Shipping container explodes, injuring worker
Date of incident: April 2013
Notice of incident number: 2013161290130
Employer: Wood frame construction company
Incident summary
At a construction site, an explosion occurred in a steel shipping container with a propane barbecue stored inside, resulting in the complete destruction of the container, severe damage to adjacent containers, and damage to surrounding houses and vehicles. A site superintendent, who was working in an adjacent container used as an office, received minor injuries when the explosion damaged that container. A burner valve on the barbecue and the valve on the propane tank had inadvertently been left open, allowing propane gas to leak from the propane tank and reach an explosive concentration in the shipping container. The flammable gas ignited when a soft drink cooler's refrigeration circuit cycled and sparked, resulting in the explosion.
Investigation conclusions
Cause
- Ignition of propane gas in closed shipping container: Propane gas had accumulated inside the closed shipping container because of a leaking barbecue. The flammable gas ignited and then exploded, tearing off the steel doors and roof. A superintendent at the construction site was injured when the blast wave damaged the adjacent container, which the superintendent was using as an office.
Underlying factors
- Improper storage of flammable material in shipping container: Flammable propane gas had been stored in a closed shipping container, which did not have adequate ventilation to prevent flammable gas from accumulating. The shipping container lacked explosion venting, and was destroyed by the explosion of propane gas.
- Uncontrolled source of ignition: The refrigerated soft drink machine stored in the shipping container along with the propane barbecue did not have an explosion-proof thermostat relay. When the cooling cycle was activated, the thermostat relay produced a spark that ignited the propane gas, which by then had reached an explosive concentration.
- Propane tank valve not closed before storing barbecue: The precaution of closing the main valve on the propane tank was not taken. Propane leaked into the shipping container because a burner valve had been left open.