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Damaging the tanks

M

Mark Jackson

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Tried to use the tank testing kit with a ballon on the vent line. Short version is the balloon didn't blow up until all of a sudden it got two feet long and shot across the room. This was after a dozen pumps from a large bicycle pump. Probably put a lot more than 1" of pressure in the tank.

Is that likely to damage the sealant?
 
Mark Jackson said:
Tried to use the tank testing kit with a ballon on the vent line. Short version is the balloon didn't blow up until all of a sudden it got two feet long and shot across the room. This was after a dozen pumps from a large bicycle pump. Probably put a lot more than 1" of pressure in the tank.

Is that likely to damage the sealant?
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No. Just think about that balloon as the pressure relief valve. It just popped off as designed. :D

I would suggest trying again but going slowly on the pump. Because of the large space you are pressurizing it will take a bit of time to get to pressure but when it reaches it the balloon will go fast. Once you see the balloon starting to expand go even slower, or better yet, stop pumping all together and observe the balloon. If you think it needs more pressure just do one pump and observe again. repeat very slowly at that point. You really do not need to have a large amount of pressure to be able to see leaks thus the recommendation to not exceed 1 psi.
 
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I used a U tube manometer. I made it from clear Tygon tubing. It reads instantly and accurately.
I used water with food color for the calibrated indicator fluid. ;)
27.7 inches of water = 1 PSI.
You could pump this up more carefully, and read the result for days, observing the change in volume from temperature changes. :)
 
I used an old bike pump to test mine too. The balloon does start expanding all of the sudden. You just have to go slowly. You might have a "better" pump than mine to that transition from the balloon being just barely inflated to fully expand might go very quickly. It was a little startling to me the first time it happened.
 
I also did what Shipchief describes and used a manometer. I believe it will give a better read than the balloon method because balloons are porous and will leak down over time. When I leak tested, I saw changes in atmospheric pressure reflected in the water level over a 24 to 36 hour period. It acted like a barometer. It is a more accurate measure in my opinion.
 
How do you know when a change in the manometer reading is from an atmospheric (barometric) change or from a leaky tank?
 
blueflyer said:
How do you know when a change in the manometer reading is from an atmospheric (barometric) change or from a leaky tank?
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Agreed! The manometer is not a leak detection tool. It is a barometer. You need to pressurize the tank and use a soapy water solution sprayed with a mister over all joints and observe for leaks while the tank is pressurized. You could have a very small leak that the manometer would never detect if you solely rely on it to tell you of leaks.
 
I used a manometer

The first few times, you learn where the major leaks are, such as the caps or threaded fittings that are not tight. They leak bad so are easy to identify.

Once you get past that, leave it for a long time. I had two physical things that came into play and had to be dismissed.

1) The tank may have stretched (elastically) because the pressure went down a whit soon after sealing it. I could watch it drop and then stop.

2) Overnight it went down more. AND THEN WENT UP. Definitely thermal influence.

My tanks are fine. No blue streaks after 200 hrs.

RVbySDI said:
Agreed! The manometer is not a leak detection tool. It is a barometer. You need to pressurize the tank and use a soapy water solution sprayed with a mister over all joints and observe for leaks while the tank is pressurized. You could have a very small leak that the manometer would never detect if you solely rely on it to tell you of leaks.
Click to expand...

That assumes you are constantly inputting air to the tank. Same applies to the balloon system. If you continue to input air at the same rate as the leak, the balloon will not change. If you stop pumping, the manometer and balloon systems will act identically.

Both systems (soapy water and manometer/balloon) are useful in leak detection. With a manometer failure, the soapy water system can tell you where it is. While it is a personal preference, I would not rely on soapy water by itself. Water immersion on the other hand....:)
 
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blueflyer said:
How do you know when a change in the manometer reading is from an atmospheric (barometric) change or from a leaky tank?
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Call your nearest AWOS or ASOS and note the local altimeter setting upon first pressurizing the tank, when using a manometer. Then at future readings, do the same and note the difference. Convert the difference between altimeter settings from inches of mercury to inches of water (google). If that explains 100% of the observed change while keeping temperature constant, then your tank is leak-free.

This is best done inside where the temperature can be held constant. If performing the test outdoors or elsewhere that the temperature also fluctuates significantly, you will also need to compensate for temperature changes. PV=NRT.

Or just leave it for several days. If there is a leak the water will eventually equalize, rather than fluctuating up and down with atmospheric temperature and pressure changes. Leaks will be (very) painfully obvious.
 
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krw5927 said:
Call your nearest AWOS or ASOS and note the local altimeter setting upon first pressurizing the tank.
Click to expand...

You need to use the local barometric pressure, not the altimeter setting. (close to sea level it won't make much difference)
 
BobTurner said:
You need to use the local barometric pressure, not the altimeter setting. (close to sea level it won't make much difference)
Click to expand...

The difference in two separate local altimeter settings at the same field is equal to the difference in local barometric pressure readings, when corrected to the same units of measurement.
 
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Party time.

I don't want to get into the barometric pressure end of this question.
We have had some of the balloons puff-up all the sudden on us. What we have found is put a little pressure in the tank, then take the balloon and stretch it with your hands. If it is ready it will blister for you. If not put a little more gas to it and stretch it again tell it does blister. Once it is going pump it up tell it is 3/4 full and start you test. If you go to the party supply store you can pick up some thin latex balloons. They are better at blistering on up with no prompting. Odds are you have not heart your seal, but test it and be sure. Hope this helps. Yours as always R.E.A. III #80888
 
Fuel Tank Pressure

I simply used a low pressure gauge. No questions here. I filled it with 1 psi and it held for days. :cool:


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krw5927 said:
The difference in two separate local altimeter settings at the same field is equal to the difference in local barometric pressure readings, when corrected to the same units of measurement.
Click to expand...

1. Sorry, this is not correct. You only want the pressure, but altimeter settings include compensation for non standard temperature.
2. But what I really meant was that you need to use the actual barometric pressure, not corrected to sea level. That's what your manometer sees.
 
You guys can use what ever procedure you want to measure pressure, and use what ever pressure reference you want, but the only way to truely check for a leak is to spray it down with soapy water.

The amount of expansion or contraction of the air that will occure with even small temp changes will make you think you have a leak when you don't or maybe fool you into thinking you don't when you really do. Baro. pressure is also a factor. What if your tank slowly leaks over a 24 hr period, but the baro also drops during the same time? Your leak indicator will say you have no leak... but you do.

The balloon (or manometer, or guage... what ever you use) is not meant to be an indicator of whether you have a leak or not. It is only to help prevent inexperienced airplane builders from destroying there fuel tanks.
 
BobTurner said:
1. Sorry, this is not correct. You only want the pressure, but altimeter settings include compensation for non standard temperature.
2. But what I really meant was that you need to use the actual barometric pressure, not corrected to sea level. That's what your manometer sees.
Click to expand...

Altitude (pressure altitude) corrected for non standard temperature is called density altitude. Altimeter settings given in ASOS or AWOS reports, or by ATC, are most certainly NOT density altitude.

Perhaps we should start a new thread however, as this discussion deviates from the topic at hand.
 
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Simply put, a U tube manometer is the most accurate, simplest method to test your tank. Don't let the precision throw you off. It is so accurate that it is effected by room temperature and barometric pressure. No balloon and few gauges can approach it's accuracy.
The air volume in the column is slight, and leaks are shown very soon.
Let it sit a few days, and you will quickly get comfortable with the variations as they average out. This is amazing in it's low cost, simplicity, accuracy, safety and ease of use.
If you have good lungs, you can charge the fuel tank to 1 PSI, and almost naught more.
Tony Spicer's pictures tell all.
 
SHIPCHIEF said:
Simply put, a U tube manometer is the most accurate, simplest method to test your tank. Don't let the precision throw you off. It is so accurate that it is effected by room temperature and barometric pressure. No balloon and few gauges can approach it's accuracy.
The air volume in the column is slight, and leaks are shown very soon.
Let it sit a few days, and you will quickly get comfortable with the variations as they average out. This is amazing in it's low cost, simplicity, accuracy, safety and ease of use.
If you have good lungs, you can charge the fuel tank to 1 PSI, and almost naught more.
Tony Spicer's pictures tell all.
Click to expand...

All true. But it does not show where the leak is if there is one.

The soapy water test with a little pressure will do that real quick.
 
Ok. First determine there is a leak and then start looking for it. Soapy water works well for that. When I tested mine with the manometer method, I detected leak down and found the only leaks were at connections and the gas cap. Covered the gas cap with duct tape and still found very small leak at an overlap of the tape. But once these miniscule leaks were corrected, my manometer rose and fell with temperature and barometric pressure.
 
Sorry.

Mr. Walton is on the right track and yes the balloon is to keep you from over doing a pressure level in the tank as it does not take more than 4-6 p.s.i.g. for one to bust a seam wide open. Sorry I did not mention the old soap trick before, it should be part of the testing of a tank. Only one comment the little bottles of soap you get down at Lows or in some hardware store aviation department, that are used to test for gas leaks on a home hot water heater.
These seam to work the best of any we have run across as the stuff bubbles up to show a leak better than any other soap we have found to date.
If it hold good pressure for a couple of days and you don't find any soap bubbles then fill it with mow-gas and let it set for a couple of days. You may still see a small wet spot. If you need to then you can drain the fuel and put it in your road mobile tell you fix that wet spot. "Don't ask the answer is yes" hope this helps Yours as always R.E.A. III #80888
 
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I ended up using 1/2 tubing to construct a manometer. It worked as advertised and I found a couple pinhole leaks in the corner seals.

Thanks very much for all the replies, like drinking from a firehose.

2eedibr.jpg
 
Trek or Canondal?

Houston, an inverted fuel tank and a good road bike tire pump.
How could we not? Yours as always R.E.A. III # 80888
 
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