LEAK DETECTION QUESTION

[MechEngToronto]

Hi,

I would like to know what would be the best way to use to detect a leak in evaporator used in sugar refinery. Has to be non-toxic, cannot be generated from a flamable source (ie.smoke). I was thinking of dye visible under UV light.
Please also mention the manufacturer of the suggested detection agent(s).
Thank you for your help.

 

[iainuts]

Can you use leak detection fluid? ie: soap solution?

 

[weeeds]

One method you may wish to consider, which appears to be perfect for this application, is Helium Leak Detection. We fabricate heat exchangers and pressure vessels and have used this process to verify a leak tight construction and to locate very small leak paths. If you would like more info on this process I can give you the name of a company in greater Toronto who can do this work. Please provide an e-mail address and I can send you the info.

 

[finman]

The UV Dye penetrants I've used are marked "Toxic, use gloves and do not swallow" why anyone would want to swallow dye pen fluid is beyond my imagination but there you go.

I think widla has the solution I'm assuming that a Water Hydrostatic test is out of the question?

 

[nbucska]

The He detector ( mass spectrometer) is very sensitive but expensive

I suggest FREON detector, used by air conditioneer tech's

<nbucska@pcperipherals.com>

 

[weeeds]

Although a mass-spectrometer is expensive there are guys around who have them and provide shop and field inspection services on an hourly basis. Take a look at:

http://www fultonenterprises.com

and go to the Cryogenic section for some information.

 

[vpl]

Something simple, non-toxic, and very cheap: bubble solution, just as iainuts said. I've seen it used at power plants and it works.

Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[shyst]

Helium leak detectors are expensive, but I've used one in a large turbine hall to look for very small leaks in piping and pressure vessels with great success. Perhaps you could rent one to try it out. Compared to soap solutions, Helium was a much quicker method.

 

[cjw81]

If we are talking sugar production, we are in a very volatile plant and combustion sources are extremely dangerous. UV lights put out a lot of heat and even though shielded, can break if mishandled or dropped. Bad news. Use the soap test, get refrigerant grade soap sprayer at a refrigerant or A/C supply house. If you use hot water with the soap, you are expanding the metal and usually the diameter of the leak hole, making it easier to find. You could also pump down the system into the condener and pump up the pressure with nitrogen to aid with leak detection. Then try the fancy stuff.

 

[unclesyd]

Watch out about using Nitrogen if you are going to be close proximity to possible leak or in an enclosed place.

How big is the evaporator, diameter?

If you go the soap bubble route use a leak detection fluid instead of soapy water unless you know the leaks are large.
Do the checking in sections. On some big exchangers where it was thought there might be a leak, we have filled the bundle with water just to cover the tubes, warmed the bundle up the applied N2 or Helium at no more than 10 or 15 lbs. We didn't want to pressure test the vessel with a gas.
We used this on HX where the process tended to plug the leaks when cold.

If nothing has filled the cracks you could use the water wash flourescent penetrant (Zyglo) and developer with a low voltage U.V. lamp. Watch your lamps because some have 400 volts at the bulb.

It is hard to locate a leak in large vessel with tubes using a helium sniffer. Helium diffuses so quick that all you will be able to determine is that there is a leak. Helium checking to locate a leak is a big job on a heat exchanger. There small portable He leak checkers that you can rent. You do loose sensitivity with these units, though the newer units are much more sensitive. We use these units almost everyday to check flanges and valves on a vaporized heating fluid system and on all new construction. Our units were made by Marks, who has since gone out of business. For higher sensitivity we use a Leybold or Edwards mass spec.


Here are a couple of sites that you might want to check out. We use the Amgas products with great success.

http://www.amgas.com/index.htm

http://www.leak-detectors.net/

 

[JKEngineer]

I am not completely clear on the nature of the sugar evaporator, so this answer may be a little off the mark, but:

If it is leaking steam or similar hot fluid or gas, then an Infrared imager will detect the hot area at the leak. Similarly if it is leaking cool material -- it will detect the cool area.

In addition to infrared, airborne ultrasonics should be able to detect the leak. That may require a leak solution.

I am assuming the leak is out to ambient environment.

If the leak is into the process from the environment then IR is still applicable, providing the equipment is, for example, normally hot and the ambient air is cooler. The incoming air will cool the area surrounding the hole and reveal it to an Infrared camera.

If this needs more, or more clear, explanation, feel free to contact me directly.

Jack

Jack M. Kleinfeld, P.E. Kleinfeld Technical Services, Inc.
Infrared Thermography, Finite Element Analysis, Process Engineering

http://www.KleinfeldTechnical.com

 

[weeeds]

Our experience is that when possible product contamination is a concern then we use Helium Leak Detection to locate small leaks. Helium is easy to work with and poses no danger. To pinpoint location of very small leaks we fill the vessel with a few PSI of Helium and &quot;bag&quot; or isolate possible locations of leaks and then &quot;sniff&quot; until the problem is found. This process is quick and leaves no mess to clean up. Also, under the proper controls, the testing can be done without cleaning out the exchanger, saving a great deal of time and money.