Choosing the Right Leak Detector

In industrial processes, leak detection is of strategic importance for economic, environmental, and safety reasons.

Energy efficiency: Compressed air leaks are responsible for higher energy consumption, placing greater demands on equipment such as compressors and increasing operating costs.
Plant safety: Leaks of noxious, flammable, or explosive gases expose operators and installations to significant risks.
Environmental impact: Some gases, notably refrigerant fluids, contribute significantly to the greenhouse effect and must be controlled.

Detecting the presence of a leak in a pressurized or vacuum system may seem straightforward, as a simple pressure measurement is often enough to identify the leak. However, pinpointing the exact location of the leak is essential if you are to intervene quickly and effectively.

This is where leak detectors come in. Their role is not simply to identify the existence of a leak, but above all to locate its origin, so that corrective action can be taken.

This buying guide explores the main leak detection technologies, detailing their advantages and disadvantages, to help you choose the solution best suited to your needs.

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  • How to detect a leak with an aerosol

    A simple and inexpensive way to detect a leak in a gas circuit is to use a leak detector spray, which usually contains a mixture of water and soap. When the aerosol is sprayed on an area where a leak is suspected, the escaping gas will cause foam or bubbles to appear at the exact location of the leak.

    OKS leak detector spray

    OKS leak detector spray

    Advantages of leak detection sprays:

    • Bubbles help locate leaks quickly and accurately
    • Can be used with all types of gas, including flammable gases
    • Inexpensive

    Disadvantages of leak detection sprays:

    • Used to locate a suspected leak. You can’t spray an entire circuit in the hope of finding the leak.
    • You need visual access to the leak site.
    • Not suitable for very small leaks that won’t cause the product to foam.
    • Cannot be used in vacuum chambers, as the product would enter by suction and contaminate it.
    • The sprayed area must be cleaned to remove the product after use.
  • How to detect a leak with a fluorescent tracer

    This method is used for refrigeration circuits, and in particular for automotive air conditioning.

    Errecom tracer liquid

    Errecom tracer liquid

    This involves injecting a fluorescent tracer compatible with the refrigerant into the circuit, and after a period of homogenization, inspecting the circuit with an ultraviolet lamp. When there’s a leak, the tracer will emerge from the circuit, forming spots that fluoresce under ultraviolet light.

    Advantages of fluorescence detection:

    • The tracer is harmless to the operation of the refrigeration circuit, so it can be injected into the circuit as a preventive measure.
    • Traces remain visible until the repair is made.

    Disadvantages of fluorescence detection:

    • This method is effective in dark environments. In brightly lit environments, the spots formed by the tracer are difficult to spot despite fluorescence.
    • Less effective on very small leaks, which will produce too small of stains.
  • How to detect a leak with an ionization, heated diode, or infrared detector

    These electronic leak detectors are used to detect leaks in circuits containing refrigerants or combustible gases, by detecting the presence in the atmosphere of the gas escaping through the leak.

    Kimo Sauermann leak detector

    Kimo Sauermann leak detector

    These portable devices are almost always fitted with a flexible hose, enabling them to inspect all leak-prone areas of a circuit, even those that are difficult to access.

    Several types of detectors are available: ionization detectors, heated diode detectors, and infrared detectors.

    Ionization detectors

    This is the oldest electronic detection technology. These detectors draw in ambient air via a built-in micro-pump and send it into an ionization chamber equipped with oppositely charged platinum electrodes.

    When halogenated refrigerant gas from the leak passes through the chamber between the electrodes, it is ionized and causes a change in the electric current.

    Advantages:

    • This detector works with all halogenated refrigerant gases.
    • It is inexpensive compared with more recent technologies.

    Heated diode detectors

    For this type of detector, a ceramic diode sensor is located at the end of the hose. This diode is heated to a temperature corresponding to the gas to be detected. The diode reacts to the presence of halogenated refrigerant gas by producing fluoride ions from the gas molecules, thereby modifying the electrical current flowing through it. This electrical signal is sent to the device’s electronics, which triggers an audible and visual alarm.

    Heated diode electronic detectors can detect both low and high concentrations of gas, and some models offer sensor temperature adjustment for precise detection of certain gases. These detectors deliver progressive signals as a function of gas concentration, enabling the search to be directed right up to the leak. These detectors are more sensitive to interference from other gases in the ambient air and may trigger false alarms. They can also become overloaded if the ambient air is saturated with gas from the leak.

    Advantages:

    • This highly sensitive detector can detect even low concentrations of gas. What’s more, the detector’s sound signals are progressive, enabling it to pinpoint the area of the leak where gas concentrations are highest.
    • Like ionization detectors, these are compatible with all halogenated refrigerant gases (CFC, HFC, HCFC).

    Disadvantages:

    • As this detector is very sensitive, it can sometimes trigger false alarms.
    • In areas saturated with refrigerant gas, the sensor may be overloaded.
    • The sensor has a service life of 100 hours.

    Infrared detectors

    Infrared leak detectors draw air through an optical sensor; refrigerant gas alters the amount of infrared transmitted to the sensor, and the detector electronics trigger an alarm. Infrared detectors are considered better than the previous two because their sensor can last up to 10 years, they are not overloaded in a gas-saturated environment, and they are less prone to triggering false alarms. On the other hand, they are more expensive to buy. Infrared electronic detectors work with all CFC, HFC, and HCFC refrigerant gases.

    Advantages:

    • These are considered the most reliable for detection.
    • The sensor has a life expectancy of 10 years.
    • Less prone to false alarms.
    • Not overloaded in gas-saturated zones.
    • They also work with all types of refrigerant gas.

    Disadvantages:

    • More expensive than the other two types of detectors.
  • How to detect a leak with an ultrasonic detector

    An ultrasonic leak detector cannot detect the presence of gas from a leak in the atmosphere, but it can detect the noise emitted by a leak.

    CS Instruments ultrasonic leak detector

    CS Instruments ultrasonic leak detector

    A leak in a pressurized circuit produces a noise whose level depends on the size of the leak and the pressure difference between the circuit and the atmosphere. Unfortunately, this noise is inaudible to the human ear, as the frequencies are in the ultrasonic range. An ultrasonic detector detects this noise and transforms it into a visual or audible alert for the operator.

    Ultrasonic detectors are equipped with a directional microphone, so they can search for the origin of a leak by scanning a circuit with the sensor. The sound or visual signal emitted by the sensor increases as you get closer to the leak.

    Ultrasonic detectors are used in particular to detect compressed air leaks, which cannot be detected with other detection technologies.

    Advantages:

    • Detects leaks of any type of gas (compressed air, nitrogen, refrigerant, propane, butane, natural gas, etc.).
    • Detection is possible even in ventilated environments where gases dissipate very quickly, or even in difficult climatic conditions (rain, wind, etc.).

    Disadvantages:

    • As it is an acoustic detector, it is sensitive to the presence of other ultrasonic sources.
  • How to detect a leak with a helium detector

    A helium leak detector can also be called a mass spectrometer leak detector (MSLD), as it uses a mass spectrometer to detect the presence of helium, which is used as a tracer gas.

    Pfeiffer Vacuum helium leak detector

    Pfeiffer Vacuum helium leak detector

    Helium is used as a tracer gas because it has a number of advantages:

    • Helium is non-toxic, chemically inert, and non-flammable.
    • Helium molecules have a very small atomic size, enabling them to squeeze through the smallest leak.
    • Helium is only present in air in trace amounts, so atmospheric helium does not interfere with the detection process.
    • Helium gas is relatively available and inexpensive.

    This type of detector can be used to search for leaks in circuits or sealed enclosures and to test how airtight a room is. It is composed of a mass spectrometer set up to detect the presence of helium, and a pumping device that draws in air and passes it through the spectrometer. This detector can be used in two ways.

    • The first is by pressurizing the inside of the circuit or room with helium (or a mixture of helium and air or nitrogen) and checking the outside with a probe connected to the leak detector inlet.
    • The second is by emptying the inside of the circuit or room by connecting the detector to the pumping system and spraying the helium outside with a calibrated micro-leak probe.

    In both cases, if helium leaks through the circuit or room wall, it is pumped through the spectrometer, which reacts by delivering an audible and visual signal that qualifies the quantity of helium detected.

    The choice between these two detection methods must be made taking into account the working conditions of the part being tested, as it is important to have the same pressure conditions during the test as during actual use of the part. Vacuum systems will therefore be tested by drawing a vacuum inside the circuit or enclosure.

    This type of detector is widely used to test vacuum systems, to check the tightness of components, or to carry out quality control on parts such as gaskets, piping, etc.

    Advantages:

    • Capable of detecting very small leaks.
    • Suitable for vacuum and pressure testing, and for testing complete systems and isolated components.

    Disadvantages:

    • More expensive and bulky than other detectors.
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