Drill rig fire due to electrical fault

Description of the incident

A reverse circulation drill rig was working when a fire occurred on the rig mounted compressor. The automatic fire suppression system was activated which partially extinguished the fire, handheld extinguishers were then used to fully extinguish the fire.

Local Fire Services were called and attended the scene as support to the drill crew.

The fire resulted in significant damage to the compressor control panel and other components of the drill rig. 

Apparent causes

Investigation of the fire concluded that the fire was caused by a short circuit in the wiring in the compressor control panel.

It was further found that the insulation on electrical wires was damaged, potentially due to vibration over a period of time and the circuit being un-fused.

Comment and recommendations

On this particular drill rig, the compressor control box was a sealed unit and so drill crew were unable to inspect the components mounted inside the control box. 

The automatic fire suppression system fitted to the drill was installed to protect the diesel engine and the compressor only, the system did not extend to the control box or other potential sources of fire. 

In this particular incident, the emergency response plan was acquitted very efficiently and the effectiveness of the fire suppression system together with the actions of the drill crew in using hand-held fire extinguishers prevented further damage to the drill rig and also prevented potential bush fires. The investigation did however highlight the critical importance of ensuring that site personnel having easy access to the communication system at all times, relying on a communication system installed in a motor vehicle is inadequate.

The following recommendations are made:

1.     Review current inspection checklists to ensure the inclusion of all electric cables at points where vibration against a steel or other component may cause the insulation to be damaged.

2.     In cases where a harness of electrical wires enters a control box, consider installing a rubber gland to prevent damage due to vibration.

3.     Ensure that the fire suppression system extends to all potentially combustible components on the drill rig.