Implementing a reliable leak detection method as part of a regular preventive maintenance program can help you easily find and repair refrigerant leaks before they cause problems for your plant.

Multipurpose borescopes slither into inaccessible areas to detect “hidden” leaks. They can be used for both conventional and behind-the-wall inspections.

In March 2008, the U.S. Environmental Protection Agency (EPA) ordered a bread-crumb manufacturing plant to pay $169,822 in penalties and another $811,097 for environmental remediation. The offense? According to the EPA, the plant failed to repair refrigeration equipment that leaked excessive amounts of ozone-depleting chlorofluorocarbons (CFCs).1 Regulations against refrigerant leaks have become so stringent in the United States that the EPA is authorized to issue fines of up to $25,000 per day per violation to anyone who vents CFCs, hydrochlorofluorocarbons (HCFCs) or hydrofluorocarbons (HFCs) into the atmosphere.

Unfortunately, refrigerant leak sites usually are discovered only after a loss of cooling has caused food spoilage, production difficulties or even, in some cases, after legal action has been pursued. While there are many ways to repair leaks, finding them can be a challenge. A single leak detection method that locates every leak in every possible situation simply does not exist. However, by carefully evaluating the most commonly used leak detection methods, you should be able to select the one that is best for your particular application.

Electronic detectors are fast: just turn them on and start leak checking. This model relies on a heated-diode sensor, which is more accurate and less prone to false alarms than corona-suppression types.

Leak Detection Methods

Bubble Solutions.The oldest method of leak detection is the bubble solution. This formula is applied at suspected leak points, usually with a squeeze bottle, brush or dauber. In principle, the escaping refrigerant will produce bubbles at the leak sites, but small leaks or windy conditions might render this technique ineffective. Additionally, the amount of labor required to apply the solution makes this method impractical for a preventive maintenance program.

Halide Torches.Halide torches are more advanced than bubble solutions and rely on the torch’s flame turning green when exposed to refrigerants containing chlorine atoms (CFCs and HCFCs). However, not all refrigerants contain chlorine atoms, and lighted torches can be dangerous or even disastrous in some applications.

Electronic Detectors (Sniffers).The two basic types of electronic detectors used to test for escaping refrigerant are corona suppression and heated diode

Corona-suppression technology calculates changes in the conductivity of gases passing between two electrodes. The instrument generates a high-voltage DC spark that jumps from one point to another in the sensor, establishing a baseline current between the two points. A decrease in current between the two points indicates the presence of an insulating gas. The greater the current drop, the higher the concentration of gas.

Heated-diode technology has a ceramic component that heats refrigerant and breaks apart the molecules, leaving positively charged chlorine or fluorine ions that are attracted to a negatively charged center collection wire. The flow of chlorine or fluorine ions to the center collection wire creates a small current. As the refrigerant concentration between the electrodes increases, the current increases to a level that sets off an audiovisual alarm. As a general rule, heated-diode detectors are more accurate and less prone to false alarms than corona-suppression detectors.

Ultrasonic Detectors.These AC- or battery-powered instruments use a sensitive microphone to “listen” for a high-pitched, inaudible sound caused by the turbulence that results when refrigerant escapes from a leak site. An audiovisual alarm resonates once the leak is detected. Better ultrasonic detectors convert and amplify the inaudible sound of a leak into a more natural sound that the human ear can distinguish with ease.

Fluorescent Leak Detection.This procedure requires adding a fluorescent dye to refrigeration system. The dye intermingles with the lubricant and circulates with the refrigerant throughout the system. Wherever refrigerant leaks out, so does the dye. When the area is scanned with an ultraviolet (UV) or blue-light lamp, the dye glows and pinpoints the exact location of every leak.

Most dyes are supplied in disposable cartridges that are assembled into dye injectors. These injectors allow precise dosing of the system, usually from the low-side service port. The amount of dye required depends on how much refrigerant or oil the system uses (information that usually is printed on a placard on the compressor or other parts of the system.) The dye comes with precise instructions on how much to add based on the refrigerant or oil charge.

When choosing this method, be sure to use an OEM-approved dye that is compatible with the system’s lubricant. Be careful of dyes containing co-solvents because they can adversely affect the lubrication qualities of the system’s oil, which can lead to premature compressor failure. You also should select an ultraviolet or blue light lamp that produces a high-intensity output. The greater the light intensity, the brighter the dye will glow and the easier it will be to spot leaks.

Because the dye remains safely in the system until the lubricant is changed, fluorescent leak detection can be used for preventive maintenance. Checking the system periodically can allow you to catch leaks before substantial amounts of refrigerant are lost.

An advantage of fluorescent leak detection is its ability to pinpoint multiple leak sites in a system precisely.

System Factors

The type of refrigerant being used is important when choosing a leak detection method. Not all methods work well with all types of refrigerants. The system size and configuration must be considered. Vast differences exist between a small refrigerator unit, a medium-sized food processing refrigeration system and a large industrial system that runs on ammonia.

Large systems are more likely to develop multiple leaks, possibly hundreds of feet apart. With some leak detection techniques, technicians might need to be hoisted up to reach piping in the ceiling, and they might also need to check behind walls and around other barriers to locate any additional problems. In a small unit, multiple leaks are more likely to be next to one another, but tight space limitations can make leak identification tedious.

The size of the leak also can affect how easily the source can be detected. In an indoor system, a large leak can raise the refrigerant concentration in the air high enough to set off an area monitor or electronic sniffer; however, finding the exact source might be impossible. Also, small leaks can be masked by larger ones and might be missed until a larger leak is repaired and the system is re-inspected. Having to repair leaks twice wastes time and labor.

When evaluating leak detection methods, consider the technology’s ability to find a leak in a location where several leak sites are in close proximity. Will a large leak hide smaller leaks from detection until after the large one is repaired? Will the detector be able to precisely identify two or more leaks that are close to each other?

A quality fluorescent dye and inspection lamp should be able to highlight almost every leak, regardless of size. For systems with challenging configurations, a multipurpose borescope with both white light and UV or blue light LED sources at the tip can facilitate conventional inspections and leak detection. High-intensity UV or blue-light lamps allow the glowing dye to be seen from as far away as 20', which enables technicians to spot leaks in overhead systems easily.

High-intensity inspection lamps cause fluorescent dye to glow brighter, making it easier to spot leaks under high-ambient-light conditions.

Environmental Factors

Electronic detectors and halide torches sample and test the air in the vicinity of the leaks and can be affected by wind and air currents, leading to a missed leak or false alarm. Wind also interferes with the definitiveness of bubble solutions. In indoor applications, shutting down fans during leak detection procedures might eliminate air currents, but convection currents can still disrupt readings and create confusion.

Ambient sound other than that caused by leaks can adversely affect the performance of some ultrasonic detectors. Noisy environments such as parallel-rack refrigeration systems might fool this type of detector as well. Using quality headphones can help minimize this shortcoming.

Ambient light can wash out the response of visual detectors such as fluorescent dyes, making leaks difficult or impossible to see in outdoor applications. However, this problem can be minimized by using high-intensity UV or blue light lamps and by shading the area with a tarp or large piece of cardboard.

Human Factors

Ease of use and maintenance also are crucial factors when choosing a leak detection method. While experience is the best teacher, choosing a technique that is easy to use and maintain can help even inexperienced personnel identify and repair leaks quickly and effectively.

Due to the high costs of refrigerants, equipment repair and the time and effort needed to locate leaks, proper preventive maintenance of refrigeration systems is essential. By finding and repairing minor leaks early, you can reduce or avoid the occurrence of major problems.