highlight=tank

The manometer test is good, but tricky. Perfect if you want to soap all the joints for leaks. Tricky if you want to use it as a leak detector like I did.

Using a manometer, the difference between the column heights is the air pressure. 12 inches of water pressure is 6" deflection from zero. Use no more that about 30 " of water to do the test. You might see bulging even at that.

Then, you can bubble test all the joints. A tiny leak will bubble a lot. Good luck.

As has been mentioned, the balloon is not meant to "test" for leaks. For that matter, a manomometer is not all that good for finding leaks either. It is much too sensitive to temp and barometric pressure. Soapy water in a spray bottle while the tank is sealed and a small amount of air pressure is applied to the tank (1 psi is plenty) will tell you if you have leaks. Think of the balloon as a "relief valve" for when you pressurize the tank. If too much pressure the balloon will burst before any seams on the tank.

Yes, sorry about not being clear with the balloon - it by itself is not the test for the leaks merely acts like an over pressure valve so you can test. The issue with the spray bubbles it that a very slow leak won't be that obvious as to create lots of instant bubbles, it may take a while for a bubble to form and if the balloon is slowly leaking down through it's membrane, you may never see the bubble before the pressure is lost. The manometer does not leak pressure but does change levels in relation to temp and atmospheric pressure changes but unless the level on both sides of the tube end up level, the tank is holding pressure and not leaking. You can set it up and come back a week later and get valid results.