Inspired by the leak measurement posting here

How far away can a leak be detected with an Ultrasonic leak detector?

Terry O

Hi Terry,
you crack open the valve over there and I'll tell you when I can hear it over here
But seriously,
the test figures I have seen for an SDT170 showed audibility at 2bar of an 0.12mm hole at 20 metres and I would expect a 6bar leak to still be audible at least double that distance.
This is using their parabolic sensor of course.
I hope that helps,

Best Regards,
Tom Murphy

Terry,

There is no standard answer, since there are no ultrasound Standards. A few factors that affect leak detection distance are:

1) Sound power produced by leak (pressure, flow rate, orifice shape)
2) Leak direction/orientation (sound is directional)
3) Backgound ultrasound (from other leaks or sources)
4) Humidity (affects excess attenuation)
5) Wind Direction if present (down-wind is better than up-wind or cross-wind situations)
6) Focused sensor (can be 5 to 25 dB more sensitive than plain microphone in meter)

Walt

Terry,
Walt is correct in his response but it did challenge me to see just how far I could detect a leak. Before our spring shutdown I performed an air leak survey. Now keep in mind that the conditions were right, and the leak was aimed downward. Using a UE 10000 set at 32kh, without a dish or long range module, an air leak around 1/8" dia. at 100 psi, two stories off the ground, I found and tracked down from over 100 feet! I believe I could have backed up another 50 ft and still heard it.

Pete

Typcial standard that most talk about in leak detection instruments.... is 5psig from .050" opening, at 50 ft.
With that in mind your leak of 100 psig from 1/8" opening at 100 feet, you probably could had backed-up another 50 feet and heard it. ESPECIALLY, if you had tuned it to 38-40kHz. A good practice to use before performing a leak audit in your plant, is to hold whatever unit you are using below your noise (several inches away) and tune your instrument to the frequency were as the sound is crisper or sound quality is the best, look at the tuner and see what frequency is selected. Most likely it will be in the 38-40kHz range.
But, as Walt and Tom did say, humidity, background noise, size of opening of leak as well as (I will add) whether it is a jagged opening versus a round or rounded opening all play a role in how far you will hear a leak.
Have fun hunting leaks, but remember SMALL, MEDIUM or LARGE and take a wrench with you when you are surveying leaks so that you can tweak those leaks that could possibly be fixed "ON-THE-SPOT".

Hi Jim,
Nice to hear from you. For some reason I knew would correct me. I actualy did as you sugested and found 32kh on this one worked best for me. The sound started to fade as I increased the frequency. It may just be my hearing or the way the sound was being produced. I usualy keep it around 38-40 and tune as I go along.
As far as the wrench goes, this was a rotton line. A hose clamp and piece of rubber would have been better. I found well over 50 leaks and most have been repaired.
I was standing outside talking to the waste treatment plant opperator and asked him if he had heard any air leaks in his area. He replied, "no, but maybe you can find some around back". I said, "are you sure"? Again he said no. There was a broken airline 10 ft from us, overhead, that he had heard for so long he thought it was part of the process! You could hear it without ultrasound from 50 ft. This shows how we can get so use to our surroundings that we no longer even pay attention.
Thought you might enjoy that one.
Pete