Fuel tanks passed 1.000 psi pressure test...what a relief

[Wayne Gillispie]

Used 2 qts proseal then brushed PR-1005-L buna-n "cherry juice" over top of all joints inside and out. Installed drain fitting, fuel outlet with AN cap, short piece of 1/4" aluminum tubing on vent fitting to connect to an electronic manometer, Van's deluxe locking fuel cap(without duct tape). Pressurized through drain valve with blow gun until reading 1.050 psi (29.06" H2O) on manometer using very low pressure 2-3 psi. It dropped back down to around 1.000 psi (27.68" H2O) after losing the heat of compression. I sprayed leak detection fluid (used in hvac business) on all rivets and joints which cooled the air inside the tank and dropped pressure down to about 0.980 psi. Found a leak at fuel cap, tightened nut inside of cap...leak fixed.

Just for fun I tested several different balloons/gloves to see what kind of pressure they exerted when filled. All balloons tested between 0.300-0.600 psi except for one...the long skinny ones you see being made into funny shapes...that one exerted 1.5 psi at full length (4'). Nitrile and latex gloves were close to balloons. Balloons would burst between 1-2 psi hence the reason for Van's recommendation.

 

[mdaniell]

Wow you had my attention, I misread.... 1,000psi! I'm a QuickBuilder though so I live in hope, congratulations for the moment.

 

[flion]

I, too, misread the title and was really impressed! Still impressed and congratulations on successfully getting tanked.

 

[rbibb]

I too had visions of exploding tanks or tanks built to a standard more aproriate to the cap holding back the oil on the bottom of the gulf. Glad it all worked out.

 

[BSwayze]

I guess that makes 4 of us! I, too, saw the title and thought at first it said 1,000 psi! Whoa!

Anyway, congrats on the successful build of the tanks. That's a great feeling that I will never forget.

 

[Steve Barnes]

Bulging fuel tanks

Recently, I helped with 3 Zodiac XL structural upgrade projects. One of the owners needed to have some welding done on his fuel tanks by a professional welder, while it was out of the plane. When the tanks came back, they were bigger than when they left. The welder used his air compressor air to look for leaks. Now the caps set proud out of the top of the wings. I think even as little as 3 PSI can severely damage Van's tanks. Oh about the structural upgrade installation on the Zenairs, well that's another story for another time.

Steve Barnes "The Builders Coach"

 

[Frank Smidler]

what precision

Wow, 1.000 psi, that is extremely accurate. In engineering, with out any tolerance listed it is assumed to be 1/10 of the decimal place used. Therefore 1.000 psi would seem to indicate 0.001 psi accuracy. That is some high tech instrumentation and testing equipment you must have. I think testing to 1.0 psi would have been sufficient.

I imagine the rest of your construction tolerances are as precise.

 

[Wayne Gillispie]

Accuracy and buldging tank...

Frank, Accuracy is plus or minus 1% (0.990-1.010 psi). I was using the electronic manometer in my conditioned shop mainly to detect for leak down but did not want to exceed 1 psi by much. I use this meter in my hvac business for measuring gas furnace manifold pressures and for diaphram switch activation setpoints. If I laid my hand on the tank it would go up immediately .001 psi every few seconds. It kept leaking down on one tank, so I sprayed everything down and found a leak at the fuel cap. Once the nut was tightened a little and everything stabilized for a half an hour or so I knew I was in good shape. I pressurize hvac systems to 200-400 psi to check for leaks with a different gage. I would not want to go any higher than 1 psi on Van's tanks. Mine were bulging out about 1/8" on the rear baffle and skins were pretty tight. Working with all these tools, numbers, gages, instrumentation as a pilot and builder is a bunch of fun. Can't wait to fly it!!

I used to overhaul jet engines to the .0001" but not on my plane thank goodness. I am not building a show plane, just a good safe faster plane to haul the family around the U.S. Renting 172's right now and building time/experience. Keeping it pretty simple, and sticking with the plans so that I can get it done maybe by snf 2012. My wife and another -10 builder (Ted Chang) has helped tremendously. I really appreciate all of you guys on here too.