Ammonia Refrigeration Systems…Good, Bad, & Ugly. What’s Better?
There are many chemicals that can be used as refrigerants and some common ones have fallen out of favour due to their environmental risks. Freon R-22 or HCFC-22 (trademark name of a type of hydrochlorofluorocarbon) was in regular use up until the 1980s when concerns about its effect on the ozone layer became apparent and as a Party to the Montreal Protocol, Canada committed to progressively phasing it out completely by 2030.
More alternative refrigerants are being used, but due to the different thermodynamic and safety properties of them, there is no one-best solution. The suitability of a certain alternative must be considered separately for each category of product and equipment. In some cases, the level of ambient temperature at the location where the product and equipment are being used must also be considered.
As fewer hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) are available for use as refrigerants, companies are looking for effective replacements. A variety of non-ozone depleting refrigerant alternatives are being used and R-407C is a common R-22 replacement as they have similar properties. Ammonia (R-717) remains the most popular refrigerant. Historically, it is one of the first used refrigerants since the 1850s for artificial ice production and the first ammonia-refrigeration machines (1870s). Most (80%-90%) large-scale industrial refrigeration operations use ammonia refrigerant and its use in commercial HVAC applications is growing. But should it?
So, what about ammonia as a refrigerant and are there any issues with it?
Ammonia is a gas comprised of two other gases; nitrogen and hydrogen. Man-made or naturally-occurring, ammonia is colorless with a sharp, pungent odor. Ammonia used commercially in large refrigeration plants is also called “anhydrous ammonia” because it contains almost no water (it is 99.98% pure). Household ammonia, by comparison, is only about 10% ammonia by weight mixed with water.
Ammonia: The Good
Advantages of ammonia over other commonly used industrial refrigerants are its:
environmental compatibility (naturally-occurring or man-made).
excellent thermodynamic qualities and approximately 3%-10% more efficient than hydrofluorocarbon refrigerants.
recognizable strong pungent odor helps as a safety asset unlike most other odorless industrial refrigerants to make leaks more easily detectable.
not as flammable as other chemicals that can be used as refrigerants (i.e., propane and butane).
Ammonia: The Bad
Major concerns of ammonia over other commonly used industrial refrigerants are that:
it’s a toxicity, freezing, fire, and an explosion hazard at concentrations between 16% and 25%. If ammonia is contaminated with lubricating oil from the refrigeration system, it may have a much broader explosive range.
ammonia is hygroscopic in that it attracts moisture from the air. If it’s present in the surrounding atmosphere, it will travel to any moist areas of your body (eyes, nose, throat, skin) and will cause chemical burns. Skin and respiratory-related diseases are aggravated for the long-term by exposure and it is quickly fatal at high concentrations (>5,000 ppm). Permissible Exposure Level (PEL) is an 8-hour time weighted average of 50 ppm. Immediately Dangerous to Life Levels (IDL) are 300 ppm.
direct skin contact with liquid ammonia will cause severe frostbite since its temperature at atmospheric pressure is -173C° (-28o F°).
ammonia is corrosive to copper, brass, and bronze which cannot be used in ammonia refrigeration systems. Metal choices are typically mild steels, stainless steels, and nickel.
ammonia systems cannot tolerate time delays for cooling to start and require pressurized storage vessels to store liquid ammonia and allow for separation of vapor and liquid. Storage containers of any size holding ammonia introduce another very concerning risk element should they ever leak.
Ammonia: The Ugly
Accidental releases of ammonia have occurred from refrigeration facilities in the past. Release incidents have typically included:
above pressure conditions and lifting of pressure relief valves.
seal leaks from rotating shafts and valve stems.
refrigerant piping failures due to loss of mechanical integrity from corrosion.
physical damage of system components from equipment collisions.
hose failures that occur during ammonia deliveries.
Ammonia release incidents have led to serious injury and fatalities. In British Columbia, between 2007 and 2017, there were 59 incidents (32 in food production and 27 in ice rink arenas) where it was reported to Technical Safety BC that ammonia refrigerant was discharged. Thirteen of these incidents resulted in 40 injuries (some life-long). In October 2017, three workers died after an ammonia release in an arena’s mechanical room in Fernie, BC. For the rest of Canada, going back to 1991, there have been other major incidents reported in Ontario, Alberta, Quebec, PEI and New Brunswick. Incidents have happened globally. Perhaps the worst event occurred in August 2013 when a liquid ammonia leak was caused from a failed fan motor which then struck a pipe in the refrigeration unit at a cold storage facility at Shanghai Weng’s Cold Storage Industrial Co. Ltd. that killed 15 people and injured 26 others.
In addition to loss of life and serious injuries, ammonia releases can cause other significant collateral damage including:
product loss due to ammonia contamination
product loss due to refrigeration interruption
interruption of refrigeration capacity
potential for equipment and property damage (past insurance claims have exceeded $1 million dollars per incident).
There’s no Canadian national standard for how often ammonia refrigeration plants across all industry sectors such as in food processing facilities and ice rinks are inspected. Each province and territory have its own criteria which varies widely. Technical Safety B.C. says that keeping an ice rink safe requires more than just inspections and rink owner/operators have a responsibility to make sure maintenance is kept up, emergency measures are in place, and the facilities are properly equipped with trained staff.
Canada’s sport and recreation infrastructure are in a state of deep physical decline and most are still using obsolete refrigeration technology with ammonia. The majority of publicly-owned recreation facilities were built between 1956 and 1980 and are nearing the end of their useful life, which is typically 32-years depending on different factors. According to the Canadian Recreation Facilities Council (CRFC) 2005 Arena Census, approximately 45% of Canada’s rinks (1,350 of 3,000) were already beyond their projected life expectancy and that was nearly 15-years ago! The MNR says ammonia refrigeration systems are in over half of them across Canada and in over 80% of Ontario’s rinks. With 86% of the rink arenas being municipally-owned, many may not be able to afford the cost of retrofitting unless they’re assisted by upper levels of government and the private sector. Regular maintenance and proper operation can help extend the arena life cycles, but even preventative maintenance only goes so far. When a municipality is in a financial position to replace a refrigeration plant, they most often replace old technology with the same old technology rather than investigating better options that are ammonia free and much more energy efficient.
When speaking of these better options, we must understand that all refrigerants are poisonous in high concentrations. This is because they all displace the oxygen you need to breathe. Hydrofluorocarbons (CFCs) are a “simple asphyxiant” and in very large volumes will dangerously displace air, but ammonia is a “chemical asphyxiant” that will attack the moisture in the mucous membranes and cause much greater damage at a quite low ppm level.
If the potential exists for just one person to die with an ammonia leak, and if ammonia has the greater lethal potential among other refrigerants, are its relatively few benefits worth the risk of a life lost when something goes wrong?
The most technically advanced refrigeration systems that use CFCs contain very little of it, are exceptionally efficient, and when part of a well-engineered and designed system that features precision Controls, Hydronic Heat Pumps, GeoExchange, and Combined Heat & Power Co-generation, it is considered cleantech and green.
For example, the TRAK International Smart Energy System (SES) only has a very small quantity of about 11 kg of R-407C refrigerant in each of its hydronic heat pumps between the unit’s heat exchangers. These modular heat pumps are their own cell in holding the R-407C. If any ever leaked, the situation would never be dangerous. The chilling and heating fluid circulating throughout an arena rink floor and anywhere else in the building or the GeoExchange system in the ground is a solution of about 70% water and 30% “food-grade”, environmentally-safe, biodegradable, propylene glycol. In-ground GeoExchange PEX piping will last well over 100-years. There are also no requirements for government-certified refrigeration plant operators or stationary engineers with a TRAK SES. Alternatively, compressor refrigeration plants with ammonia typically require a government certified operator present 8-24 hours/day when they are rated above 75 kW or 100 BHP, depending on the provincial regulations.
For Canada as a whole, the energy consumption of a single ice rink arena operating for 9-months could reach 1,780 MWh. Currently, evolution in the design and operation of ice rinks has helped to considerably reduce both energy consumption and GHG emissions. TRAK International’s Smart Energy System reduces an arena’s energy operating costs a proven 40% to 60% compared to conventional systems and technology.