wcalvert
Well Known Member
I've been looking hard at a way to provide a safe stable pressure to my new tanks while they are being tested with the soapy water method. It seemed like too many builders have used a balloon and then found later that there were leaks that went undetected.
A reputable source familiar with the RV series told me that the "design" pressure of the tanks was about 3 psi, with failure pressure being about 5. My goal was to find a way to produce a 2 psi test pressure without destroying the tank. I think the tank should never be anywhere near 2 psi, and if they will pass at that pressure they should not leak.
Looking at the photos (hopefully), you can see that the tank uses a column of water to measure (and limit) the pressure applied. Compressor air, stepped down through a local regulator allows the pressure to be raised slowly, until the water column reaches the desired height or overspills the tube. Add air slowly to allow the tank to pressurize and give the water time to head up the tube. Leave the tube open and cut the top off at the desired height (pressure) so that an inadvertent high pressure will simply blow out the top.
https://lh3.googleusercontent.com/D...gELWbkvPVjVtz2o_t3cSoEU-tai65elQ=w696-h928-no
https://lh3.googleusercontent.com/6...xs4nw9aWcyInsiDHsAxjczBBR-LEB9Q=w1238-h928-no
https://lh3.googleusercontent.com/_...56Q9cpq0D3RfVzlNQ-lQKMpaGQBKbiA=w1238-h928-no
(Air goes into the "Fuel Out" tank fitting. Air comes out of the fuel tank from the "Vent" fitting into the top of the soda tank. The water column comes out of the soda tank via a dip tube that reaches down to the bottom. About and inch of water in the pressure tank acts as the source of fluid to travel up the sight hose.)
A quick calculation shows that a 55" water column equals 2 psi. I backed off a bit and used 46" to be a little conservative (1.7 psi). At that pressure the skit on the rear baffle bulged ever so slightly, I could press it down with my finger and feel a little give. The tank didn't make any sounds or creaks. They look straight and normal after the test.
The only leaks I discovered on my tanks were around the filler cap. At this pressure no tape I used would seem to seal the cap. I tried the trick of putting a glove over the cap but that only helped slightly. Remember that the purpose of this test is to create a pressure while you spray a soapy solution looking for bubbles. The tank will leak down eventually.
The equipment I used was from my beer making kit, so the soda tank with a dip tube was just the ticket for this job. Maybe you have a friend who brews that would loan you his keg for a day?
My next test will include pressurizing about a gallon of 100ll with some UV tracer dye. More to come...
A reputable source familiar with the RV series told me that the "design" pressure of the tanks was about 3 psi, with failure pressure being about 5. My goal was to find a way to produce a 2 psi test pressure without destroying the tank. I think the tank should never be anywhere near 2 psi, and if they will pass at that pressure they should not leak.
Looking at the photos (hopefully), you can see that the tank uses a column of water to measure (and limit) the pressure applied. Compressor air, stepped down through a local regulator allows the pressure to be raised slowly, until the water column reaches the desired height or overspills the tube. Add air slowly to allow the tank to pressurize and give the water time to head up the tube. Leave the tube open and cut the top off at the desired height (pressure) so that an inadvertent high pressure will simply blow out the top.
https://lh3.googleusercontent.com/D...gELWbkvPVjVtz2o_t3cSoEU-tai65elQ=w696-h928-no
https://lh3.googleusercontent.com/6...xs4nw9aWcyInsiDHsAxjczBBR-LEB9Q=w1238-h928-no
https://lh3.googleusercontent.com/_...56Q9cpq0D3RfVzlNQ-lQKMpaGQBKbiA=w1238-h928-no
(Air goes into the "Fuel Out" tank fitting. Air comes out of the fuel tank from the "Vent" fitting into the top of the soda tank. The water column comes out of the soda tank via a dip tube that reaches down to the bottom. About and inch of water in the pressure tank acts as the source of fluid to travel up the sight hose.)
A quick calculation shows that a 55" water column equals 2 psi. I backed off a bit and used 46" to be a little conservative (1.7 psi). At that pressure the skit on the rear baffle bulged ever so slightly, I could press it down with my finger and feel a little give. The tank didn't make any sounds or creaks. They look straight and normal after the test.
The only leaks I discovered on my tanks were around the filler cap. At this pressure no tape I used would seem to seal the cap. I tried the trick of putting a glove over the cap but that only helped slightly. Remember that the purpose of this test is to create a pressure while you spray a soapy solution looking for bubbles. The tank will leak down eventually.
The equipment I used was from my beer making kit, so the soda tank with a dip tube was just the ticket for this job. Maybe you have a friend who brews that would loan you his keg for a day?
My next test will include pressurizing about a gallon of 100ll with some UV tracer dye. More to come...
