Air Leak Tester

I assume you're using a pressure bleed-down method. Have you tried the fluorescent leak detector kits? You inject a small amount of fluorescent dye into the system and then use a special light and glasses to detect where the dye is leaking out from. The kits are pretty reasonable and make it amazingly easy to quickly find even the smallest leak. Check out Spectroline.

Once test fails turn the air back on, air will make some sound as it escapes, use a stethoscope type sound detector to find the leak.

we have stronger noises in that area, like impact tools etc etc., that is another reason why we can not detect by sound

A spray bottle with soapy water in it--Spray it on all suspect joints. Surprising how effective this is for air, propane, even Freon. If it is soapy enough the leak will build a lot of foam and will be easy to find.

Just dish soap will work, but in a pinch I have used 409 and it isn't as sudsy--It still bubbles and you have to look harder, but it will work.

K.T.

My most annoying problem over the last 25 years has been air leaks on my fire engines.

The best way that I have developed is an air flow meter. Use shop air to fill the system. Once the air is stabilized, connect an air flow meter in line to measure the air going into the truck. The only reading on the flow meter will be the air leaking out.

If you are filling the truck from 0 with the truck's compressor to test for time to build, do that first, then after you have passed that test, go to the flow meter. I have a few different ranges of meters. I think the ones I have been using are made by Dyer, or Dwyer. I get them from Grainger.

If the air that is showing on the flow meter is too high for your standard, NOW your work in starting. Some of the things that have been a problem to me in the past have been the parking brake valve around the knob. Air pressure gauges, brake relay valves, and brake chamber(only when the parking brake is released). If soaping the air tanks and attached fittings, along with the above mentioned parts, I would next go to isolation valves between the air tanks. That will allow me to decide which section of the air system is leaking.

I have made up sections of airline that I can use to extend the existing line, with a big loop in it with a shut off valve in the fitting. Just shut off the lines coming out of the wet tank and see if it stops the air leek. If not the leek is on something attached directly to the wet tank ( the first tank after the compressor, or air dryer) Don't forget that there is air pressure at the air compressor. (air governor and unloader valves in the compressor)

If the air leak stopped when the wet tank was isolated, the leak is further down the system. next allow air to only the front air system air tank. If the leak stops, the leak in in the REAR air system. If air leak continues, it is in the front air system. At this point do not get too confident. It is possible that there is more than one air leak. just because you find one leak, does not mean all is well.

What I have not had good luck using, an ultrasonic leak detector. There were air leaks that my deaf ears could hear, that the U.L.D. did not hear. Charging the air system with freon, and using a freon leak detector. Bendix sales people warned that the rubber components in the brake air system will deteriorate in the presence of freon.

I hope this will give you some tools to go after your air systems. If I can help you in any other way please let me know. Good luck.

GA as I liked your post.

You have the same ideas as I with regard to Ultrasonics (my God, I had my first Ultrasonic leak tester in the RN in 1966!!), but the thermal imaging idea is new and sounds good as I am sure the area around the leak will be cooler as the air expands.....

I feel that a good Ultrasonic leak tester will ignore lower frequencies and noise, so it will work in spite of the other noises.....also the funnel could be insulated to stop them getting through in any large quantity.....

I like that simple solution, bits of paper are always available, a GA for you sir.

So its back to school for me and my ultrasonic tester. I do like the idea of a thermal imager. As soon as I get my steering box rebuilt, I will try the TIC on a known air leak. GA to you.

Hello Juan,

There is a somewhat new technology being applies in both medical and rescue operations using and electronic device to detect a heartbeat midst wreckage. The device can be attached to the frame and detect vibrations. I think this type device may help your endeavor, possibly another here can help you google for it

Try an ultra-sonic leak detectors are a viable way to do what you want to do. The addition of a flowmeter to the incoming gas is problematic because of the time issue and the fact that it does not find the leak.

LIFTANDLUBE.COM HAS THE LEAK DETECTOR YOU ARE LOOKING FOR JUST ADD SOME DYE TO THE AIR AND THE LIGHT WILL FIND IT NO PROBLEM

http://www.liftandlube.com/Yellow_Jacket_69770_Pure_UV_p/yj%2069770.htm

here is the light most industrial oils and fluids like those used in air compressors luibricating lines, will show up without the need to add extra dye to the air line, as long as you already have a lubricator in line like for running tools, if not pick up this handy one witha filter and regulator built in;

http://www.liftandlube.com/1_4_FRL_p/aml%20p29122-624.htm

its a 1/4" for $40 from American Lube cant beet the price for the quality

but if you need the dye just write to me and i can get it for you

A differential pressure gauge, along with a reference volume may allow you to detect the leak faster (a bit along the line of the flow meter). This will work as long as there are no significant temperature differences between the reference volume and the actual pressurized system under test, for the duration of the test.

I am sure that what you say would work with significant leaks quite well, but I could guess that you could also feel, see and hear such a leak.

My limited experience with leaks many years ago and an ultrasound leak chaser, showed me that really tiny leaks can be found that no human could hear in dead silence, or see or feel......you would not even smell it if it was a strong smelling gas. We are talking about really tiny leaks......and we were working in the bowels of an Aircraft Carrier....

The reason we had to fix them was because the gas was really expensive....

Absolutely correct however the OP cannot produce the environment necessary to use these devices effectively.

Unless the environment has vehicles producing LARGE quantities of ultrasound, yes it will still work. The detectors are also very, very directional also, that will help.....

I have to admit that I was not having good results with the ultrasonic tester that I had, and I will accept blame for not working with it more, to become better. But faced with air leaks that were annoying, I used what worked for me.

The statement from the OP led me to believe that he is doing air leak testing on newly assembled trucks, or something similar. The procedure for leak testing for him must be simple, accurate, and fast.

I would suggest an air chuck that could fill the vehicles air system from the pressure that the onboard air compressor built to, up to 130 PSI. This could be done with an inline air flow meter, equipped with a bypass valve to quickly fill the vehicle. If the vehicle is already at 120 PSI, connecting the open valved air chuck should fill the last 10 PSI in only seconds. Once the pressure is at 130, (this becomes evident when the air chuck stops making noise), the OP would shut the bypass valve off, causing all air entering to register on the flow meter. My experience says this should slowly drop to the actual air leakage rate in about another 8-10 seconds. At that point the vehicle is pass, or fail, depending on what is an acceptable rate of leak for that manufacturer.

If it is a fail, the first thing to do would be to listen. Most air leaks on new equipment are due to a defective part, not a worn out part. That means that a large air leak is more likely, and easier to hear and find. If not an easy to find leak, it will mean removing the vehicle from the assembly line for repair.

I still stand by this as a valid test procedure.