Ammonia refrigeration systems : process safety management is vital to employee safety

IM.C. Department of Labor Cherie Berry, Commissioner of Labor 1-800-625-2267 ♦ www.nclabor.com HAZARD ///AIERTH Occupational Safety and Health Division HOI Mail Service Center, Raleigh, NC 27699-1101 Ammonia Refrigeration Systems: Process Safety Management Is Vital to Employee Safety On June 20, 2009, an ammonia line ruptured during mainte¬ nance at a poultry processing plant in Robeson County, N.C., killing one employee and injuring several others. This accident should remind employers of the hazards associated with the use of anhydrous ammonia as a refrigerant at food processing plants. What Is Anhydrous Ammonia? Anhydrous ammonia (ammonia gas) occurs naturally and is an important source of nitrogen that is needed by plants and animals. It is commercially produced by the reaction of nitrogen and hydrogen under conditions of high temperature and pressure. Ammonia (Chemical Abstracts Sendee No. 7664-41-7) boils at -28. 1 degrees F and is highly soluble in water. Anhydrous ammonia is typically shipped as a liquid under pressure and readily converts to a gas when released to air, forming a white “smoke” by freezing moisture in the air. Why Is Ammonia Hazardous? Ammonia is considered a high health hazard because it is corrosive to the skin, eyes and lungs. Exposure to 300 parts per million (ppm) is immediately dangerous to life and health. Ammonia is also flammable at concentrations of about 15 percent to 28 percent by volume in air. When mixed with lubricating oils, its flammable concentration range is increased. It can explode if released in an enclosed space with a source of ignition present, or if a vessel containing anhydrous ammonia is exposed to fire. Fortunately, ammonia has a low odor threshold (20 ppm), so most people will seek relief at much lower concentrations. W hat Industries Arc at Risk? Ammonia is widely used as a refrigerant in a variety of industries, including: • Meat, poultry and fish processing facilities • Dairy and ice eream plants • Wineries and breweries • Fruit juiee, vegetable juice and soft drink processing facilities • Cold storage warehouses • Other food processing facilities • Seafood processing facilities aboard ships • Petrochemical facilities Process Safety' Management The key to preventing ammonia leaks is hazard recognition. Facilities that use 10,000 pounds or more of anhydrous ammonia must comply with the Process Safety Management (PSM) Standard, 29 CFR 1 9 1 0. 1 1 9. A key provision of this standard is the requirement for the employer to conduct a hazard analysis for each process,1 i.e., a careful review of what could go wrong and what safeguards must be implemented to prevent releases of highly hazardous chemicals. Process hazard analyses must be updated and revalidated at least every five years and retained for the life of the process. /. A process includes any activity or combination of activities including any use, storage, manufacturing, handling or the on-site movement of highly hazardous chemicals (HlIC). A process includes any group of vessels that are interconnected and separate vessels located such that HHC could be in volved in a potential release.