An explosion occurred within the hydrogen processing system of a chemical plant that produces sodium chlorate for bleaching pulp and paper. The chemical process utilizes electrolytic cells and is pH-dependent. Hydrogen is produced as a byproduct and is utilized as a fuel.

At the time of the incident, the plant was at an abnormal operating level of 25% capacity. A non-routine maintenance operation to repair high-pH liquid piping was in progress. To assist, operations personnel rerouted the high-pH liquid stream to the plant sump. However, in doing this, the liquid eventually made its way back into the electrolytic process by design. Ultimately this created the root cause of the explosive condition in that the pH of the electrolytic process increased faster than the computer- view more


The catalyst in a dehydrogenation reactor, which was usually operated under a hydrogen atmosphere, was changed while the reactor was isolated from the peripheral equipment by closing a 20-inch remotely controlled valve. The hydrogen pressure in the peripheral equipment was set at 20 KPaG, and the reactor was opened to the atmosphere. Anticipating some hydrogen leakage, suction from the piping was accomplished with a vacuum device and, nitrogen sealing was performed. When the piping connections were restored after changing the catalyst, flames spouted from the flange clearance and two workers were burned. One cause of the fire was poor management of the catalyst replacement process.

Incident Synopsis

A catalyst exchange was carried out in a dehydrogenation view more

During start-up operation of a high-temperature, high-pressure plant using hydrogen, hydrogen gas leaked from the flange of a heat exchanger and a fire occurred. The leakage occurred for two reasons:

Insufficient tightening torque control was carried out during hot-bolting and an unbalanced force was generated across the bolts.
A temperature rise was induced across the heat exchanger as a result of a revamping activity, during a turnaround shutdown.

Hot-bolting: In equipment and piping that operate at high temperatures, as the temperatures rise, the tightening force decreases, thus re-tightening of bolts is necessary. This work is called hot-bolting. The design conditions of the evaporator where the fire occurred were 2.4 MPaG, view more

A hydrogen explosion occurred in an Uninterruptible Power Source (UPS) battery room. The explosion blew a 400 ft2 hole in the roof, collapsed numerous walls and ceilings throughout the building, and significantly damaged a large portion of the 50,000 ft2 building. Fortunately, the computer/data center was vacant at the time and there were no injuries.

The facility was formerly a large computer/data center with a battery room and emergency generators. The company vacated the building and moved out the computer equipment; however the battery back-up system was left behind. The ventilation for the battery room appeared to be tied into a hydrogen monitoring system. The hydrogen sensor was in alarm upon emergency responders arriving at the scene (post-explosion). 911 callers view more