Industrial Refrigeration

The accidental release of anhydrous ammonia gas from a California meat packing facility in 2009 caused the hospitalization of 17 people who worked near the facility, as well as the closure of local streets and highway ramps.

While keeping food at an appropriate temperature to prevent spoilage or unscheduled defrosting in storage or transit is an obvious reason for maintaining an effective refrigeration system, careful attention must also be given to the potential safety risks associated with the use of ammonia in refrigeration.

Anhydrous ammonia is the most commonly used industrial refrigerant, according to the International Institute of Ammonia Refrigeration. The material is commonly used in food processing facilities, dairies, cold storage warehouses and other facilities where temperature control is critical.

Ammonia is a cost-effective and efficient cooling material with excellent heat transfer characteristics, but companies using it must recognize that anhydrous ammonia is classified as a poisonous gas.

Unprotected exposure to ammonia vapors at a high enough concentration can be fatal. Lower-level exposures can cause temporary blindness and eye damage, as well as irritation of the skin, mouth, throat, lungs and mucous membranes.

An ammonia leak can also contaminate the food items that the refrigeration system was designed to protect.

Sources of Leaks

To guard against accidental release, companies using anhydrous ammonia should understand the common causes of ammonia leaks. Many incidents result from inadequate operating procedures or employee training about the hazards, as well as improperly used or poorly maintained equipment.

Other common causes or contributing events include:

  • Piping or pressure vessel failures caused by excessive vibration, poor weld quality, electrolytic corrosion or other causes.
  • Damage to ammonia piping or pressure coils by forklifts or other industrial equipment.
  • Improper response to minor refrigeration system problems.
  • Failure to observe proper safety procedures (such as lockout/tagout and hot work permits) during routine maintenance or repairs.

To reduce the severity of an accidental release, a number of important safeguards should be installed. For instance, early-warning ammonia-detection devices, emergency and portable ventilation systems, overpressure relief valves and emergency shutoff switches can help mitigate the effects of ammonia gas releases.

Design Considerations

Careful attention to facility design and construction, and adherence to federal regulations and established industry standards can help companies use ammonia safely and efficiently.

For example, a basic consideration to keep in mind when installing ammonia refrigeration equipment is the need to locate the system’s machinery in a detached building, if possible, or in a room separate from the rest of the facility.

Similarly, companies should segregate as many areas of the facility as possible with vapor tight separations, mechanical gasket-sealed doors and other protective measures to reduce the risk of an ammonia leak spreading within the facility.

Electrical distribution equipment should be rated properly, and combustible or flammable materials should not be used or stored in ammonia refrigeration machinery rooms.

Procedural requirements to reduce the risk of ammonia leak should include lockout/tagout and other safety measures during system maintenance and repairs.

Ammonia-detection systems should be installed near any location where a substantial leak might occur, and system piping and vessels should be inspected on a regular basis for signs of leaks, corrosion, ice accumulation or other potential hazards.

Understanding the hazards, worker education and routine system maintenance can help ensure ammonia refrigeration equipment operates at maximum efficiency and reduces the risk of hazardous accidental ammonia releases.

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