United States. A hydraulic impact has been the cause of an ammonia leak in 2010 at a chicken cooling plant that affected 153 workers and sent 32 to the hospital.
The cause was revealed by the U.S. Chemical Safety Board (CSB), with the publication of a safety bulletin for users of anhydrous ammonia in bulk refrigeration operations. The CSB is an independent federal agency in the United States charged with investigating serious chemical accidents.
The safety lessons stem from an investigation into the release of anhydrous ammonia at Millard Refrigerated Services Inc, located in Theodore, Alabama, on August 23, 2010. Of the 153 ammonia exposures reported as a result of the leak, 32 workers were admitted to hospital and four were placed in intensive care. More than 14 tons of ammonia were released according to reports from the poultry plant that handled up to 2.5 million pounds of chicken each day.
The 143,000-pound ammonia refrigeration system supplies five product storage freezers and three freezing tunnels. The facility was designed to handle liquid ammonia at a minimum temperature of -40 °C and a maximum temperature of 43 °C, and the operating pressure of the normal design system ranged from 8.8in mercury (Hg) vacuum to 210psig.
The accident occurred while two international ships were being loaded, the low temperature of liquid ammonia in the cooling system of the plant came into contact with the hot ammonia gas in the evaporator coils. The resulting hydraulic shock caused a failure in the 12-inch roof-mounted suction tube, resulting in the release of more than 32,000 pounds of anhydrous ammonia.
