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We often get questions regarding gas alarms for refrigerating systems, which is why we have written this article, as we know that many of you are wondering the same. In this article, we will explain why gas alarms for refrigerating systems are necessary as well as the requirements and rules for placement, service and maintenance.
What is a refrigerant?
Refrigerants are divided into two groups:
Group 1 deals with explosive, flammable and / or toxic substances e.g. ammonia NH3 and propane C3H8.
Group 2 are substances that are not covered by group 1, e.g. carbon dioxide CO2. CO2 is not in itself toxic and is part of our exhalation, but if the concentration is high enough, it displaces the oxygen content of the air and has a suffocating effect.
What do gas alarms do?
Whether we are talking about toxic, explosive or suffocating substances, emissions of these can have fatal consequences for the environment, for users and employees. In the event of a gas leak, the purpose of the gas detection must be to shut down the plant or process and alert the employees, while the level of the leak is still low with minimal risks as a result.
In short, gas alarms help to ensure the environment and life, and therefore they are often necessary on e.g. workplaces where there are risks of release of hazardous substances.
Where should we place our gas alarms?
Gas alarms are placed where it makes the most sense, ie. where it is easiest to catch a spill and greatest possibility of a leak e.g. at flange joints.
There should be at least one suitable gas alarm in each engine room. Please see AT Guide B.4.4 page 16 and DS / EN378-3: 2016 page 19.
Light gases (e.g. ammonia NH3) rise into the air, and therefore the gas detectors are placed up under the ceiling or e.g. over each NH3 refrigeration compressor.
Be aware that with suspended ceilings, detectors are placed above and below the suspended ceiling.
Heavy gases (e.g. propane C3H8) will settle as a “duvet” at the floor, and therefore the detectors are placed at floor level. The vast majority of gases are heavier than air, ie. their molecular weight is> 28.96 g / mol and they will therefore drop and settle at floor level.
What about carbon dioxide CO2?
Carbon dioxide has a molecular weight of 44.01 g / mol and is thus heavier than atmospheric air, so it seeks the floor. Theoretically, the detectors should thereby be placed at floor level, but since the carbon dioxide molecules travel at speeds of approx. 400 m / s, an emission will quickly mix with the rest of the air / other molecules. The carbon dioxide detectors are therefore typically placed at breathing height, as carbon dioxide in high concentrations displaces the oxygen level of the air. Therefore, one often chooses to install an oxygen alarm.
What are the requirements for warning in the event of an alarm (light / sound)?
The alarm system must warn both audibly and visibly according to DS / EN378-3: 2016 page 18, if the optimal safety must be present. See also AT Guide B.4.4 page 12.
In practice, this means that e.g. a combination of flash and horn is placed at each entrance door and inside the room for the notice of the staff. The staff is clearly “warned” whether they are inside the room or before entering the room. It is good practice to place a sign at each flash and/or horn so that employees know what the warning is about.
What are the requirements for run-in and commissioning?
In general, it is always a good idea to have run-in and commissioning of your gas alarm system, as it is function tested with the correct gas type, flash / horn, etc. as well as any signal transmissions, and you therefore know if it works as intended.
Are we talking about flammable and explosive cooling gases e.g. propane C3H8 and ammonia NH3 in high concentrations, then it is clearly described in EN 60079-29-2 Explosive Atmospheres page 68-69, pkt. 8.11.
What do we do with safety and maintenance?
When installing safety equipment such as gas alarms, it is important that they work as intended so that it is not a false security, which can have fatal consequences, both for the environment and people. The safety equipment must always be serviced according to the supplier’s instructions, at least once a year, but sometimes there may be circumstances that require it to be serviced / calibrated more often than once a year, which is the typical interval according to AT Guide B.4.4 page 16 and 17.
Gas alarms must be suitable for the use in question and calibrated by a competent company. The user / owner must regularly check the gas alarms at least once a year to ensure that they function properly as intended according to DS / EN 378-3.
At Geopal, we have experts who can advise you and your company on the various gases as well as gas alarms. It is important that you and your employees can work safely and securely every single day. We also have competent and specially trained technicians who are evenly distributed in Denmark, and therefore we can offer you nationwide, fast and flexible service.
If you have questions about gas detection and your workplace, do not hesitate to contact us:
Give us as call +45 4567 0600 or send us an e-mail info@geopal.dk
Sources:
AT Guide: Refrigeration systems and heat pumps – Arbejdstilsynet (at.dk) (Danish)
DS Danish Standards Foundation: DS/EN 378-3:2016 – Webshop Danish Standards Foundation, DS/EN 378-3:2016+A1:2020 – Webshop Danish Standards Foundation and DS/EN 60079-29-2:2015 – Webshop Danish Standards Foundation
