Drill rigs have hazards that other mobile plant does not: a tall mast that is raised, lowered and worked under load; rotating drill strings and rod handling systems that have caused entanglement fatalities; and high-pressure hydraulic and air systems close to people. The structural load path runs through the mast, mast raise cylinders and pivot pins, and the jacks that level the machine.
A drill rig inspection covers the mast and raise structure, feed and rotary head systems, rod handling and guarding, levelling jacks and carrier, hydraulics and pneumatics, and the operator cab and protective structures.
Inspection checklist areas
- Mast and mast raise
- MT of mast chord and lacing welds, mast foot and pivot pin bores, raise cylinder mounts and pins, mast locking pins and their engagement indication.
- Feed and rotary head
- Feed cable or chain condition and tension, feed cylinder and sheave wear, rotary head mounting and carriage guides, head lock and travel limits.
- Rod handling and guarding
- Rod changer and carousel function and retention, rotation and rod handling interlocks and emergency stops, guarding of the drill string to AS/NZS 4024, deck and hole-collar guarding.
- Levelling jacks and carrier
- Jack cylinder and pad condition, jack mounting welds, jack interlocks with mast raise, undercarriage or truck chassis condition, track frame welds.
- Hydraulic and pneumatic systems
- Hose condition, routing and burst protection near the operator, accumulator and pressure relief function, air receiver inspection status under AS/NZS 3788, dust collector and water injection systems.
- Cab, access and protection
- ROPS/FOPS identification where applicable, cab and mast-side access, working-at-height provisions on the mast, emergency egress, fire suppression.
Known failure modes
Mast structural failure
Fatigue cracking in mast chords, lacing and the mast foot from repeated raising and drilling loads, or damage from mast strikes.
Uncontrolled mast lowering
Mast raise cylinder, hose or pin failure, or mast lock pins not fully engaged while drilling.
Entanglement in the drill string
Contact with rotating rods during rod changes where guarding or interlocks are absent or bypassed.
Rod drop or carousel release
Worn or faulty rod retention in the carousel or rod handler.
Hydraulic injection or burst
High-pressure hose failure near operators without shielding or burst protection.
Applicable standards and regulations
| Reference | Title | Relevance |
|---|---|---|
| AS/NZS 4024 series | Safety of machinery | Guarding, interlocking and emergency stop requirements for rotating drill strings and rod handling. |
| AS 2294.1 / ISO 3471 and ISO 3449 | Earth-moving machinery — Protective structures | Operator protective structure identification where fitted. |
| AS/NZS 3788 | Pressure equipment — In-service inspection | Inspection of on-board air receivers. |
| AS/NZS 1554.1 and 1554.5 | Structural steel welding | Acceptance criteria for mast and frame repair welds. |
| AS/NZS 1891 and AS 1657 | Industrial fall-arrest systems; fixed platforms, walkways, stairways and ladders | Working-at-height provisions on the mast and deck. |
| NSW MDG 15 and MDG 41 | Mobile plant at mines; Fluid power system safety at mines | Design and maintenance expectations for drill rigs and their hydraulic systems. |
When to inspect
- Introduction to site and pre-hire inspection
- Scheduled mast structural inspection at OEM hour intervals
- After a mast strike, mast lowering incident or rod handling incident
- After guarding or interlock modification
- Air receiver inspection due date under AS/NZS 3788
Frequently asked questions
What is inspected on the drill mast?
Chord and lacing welds, the mast foot and pivot bores, raise cylinder mounts and pins, and the mast lock pins and their engagement indication. Mast welds are examined by MT after cleaning at the critical joints, with the mast in the supported position.
How is rod handling safety assessed?
By checking that the drill string is guarded to AS/NZS 4024 during rotation, that rod handling interlocks and emergency stops function, that guards have not been removed or bypassed, and that the rod carousel and changer retain rods positively.
Does the on-board air receiver need a separate inspection?
Air receivers on drill rigs are pressure equipment and are inspected under AS/NZS 3788 at the intervals set for their hazard level. We check inspection status and can include the receiver inspection in the rig scope.