The causes and judgments of the drill pipe sliding down in rotary drilling RIGS

1. Cause of the malfunction

The drill pipe is fixed to the main hoist drum by steel wire rope. Only when the drum is wound or released by the steel wire rope can the drill pipe be raised or lowered accordingly. The power of the drum comes from the main hoist motor that has been decelerated many times, and its stop is achieved by the brake directly installed on the reducer. During the process of lifting or lowering the drill pipe, if the operation handle is returned to the center position but the drill pipe cannot stop quickly, there may be three reasons: the first is braking lag; The second issue is that the two hydraulic locks at the motor's end outlet are malfunctioning, and the motor cannot stop rotating immediately under the torque of the steel wire rope. The third reason is often overlooked. All drilling RIGS have a drill pipe release function. This function is provided by solenoid valve 3 to release the brake signal oil, and then solenoid valve 2 connects the oil inlet and outlet ports of the main hoist motor through two oil pipes, thus ensuring that the drill bit can always be in contact with the working surface and maintain a certain pressure during the drilling process. Under other working conditions, the solenoid valve 2 will disconnect the two oil pipes leading to the motor's oil inlet and outlet. If the disconnection is not timely, the above-mentioned fault phenomenon will occur.

2. Judgment Method

(1) Judge solenoid valve 2

To determine whether the solenoid valve 2 is tightly closed: Remove the two oil pipes leading from the motor to the solenoid valve 2, and use two plugs to block the two oil ports at the motor end respectively. Then operate the main winch mechanism. If it works normally, it indicates that the fault is caused by the solenoid valve 2 not being tightly closed. If it is still abnormal, its components need to be inspected.

(2) Determine the hydraulic lock

To determine if there is a problem with the hydraulic lock: First, adjust its two lock cores. If they do not work, then disassemble the lock for a thorough inspection. If the cause cannot be found, use an existing lock for an installation test to identify the cause of the fault. Since the hydraulic lock of the secondary hoist is the same as that of the main hoist, the lock of the secondary hoist can also be borrowed and replaced one by one to identify the quality of the main hoist lock. If both locks are fine, proceed to the next step of inspection.

(3) Determine the brake signal fluid

Check the speed of the brake signal oil supply and cut-off: For the current drilling rig, the flow rate of the signal oil can be adjusted, that is, the time for the main hoist to release the brake can be adjusted. Therefore, for both types of drilling RIGS, the flow rate of the signal oil can be adjusted through their regulating valves. If the machine's working condition remains abnormal, it is necessary to check whether the oil pipe of the brake signal oil is blocked. If all these examination areas are normal, we can only continue the examination

(4) Determine the brake

Disassemble and inspect the brake: Check whether the brake piston moves smoothly within the working line. Repair or replace it based on the cause of the fault.

At present, Yang Yufeng, Zhang Zhonghai and Zhang Qijun from XCMG Research Institute have been using the rotary drilling rig for a period of time. During the process of lifting or lowering the drill pipe, when the operation handle is returned to the middle position, the drill pipe does not stop immediately. It always slides down several tens of centimeters before it stops moving. This article discusses the common causes and conventional judgments of the drill pipe sliding down in rotary drilling RIGS.

1. Cause of the malfunction

The drill pipe is fixed to the main hoist drum by steel wire rope. Only when the drum is wound or released by the steel wire rope can the drill pipe be raised or lowered accordingly. The power of the drum comes from the main hoist motor that has been decelerated many times, and its stop is achieved by the brake directly installed on the reducer. During the process of lifting or lowering the drill pipe, if the operation handle is returned to the center position but the drill pipe cannot stop quickly, there may be three reasons: the first is braking lag; The second issue is that the two hydraulic locks at the motor's end outlet are malfunctioning, and the motor cannot stop rotating immediately under the torque of the steel wire rope. The third reason is often overlooked. All drilling RIGS have a drill pipe release function. This function is provided by solenoid valve 3 to release the brake signal oil, and then solenoid valve 2 connects the oil inlet and outlet ports of the main hoist motor through two oil pipes, thus ensuring that the drill bit can always be in contact with the working surface and maintain a certain pressure during the drilling process. Under other working conditions, the solenoid valve 2 will disconnect the two oil pipes leading to the motor's oil inlet and outlet. If the disconnection is not timely, the above-mentioned fault phenomenon will occur.

2. Judgment Method

(1) Judge solenoid valve 2

To determine whether the solenoid valve 2 is tightly closed: Remove the two oil pipes leading from the motor to the solenoid valve 2, and use two plugs to block the two oil ports at the motor end respectively. Then operate the main winch mechanism. If it works normally, it indicates that the fault is caused by the solenoid valve 2 not being tightly closed. If it is still abnormal, its components need to be inspected.

(2) Determine the hydraulic lock

To determine if there is a problem with the hydraulic lock: First, adjust its two lock cores. If they do not work, then disassemble the lock for a thorough inspection. If the cause cannot be found, use an existing lock for an installation test to identify the cause of the fault. Since the hydraulic lock of the secondary hoist is the same as that of the main hoist, the lock of the secondary hoist can also be borrowed and replaced one by one to identify the quality of the main hoist lock. If both locks are fine, proceed to the next step of inspection.

(3) Determine the brake signal fluid

Check the speed of the brake signal oil supply and cut-off: For the current drilling rig, the flow rate of the signal oil can be adjusted, that is, the time for the main hoist to release the brake can be adjusted. Therefore, for both types of drilling RIGS, the flow rate of the signal oil can be adjusted through their regulating valves. If the machine's working condition remains abnormal, it is necessary to check whether the oil pipe of the brake signal oil is blocked. If all these examination areas are normal, we can only continue the examination

(4) Determine the brake

Disassemble and inspect the brake: Check whether the brake piston moves smoothly within the working line. Repair or replace it based on the cause of the fault.