Helium for leak detection

[chemi-cool]

I have just heard from a friend that Helium is used for detecting the smallest leaks in a system.
The system evacuates and filled with Helium up to 15psi and the leak is detected with th regular electronic leak detector.

Any comments?

Chemi

[Peter Croxall]

Hi Chemi,
Are you sure that it is an electronic leak detector and not an ultrasonic leak detector?

[donhoban]

Helium was used more by manufacturers previously because the detector was hugely expensive, however I believe cheaper detectors have become available in the last few years.

Helium doesn't detect smaller holes, however it does show leaks more quickly than standard leak tests, and that's why it was advantageous to manufacturers of coils who could process their production more cost effectively

[chemi-cool]

Hi donhoban.

Isn't the molecule of Helium smaller, allow the gas to come out in smaller holes then refrigerants?

Peter, I haven't a clue but ultrasonic detector is very uncommon with fridgy's.

Chemi

[donhoban]

Isn't the molecule of Helium smaller, allow the gas to come out in smaller holes then refrigerants?

As I understand it, bearing in mind, I'm an engineer,not a phyisicist or chemist - molecular size of helium is about 10-10m or 0.0000000001 meters

Say we assume the leak is 1/1000 of a mm across - we'd still potentially fit 1000 molecules of helium across the gap at any one time!

So really, unless we start dealing with monster molecules, I don't think the relative size difference between helium and refrigerant is important.

I could of course be wrong

[chemi-cool]

Hi donhoban.
From what I've heard, this is why Helium is being used.

I dont see any other reason.

Chemi

[Argus]

Helium has been used for many years in certain production methods where a high degree of system tightness is demanded. Typically it could be used for measuring the porosity of high end spec castings.

The ?detector? as such is a mass spectrometer. Despite its very high level of efficiency it is also potentially the most expensive because of the equipment needed.

I saw it used by Carrier many years ago in Syracuse where they were testing Absorption system unishells. The whole machine would be wrapped in a plastic ?tent? and a measured amount of helium admitted to it. A vacuum pump would then draw a vacuum on the inside of the system and the exhaust of the pump would be directed through a mass spectrometer.

Not a technique for your average site??.
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[Peter_1]

Hi donhoban.

Isn't the molecule of Helium smaller, allow the gas to come out in smaller holes then refrigerants?

Peter, I haven't a clue but ultrasonic detector is very uncommon with fridgy's.

Chemi

I have an ultrasonic but it's only usable to search for leaks in gaskets around the doors.
You must almost hear and know where the ***** leak is to find it with an ultrasonic.

[Latte]

Surely if we start using Helium for leak detection we are going to all start talking like Joe Pasquale

Regards

Raymond

[RogGoetsch]

...but ultrasonic detector is very uncommon with fridgy's.

True, but I recommend it as a very valuable tool under some conditions. I finally broke down and bought one a few years ago when a leak was driving me crazy. They had come down to about $200. Mine uses earphones and supplies a hiss in the hearing range proportional to what the detector is receiving, with a sensitivity adjustment.

They are excellent when a system is out of gas, since that usually means a large leak which overwhelms most halide detectors. Of course the oil often shows such a leak, or you can find it quickly by pressurizing with nitrogen and listening for the hiss, but when this fails, the best feature of the ultrasonic detector is that you can use it directionally.

You need to pressurize with nitrogen if the system is empty and shutdown fans and adjacent equipment to eliminate background ultrasonics but then you can home in on the source very quickly, in many cases. With a thumb on the sensitivity adjustment, you track the noise right to the source. Last time, I found a leak in the interior of an evaporator coil in minutes, which was losing about 2 ounces per day. (Pressurized to 100 psi first.)

For very small leaks and on rooftops where there is too much background ultrasonic noise (wind, traffic) it is not effective.

Rog

[botrous]

The more the technology advances the more tests needed , the more atmospher polluted the more tests needed .
Unfortunably high tec technics are still very expensive to use by small and medium companies . . . the goverments should support the price of such testing materials in order to develope their countries industries and their contribution in the atmospher clearness preservation