NSW: fuel service truck catches fire at coal mine

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Tuesday, 22 January, 2019 - 12:15
Incidents & prosecutions
New South Wales

A fuel service truck recently caught fire at the open cut coal Maules Creek coal mine in Boggabri, NSW, after diesel fuel from a breather assembly on top of the fuel tank flowed directly onto hot engine surfaces.

The onboard fire suppression systems on the truck were unable to extinguish the fire, and the operator escaped from the truck without injury.

The fuel service truck with a full diesel storage tank (33,400 litres calculated) reversed and parked on a ramp to access an excavator.

The excavator had run out of fuel and could not be moved for refueling, and the fuel truck operator exited the cabin and saw diesel flowing from underneath the filter on the front diesel breather assembly.

Due to the incline of the truck (about 11.9° according to survey estimate) the diesel flowed from the breather vent directly onto hot surfaces on the engine.

Back on ground level the operator saw flames around the engine turbo and unsuccessfully tried to extinguish the fire with a dry chemical fire extinguisher.

Another worker activated the truck’s onboard fire suppression system, which failed to extinguish the fire that had spread to the cabin and tank.

The NSW Resources Regulator conducted an investigation and identified:

  • The diesel tank ball float had been raised to the top position on the support bracket to increase the capacity of the diesel tank from 30,000 litres to 33,400 litres.
  • The breather assembly was designed to allow air to ventilate during filling and discharge of the diesel tank. The breather paper filter base was 420 mm above the top of the tank. The breather assembly components had been replaced and were not as originally designed.
  • When the tank was filled to 33,400 litres, the angle of inclination for fuel to run out through the breather assembly filter base (420 mm above the tank) was 10.5° (OEM calculated)
  • The roll over adapter on the breather assembly consists of a steel ball locating onto a metal seat and relies on gravity to close fuel flow in a roll over. The rollover adapter was not designed to shut off fuel flow on a low incline. Fuel continued to flow through the roll over adapter at the 11.9° angle on the ramp.
  • Fuel was initially observed to flow from the base of the paper filter on the breather assembly. The original design was a desiccant-type filter that would have reduced the volume of diesel flow.
  • Fuel was later seen to flow through the check valve on the breather assembly after the fire was extinguished. Testing of the check valve confirmed the observation that diesel would continue to flow through the fire-damaged check valve.

The NSW Resources Regulator subsequently made a number of recommendations, and said mine operators must review:

  1. The principal hazard management plan (fire and explosion) and mechanical engineering control plan risk assessments for fuel service trucks to ensure control measures are effective to contain and redirect flammable liquids spilled from the top of the tank away from hot surfaces
  2. The design arrangements of the ball float and breather vent settings on fuel service trucks to ensure that they meet OEM specifications
  3. Controls to manage the hazard of fuel venting through breathers during fuelling and roll-over event are effective
  4. The operating gradients of fuel service trucks are within OEM design specifications
  5. Maintenance practices of ball float and breather vent settings on fuel service trucks to ensure life cycle inspections and maintenance programs are effectively performed
  6. Change management systems to ensure modifications of fuel storage and delivery systems on fuel service trucks are appropriately assessed and include consultation with OEM.