All types of refrigeration appliances and systems contain condenser coils. Though they may vary in size and design, they share the common need for leak testing in manufacturing. Their shape and the number of brazed joints to be checked can make detecting leaks a challenge, and the use of more energy-efficient and environmentally safe refrigerants such as R1234yf and R600, has also reduced the allowable leak rate.
Choosing the most effective leak testing method depends upon a few factors. The target leak rate is certainly the driving influence, but cost is, as always, another consideration. This can lead to trade-offs on such things as cycle time versus cost.
Here are 5 ways to test refrigeration condenser coils and the pros and cons of each testing method:
1. Using a dunk tank for bubble testing leaks in refrigeration coils
The dunk tank is the basic test that many manufacturers start with. It can be an acceptable method, but bubble testing is only good down to leak rates in the range of 10-4 scc/sec. The permissible leak rate is now 0.5 grams of refrigerant loss per year, which is comparable to one 3mm bubble being released underwater, every 1.2 hours. This equates to the mid 10-6 scc/sec range which means dunk testing may not be the most effective test for this type of part.
2. Sniffer leak detection of cooling coils
One of the most popular tracer gas techniques for this application, it is used in a couple of ways. One is to find the location of a leak on a coil assembly that has failed a leak test through other means, such as after a hard vacuum test. This allows repair of a completed assembly to meet the specification.
Or a sniffer is used to find the leak: an operator scans the coil from top to bottom, spending less than a half a second on any joint kind of fanning down through the air over the part. Then if they get a leak measurement signal, they slow down their motion to locate where it's at and then they'll go do the same at the other end of the coil.
In a clean air sniffer booth this method may successfully find leaks in the high 10-5 scc/sec range, but it is not very fast. If the requirement is down to mid 10-6 scc/sec, sniff testing will not be enough due to background noise issues.
3. Leak testing with accumulation tracer gas systems
An accumulation leak test system is similar to sniffing but uses an enclosure to isolate the part in a fixed volume for a more measurable leak rate by containing the tracer gas to measure a concentration rate of rise. Once the tracer gas has accumulated, a mass spectrometer is used to measure how much, if any, gas has leaked from the test part into the fixed volume chamber over a set amount of time.
Another affordable type of test, accumulation offers similar accuracy as the bubble tank or sniff testing, in the 10-4 to 10-5 scc/sec range dependent upon chamber size, test time, and trace gas background levels. Because of this and the demands of the new leak rates, hard vacuum is really a better option.
4. Hard vacuum helium leak testing of condensers
A vacuum leak test uses a vacuum chamber to test the part. Atmosphere is evacuated from the chamber and from inside the part, and when the vacuum level stabilizes, the mass spectrometer or residual gas analyzer measures the baseline level of the tracer gas.
One of the most effective techniques, hard vacuum tracer gas testing is the most accurate, efficient, and repeatable of the leak test methods to meet the low leak rates of condenser coils. It also provides shorter cycle times when performed with the appropriate pumping packages. All of this comes at a higher cost than other methods.
5. Leak testing connections to the refrigeration assembly using nitrogen purge clamshell
Nitrogen purge clamshells enable you to clamp down on a joint, remove the influence of atmospheric background from the test without an expensive vacuum chamber, and get a reliable result down to low 10-5 scc/sec and mid 10-6 scc/sec ranges.
Though accurate, the number of joints in a typical coil assembly does not make this a suitable solution for general production. That’s why nitrogen purge is usually used further down the line, after the assembly has passed its first leak test and after it has the additional high and low side or inlet and outlet braised into it. The clamshell is used to test those final critical braised joints.
Download our new guide to learn how to choose the right testing methodology for your refrigerant system and optimize your current testing process.
Leak testing solutions for refrigeration and cooling component manufacturers
CTS has worked with the world’s top manufacturers of refrigeration coils and condensers. Put our expertise to work for you to meet your target specification. We have a complete range of solutions to help you at every stage of coil assembly. If you have questions on the appropriate leak test methods, contact us to talk to a specialist.
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