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Date: Wed, 28 Jan 2009 14:24:27 -0500
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From: Joe Trepicone <aviation@trepicone.com>
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Subject: Re: [LML] Re: Fuel Tank Testing
References: <list-3455887@logan.com>

I sealed up the entire fuel system (tanks and tubing, caps, etc) and  
attached a large balloon to one of fitting. Left it for a week. If the  
balloon is still inflated you don't have any leaks. Joe. Trepicone

Sent from my iPhone

On Jan 27, 2009, at 7:15 PM, vonjet@gmail.com wrote:

> I used a vacuum pump to pull vacuum in my tank and it held for an  
> hour. I didnt test it longer than that. Is an hour long enough?
> Bryan
>
> Sent from my Verizon Wireless BlackBerry
>
> -----Original Message-----
> From: "Ted Noel" <tednoel@cfl.rr.com>
>
> Date: Tue, 27 Jan 2009 18:46:23
> To: <lml@lancaironline.net>
> Subject: [LML] Re: Fuel Tank Testing
>
> Bob,
>
> I'm glad you mentioned the vacuum cleaner in the end of your post. I  
> tested
> my tanks with a ShopVac. After sealing carefully all openings  
> (reversibly!),
> I attached a ShopVac. It pulled about 3" of negative pressure. I  
> measured
> this with a fuel system pressure gauge. Having pulled this relative  
> vacuum,
> I used a ball shut-off valve from an air tool system to seal the  
> system and
> shut off the ShopVac. 24 hours later, I still had 3" of vacuum.
>
> Ted Noel
> N540TF
>
> ----- Original Message -----
> From: "Robert Pastusek" <rpastusek@htii.com>
> To: <lml@lancaironline.net>
> Sent: Monday, January 26, 2009 7:42 AM
> Subject: [LML] Re: Fuel Tank Testing
>
>
>> Bryan wrote:
>>
>> I am in the middle of testing my fuel tanks for leaks with a vacuum
>> pump.  How long is long enough to hold vacuum to prove it wont leak?
>>
>>
>> Be very careful with the vacuum pump. More than one Lancair builder  
>> has
>> "imploded" his wing tanks with this not-so tried and true method.  
>> There
>> have
>> also been several mishaps from people trying to use compressed air  
>> to test
>> for leaks. This method is almost certain to provide comic relief to
>> others...don't even consider it. You might, however, consider an
>> alternative
>> method that worked well for me:
>>
>> Carefully seal all openings/vents, etc except one--the fuel pickup  
>> port,
>> or
>> the return line work well because you can provide it with a very  
>> air-tight
>> fitting to your "test rig." Make a test rig from a good-quality latex
>> balloon--the kind used for filling with helium are generally OK-- 
>> and a
>> short
>> piece of aluminum pipe with a fitting that will attach to your fuel  
>> tank
>> opening. CAREFULLY seal the balloon to the pipe. RTV on the pipe,  
>> and a
>> rubber band wrapped over the neck of the balloon to hold it tightly  
>> to the
>> pipe works well. Blow up the balloon and twist the neck to keep the  
>> air
>> inside while you attach the fitting end to your tank. When you  
>> allow the
>> balloon to un-twist, most of the air will rush into the tank until  
>> the
>> (very
>> small) pressure is equalized, but the balloon needs to remain  
>> partially
>> inflated. You may need a couple of tries to get it right... You  
>> have a
>> fuel-tight tank when the size of the balloon changes with the  
>> barometric
>> pressure over 2-3 days, but does not go flat during that time.
>>
>> You can make a fancy test rig with a Tee and valve, etc, to aid in  
>> filling
>> the balloon, but everything you add must be absolutely air tight or  
>> you're
>> adding complications with negative benefit. I can't over-emphasize  
>> the
>> need
>> for careful sealing of all openings/fittings. For example, I used  
>> clear
>> packaging (release) tape to seal the filler cap opening on my  
>> tanks. Since
>> the cap was larger than the width of my tape, I used two strips,  
>> carefully
>> overlapped and pressed down. My balloon went flat in about two days.
>> Double
>> checked every joint/connection and opening with soapy water and  
>> concluded
>> I
>> had a leak in the tank, but before proceeding with "dunking the  
>> wing" to
>> find it, I tested the second wing tank. Same results...a very slow  
>> leak
>> that
>> deflated the balloon in a couple of days. I then went back with the  
>> soapy
>> water around the openings and discovered air leaking along the  
>> inside edge
>> of the clear packaging tape where I'd overlapped them across the  
>> top of
>> the
>> filler cap. One very small bubble every half minute or so at each  
>> end of
>> the
>> tape where one strip laid across the other! YGBSM! Anyway, it was  
>> enough
>> of
>> a leak to deflate the balloon--in time. Re-applied the tape strips  
>> with a
>> very small wipe of RTV at the edge of the first tape and both tanks  
>> tested
>> well. The balloon stayed inflated for a week or so for each tank.
>>
>> Bottom line: This method works well, and is safe to use. The tanks  
>> can
>> stand
>> VERY LITTLE positive or negative pressure, so no matter what method  
>> you
>> use,
>> be very careful, and don't even think about approaching your tanks  
>> with a
>> compressed air hose...or even a vacuum cleaner hose for that matter!
>>
>> Bob Pastusek
>>
>>
>>
>> --
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>> http://mail.lancaironline.net:81/lists/lml/List.html
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