Damaged oxygen scavenger storage tank due to over-pressurization by decomposition products under heat.

A bisulphite oxygen scavenger tank was found swollen on an offshore platform. The tank lid was open, and the chemical had spilled from the tank lid. There were no injuries and the tank was removed from service.

Root cause and contributing factors

  • Bisulphite Oxygen Scavengers decompose and release sulfur dioxide (SO2) gas.
  • The rate of decomposition increases with temperature.
  • The tank was stored in direct sunlight and close to a hot exhaust for about one year.
  • There were no means to relieve pressure on the tank.

Lessons learned

  • Bisulphite Oxygen Scavengers should be stored out of sunlight, in well-ventilated areas and used within three months.
  • Tanks should be stored away from any heat source that will increase the rate of decomposition.
  • Tanks should be fitted with a certified and tested Pressure Relief Valve to protect the integrity of the tank.
  • Tank lid seals should be replaced after six months of service.
  • All chemical tanks should be included in a maintenance program, which includes inspection, testing and routine maintenance of all parts.