Ammonia (R-717) Gas Detection
With zero global warming potential (GWP) and ozone depletion potential (ODP), ammonia is considered one of the most cost effective, energy efficient, natural refrigerants for industrial refrigeration. However, ammonia is classified as a B2L refrigerant, which means it is toxic and flammable. As such, ammonia gas detection is critical for on-site safety.
Safety is paramount for ammonia refrigeration systems. Ammonia is corrosive and human exposure will result in a chemical type burn. As ammonia is extremely hygroscopic (rapidly absorbing moisture), it readily migrates to moist areas of the body such as eyes, nose, throat and lungs. Even low levels of ammonia gas is harmful which is why strict compliance is required.
|0-25 ppm||Low odor threshold for most people, slight irritation to eyes and breathing tracts.|
|25 ppm TWA||8 hour TWA||NIOSH|
|35 ppm STEL||15 minute reference period||NIOSH|
|50 ppm TWA||8 hour TWA, perceptible eye and throat irritation||OSHA|
|50-100 ppm||Swollen eyelids, conjunctivitis, nausea / vomiting, irritated throat|
|300 ppm IDLH||Immediate danger to life and health||NIOSH, OSHA|
TWA = time weighted average
STEL = short term exposure limit
IDLH- Immediately dangerous to life of health
Ammonia is considered a flammable hazard between concentrations of approximately 15% to 28% by volume in air. EN 378 stipulates that for flammable levels of ammonia, alarms should be set as follows:
- At low alarm level 500 ppm (0.33% lower exposure limit (LEL)) alarm and mechanical ventilation to be activated
- At high alarm level 30,000 ppm (20% LEL) refrigerating system to be automatically stopped
Guidance following the withdrawal of HSE’s PM81 publication, “Safe Management of ammonia refrigeration systems” for the food and drinks industries and other workplaces, states levels of 500 ppm for fan ventilation and alarm and a “practical” shut down level of 6.6% LEL or 10,000 ppm.
With 20 tons of ammonia on site to support its packing lines and blast freezers, effective gas detection is a top priority for Greenyard Frozen. Learn how Bacharach helps this food processor protect its personnel while providing robust data-driven notifications. Read More
Ammonia leak detection
Considering the hazardous nature of Ammonia, clear instructions ensure that a properly designed, constructed, operated, and maintained ammonia refrigeration system can be safely achieved.
The EPA states two requirements relative to leak detection::
- Maintain a leak-free ammonia refrigeration system. Investigate all reports of an ammonia odor and repair all leaks immediately.
- Consider installing ammonia detectors in areas where a substantial leak could occur if the facility is not manned 24 hours/day.
In addition, The International Institute of Ammonia Refrigeration (IIAR) provide codes and standards in their document: “Ammonia Leak Detection in Refrigeration Systems (2004)”.
Leak detection alarm levels and required responses vary depending on where the refrigeration equipment is installed, summarized as:
|Room Type||Alarm levels and actions|
|Compressor room alarm||25ppm: alarm to monitored location and horn strobe outside each entrance and inside the compressor room
150ppm: emergency ventilation activated
|Compressor room shutdown||10,000ppm: Redundant emergency ventilation
20,000ppm: De-energize pumps, compressors and valves that are normally closed
|Refrigerated area||25ppm: alarm to monitored location
35ppm: close liquid and hot gas solenoid valves
|Packaged systems||25ppm: alarm to monitored location and horn strobe outside each entrance and inside the compressor room|
|Machinery under 100HP and Equipment Pots (not located in Machine Rooms)||25ppm: alarm to monitored location and horn strobe outside each entrance and inside the compressor room
25ppm: close liquid and hot gas solenoid valves,
25ppm: de-energize pumps, motors and non-emergency fans
25ppm: Emergency ventilation
Ammonia leak detectors
Bacharach offers a wide range of ammonia safety gas detection solutions. These innovative solutions are designed for extreme temperature refrigeration environments and provide robust refrigerant safety compliance. The Multi-Zone aspirated system provides industry leading low-level leak detection and the MGS-400 and MGS-550 diffusion systems offer exceptional low level temperature performance down to -40ºF/C.
Deciding which system is right for you depends on the total number of sampling areas, ammonia levels you want to detect, sampling frequency, integration with BMS / BAS control systems, maintenance requirements, and CAPEX and associated OPEX cost.
|Multi-Zone||MGS-400 Series||MGS-550 Series|
|Integration with BMS / BAS control system||Modbus, BACnet, LonWork and analog communications||Modbus, Digital and analog communications||Modbus, Digital and analog communications|
|Temperature Zone / Application||Low and Medium||Low and Medium||Low and Medium|
|Sensing Medium||Infrared||Electrochemical (EC), Catalytic Bead (CAT)||Electrochemical (EC), Catalytic Bead (CAT) or Semi Conductor (depending on PPM alarm range)|
|Remote placement of sensors / sample points||Up to 1200ft from leak detection monitor||MGS-460: 5m from transmitter MGS-410 with MGS-402: 1,000m from transmitter||5m from transmitter|
|Sensor Typical Life Span||Up to 10 years||Up to 7 years||Up to 7 years|
|Maintenance (functional test / calibration)||Annual||Annual||Annual|
|Sensor Hot Swap||N/A||Plug and play pre-calibrated sensor modules for quick, simple sensor replacement||Plug and play pre-calibrated sensor modules for quick, simple sensor replacement|
|Sensor channels||4 - 16||1||2|
|Sensor Range||25 - 10,000 ppm on one sensor||0-100 PPM
|User Interface||Large graphic LCD display and on-board controls||Mobile app interface with Bluetooth connectivity||On board controls and LCD screen|
|Find out more||Find out more||Find out more|
Learn more about ammonia refrigerant gas safety:
Certain industrial ammonia refrigeration systems are subject to OSHA’s Process Safety Management (PSM) Standard. Here’s a brief overview of ammonia PSM requirements and how compliance ensures personnel are kept safe.
Left unchecked, refrigerant leaks can be dangerous. And while there are a variety of reasons for employing leak detection, the foremost reason remains the safety of personnel working with or in proximity to refrigeration systems.
Being responsible for the installation and upkeep of the gas monitoring system in your building is an important task, and one that should not be taken lightly. Industrial, commercial and public sector buildings all produce and consume a certain amount of toxic gases.