How to: Leak detection
How to: Leak detection
(OP)
We are at a bit of a dead end here needing some ideas on which direction to pursue.
We are building a unit that is required to be water tight. It should be able to withstand being submerged in a meter of water for 30 minutes without water passing any of the seals.
The problem we are currently experiencing is this:
There are 26 seals in the unit with several having the potential to leak. The best method we currently have to detect where a leak is occurring is to apply positive pressure to the unit with helium at about 0.5 PSI. We then use a handheld helium detector and sniff around the unit to determine where the helium is leaking. Obvious problems here are if we set the detector to detect even the smallest amount of helium it detects false fails as very small amounts of helium pass through the seals. The other problem is the test is very time consuming and often does not catch all of the leaks the first or second time so we are spending manufacturing time pulling the units apart several times before they eventually seal.
The only other method we have used is applying positive pressure to the unit and dunking it in a tank of water to see where the leaks come from. This is not what we want to be doing at $3000+ per unit. The risk of damaging the internal electronics is high.
Anyone have any experience or ideas on this subject. We have been kicking around the idea of trying to use some type of thermal imaging camera but I am no chemist so we haven't really figured if any type of gas would work well to inject and use the thermal camera to detect leaks.
Thanks for any help/suggestions.
We are building a unit that is required to be water tight. It should be able to withstand being submerged in a meter of water for 30 minutes without water passing any of the seals.
The problem we are currently experiencing is this:
There are 26 seals in the unit with several having the potential to leak. The best method we currently have to detect where a leak is occurring is to apply positive pressure to the unit with helium at about 0.5 PSI. We then use a handheld helium detector and sniff around the unit to determine where the helium is leaking. Obvious problems here are if we set the detector to detect even the smallest amount of helium it detects false fails as very small amounts of helium pass through the seals. The other problem is the test is very time consuming and often does not catch all of the leaks the first or second time so we are spending manufacturing time pulling the units apart several times before they eventually seal.
The only other method we have used is applying positive pressure to the unit and dunking it in a tank of water to see where the leaks come from. This is not what we want to be doing at $3000+ per unit. The risk of damaging the internal electronics is high.
Anyone have any experience or ideas on this subject. We have been kicking around the idea of trying to use some type of thermal imaging camera but I am no chemist so we haven't really figured if any type of gas would work well to inject and use the thermal camera to detect leaks.
Thanks for any help/suggestions.





RE: How to: Leak detection
RE: How to: Leak detection
I would establish a submersion test in 3 meters of water to verify what you actually want to know. Inspect the sample. Then establish testing samples of boxes to verify seal integrity on a production basis before installing the electronics. Maybe dye the water so that leaks are visible when the test box is opened.
Ted
RE: How to: Leak detection
RE: How to: Leak detection
To find leak, spray soap water on the seals and if you see bubbles, you found the leak.
good luck
Tobalcane
"If you avoid failure, you also avoid success."
RE: How to: Leak detection
Dennis
RE: How to: Leak detection
Is this thing supposed to be serviceable?
RE: How to: Leak detection
How do you know you are getting false fails?
The best way to find a leak if you are using helium is to first find a possible leak, then add a dab of alchole to the suspected area, then run the wond over the suspected area again. If the spectrometer did not pick anything up again, you got a leak.
What is the material used for the seals? If it is not Buena N, helum will pass right thru it.
Tobalcane
"If you avoid failure, you also avoid success."
RE: How to: Leak detection
GTstartup: Not sure what you are referring to when you say "What about snoop"
hydtools: The tests have been done to determine what amount of pressure leak down is acceptable per the customer. The allowable leak down over 7 minutes is 0.2 PSI. Anything more and the unit is said to fail and subsequently have to be opened and reworked. Unfortunately the unity cannot be built without the electronics to determine if the seals are all good as some of the electronics make up the seals too.
TheTick and Twoballcane: We currently pull vacuum for the initial test. If the unity holds vacuum for 7 minutes it's said to be a good unit and no leak discovery is necessary. The problem is when the unity does not hold vacuum. It's not as easy as putting soap on the unit to see where it leaks. There are MANY points that can leak on the unit and a soap test will not work for several of them.
What I am kind of envisioning is in a perfect world a Thermal Camera would be able to detect helium and we could just pressurize the unit and see where the helium is leaking as it would show a nice difference compared to ambient temperature. I also kicked around the idea of potentially positive pressurizing the unit and the leak being able to displace something (material/dense gas/I don’t know) to where we could have the unit sitting on the bench in a case or whatever and the introduction of positive pressure into the unit would then displace whatever was around the unit so we could physically see where the thing is leaking.
RE: How to: Leak detection
TTFN
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RE: How to: Leak detection
RE: How to: Leak detection
TTFN
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RE: How to: Leak detection
Guess I’ll keep throwing darts until we can come up with a better method for leak detection.
RE: How to: Leak detection
now if your spec calls for heliem testing that is a different story.
RE: How to: Leak detection
Any good information you could link about the ultrasound detectors you mentioned?
Thanks
RE: How to: Leak detection
RE: How to: Leak detection
I can't think of any simpler test than dunking the box in a transparent tank of warm water. You do not need to pressurize your box. The air will expand as it gets warmer. You will test all the seals simultaneously and instantly see where the leak is.
RE: How to: Leak detection
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Ted
RE: How to: Leak detection
Better, reduce the number of seals to ~<2.
Mike Halloran
Pembroke Pines, FL, USA
RE: How to: Leak detection
1. Build vacuum chamber to enclose your unit
2. Pull vacuum in chamber
3. Evacuate the unit
4. Pressurize unit with helium
5. Sample gas from the chamber for helium.
You need to create a reference leak that leaks at the maximum allowed amount. Compare your detector reading on the reference leak to the detector reading on your unit. That will give you a quantifiable comparison, and it will check the sum of all leaks in the system. The downside is that it won't tell you which seal is leaking.
A similar process can be done with hydrogen (yes, hydrogen). The gas used is actually nitrogen/hydrogen mixture at a level below the LEL, so it is completely safe and less costly than helium gas. Check out http://urltea.com/2wis
RE: How to: Leak detection
RE: How to: Leak detection
In a previous life, we used to this kit for leak testing domestic gas appliances. Took about 10 seconds each if I remember (on an assembly line):
htt
A quick discussion with them (as leak test experts) might be fruitful...
I would have thought helium a poor choice to test for water leaks - the stuff will leak through anything due to it's low molecular size! (e.g. party balloons in hours)
Cheers
Harry
RE: How to: Leak detection
You will note from that soap solutions are out of favor and in most cases not acceptable.
Though there are many others AmGas covers the field when it comes to practical leak detection as far as I'm concerned. I would give them a call.
http://www.amgas.com/ldrefpage.htm
http://www.amgas.com/large_containers.htm
http://www.amgas.com/clmwhite.htm
We used NH3 as a tracer for leak detection on equipment used in Therminol service and our high pressure hydrogenation equipment.
RE: How to: Leak detection
Note - this is a very sensitive test - volume changes due to thermal expansion/contraction will be easily observable, so you won't have valid results until everything has reached thermal equilibrium.
If small leaks are possible and are likely to cause expensive damage, this might not be a great approach.
RE: How to: Leak detection
1) With the ue systems ultraprobe you have a small warbletone generator (battery operated), put it in the box and scan the seals from the outside. (very fast !!!)
2) Put air pressure on the box, and scan from the outside if something coming out (also fast)
At least compressed air is cheaper than helium, and the sensor is much more sensitive.
RE: How to: Leak detection
Fuji film works good for trouble shooting this kind of problem with leaks on seals.
As other have said He will leak into and through rubber and silicone seals that will hold water forever.
Can you use a product like green locktite to make a permanent seal on some of the locations?
RE: How to: Leak detection
RE: How to: Leak detection
I have used the Ultrasonic Detector SDT170 in several situations with good result.
Even a verry small Freon leak was detected.
You can find information at:
http://www.sdt.be
The principal of the detector is that every leak produces an ultrasonic sound.
So pressurise your unit and check it with the detector
succes
Harry