a gas leakage (approximately 70% hydrogen, 21% nitrogen and the rest carbon monoxide and other impurities) occurred at the connection between a temperature measurement casing and a flange in the carbonization workshop cleaning tower. The leakage was reported to the plant leader, who issued the request to the workers to use iron cards and rubber plates to plug the leak. The operation failed and the leakage continued. At 17:00, at the request of the plant leader, the workers used a tire inner tube to wrap the leak.

A gas release occurred in the building for the recirculation of processes gas. The gas was a mixture of hydrogen and nitrogen. It occurred at the outlet valve, during works aiming to replace it. This caused the creation of an explosive gas mixture and the surrounding spaces. The defective valve has been identified several years before, its poor design and ageing caused the gas leakage. The ignition took place with 9 minutes delay after initial leakage.

the fire was detected by an employee during the normal inspection tour, . It was caused by the ignition of a leak of process gas (hydrogen, methane and water vapour) from the reforming furnaces. The plant operator stopped the ammonia unit by manually triggering the safety emergency procedure. The natural gas supply was cut off, and this immediately extinguished the flame.The nitric acid unit was kept running at minimum rate. The hot ammonium nitrate solution and ammonium nitrate units are shut down due to lack of ammonia.

In a fertilizer manufacturing plant, a gas leak occurred at an ammonia unit heat exchanger located in a ventilated area outside. The operator partially stopped the unit, set up steam hoses and monitored the situation by taking measurements outside in the field. At this stage of the process, the gas is composed of hydrogen, water vapour, methane and nitrogen.The unit restarted the next day.

The syngas leak (hydrogen + methane) occurred at exit of the ammonia production reactor and led to an explosion followed by a fire.The start point of the sequence of events was the syngas at the reactor outlet reaching an abnormal pressure of 150 bar and a temperature of 300C. This caused a flange seal to move, causing the gases to leak. The accident caused a pressure waves and fire observed on the installations over a distance of 450 metres.

In a fertilizer manufacturing plant, during his inspection round, an operator detected a hydrogen leak at a flange of an exchanger located between the conversion and decarbonisation stages of the ammonia processing unit. He alerted the control room. A steam hose is installed blowing towards the flange to dilute the leak. Explosive gas measurements are taken twice per shift to ensure that the consequences of the leak are under control. The area is placed under surveillance. A few days later, 2 vapour rings were placed around the flange.

In a fertiliser plant, an ammonia synthesis unit stopped following the malfunction of an alternator (due to a thunderstorm). The safety features were operating normally, yet the synthesis gas (N2 / H2) emitted into the atmosphere ignited in the chimney (sparked by lightning?). Alerted by the noise and after noticing the flames raging for 15 min, neighbours contacted the fire department. During this time, the facility operator cut the natural gas intake that supplied the unit and secured the installation. Fire-fighter presence was not required at the site.

A hydrogen leakage occurred in the ammonia workshop of a plant manufacturing nitrogen products and fertilizer (classified SEVESO high threshold). It was detected by an operator in charge of safety checks, by the noise and by his portable gas detector. After confirming the leak, the operator stopped the piping (30 bar) to repair it. The ammonia workshop was also partially shut down. The operator closed the section at the origin of the leak by installing a threaded and welded plug.The leak was due to corrosion under insulation on a DN50 dead arm: a 90 elbow punctured on DN400 piping.

In this plant, after conversion of the major part of the carbon dioxide into urea, the off-gasses from the reactor consist of ammonia, carbon dioxide, hydrogen, oxygen and nitrogen. Prior to venting this gas into the atmosphere it is washed with a carbamate solution. This absorption is carried out in a high pressure scrubber, where the explosion occurred. The internals were damaged without affecting the vessel itself as it was designed to take an explosion. A second explosion occurred in April 1974 and also damaged the internals.

An explosion and fire occurred on a reformer at a fertiliser plant. Source of ignition was autoignition or electric motor.