A loss of electrical power at an industrial site of a chemical platform caused two air compressors to shut down at the same time. The backup compressor took over, but lacked the capacity to produce all the air needed to power the platform’s industrial sites. One operator reported equipment defects, such as the opening of its site’s fire network and an inerting failure due to a lack of air. Another operator reported that the pressure in his boiler rose, causing the valves to open periodically (the relief valves do not operate in the absence of compressed air). He also reported that the level in feed water tanks fell and that the acid water drip tray overflowed and the drip tray’s fasteners were pushed upwards and ripped off (Archimedes’ principle). Chlorine began leaking on a heat exchanger of a third operator’s potline. The lack of compressed air had led to a loss of control on the potline, causing the safety devices on the valves in the workshop to switch to their fallback positions. The valves switched to their fallback positions and the chlorine manifold was abated with nitrogen. The pressure in the circuit rose slightly (300 mbar) and a chlorine leak was found on a heat exchanger whose seal had already been reported as leaking. The operator had set up a system to channel the leak to the sanitation system and was going to change it in 10 days, but then the electrical failure occurred.

The loss of electrical power that caused the compressors to shut off was caused by the triggering of a phase in the compressor power cable. In addition, both compressors shared a common power supply mode. The backup compressor was sized to take over for one compressor, not both at the same time.

The inspection service asked the main operator of the platform to revise his analysis of all hazardous scenarios and phenomena initiated by the loss of compressed air.