A spotter in a hurry almost caused a ‘slap, snap, shoot’ explosion at a Western Australian mine site, according to the latest Significant Incident Report from Resources Safety.
The incident at the unnamed mine occurred during a blasting operation when a spooled downline lead become tangled in the rear protection bar of a mobile processing unit (MPU) when the vehicle moved forward. The spotter had already moved forward to the next row of drill holes to prepare for loading and did not see the lead start to get tangled.
In this incident the downline lead stretched until it snapped. Fortunately, the detonator did not initiate.
“Snap, slap and shoot” is possible when signal tube detonator plastic tubing is stretched to snapping point. When the plastic tubing recoils after snapping, percussive slapping can initiate the thin layer of high explosives contained within the plastic tube and cause the detonator to fire (or shoot).
The Incident Report says the direct cause of the incident was the design of the MPU’s rear protection bar which allowed the downline lead to become entangled. A contributory cause of the incident was the position of the spotter.
The Report goes on to say, “Mine operators are reminded of the importance of maintaining safe work practices for all charging tasks. They should ensure that:
equipment is designed or modified to eliminate the risk of entanglement where a task requires a spotter, this person is positioned where they can observe the safe and unhindered movement of equipment.
Click here to read the SRS-Publications-Mining and Explorations-Significant Incident Reports