Low temperatures must be generated wherever food and beverages are produced, processed or stored. Ammonia is primarily used in industrial refrigeration, particularly in the food industry, for several reasons: energy efficiency, lower cost and environmental friendliness. Refrigeration systems based on Ammonia (NH3, R717) are common in such applications as:
- Food processing facilities (slaughterhouses, fish plants, dairy factories, canneries, etc.)
- Bottling plants
- Cold storage warehouses
Any refrigeration system based on NH3 poses a risk of leakage, the main causes of which can be: corrosion, leaking valves or operating errors. Since Ammonia is toxic at low concentrations and flammable at higher ppm levels (classified as B2L by hazard level), all Ammonia systems must be designed with safety in mind. This is necessary for fast and accurate detection of leaks and, as a result, for:
- employee safety and protection from exposure to high concentrations;
- damage prevent of system and food stored in the refrigerator;
- minimizing the cost of stopping production, whether it is a real alarm due to dangerous concentrations or just a false alarm;
- reducing the cost of refrigerant topping up.
Industrial refrigeration facilities have to follow the guidelines laid out in EN 378, which implies Ammonia gas detection. According to this standard, the low NH3 hazard level is not more than 500 ppm by volume, and the high hazard level is 30 000 ppm or more. For people safety it is also necessary to comply with the following standards:
EU-OSHA: maximum permissible short-term exposure limit for NH3 - 50 ppm;
WEL: 8hr exposure limit - 25 ppm (TWA);
exposure limit for 15min - 35 ppm (STEL)
Depending on the place type in a plant, certain codes and regulations will apply in each of them.
Requirements for refrigerant leaks detection in machinery rooms are clearly defined in the EN 378 standard. Section 9.1 of EN 378-3:2016 states that “When the concentration of the refrigerant can exceed the practical limit in accordance with EN 378-1:2016, Annex C, detectors shall at least actuate an alarm and in the case of a machinery room the emergency mechanical ventilation.” Practical limit (or pre-alarm level) for R717 refrigerant is 500 ppm, and main-alarm concentration is 30 000 ppm.
In Section 9.2, also stating “At least one detector shall be installed in each machinery room or the occupied space being considered.”
Regarding the requirements for gas detectors in a machinery room, EN 378-3:2016, Section 8.3 highlights that they must activate audible and visual alarms both inside and outside the given place (alarms outside the machinery room may be installed in a monitored location).
In addition to complying with all of the above EN 378 requirements, people safety standards must also be taken into account in refrigerated rooms such as walk-in freezers and cold storages. For personnel protection and early leaks detection inside these places, it is necessary to measure not only high but also low Ammonia concentrations (25 and 35 ppm).
By the standard, audible and visual alarms must be present inside the refrigerated room, however, alarm installation outside walk-in freezers and cold rooms is also widespread. This is important to alert employees who may be entering potentially hazardous areas.
Important requirement for gas detectors in refrigerated rooms is the reliable control of a highly toxic hazardous substance in unfavorable climatic conditions, such as temperature fluctuations or high humidity. Installing Evikon MCI gas detectors is an effective method for threshold violations detection and staff alerting as quickly as possible. A built-in heating element not only allows the detectors to operate at temperatures down to -40℃, but also prevents condensation forming and freezing on the sensor, which ensures accurate readings.
Along with Ammonia detection in machinery and refrigerated rooms, it is also recommended to control R717 levels in ventilation lines to reduce emissions into the atmosphere. Typically, leakage at this point occurs due to overpressure on a safety relief valve, and as a result, its opening. Installing a NH3 gas detector will help alert personnel to increased concentrations and the need to quickly take safety measures to avoid potential hazardous Ammonia exposure.
All occupied spaces such as processing areas need to measure low Ammonia concentrations for employees safety and quick leaks detection. Recommended alarm setpoints for such rooms are 25 and 35 ppm.
Jointly with a sister company Evikontroll Systems it is possible to offer full solutions as well.
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