Refrigerant leaks can be a big problem in just about any commercial refrigeration system.
According to the Environmental Protection Agency (EPA), a typical food retail store leaks an estimated 25 percent of refrigerant, or approximately 1,000 pounds, annually. Depending on the type of refrigerant involved, this can result in everything from hazardous conditions for occupants to environmental ramifications to reduced efficiency of equipment. Not to mention the expenses involved in replacing the refrigerant and filling out leak compliance paperwork.
That is why every food retailer ought to have a comprehensive refrigerant management program in place. Creating this type of program ultimately saves money because preventing leaks is almost always less expensive than repairing them. In fact, the EPA estimates that if every food retailer in the U.S. reduced its refrigeration system’s leak rate to the GreenChill Partner average of 12.9 percent, the industry would save approximately $212 million in annual refrigerant replacement costs.
WHERE THE LEAKS ARE FOUND
When it comes to supermarket refrigeration systems, refrigerants can be a curse, said Jason Ayres, application support engineer with Parasense, a Bacharach company. That’s because, as mentioned above, the leakage of all refrigerants, whether they are HFOs, HFCs, HCFCs, CFCs, or naturals, can have serious consequences.
“Irrespective of the type of refrigerant concerned, the answer is to reduce leakage to an absolute minimum by careful husbandry and training of the contractor base to understand that there is a zero-tolerance policy when it comes to refrigerant leakage,” he said.
However, tracking down every leak can be difficult because large food retailers have expansive refrigeration systems, and leaks can occur just about anywhere. And they can be tiny. As Ayres noted, the majority of refrigerant leakage is due to a number of small leaks that have existed for a very long time, often in these locations:
- Flange joints;
- Flare or compression joints;
- Schrader valves;
- Gauge lines;
- Solenoid valves;
- Expansion valves;
- Compressor shaft seals;
- Liquid line driers;
- Oil reservoirs;
- High-pressure relief valves;
- Sight glasses;
- Isolation valves; and
- Any device that is part of the system and is poorly supported, including pipework.
“Leaks typically occur in areas that have significant changes in temperature, pressure, and vibration,” Ayers said. “That usually includes the rack/pack (e.g., valves, pipe joints, compressors) and evaporators. To a lesser extent, leaks can also occur in piping runs that experience some vibration. Leaks can also come and go, making them very difficult and time consuming to find.”
Karl Johnson, engineering director, Ritchie Engineering Co. Inc./Yellow Jacket, agrees that while leaks can be challenging to find, they often occur in likely spots, such as joints and connections.
“Refrigerant vapor density affects which direction the gas will move and accumulate,” he said. “Hints like oil leakage can also pinpoint likely leak locations. When a leak is suspected, a handheld leak detector designed for the purpose can be used to precisely locate the leak. The leak can then be marked and appropriate measures taken to fix or monitor it.”
That said, Johnson noted that tracking down leaks would not be such an issue if more care were taken during the installation and servicing of refrigeration systems.
“A well-designed and operating refrigeration system should run essentially trouble-free,” he said. “Installation and commissioning procedures must ensure a leak-free system, and subsequent maintenance should include testing the system to ensure it is leak free.”
Indeed, leaks often occur at the weakest points in a refrigeration system, which can be a result of poor installation.
“These points are typically assembled joints that can flex or loosen over time,” said Keith Baughman, training manager, Danfoss. “Any joint that has excessive movement — such as those not properly installed — will break down over time. In addition, improper installation with poorly soldered joints, nonconforming clamping/hangers, and excessive vibration will create weak points that can lead to a leak. Packing nuts are also a known failure point.”
Aging equipment, improper design, and lack of maintenance can also contribute to leaks in a refrigeration system, said Matthew Cowley, North America sales accounts manager of leak detection, Spectronics Corp. That is why having a proper refrigerant management program in place is so important.
CREATING A PROGRAM
While many food retailers maintain a leak detection program to meet and comply with EPA standards, their programs are not necessarily comprehensive enough, said Baughman.
“Retailers are only required to find and fix a leak when it becomes necessary to add additional refrigerant to the system,” he said. “This must be logged with details on the amount and what was repaired. But a refrigeration system should also be constantly monitored for leaks by tracking receiver levels trends and using a leak detection system with enough zones to cover the entire system.”
Many small food retailers, such as restaurants and convenience stores, tend to have little or no proactive leak detection programs, and they typically do not address leaks until they have equipment failures, said Cowley. He added that larger food retailers, such as supermarkets, sports arenas, and food processing facilities, are usually more proactive regarding leak detection.
“Facilities with leak detection programs in place usually include a variety of automatic alarms and portable devices like sniffers,” said Cowley. “But there’s a big difference between knowing if there’s a leak versus finding it. Even advanced alarm systems cannot help a technician pinpoint the exact leak area.”
That’s why a good preventative maintenance plan relies on a variety of tools including fluorescent leak detection dye, which helps technicians visually find leaks, said Cowley.
“Alarm systems and sniffers can help determine if there’s a problem, but fluorescent dye visually shows the precise locations of all leak areas,” he said. “This is important because aging systems may have multiple leak areas, and a technician can mistakenly think a repair was successful. These false-positive repairs cause a lot of frustration and expense. Fluorescent leak detection dye is a vital tool for any visual, 24/7 leak detection and preventative maintenance plan.”
A comprehensive leak detection program should also include real-time monitoring and alarming capability that can improve safety, said Baughman. Additionally, the detector system needs to have history logging capabilities that allow maintenance personnel to look for patterns and better deduce the causes of leaks, he said. For example, a leak that recurs at specific times could be related to defrosting or when there is a change in outside temperature.
“There are different monitoring systems available that can deliver different end results,” said Baughman. “The better PPM detail will come from infrared technology, but these systems are typically more expensive. That is why this style will typically share a common infrared bench for analyzing and uses tubes and solenoid valves to incorporate multiple zones into a single bench (analyzing chamber) application. Because of the multiple-zone application, and the need to draw a fresh sample several hundred feet at times, the reading of any specific zone may have a delay as the unit cycles through all the zones.”
The solid-state style of detector is typically not as accurate on the PPM reading, said Baughman, but it can deliver an acceptable reading that is instantly measured and reported. This application is better suited for walk-ins, as people are present in these areas and evacuation is important.
“Using receiver level gauges can also help identify leaks in areas in which it is not practical to place leak detection devices,” he said. “These systems should have the capability to constantly log the PPM value of every zone and liquid level with a time and date stamp. This can also be done through other control platforms via a communication loop. Regardless of the device recording this information, it is important to have the ability to report leaks to a monitoring center and remotely review trends and other factors that influence liquid levels for real-time action. For example, Danfoss Enterprise Services offers a data integration and connectivity platform that provides 24x365 alarm monitoring and alarm callout notification for refrigeration, HVAC, energy, lighting, and other equipment in the supermarket ecosystem.”
A truly proactive refrigerant management program includes the correct type of leak detection technology (e.g., aspirated infrared multipoint system) coupled with a comprehensive remote monitoring and refrigerant tracking system, said Ayres.
“We have developed two statistics that measure the effectiveness of the detection systems employed,” he said. “The first is the leak index, and it is defined as the number of leak events that occur. Each leak event is also weighed by its status — alert, alarm, or critical — allowing for the amount of refrigerant lost to the atmosphere. This technique provides a very useful method of comparing the integrity of the same or different types of equipment using a single statistic.”
The second statistic is the leak rate, which is used to measure the amount of leakage due to a single piece of equipment. Ayres said this is defined as the amount of refrigerant used divided by the total entrained charge expressed as a percentage over a 12-month rolling period.
“The leak index acts as an early warning for a pending increased usage of refrigerant, while the leak rate defines the long-term performance,” said Ayres. “The secret in getting and keeping a low leak rate is to manage the leak index by quickly and effectively responding to leak events detected by the monitor.”
That is why creating a comprehensive leak detection program is more than having the right tools and equipment. Protocols for notifying the right person should also be established prior to a leak, said Cowley, as this will ensure expediency in either getting a service technician there quickly or having experts diagnose the issue remotely. While this may seem like a daunting task, creating a comprehensive refrigerant management program is worth it in the long run.
PROPER TOOLS: The tools to compare both leak rate and leak index are available on the Parasense Refrigerant Management Platform.
“Ultimately, preventative maintenance relies on a variety of tools and leak detection methods,” said Cowley. “To maximize the return on your investment, test what combination of tools best fit your exact equipment and maintenance needs. Some tools are easier to integrate into existing maintenance plans than others. Regardless, the goal is the same: to improve facility operations. Experiment with different tools, collect data, and create a regular maintenance schedule. These are the keys to starting an effective leak detection and preventative maintenance plan.”
Publication date: 4/1/2019