Leak testing of refrigerant circulation systems


Important for people, nature and economy

Regulations governing the leak tightness of refrigerants are becoming increasingly strict. No wonder, since the immense potential of refrigerants to generate greenhouse gases is increasingly in the spotlight in the context of global warming.

To meet regulations and reduce carbon emissions, there is a growing demand for improved, energy-efficient HVAC-R (heating, ventilation, air conditioning and refrigeration) systems and their quality and productivity standards. These demands are supported by modern leak detection systems that precisely ensure the leak tightness of cooling and refrigeration circuits.


Basic operation of refrigeration and air conditioning
A cold beer from the fridge or a pleasant 20 degrees (70°F) in the office: people encounter refrigeration and air conditioning every day. While the refrigerator cools a small, insulated space, air conditioners keep our home, office space or a supermarket at a comfortable temperature. This is due to a physical principle that has been known for a long time: the alternation of gaseous and liquid states of aggregation.

Liquids that expand into a gaseous state extract heat from the surrounding material or surface. In an industrial setting, this process is facilitated by refrigerants. These evaporate or boil at much lower temperatures than water and enable heat to be extracted more quickly from their surroundings. In a nutshell, the refrigeration cycle essentially consists of a compressor, evaporator, condenser, expansion valve and various connection points. It also includes, for example, welds and bolted connections between the individual components. Each of these components must be leak tested to ensure that the complete system functions efficiently and sustainably throughout its life cycle. The significant global warming potential (GWP) of refrigerants is the basis for increasingly stringent regulations and standards in refrigeration and air conditioning.

Rules and standards for refrigeration and air conditioning
The leak tightness of refrigeration and cooling systems is described by means of a loss in mass that occurs over a certain time. In refrigeration and air conditioning technology, the loss of refrigerant in a system is measured in grams per year (g/y). In homes and smaller restaurants and stores, refrigerant loss of 2 to 5 g/y is tolerated. If the refrigerant loss is converted to an equivalent leak rate with a tracer gas concentration of 100%, this corresponds to a leak rate of 1-5 · 10-5 mbar l/s. This defines a leak rate limit in the leak testing process in production. In commercial applications, such as hotels, office buildings and hospitals, the systems differ in size and complexity from residential applications. As a result, these systems have a higher susceptibility to leakage. In sum, a maximum refrigerant loss of 5 to 15 g/y is allowed here. In the industrial sector, the sum of potential leakage is a refrigerant loss of 15 to 30 g/y. This relates to chemical processes that use large-scale process cooling, such as in the production of food or pharmaceuticals.

To adhere to the requirements of regulations and standards, refrigeration circuits must be kept as leak tight as possible. Even the smallest leaks of 10 μm (by comparison: a human hair has a cross-section of 40 μm) can cause immense damage. Consequences may include:

  • Reduced system performance
  • Increased energy demand
  • Overheating
  • Compressor damage and failure

This damage increases downtime as well as operating costs in relation to refrigerants, servicing and electricity – to name but a few. In addition, it can have negative effects on sales, the corporate image and above all: the acceleration of climate change.

At the same time, increasingly stringent regulations and standards present the industry with an ever greater challenge. The Kigali agreement is applicable at an international level. In Europe, the European F-Gas Regulation – EU No. 517/2014 applies. This is the origin of the various regulations and includes the restriction of various refrigerants that have a high GWP. By 2030, a number of refrigerants will be banned through a step-by-step reduction, which will entail a great effort on the part of suppliers and manufacturers: the entire system needs to be revised to ensure efficient and at the same time cost-effective operation of the overall system.

This is only an excerpt.
You can download the full application report as a PDF file.

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