Electronic leak detectors used in refrigeration

Electronic leak detectors (alongside fluorescent detection fluids, dyes, and foaming agents – foams and soapy solutions) represent one of the methods of performing direct measurements used for leak checking of equipment and installations containing refrigerant. In turn, performing indirect measurements is associated with manual or visual assessment of equipment operating parameters (such as pressure, temperature, current drawn by the compressor, and fluid volumes and levels in the system). The popularity of portable refrigerant leak detectors relative to other methods of locating leaks (e.g. fluorescent agents) is linked to the fact that the use of detection fluids or dyes is possible only when the equipment manufacturer provides for such a possibility.

Obligations arising from regulations and guidelines based on reference documents

The guidelines of the Regulation of the Minister of Development and Finance of 7 December 2017 “On the minimum technical equipment, procedures and system for documenting activities in the conduct of business consisting in the installation, maintenance or servicing, repair or decommissioning of equipment containing fluorinated greenhouse gases” indicate the need to perform checks every 12 months of electronic leak detectors, which should have a minimum sensitivity of 5 g/year.

Technical requirements for electronic leak detection instruments have been defined by standard PN-EN 14624:2020-08 “Performance of portable leak detectors and of room monitors for halogenated refrigerants”. This document contains information on, among other things:

• the application of detectors and the environments in which they may operate;
• requirements for equipment operating parameters (range, sensitivity, response time to a leak);
• servicing of sensors, verification of their correct operation – testing methods;
• performance tests, types of leak standards;
• marking and equipment parameters that should be declared by the manufacturer.

Components and construction of an electronic leak detector

An electronic leak detector is most often composed of the following elements:

• sensor;
• sensor cover (with replaceable filter);
• sensor stem;
• display (or LEDs indicating a detected leak);
• buttons enabling adjustment of detector sensitivity and resetting of indications.

In many devices, air is delivered to the transducer by means of a suction pump. The equipment sensor may use technology based inter alia on infrared (IR) or metal-oxide semiconductor (MOS).

The operating principle of a sensor containing a metal-oxide semiconductor consists in a change in semiconductor resistance as a result of contact with gas (refrigerant) moving towards it. Based on the resistance measurement, the concentration of the detected gas is determined. A drawback of the above technology is the possibility of sensor damage after a single contact with a very high refrigerant concentration, and false reaction to a leak in the case of certain substances of organic origin.

In the case of sensors using infrared (IR) technology, refrigerant concentration is measured on the basis of a drop in infrared transmittance – as a result of its absorption by the gas. The above technology is characterised by greater stability and accuracy of the readings obtained than that based on metal-oxide semiconductor (MOS) technology, but it is more expensive.

Pressing the button responsible for resetting indications while locating a leak will set the detected refrigerant concentration as the reference point for further measurements.

Types of electronic leak detectors

Leak meters indicate the concentration value of the detected refrigerant leak, whereas leak indicators only signal the leak level (without giving a specific concentration value).

Measurement sensors – signs of wear and damage

Incorrect detector response manifested by the device signalling an alarm in a clean environment (free of refrigerant content) is the most common sign of sensor wear. Another sign indicating sensor exhaustion is a significantly extended waiting time for indications to return to the original state – before leak detection (zeroing time to normal operating mode). Falsified leak indication or reduced device sensitivity may result from sensor contamination caused by accumulation of contaminants such as oils or greases in its area. Rapid sensor contamination can occur when operating the detector without the attached cover and filter. Inappropriate response to a refrigerant leak may also indicate incorrect insertion of the sensor pins into the socket located in the head. In some detector models, a sign of twisted sensor pins is incorrect response to a leak when moving the detector. False reaction to a leak may also be caused by contact of the measuring tip with chemical agents (e.g. solvents) or, depending on the device design, with moisture. Sensor life ranges from a dozen or so to several dozen hours of continuous device operation.

Bibliography

Commission Regulation (EC) No 1516/2007 of 19 December 2007 establishing, pursuant to Regulation (EC) No 842/2006 of the European Parliament and of the Council, standard leakage checking requirements for stationary refrigeration, air conditioning and heat pump equipment containing certain fluorinated greenhouse gases
Regulation of the Minister of Development and Finance of 7 December 2017 on the minimum technical equipment, procedures and system for documenting activities in the conduct of business consisting in the installation, maintenance or servicing, repair or decommissioning of equipment containing fluorinated greenhouse gases. Journal of Laws 2017 item 2410.
PN-EN 14624:2020-08 Performance of portable leak detectors and of room monitors for all refrigerants
Tapscott, Robert E.; Sohn, Chang W. Halocarbon Refrigerant Detection Methods. CONSTRUCTION ENGINEERING RESEARCH LAB (ARMY) CHAMPAIGN IL, 1996.
Głąb, M: Leak checking and measuring instruments in refrigeration, wentylacja.com.pl. Access: kontrola szczelnosci i urzadzenia pomiarowe w chlodnictwie 66825.html
Głąb, M: Leak checking and measuring instruments in refrigeration. Chłodnictwo i Klimatyzacja, No. 2, 2019.
Gratkowski, M: Electronic refrigerant leak detectors – equipment characteristics and detector control methods. Chłodnictwo i Klimatyzacja, No. 3, 2023.

Author: Miłosz Gratkowski