The leakage of refrigerant gas is currently one of the major issues in industrial and commercial refrigeration, largely driven by the ongoing uncertainty in the refrigerant gas market, including its prices and availability. Therefore, the analysis and detection of refrigerant gas in the broader context of industrial and commercial refrigeration should be a priority for every operator and maintainer of refrigeration systems. In this new installment, based on the extensive and detailed technical article by our colleague Xavier Albets-Chico, “Manual for the detection and reduction of refrigerant gas leaks,” I will explain:
- The main reasons for refrigerant gas leaks
- The consequences of these leaks
- Where leaks commonly occur
- How to prevent them
The total tightness of a refrigeration system throughout its lifespan is very difficult to achieve, as there are variations in pressure and temperature, vibrations, and maintenance activities that can alter the initial tightness of the system.
Specifically, the study “Refrigerant Containment Study. Eric Devin et al. Conducted for ADEME by Cemafroid and IRSTEA. September 2015” indicated that the degradation of the original tightness of the installation is mainly attributed to up to nine distinct causes, among others:
- Imperfect welds
- Imperfect tightening (insufficient or excessive) of nuts and bolts
- Uninstalled valve caps
- Incompatibility of mechanical elements with lubrication oils (retrofit)
- Vibrations near compressors
- Thermal expansions (defrost cycles)
- Corrosion with food products (furniture, refrigerated islands, display cases, etc.)
- Metal contact (copper-iron) causing abrasion and/or galvanic corrosion
- Poor support of pipes and mechanical stress
Refrigerant leaks have consequences primarily in five distinct yet interconnected aspects:
- Refrigeration operation
- Economic and product preservation
- Environmental impact
- Safety
2.1 Consequences for Refrigeration Operation:
Small-capacity refrigeration systems with capillary tubes, lacking a liquid receiver, are considered “critical charge” systems. Any refrigerant loss immediately results in a lack of refrigerant supply to the evaporator, causing an immediate decrease in refrigeration capacity, an increase in compressor consumption, and quickly leading to a situation where the refrigeration system cannot maintain the temperature of the cooled space.
In refrigeration systems with a liquid receiver and expansion valve, symptoms of refrigerant shortage do not manifest until a certain minimum level of refrigerant in the receiver is reached. Below this level, vortex effects cause gas bubbles to enter the liquid line, and these bubbles become visible in the sight glass.
When this occurs, the system’s efficiency begins to deteriorate. Gas bubbles in the liquid line (known as flash gas) reduce the capacity of expansion valves, increase the superheat of evaporators, and prolong compressor runtime to reach the temperature setpoint. As a result, the energy consumption of the system increases (see Figure 1).
From that point forward, if the leak continues to increase, there will come a moment when the system pressures decrease, and the desired setpoint temperature in refrigerated services cannot be achieved (lack of cooling). In the case of refrigeration plants, typically, the service furthest away is the first to exhibit symptoms of refrigerant shortage, with an evident difficulty in reaching its setpoint temperature.
2.2 Economic and Product Preservation Consequences:
As previously mentioned, refrigerant leaks increase the energy consumption of the refrigeration system, raising the economic cost of its operation.
For instance, a commercial refrigeration system operating with only 80% of the minimum required refrigerant charge consumes an additional 15% of energy, on average.
Figure 2 illustrates the evolution of the increased operating cost of the refrigeration installation with the percentage of leakage (‘Refrigerant Loss, System Efficiency and Reliability– A Global Perspective; GEA Refrigeration UK Ltd for Institute Of Refrigeration (IOR). ©Institute of Refrigeration Annual Conference 2013’).
Other associated economic costs include:
- Cost of recharged refrigerant, along with associated taxes and fees in Spain.
- Cost for potential merchandise losses due to the breakage of the cold chain.
- Cost of temporary cessation of economic activity due to a lack of refrigeration.
- Cost incurred due to product losses and/or deterioration when not properly preserved at the correct temperature due to a lack of gas.
These costs increase the longer it takes us to detect the leak, as we can see in Figure 3:
2.3 Environmental Consequences:
The release of CO2 into the atmosphere is another significant adverse effect of refrigerant gas leaks. The molecules of HFC gases released into the atmosphere contribute to the well-known greenhouse effect, persisting for several decades, making it a long-lasting environmental problem.
The so-called GWP (Global Warming Potential) indicates the equivalent in kilograms of CO2, in terms of global warming, for each kilogram of refrigerant. For example, 1 kg of R404A emitted into the atmosphere is equivalent to 3922 kgs of CO2 emitted. This data takes into account its thermal absorption and radiation activity, as well as the atmospheric stability period during which this “greenhouse effect” activity is present.
There is also an indirect environmental effect due to increased electricity consumption, as analyzed previously when a leak occurs, along with the loss and deterioration of products, collectively resulting in even higher CO2 emissions.
2.4 Consequences for Safety:
A refrigerant leak in an enclosed space poses a potential danger to people, leading to drowsiness, loss of consciousness, and even suffocation (due to oxygen displacement) at elevated concentrations.
Currently, the increased use of low GWP refrigerants (thanks to their low stability in the atmosphere) introduces certain degrees of flammability precisely because of their low stability, corresponding to groups A2L, A2, and A3 (see Table 2). These gases present a challenge to the safety of installations in the event of leaks. The risk of flammability, if not properly addressed, can endanger the safety of people and property, making early detection crucial for both human safety and the proper functioning of the installation, as these systems often operate with very low gas charges.
This specific aspect of safety is addressed in the Spanish Regulation for the Safety of Refrigeration Installations (RSIF, published in October 2019 in RD552/2019), and the European standard EN 378:2016 and previous versions.”
The most likely leakage points in a refrigeration system, based on the previously mentioned causes of leaks and emissions, have been studied by multiple sources. We present a summary of them. See Figure 4:
Manipulable Components:
- Service valves
- Caps
Threaded Components:
- Valve cores
- Flared connections
- SAE connections
Removable Components:
- Filters
- Flanges
Other Components:
- Condensers
- Evaporators
And after all this, what can we do to combat leaks?
4.1 Regular and Planned Maintenance
The foundation of any leak prevention strategy is a rigorous maintenance plan. Refrigeration systems should be regularly inspected and maintained by trained professionals. This includes checking key components, early detection of wear, and repairing or replacing deteriorated parts before they cause leaks.
4.2 Training and Awareness
Training staff in the early detection of leaks and proper handling practices is essential. A culture of awareness about the importance of leak prevention can lead to increased vigilance and the adoption of responsible practices. It’s important to note that proactive gas leak detection requires different knowledge and techniques compared to dealing with existing and significant leaks, emphasizing the crucial role of training for refrigeration professionals.
4.3 Use of Advanced Technologies
As discussed on numerous occasions, at AKO Group, we have a continuous monitoring system for the early detection and repair of gas leaks, AKOGAS NDIR, which can reduce refrigerant gas leaks by up to 95%. Monitoring, as mentioned in the first article of this newsletter, is crucial for proper maintenance and brings significant economic benefits.
4.4 Inspections at Critical Points
Refrigeration systems have critical points where leaks are more likely, as discussed in this article. Focusing inspections and maintenance on these areas can significantly reduce the risk.
4.5 Sealing Connections and Fixtures
Components of refrigeration systems must be properly sealed and fastened to prevent leaks. Using high-quality materials, along with appropriate installation techniques and fastening elements, can prevent problems from the outset.
4.6 Regulatory Compliance
Compliance with regulations and standards related to refrigerant gas management is essential. Staying up-to-date with local and international standards is not only a legal requirement but also a measure to ensure safety and sustainability.
In summary, preventing refrigerant gas leaks in refrigeration systems requires a combination of constant maintenance, advanced technology, and a proactive mindset. Adopting these key steps not only contributes to environmental conservation but also saves long-term operational costs and strengthens the corporate responsibility reputation. In a world where sustainability is increasingly valued, preventing refrigerant gas leaks is a necessary step toward a cleaner and more efficient future.
Author: José María Cabria
Business Development, Food Retail Iberia