This article is authored by Victoria Vernacchio, a product line manager for MSA Bacharach, specialising in fixed diffusion refrigerant sensors for HVAC and Refrigeration applications.
This article looks at compliance and safety standards for ammonia leak detection and how this helps avoid serious accidental injury or death. Refrigeration systems using ammonia are often considered cost-effective, energy-efficient and environmentally friendly. Ammonia has zero ozone depletion potential and zero global warming potential. However, ammonia is classified as a B2 refrigerant under the ISO 817 classification scheme, meaning it has higher toxicity and flammability than other A1 and A2L refrigerants.
Ammonia was first used as a refrigerant in France, in 1959 by Ferdinand Carré. His invention was a system known as absorption refrigeration that used water and ammonia. In the 1860s, ammonia was applied to artificial ice production in the US. Now, ammonia refrigeration systems can be found in a wide range of HVAC&R applications; from occupied spaces such as hospitals, hotels and public buildings to commercial applications such as cold storage, food processing, ice rinks and more.
The requirements for ammonia gas detection systems are regulated by various standards but can vary depending on regulations in particular countries. Widely recognised safety standards for ammonia refrigeration systems are:
- EN 378 Refrigerating systems and heat pumps – Safety and environmental requirements
- ISO 5149 Refrigerating systems and heat pumps – Safety and environmental requirements
- ANSI/IIAR 2 Equipment, Design and Installation of Closed-Circuit Ammonia Mechanical Refrigerating Systems
- SANS 10147:2014 Refrigerating systems, Including Plants Associated with Air-Conditioning Systems
EN 378 is published in Europe by the European Committee for Standardisation and applies to EU member states for the majority of refrigeration systems, including commercial refrigeration and stationary air-conditioning applications. The standard indicates the requirement for gas detection where the concentration of ammonia in an occupied space may exceed the practical limit which is defined at 0.00035kg/m3 (see Table 1).
ISO 5149 is published by the International Organisation for Standardisation (ISO). It applies to all refrigerating systems where the refrigerant is evaporated and
condensed in a closed circuit, including heat pumps and absorption systems. The standard indicates the requirement for gas detection where the concentration of ammonia in an occupied space may exceed the practical limit. It has its equivalent standard in Europe which is EN 378 (see Table 1).
ANSI/IIAR 2 is published by the USbased, International Institute of Ammonia Refrigeration (IIAR) and approved by the American National Standards Institute (ANSI). The standard applies to any closed-circuit mechanical refrigerating system using ammonia specifically as a refrigerant. It is largely harmonised with ASHRAE Standard 15 – Safety Standard or Refrigeration Systems and captures the industry best practices for using ammonia in industrial applications (see Table 2).
SANS 10147:2014 is the South African National Standard (SANS) for Refrigerating systems, Including Plants Associated with Air-Conditioning Systems. The current standard (Edition 5, 2014) is under review with the updated Edition 6 not yet finalised (see Table 3).
ADDITIONAL CONSIDERATIONS REGARDING THE PHYSICAL LOCATION OF DETECTORS
As indicated by ANSI/IIAR 2, ammonia as a vapour is lighter than air. It rises and diffuses simultaneously when released into the atmosphere, which
indicates the location of the detectors above possible leak sources or at ceiling height. However, other conditions should be considered, such as those mentioned in EN 378-3 (p. 9.2) indicating that the location of gas detectors should be planned with local airflow patterns taken into account – which are affected by ventilation sources or louvres. The possibility of mechanical damage or contamination should also be considered.
AMMONIA LEAK DETECTION SOLUTIONS
Aspirated monitoring Aspirated monitoring is considered a reliable ammonia detection method that contributes to personnel safety and plant operability. It protects equipment and people around a wide area due to its stable and selective sensing technology employed within an internal sampling system. Aspirated systems help to comply with EN 378 and ANSI/IIAR 2. It’s important to consider an aspirated system that employs selective and sensitive ammonia leak detection with the ability to read down to at least 10ppm. Low level monitoring provides an early response to ammonia leaks. Unnecessary maintenance costs associated with calibration and exchange of sensors of multiple point detectors can be minimised by using a centralised sample draw system, with a single source Photoacoustic Infrared (PAIR) sensor technology or similar.
Consider employing a system that is equipped with internal relays for fault, three levels of alarm and an external horn option for effective personnel warning as required by standards. Point ammonia monitoring In addition to multiple-point monitoring for ammonia leaks, it is important to monitor specific locations in machine rooms with compressed system equipment, where a leak is likely to occur. One possible solution utilises electrochemical sensors, which address the challenges of short life and stability problems with traditional electrochemical cells.
Consider a device that features ionic liquid electrolyte, which is characterised by extremely low vapour pressure, preventing evaporation within a changing environment. This reduces maintenance as contact with ammonia has virtually no effect on the lifespan of the sensor. Such devices can withstand background gas concentrations due to the choice of the catalyst in the electrode material, which is not consumed during the chemical reaction with the target gas. This allows for an enhanced efficiency for interaction of the electrolyte, the electrode catalyst, and the target gas, regardless of environmental conditions, enabling the sensor to overcome extreme humidity and temperature levels.
The result of breakthrough designs such as this provides a stable, dependable sensor performance, over a longer life span under demanding operating conditions and environments. Perimeter ammonia monitoring Certain plants require ammonia monitoring over wide areas where a large number of detectors may have to be installed. In such cases, perimeter monitoring with open path detectors is an ideal solution, complementing traditional technologies to help enhance the overall safety performance of the gas detection system.
These devices are typically located around the perimeter of a plant, process or storage area; or positioned in close proximity to specific items of a plant, that pose a real risk of gas escape, like compressors, pump sets, pressure reducers, valves and pipe flanges. Consider a gas detector that creates a highly reliable entire detection perimeter around any plant for the detection of ammonia, and one that is suitable for use inside the plant as well as in process areas.
Technology that relies on Enhanced Laser Diode Spectroscopy (ELDS) to detect a specific toxic gas provides an enhanced solution. So, in the event of a gas leak, the sensor’s laser technology recognises and analyses a gas’ specific harmonic fingerprint and issues an alarm when the gas is present. Moreover, ELDS technology has a speed of response of <3 seconds and will detect ammonia anywhere it intercepts the beam. This can result in faster isolation of the leak and a reduction in the volume of ammonia that escapes.
CONCLUSION
The use of ammonia as a refrigerant in industrial applications offers significant benefits in terms of efficiency and cost-effectiveness. However, it comes with inherent risks, including toxicity and flammability, which requires the implementation of effective ammonia detection systems. As technology continues to advance, ammonia detection solutions are becoming more sophisticated and reliable, providing industries with enhanced capabilities to detect and respond to ammonia leaks promptly.
In the ever-evolving landscape of regulations and safety standards, businesses must remain vigilant and proactive in adopting the most suitable ammonia detection systems for their specific refrigeration applications. By doing so, they can safeguard their people, their places, and the planet.
SOURCE
Supplied by MSA Safety
REFERENCES
IIAR, “The History of Ammonia Refrigeration” (https://www.iiar.org/iiar/About_Ammonia_Refrigeration/The_History_of_Ammonia_Refrgeration.aspx)
2. Air conditioning and Refrigeration European Association (AREA), “Introduction to Refrigeration Standard EN378” (https://area-eur.be/publications/introduction-refrigeration-standard-en-378)
3. ISO 5149-3 Refrigerating systems and heat pumps, Safety and environmental requirements, Part 3: Installation site, (https://www.iso.org/standard/54981.html)
4. Brittanica, David Hosansky, “Adsorption Chiller”, (https://www.britannica.com/topic/adsorption-chiller#ref1201934)
5. British Frozen Food Federation, “Safe management of ammonia refrigeration systems”, (https://bfff.co.uk/wp-content/uploads/2016/11/ammonia-guide-smars-2016_copy-0023_stephen-crocker.pdf)
6. Occupational Safety and Health Administration (OSHA). (n.d.). Process Safety Management (PSM) Standard (29 CFR 1910.119) (https://www.osha.gov/lawsregs/regulations/standardnumber/1910/1910.119)
7. MSA Safety, Ammonia Detection Solutions (https://us.msasafety.com/ammonia-detection)
8. South African National Standard (SANS) 10147:2014, SANS 10147 (SABS 0147)
9. Cold Link Africa, “Ammonia refrigeration plants – SANS 10147 Compliant issues”, September 2021,
(https://coldlinkafrica.co.za/ammonia-refrigeration-plants-sans-10147-compliant-issues/)