A study of accidents related to ammonia refrigeration has found that line-opening operations, along with liquid transfer and oil-draining activities, were responsible for the second largest number of incidents and the majority of 11 incidents that had catastrophic consequences.
The study – “Case History: A Study of Incidents in the Ammonia Refrigeration Industry” – was conducted by Peter R. Jordan, Senior Principal Engineer, MBD Risk Management Services, Langhorne, Pennsylvania (U.S.) Jordan was scheduled to present the study as a technical paper at the IIAR Natural Refrigeration Conference & Heavy Equipment Expo in mid-March, but the event was cancelled due to the corona-virus pandemic.
Jordan largely referenced an “Ammonia Incident Database” that he compiled between 2005 and 2019, based on publicly available sources. The database identified meat and poultry processing (159 incidents), cold storage (134) and ice rinks (103) as having the most ammonia-related incidents.
He also alluded to data provided in 2004 to the IIAR Ammonia Release Task Force by the U.S. Chemical Safety and Hazard Investigation Board (CSB), and to a 2008 survey that IIAR sent to its members.
His assessment of the data pointed to adverse incidents occurring in the ammonia refrigeration industry approx- imately once every three to six days. “These incidents often result in people being injured and sent to the hospital for treatment (more than 1,500 during a 14-year period),” he wrote in the paper.
To improve the safety of ammonia refrigeration systems, Jordan called for the industrial sector to adopt designs that “minimize the total ammonia charge” and “eliminate the use of ammonia equipment outside of machinery rooms.”
The Ammonia Incident Database included 11 incidents that resulted in catastrophic consequences – nine fatalities at facilities operating ammonia refrigeration systems and two at ammonia storage terminals.
Nine of these 11 incidents were related to line opening, liquid transfer, or oil-draining operations. “This supports the hypothesis that these operations are the most hazardous conducted in the ammonia refrigeration industry,” wrote Jordan.
To prevent incidents stemming from line opening, liquid transfer, or oil-draining operations, Jordan suggested engineering controls (such as spring-loaded valves and pump- out systems) and training for system personnel. He also referenced IIAR administrative control standards, such as line opening procedures (IIAR 7), and written operating and maintenance procedures (IIAR 7 and IIAR 6, respectively).
The location of ammonia equipment and possible escape routes must be considered during the design of the system and all subsequent hazard analyses.Peter R. Jordan, MBD Risk Management Services
In addition, during liquid transfer operations, he wrote, “facilities must ensure that the transfer line/hose is suitable for ammonia, has been properly maintained, and contains appropriate devices to limit the size of an ammonia leak if the line/ hose were to rupture.”
Three of the 11 fatal incidents involved persons trapped in limited access areas. “The location of ammonia equipment and possible escape routes must be consid- ered during the design of the system and all subsequent hazard analyses,” Jordan noted.
He suggested following options, preferably in this order:
Relocate the ammonia refrigeration equipment.
Provide a secondary (back- up) emergency exit.
Provide personal protective equipment (PPE) that would enable personnel to escape the area in an emergency.
Human error vs. equipment failure
In an analysis of all incidents in the Ammonia Incident Database, Jordan found that 33% were the result of human error, including 27% attributed to line opening operations, and the rest to transferring liquid, oil draining and improper valve opening. He also found that 36% were due to equipment failure, including faulty equipment, leaks from seals/ gaskets, corrosion and faulty pressure relief valves.
Jordan noted that IIAR has established procedural standards to address faulty and poorly maintained equipment, such as improvements to system design (IIAR 2 and IIAR 4) and mechanical integrity procedures (IIAR 6). In addition, facilities should “identify and replace older, obsolete equipment on a timely basis,” Jordan advised.
The Ammonia Incident Database also revealed that 28% of incidents occurred in machinery rooms, while 22% took place in production areas and 50% happened outdoors. About 73% of the outdoor incidents were releases from pressure relief valves, most of which resulted in injuries and/or off-site consequences.
To address pressure relief valve releases, Jordan suggested that “additional emphasis must also be placed on the design, operation, and maintenance of overpressure relief protection systems.” He also recommended that hazard analyses be conducted to identify the potential circumstances that cause pressure relief valves to open.
Jordan addressed other areas in the Ammonia Incident Database that were responsible for fewer incidents. For example, he proposed additional protections for refrigeration equipment from motorized equipment, especially forklifts (6% of incidents), and from structural or building failures (3%).
He recommended that IIAR standards 4, 5 and 8 should be followed to prevent incidents (6%) that occur during the commissioning and the decommissioning of ammonia refrigeration systems.
Fires, which were responsible for approximately 5% of the incidents in the database, can be prevented or minimized through “the implementation of hot-work permit procedures, the relocation of flammable materials, and improvements to fire suppression systems,” he wrote.
Jordan urged a continuation of ammonia incident research, suggesting that the EPA and CSB could be queried about whether up-to-date data can be obtained from EPA’s five-year accident history database. He also recommended that IIAR contact its members “to determine if they would be willing to share, on a confidential basis, reports conducted to investigate incidents that have occurred in their ammonia refrigeration systems.”
This article originally appeared in the April/May issue of Accelerate Magazine.