Tank pressure testing... Nitrogen?

danielhv · #1 02-10-2009, 10:11 AM

I know some of you have filled with water, and marked clear tubing etc... and some have used air which changes with environmental conditions... I have access to nitrogen which is not near as sensitive to environmental conditions as air... anybody used nitrogen for tank testing? What psi did you test at?

n5lp · #2 02-10-2009, 10:15 AM

Nitrogen expands and contracts just the same as air, if that is what you are referring to.

N941WR · #3 02-10-2009, 10:47 AM

Don't over think this. The balloon and bicycle pump method worked great for me.

BTW, Van's does not recommend filling the tanks with water. Should you have a leak, you need to get all the water out before you can patch it.

rwshooter · #4 02-10-2009, 10:51 AM

Daniel.......I pressure tested mine with the cheap $5 kit from vans.....Pressurized the tank just enough to fill the balloon....sprayed it with soapy water. Let it sit over night....not much change....put it in the sun the next day and in under five minutes the balloon popped due to expansion.

Good nuf for me. I know you have all the parts to do this cuz I ordered the exact same stuff as you.

Robb.....7A

airguy · #5 02-10-2009, 11:11 AM

If you have the tank in a non-temperature-stabilized area, you won't be able to see the difference between air and pure nitrogen with respect to expansion and contraction from thermal variation, so there is no reason to use the nitrogen there.

If you have it in a temperature-stabilized area, there won't BE any expansion or contraction from thermal variation, so there is no reason to use the nitrogen there.

The laws of gas behavior (Boyle, Charles, etc) do give some difference between pure gases (such as pure nitrogen) and mixes (such as atmospheric air), but the difference that you can see will be lost in the "noise" of thermal variation and atmospheric pressure changes. Don't try to reinvent the wheel.

danielhv · #6 02-10-2009, 11:11 AM

Quote:

Originally Posted by n5lp

Nitrogen expands and contracts just the same as air, if that is what you are referring to.

oh...

I was under the impression nitrogen did not expand or contract as much as air... guess that rules that out!

danielhv · #7 02-10-2009, 11:12 AM

Quote:

Originally Posted by airguy

If you have the tank in a non-temperature-stabilized area, you won't be able to see the difference between air and pure nitrogen with respect to expansion and contraction from thermal variation, so there is no reason to use the nitrogen there.

If you have it in a temperature-stabilized area, there won't BE any expansion or contraction from thermal variation, so there is no reason to use the nitrogen there.

The laws of gas behavior (Boyle, Charles, etc) do give some difference between pure gases (such as pure nitrogen) and mixes (such as atmospheric air), but the difference that you can see will be lost in the "noise" of thermal variation and atmospheric pressure changes. Don't try to reinvent the wheel.

ah but the wheel is boring! lol... ok, ill just stick to the norm and use a baloon and bicycle pump.

DanH · #8 02-10-2009, 11:16 AM

1 or 2 psi air and a bottle of kid's bubble solution. Just slop it on the seams. When you don't find any leaks go outside and wave the bubble wand around for a few minutes. You'll feel so much younger <g>

airguy · #9 02-10-2009, 11:16 AM

Quote:

Originally Posted by danielhv

oh...

I was under the impression nitrogen did not expand or contract as much as air... guess that rules that out!

You mean - as quoted from the local tire shop, that promises you "more stable tire pressure"? That refers to the permeability of the rubber in the tire or tube. Oxygen molecules slip through the permeable rubber slightly faster than nitrogen molecules, with the end result that pure nitrogen in tires will leak out slightly slower than plain air. This, in combination with being extremely low water content and a non-flammable mixture, is the primary reason for nitrogen use in tires for aviation. The auto tire industry took that and ran with it with a borderline false-advertising marketing campaign.

Steve · #10 02-10-2009, 12:01 PM

I used the balloon and bubble method. The balloon is the safety valve and not really the leak indicator. The soap solution is the key. Close visual inspection of ALL the rivets and seams for soap bubbles is what you want to do.
Note: It's hard to get the balloon to seal at the tank vent fitting. It's hard to get an airtight seal at the gas cap as soapy water makes duct tape come unstuck. Add more air and keep inspecting rivets and seams.
Clean the tank and perform the inspection a second time.
Steve