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 , energyefficient 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
Ammonia refrigeration system .
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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
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• 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
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All images supplied by MSA Safety
Victoria Vernacchio , a Product Line Manager for MSA Bacharach , specialising in fixed diffusion refrigerant sensors for HVAC and Refrigeration applications .
for 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 ).
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EN 378-3 / ISO 5149-3 |
Europe |
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One refrigerant detector is required as a minimum for each refrigeration machinery room and / or occupied space .
Note :
• Ammonia systems with charge greater than 500kg , require gas detectors within heat transfer circuit of indirect systems .
• Machinery rooms with compressors require a minimum of one detector placed over the compressor unit .
• Refrigerant pumps in any areas require a detector placed over or near the pumps .
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Ammonia system with charge greater than 50kg require a gas detector to warn in case of fire risk and for control purposes .
Alarming levels and actions : ( 1st ) Pre-alarm – Mechanical ventilation activated for concentrations not exceeding 500 ppm ( EN ) or 200 ppm ( ISO ).
( 2nd ) Main alarm – both refrigerating system and mechanical ventilation stopped , power supply to machinery rooms Isolated automatically – for concentrations not exceeding 30 000 ppm .
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Visual and audible alarms triggered with both a loud beacon and a flashing lamp , within :
• Machinery room – warning inside and outside the machinery room . The alarm outside the machinery room may be installed in a supervised location .
• Occupied space – warning at least inside the occupied space . Additional alarm system requirements for charges above 3 000kg ( EN ) or 4 500kg ( ISO ):
• User or owner responsibility is to ensure that a continuously attended station is provided as a central alarm station .
• Specialised personnel are required on site within 60 minutes of an alarm .
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Testing of ammonia detectors is required at appropriate intervals established at the facility .
Correct functioning of alarms , mechanical ventilation and detectors needs to be regularly checked at least once a year .
EN 60079 – 29 – 2 specifies in detail the requirements for selection , installation , use and maintenance of detectors of flammable gases .
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European Union exposure limits for ammonia are defined in Directive 2000 / 39 / EC as following :
• TWA 20ppm and 14mg / m 3
• STEL 50ppm and 35mg / m 3
The community limits are set by the European Agency for Safety and Health at Work .
National limits are defined by country regulatory bodies . For example : UK – Health and Safety Executive – HSE . EH40 / 2005 :
• TWA 25ppm / STEL 35ppm
France - National Institute of Research and Safety – INRS . ED 984 :
• TWA 10ppm / STEL 20ppm
Germany - Federal Institute for Occupational Safety and Health – BAuA . TRGS 900 :
• TWA 20ppm
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