Incident due to lack of conduct of operations

During a summer day a violent storm hit an ammonia production plant. The thunderstorm caused the failure of the external power supply and trip of the plant at 15:20. After safely isolating the affected unit, operators prepared the start-up during the night shift. First steam had to be imported to be able to start the primary furnace the following day.
However, at 00:55 the top fired reformer blew up. The procedure required many valves to be in the closed position and for these to be verified. The shift leader, however, did not ask the workers to check the valves because he was convinced that the valves were closed following his site walkaround. Even though the display in the control room showed that the valves were open, he insisted that the reading was wrong and continued the start-up. With that, he opened the natural gas supply valve, resulting in triggering a series of alarms and a minute later, the explosion occurred. The explosion injured two workers and destroyed the steam reformer.
Key learning points
The shift leader was convinced that the valves were closed and that was never double checked. To confirm that all safety critical equipment are in the correct position prior to start-up is a crucial step. It should be included in the operating procedures and those procedures should always be followed. There was no redundant system in place to prevent operators from introducing natural gas in the process while the valves were open. The investigation revealed that no log book entry indicated the positions of the valves and any readings from the display. The start-up procedure was used sometimes as a check list but no signature or approval was requested. It was, however, not used this time to check the valves for the arch burners. Lack of training and competence were also factors that could contributed to the accident. Start-ups are rare, and as such, regular refresher training is necessary. In case of emergency shutdown,
a risk assessment should be undertaken to understand any changes or issues prior to starting up. This may include a formal Management of Change.

Source:IChemE