Explosion on a electrolyser

An explosion occurs in the oxygen gas holder in an electrolysis plant.
The explosion was due to the entry of hydrogen in the oxygen gas holder.
The dome of the gas holder and the collar were blown away.

Electrolyser, oxygen holder

The dome of the gas holder (1060 kg) was blown 135m away, the collar (1150 kg) 33m away and concrete elements 80m away.

The incident occurred at the hydrogen storage tank, but it was caused by a cross-over of oxygen into the hydrogen stream flow.
Oxygen and hydrogen cross-over in the electrolytic cell is a well-known phenomenon, and seems to occurr regularly throughout decades of technology developemts. HIAD_664 reprot a similar case occurred in 1968, and HIAD_970 a recent one occurred in 2019.

The severity of the occurrence depends on the electrolysis technology and the operative parameter, nevertheless it is a hazard which must be monitored, and its consequences prevented. Without proper diagnostic able to detect timely the formation of flammable mixture in the hydrogen line, this is not possible. Little is known about this incident, but an automatic system able to stop hydrogen production when concentrations trespass a threshold would have been able to avoid the creation of flammable mixture in the gas holder.