The power head is the main working component of a small rotary drilling rig. It is subjected to significant loads and load variations, making power head malfunctions very common during rotary drilling operations. These malfunctions often necessitate downtime for repairs, resulting in substantial economic losses for the rig owner. Abnormal power head rotation mainly manifests in the following three ways.#accessories for drill#
1. Main pump pressure too low, power head rotation abnormal#accessories for drill#
(1) The overflow valve on the power head oil seat is stuck or damaged, resulting in low overflow pressure. This situation often presents with normal rotation under no-load, but weak or no rotation under load. This is often due to the owner neglecting routine machine maintenance, failing to change or filter the hydraulic oil for extended periods, leading to valve core sticking. Cleaning the overflow valve core and readjusting the overflow pressure or replacing the overflow valve will eliminate this fault.
(2) The main valve safety valve overflow pressure is too low. The main valve typically has a main safety valve and independent overflow valves for each valve plate. Pressure leakage from the main safety valve and the overflow valves controlling the power head valve plates will both cause the power head to rotate weakly. If the main safety valve overflows, not only will the power head rotate weakly, but the traveling, main hoist, auxiliary hoist, and slewing will also be weak. Readjusting the overflow pressure of the main safety valve or the power head valve plate overflow valve will eliminate this fault.#accessories for drill#
(3) Due to prolonged use, the main pump experiences excessive wear, leading to oil leakage between the high and low pressure chambers and causing low system pressure. In this case, all machine movements will be weak, requiring repair or replacement of the main pump.
(4) Excessive wear of the power head motor causes oil leakage between the high and low pressure chambers, resulting in relatively low pressure at the motor's inlet and outlet, causing abnormal power head rotation. This requires repair or replacement of the motor.
II: Main pump displays normal pressure, but power head rotation is abnormal
(1) All bolts connecting the hub and slewing bearing are sheared. This can be determined by observing the gear oil sight glass in the housing to see if the large gear ring can rotate, or by listening for metallic friction sounds inside the power head housing. The root cause is that the bolts did not reach the designed preload torque during assembly.
(2) The spline sleeve connecting the motor and reducer is severely worn or broken. To determine this, rotate the power head under load; one motor should heat up very quickly. Analyzing the hydraulic oil's inertia, the motor with severely worn or broken spline sleeves experiences very little load during operation, while the other motor experiences a very large load. Most of the hydraulic oil flows through the less loaded motor, causing its speed to be approximately twice its normal speed, resulting in faster heat generation. Replacing the spline sleeve will eliminate this type of fault.
(3) Damaged gears or broken drive shaft inside the reducer. The method for judging this situation is similar to that for severely worn or broken spline sleeves. In this case, the reducer gears or drive shaft need to be replaced.
(4) If it is a rotary drilling rig with a high-speed soil-throwing function, a stuck or damaged sequence valve controlling the soil-throwing action can cause poor oil return in the friction plate opening circuit, resulting in the friction plate being in a semi-engaged state, which can also cause abnormal rotation of the power head. In this case, cleaning or replacing the sequence valve will solve the problem. Alternatively, the sequence valve can be removed to disable the high-speed soil-throwing function to ensure normal construction. Oil pipe blockage can also cause similar fault phenomena; the solution is to unclog the oil pipes.#accessories for drill#
(5) Severe wear and excessive leakage of the proportional pressure reducing valve on the handle leads to abnormal rotation of the power head. Excessive leakage from the proportional pressure reducing valve prevents the main valve core from fully opening, resulting in insufficient oil supply to the power head motor and slow rotation speed. The proportional pressure reducing valve needs to be replaced.
(6) Sticking or incomplete opening of the solenoid valve core, or insufficient pilot oil pressure, will cause weak rotation of the power head, even though the main pump displays normal pressure. Depending on the specific situation, parts need to be replaced or adjusted.
III: High pressure displayed by the main pump, abnormal rotation of the power head
(1) Damage to the slewing bearing or slewing support inside the power head causes abnormal rotation. This is often accompanied by unexplained noises inside the power head housing. The slewing bearing or slewing support should be replaced.
(2) Damage to the slewing bearing of the follower frame; replace the slewing bearing.#accessories for drill#
