Absorption Chiller

When I worked for the Trane company (~1976) they manufactured these systems, they used helium. They placed a poly sheet over the unit under test, and flooded this tent area with helium. And via some sort of sensor inside the absorption pressure vessel, helium could be detected. I did not work on this product line, so it was only hear-say that I recall this leak test method. And my memory could be wrong. Helium was used as the atom is small, and could find the leak holes.

He leak tests are common but require special equipment.

You probably need to call a specialist...and then another specialist....

http://en.wikipedia.org/wiki/Helium_mass_spectrometer

http://www.lbdassociates.com/libr/index.html

Way back when ... I was working in the field, when I had an absorption (NHH20) unit with a leak, I would apply a coat of rubberized paint on everything except the generator section. Let it cure then service the system. It was quick fix and didn't require a bunch of test equipment or pulling your hair out. I had about a 98% success rate and still have a full head of hair too

Why can't the equipment manufacturer advise? Make a telephone call!

I know nothing about this type of chiller other than having looked at them in operation. Vacuum leaks are very hard to detect and I know nothing of the vacuum levels in this system. However, I did a lot of work on power transformers which on a sealed unit can run from around +7 to -5 psi in the gas space. We used an ultrasonic detector to pick up the sound made by a leak when the system was under vacuum. These also worked fine when under pressure also but then so did soap solutions, so we mainly used the ultrasonic leak detectors when we could not pressurize the units, or the customers did not want us to. They seem tricky to use at first but once you have a little practice they are great.

Do these chillers have readouts for the vacuum level? If they do wouldn't changes correlated with temperature readings give some indication of whether the unit even has a leak at all?

Duct tape!

UltraSound detection may work from the outside as it will pick up the noise from air rushing in the leak. If it is tiny such as much smaller than a pinhole the signature will be quite small but will show. Contact UE or SDT for more info as it is a valuable technology very useful in vacuum leaks of most varieties.

In a power plant setting we have used foamy shaving cream to test suspect areas, however, this might contaminate your LiBr system if the leak is big, and if small leak, probably not going to see it. Typically the shaving cream gets sucked in where the leak is.

If you can afford it, paint the suspected leaky joints with rubberized paint, as was suggested by another responder. That is a good idea.

hi james,

thanks for comment. i personally think that ur suggestion is more practical at the moment.

The shaving cream idea was for testing vacuum leaks on condensate pump seals where the hotwell is under approximately 23-25.5" Hg vacuum. (Based on local absolute barometric pressure of 27-27.5" Hg.) One does not allow a lot of the soapy foam to enter the system.

If it is a large enough leak to suck in a lot of soap foam, you could find the leak by listening or smoke testing. Granted, introduction of something that could lower the surface tension of the LiBr solution in the chiller might cause a foaming issue, then you would have to add some defoamer. Better to use the plastic sheet, Helium, and a helium leak detector. Or - just go around with a helium bottle and a section of tubing so you can place the helium flow in one localized area. The helium detector is pulling its sample from within the vacuum section of the chiller, and you will either see an increase or not within a few minutes of starting helium in a localized area.

I am sure there are contractors that would be more than happy to come out and help you with this for a fee. Why not contact the OEM, or the people that installed this piece of equipment?

Hi James, I meant no offence to your idea of the shaving cream trick. I like it, and could be very practical troubleshooting tool for other things besides refrigeration systems . The trouble with any absorption refrigeration system is the pH balance. What's passive on mild steel components destroys copper components and and just the opposite is true, what's passive for copper attacks the mild steel. And that's not even going into non-condensables.

Also,there's been suggestions about using duct tape, that might work temporary, but what I know from experience is, refrigeration systems are not closely watched, you don't think about them until something goes wrong. And probably the most neglected piece of equipment in use, both industrial and households.

Being the OP didn't mention what make, model or size this unit is, I totally agree with you, the OP should call a professional that deals with absorption systems. This is not something you can repair by a "U-tube" video.

Different system, but similar problem...

I used to work with high-vacuum (chemical) reactors. We routinely wrapped duct tape around each flanged connection. These were big batch reactors, and there were wide temperature-swings as each batch was heated-up, reacted, and cooled-down. After countless temperature & vacuum cycles, the inevitable expansions & contractions of the gaskets, bolts and flanges eventually resulted in small leaks. The duct tape did a good job of sealing the connection and we could see the duct tape getting sucked in as a gasket leak developed. When we needed to open a connection, duct tape was easy to remove/replace.

Just do a pressure test with nitrogen and after you have identified and repaired the leak pull the system back down with a vacuum pump. If it will hold twice design pressure it will hold vacuum.

Cheers!