Date of incident: June 2017
Notice of incident number: 2017179030012
Employer: Fuel distribution company

Incident summary
A worker was standing on top of a tanker truck to transfer gasoline from a tanker trailer to the tanker truck. The tanker truck’s engine was running, and the pumping system was engaged. The worker opened an access hole cover to a compartment in the truck that held diesel, and another to a compartment that was empty. Some diesel remained in the hose (mounted on a reel in a cabinet on the side of the truck) because the worker had used the hose and nozzle to pump diesel earlier that day. The worker pumped gasoline from the tanker trailer and used the gasoline to push the remaining diesel from the hose into the truck’s diesel compartment. Once all the diesel had been displaced from the hose, he moved the nozzle to the empty compartment to complete the transfer of gasoline. Soon after the worker started pumping gasoline into the compartment, an explosion occurred on the tanker truck. Liquid gasoline then spilled from the hose and nozzle onto the side of the truck and to the ground below. The spilled gasoline ignited and burned. The worker fell off the truck and was engulfed in the ground fire. He was seriously injured and did not survive.

Investigation conclusions

Cause

• Flammable vapour ignited from electrostatic discharge, resulting in vapour cloud explosion. While the worker was transferring gasoline through the open access hole, a plume of flammable vapour was displaced from the tanker truck compartment. The flammable vapour mixed with air (oxygen), and some parts of the plume reached the explosive limit for the fuel vapour. Ignition of the fuel-air mixture likely occurred as a result of electrostatic discharge, which could have originated from several sources.

Contributing factors

• Ineffective control of known ignition source. Ignition from electrostatic discharge is a hazard associated with the storage, handling, and transfer of petroleum distillates (gasoline). This hazard is well known in the industry. The worker’s employer failed to ensure that the worksite, where bulk fuels were routinely stored and transferred, was equipped with a grounding system for the control of electrostatic charges. The different types of hoses (conductive and non-conductive) supplied for transferring flammable liquids were not marked to indicate whether continuity existed through the hose assemblies. The hose being used by the worker at the time of the incident was not bonded, and the nozzle was an insulated conductor capable of reaching a different electrostatic potential than the tank. A gap existed between the nozzle and the tank in an atmosphere that was within the explosive limit, and this condition made it possible for the insulated conductor (the nozzle) to produce an ignition spark (electrostatic discharge).
• Occupational health and safety program did not ensure ignition hazard from electrostatic discharge was adequately controlled. Several safe work procedures in the employer’s health and safety program required bonding and grounding to be in place before work activities began. However, the health and safety program did not have provisions to ensure that a bonding and grounding system was in fact present, tested for effectiveness by a qualified person, maintained, and inspected at the employer’s workplaces. The employer did not provide its workers with a method or the necessary equipment for verifying that bonding and grounding had been achieved at the worksite. The information and instruction provided to workers varied, and different understandings of what constitutes effective hazard control developed. At the incident site, it was proven that connecting grounding wires to a nearby fence structure did not provide sufficient electrical pathway to achieve charge relaxation (reduction of electrostatic charge) during truck-to-truck fuel transfers. The responsibility to ensure the presence of effective bonding and grounding was left to the workers, with infrequent supervisory oversight or independent verification from the health and safety program.
• Inadequate supervision. Supervisors did not assess the worker’s work for nearly a year prior to the incident. The employer did not ensure that all of its workers, including supervisors, received training in safe work procedures and the recommended industry practices provided by the Canadian Fuels Association. Workplace safety inspections did not occur at the worksite in accordance with the frequency prescribed by the employer’s health and safety program, and the inspection process did not include measures to ensure that bonding and grounding were in place and regularly checked at all work locations. These oversights were not detected and/or corrected at a senior management level, which allowed for unsafe working conditions to develop at the worksite for at least eight months prior to the incident.
• Procedures were not followed. The worker did not use the collapsible guardrail system (required by the employer’s safe work procedures) when he was working on top of the tanker truck. He did not use personal protective equipment (a respirator, safety glasses, hard hat, safety boots, and fire-retardant clothing, required by the employer’s safe work procedures and the Canadian Fuels Association’s Professional Petroleum Driver’s Manual), which could have reduced his initial exposure to the fire. He was wearing synthetic clothing, which may have contributed to the buildup of electrostatic charge. In addition, the worker was splash loading the gasoline into the empty compartment of the tanker truck. The employer’s safe work procedures and the Professional Petroleum Driver’s Manual warn against splash loading as it can generate a high electrostatic charge in the fuel and components of the tanker truck.
• Working alone or in isolation with no emergency measures in place. The worker was working alone or in isolation during the fuel transfer. The employer did not assess the risk of working alone or in isolation for work activities assigned at the workplace and did not have adequate safeguards in place to ensure that assistance was readily available when the worker was injured and an emergency situation developed. The employer did not inform the local fire department that bulk fuels, which are hazardous products, were being stored and handled at the worksite for extended periods of time. There was no water or deluge system in place as recommended by the fuel supplier’s safety data sheets. The spread of fire was mitigated by the actions of workers from nearby businesses who were alerted by the sound of the explosion — not through a coordinated emergency response plan developed and maintained by the worker’s employer. The workers who responded were placed at additional risk of injury from fire, explosion, and post-traumatic stress.

Request the full report

Additional resources:
Bulletin
Audio slide show