Lessons from a liquid ammonia leak incident

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Regarding the lifespan of liquid ammonia hoses mentioned by a friend, I’ve written an article for you; I hope it will be helpful. At 21:35 on May 21, 1998, an accident involving a leak of liquid ammonia occurred at the former Changji Fertilizer Factory. A total of 11.32 tons of liquid ammonia were leaked in this incident, resulting in direct economic losses of 30,000 yuan. Since the wind was not strong at the time of the accident, the ammonia gas spread slowly, and its impact was limited to a narrow area along the Tuitun River, about 0.5 km to the northeast of the factory complex. At that time, the oxygen production plants and sand and gravel factories in the Tiantun River area had already closed for the day; only a few residents were there. Thanks to effective rescue efforts and rapid action, no casualties were reported. Only two firefighters suffered minor burns to their throats. However, this accident was of serious nature and had a negative impact on society. Today, as part of the autonomous region’s efforts to carry out more thorough inspections of hazardous chemicals, its lessons are ones we should learn from. The liquid ammonia station of Changji Fertilizer Factory is located in the southeast corner of the factory complex. For production needs, the company rents liquid ammonia tankers from Shihezi Liquid Ammonia Fertilization Technology Company, and purchases liquid ammonia from Xinjiang Fertilizer Factory to store it in the liquid ammonia storage tanks at its own station for future use. At 21:20 on May 21, the liquid ammonia tank truck arrived. At 21:25, the on-duty operator and the truck driver connected a 2.5-meter long, φ50mm metal hose for transporting liquid ammonia to the truck’s outlet, opened the valves, and started the ammonia compressor to release the ammonia. At that time, the pressure in the liquid ammonia storage tank was 0.6 Mpa, while the pressure in the tank truck was 1.1 Mpa. At 21:35, while the operator was filling out records in the control room, he heard a loud explosion sound. When he opened the door, pungent ammonia gas rushed into the control room; unable to exit, he immediately turned off the power to the ammonia compressor and escaped through the back window of the control room. He then reported the incident to the factory management right away. The factory’s management and relevant staff immediately informed the relevant departments in Changji City, such as the emergency services, fire department, ambulance services, and television station. By around 22:00, the leaders of Changji City and relevant personnel had gathered at the accident site. After consultation, a high-pressure gun was used to spray the leak source in order to absorb ammonia, thereby allowing the valves of the tank trucks to be closed. In collaboration with local police, emergency services, and other agencies, teams were sent into the ammonia-filled areas of the ammonia production plants and sandstone factories, where more than 30 people were evacuated from house to house to safe locations. The public security authorities closed Tunhe Road, the main route for ammonia gas to spread, and directed the residents living in areas downwind to evacuate. Residents living around Changji Fertilizer Factory, who learned of the situation through Changji City’s television station, also moved voluntarily towards the city center. According to witnesses, the leaked liquid ammonia vaporized instantly, rising slowly in the form of a mushroom cloud before gradually dispersing in the sky. At 23:00, with the assistance of firefighters, the on-duty operator closed the valves of the liquid ammonia tank truck, thereby bringing the leak under complete control; almost no liquid ammonia remained leaked from the tank. Upon inspection, a 6 cm long crack was found on the liquid ammonia metal flexible hose. After the accident, the former Xinjiang Chemical Industry Department immediately organized enterprises and relevant personnel to conduct a thorough investigation into the incident in accordance with the principle of \"not letting it go until three aspects are addressed,\" in order to analyze the causes of the accident. Since its commissioning in 1991, the liquid ammonia station at Changji Fertilizer Plant has never conducted any inspections or pressure tests on the metal hoses in use. Prolonged exposure to the elements, with exposure to wind, sun, and rain, causes severe aging of the metal hose. Based on the on-site inspection, in addition to the area where it burst, there are other obvious signs of wear on the surface of the hose, yet its strength still meets the requirements for use. Therefore, the rupture of the metal hose was the direct cause of the accident. (l) In the Changji liquid ammonia station, the loading and unloading area for liquid ammonia tank trucks is too close to the control room and storage tanks; as a result, when the metal hoses burst, the high-speed jet of liquid ammonia creates air currents that prevent operators from entering or exiting the control room properly, let alone approaching the tank trucks and storage tanks to shut off the valves. When designing the liquid ammonia station at Changji Fertilizer Factory, only consideration was given to storing the liquid ammonia produced by the company itself and filling cylinders with it; the unloading of liquid ammonia purchased from outside was not taken into account. As a result, the space between the control room and the storage tanks is limited, and the presence of tank trucks creates obstacles that hinder emergency response efforts. The design of such liquid ammonia stations must be carried out in strict accordance with relevant standards, with their production processes, equipment, and safety facilities meeting the requirements of ** standards. (2) The safety management system at the liquid ammonia station is inadequate, and safety inspections are not thorough. Metal hoses are considered pressure pipelines; their procurement, use, and management must comply with relevant regulations. It is necessary to choose qualified products manufactured by manufacturers with the appropriate production qualifications, along with complete quality certification documents. During use, in addition to routine visual inspections of the surface, qualified testing institutions should be engaged to conduct periodic inspections and issue inspection reports. Ensure reasonable use, proper storage, and maintain its integrity. Liquid ammonia stations should further improve their safety responsibility systems and safety inspection protocols, ensuring that the safe management of equipment, process pipelines, and auxiliary facilities is assigned to specific departments and individuals, with regular inspections carried out to assess compliance. Eliminate blind spots in safety management. (3) The liquid ammonia station lacks specific protective equipment, being equipped only with ordinary gas masks. The liquid ammonia station should also be equipped with self-contained breathing apparatus and full-body protective suits to meet the requirements for dealing with emergencies. This post was last edited by Logistics Engineer on 2008-6-3 22:30.]