TL;DR
Low rotary head speed means the rotation hydraulic motor or its control valve is restricting flow. Measure rotation circuit pressure and compare to the relief valve setting.
What you might see
- rotary head speed below commanded value
- rotary torque alarm active
- hydraulic oil temperature high on rotation circuit
- rotation motor making unusual noise
Likely causes
Rotation circuit relief valve set too low or worn, limiting torque delivery
Hydraulic rotation motor worn, reducing volumetric efficiency
Rotation control valve spool sticking from contamination in the hydraulic oil
Hydraulic oil temperature elevated, reducing oil viscosity and motor efficiency
Required tools
- Calibrated hydraulic pressure gauge
- Hydraulic oil sample kit
- LOTO kit
Safety first
- Lower the drill mast to the travel position before any hydraulic work on the rotary head.
- Hydraulic oil under high pressure. Bleed pressure from the circuit before opening fittings.
Procedure
- 1
Stop drilling and lower the mast to the transport position. Lock out the engine.
Warning: Do not work on the mast or rotary head with the mast raised. Lower to travel position before any maintenance. - 2
Restart the engine and connect a pressure gauge to the rotation circuit test point.
- 3
Activate the rotation function with the drill string free (no load). Record the no-load pressure.[1]
- 4
Activate the rotation with the drill string engaged and a moderate pulldown load. Record the loaded pressure and compare to the circuit relief setting.[1]
- 5
If loaded pressure reaches the relief valve setting before the torque setpoint is met, the relief valve may need resetting or replacement.
- 6
Pull a hydraulic oil sample and send for particle count and viscosity analysis. Contaminated oil degrades motor and valve performance.
- 7
If the motor is making noise and pressures are in spec, the rotation motor has internal wear. Schedule a motor overhaul.
Sources
Sandvik Sandvik DR / DI / DT Drill Rig (Surface / Underground) general technical documentation, Sandvik
Sandvik surface and underground drill rig service documentation, rotation circuit and hydraulic system checks (general)
More guides for Sandvik Sandvik DR / DI / DT
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A rig that pulls to one side has a track tension or drive motor imbalance. Check and equalize track tension before looking at the hydraulic drive motors.
Stop fixing the same fault twice.
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