Although some leak detection methods are now dated compared to newer test instruments, the old techniques may still be reliable and useful.
Advanced Test Products (ATP), manufacturer of the Amprobe, TIF, Promax, and Robinair lines of test equipment, offers a number of leak detection options. With the amount of equipment available for leak detection, the decisions about which method to use in a given situation can be confusing.
Roger Seymour has been with ATP for decades. He retired as the company’s service department manager, but still assists the manufacturer with answering technical questions.
Seymour has seen the changes in leak detection over the years and has been able to provide insight on where and when each method is best utilized.
One of the earliest electronic leak detectors to be introduced to the industry was the negative corona discharge model. The instrument works by creating a high voltage corona in the sensing tip. When the corona senses refrigerant, the device will sound an alarm.
According to Seymour, early models of the negative corona discharge detector had some problems when they were first introduced. Large doses of refrigerant could “poison” the detector and cause it to malfunction.
The other type of electronic detector is the heated diode model. The technology heats the refrigerant and breaks the molecules apart, creating positively charged chlorine or fluorine ions. The heated diode detector will sense these ions and set off an alarm.
Both the negative corona and heated diode detectors have been improved over the years to prevent them from being too sensitive to large refrigerant leaks.
In fact, TIF has made an improvement on leak detection with its ZX-1 Heated Pentode™ refrigerant detector. According to the company, the heated Pentode eliminates false alarms and detector poisoning. The product can be exposed to 100 percent refrigerant and still keep working.
A false alarm is another disadvantage to some electronic leak detectors, but Seymour said that many manufacturers have been able to overcome this problem as tools become more and more sophisticated.
He explained that earlier models could detect other chemicals, which could interfere with the test. These would produce false results and indicate leaks where no leak exists.
To avoid this problem, another method of electronic leak detector was developed — the ultrasonic type. Ultrasonic detectors do not sense refrigerant. The device is used to detect the high-pitched sound of refrigerant escaping from the system.
“The advantage of these devices is that they are not gas sensitive,” said Seymour. “They are useful for sensing pressure.”
He noted that, as in the cases of the heated diode and the negative corona models, improvements in technology have eliminated many of the problems associated with ultrasonic detectors, but problems can still crop up. One of the biggest complications with an ultrasonic leak detector is the possibility of background interference. Some models, especially earlier versions, can pick up other inaudible sounds not associated with the refrigeration system and sound the alarm on the detector.
To perform this method, a soapy solution is applied to points where a leak is suspected. If there is a leak, the solution will begin to bubble up due to escaping refrigerant.
Seymour said that the bubble method can be used along with some modern technology.
“You can use an ultrasonic detector with a bubble solution,” he said.
The motive behind this is to detect the inaudible crackling sound that will be made due to the refrigerant bursting the small bubbles in the solution.
A more updated method for clearly seeing refrigerant leaks is through the use of a fluorescent dye kit. A dye is injected into the refrigeration system and circulates through the refrigerant. The next step is to shine a UV light on the various parts of the system where a leak could occur. If there is a leak, the refrigerant dye will glow when detected under the UV light.
“With the UV light there are no false indications,” said Seymour. “If it shines, there is no question about it that there is a leak.”
He added that dye kits are even beneficial in automotive refrigerant systems. According to Seymour, engine oils and vapors from a car engine could skew the readings from an electronic leak detector.
But UV lights and dye kits do have drawbacks, he noted.
First, Seymour said that UV lights only work on parts of the refrigeration system that are accessible. If part of the system is hidden from view, the lights cannot be used.
Second, in some applications, dye kits cannot give instant results. According to Seymour, if the leak is very small, it could take time before the UV light can expose any seeping refrigerant.
“The limitation on dyes is that you may have to wait a day or longer for the dye to be detected,” said Seymour. “This means having to make more than one trip to the jobsite.”
He said the long wait is usually due to the size of the leak. Larger leaks will produce quicker results, but if the leaks are very small, it could take a great deal more time.
The intensity of the change in the flame will vary depending on the size of the leaks. One of the most obvious disadvantages to this method is the fact that the halide torch will only be affected by CFCs or HCFCs.
Seymour said that halide torches are still effective, but many contractors do not like the idea of using an open flame near refrigerants.
For those who do elect to use the halide torch, Seymour said there are a few things contractors should remember.
Environment and application will play a big role in the effectiveness of the instrument. Windy conditions will make it difficult for the flame to suck up the gas. Sunlight can also be a problem. If the leak is small, the flame could change to a subtle green color. If the outdoor light is too bright, it could drown out the changing color in the flame.
That is why Seymour discourages contractors from using this method outdoors, especially on rooftop units.
Publication date: 02/10/2003