A worker sustained a hand injury after stored energy released from a drill string during blockage-clearing activities on a blasthole drill rig. The operator identified elevated pressure readings that indicated a blockage in the drill bit and began dismantling the down-the-hole (DTH) hammer assembly to relieve pressure.
The operator separated the upper section of the DTH hammer from the drill rod string while the drill mast remained angled. Although the operator released pressure from the upper hammer section, pressurised air remained trapped within the drill string and drill bit. The operator then reconnected the assembly and directed a washdown hose into the drill bit ports to clear the blockage. When the obstruction cleared, a high-velocity discharge of air, water, oil and rock fragments expelled from the drill bit ports and struck the worker’s hand.
The incident shows how residual stored energy can remain within drilling equipment even after workers complete partial depressurisation. Workers performing fault-finding and maintenance tasks can enter the line of fire when pressure sources remain trapped and work teams do not fully isolate or release stored energy before commencing work.
Takeaways
- Follow correct depressurisation procedures: Release all stored energy before disconnecting or dismantling drill string components.
- Position equipment appropriately: Set the drill mast to allow safe depressurisation of the drill bit and hammer assembly.
- Control residual pressure: Treat drill strings, DTH hammers and drill bits as potentially pressurised until verification confirms otherwise.
- Remove workers from the line of fire: Maintain exclusion zones around potential discharge points during pressure-release tasks.
- Verify work methods: Apply manufacturer instructions and site procedures during maintenance and fault-finding activities.
- Supervise high-risk work: Confirm workers have the training and competency to manage stored-energy hazards.
