DTH Hammer is a positive displacement downhole power drilling tool that uses drilling fluid as power and converts hydraulic pressure energy into mechanical energy. When the mud pumped by the mud pump enters the motor through the bypass valve, a certain pressure difference is formed at the inlet and outlet of the motor, which pushes the rotor to rotate around the axis of the stator, and transmits the speed and torque to the drill bit through the cardan shaft and the drive shaft. So as to realize the drilling operation.
The screw drilling tool is mainly composed of four major assemblies: bypass valve, hydraulic motor, cardan shaft and drive shaft. The screw motor is the main component of the drilling tool. Many practical and theoretical analysis results show that if the motor is to work normally and effectively, the pressure drop that each stage of the motor can withstand should not exceed 0.8Mpa, otherwise the motor will leak. The speed drops quickly, and in severe cases, it stops rotating completely and the motor is damaged. (One lead of the motor is one level) The mud flow rate used on site should be within the recommended use range, otherwise it will affect the efficiency of the motor and even increase the wear. The performance parameters of the screw motor are the main performance parameters of the screw drilling tool. The theoretical output torque of the motor is proportional to the pressure drop of the motor, and the output revolutions are proportional to the input mud flow. As the load increases, the drilling tool revolutions decrease. So as long as you control the readings of the pressure gauge on the ground and the flow of the pump, you can Control the torque and speed of the downhole drilling tool.
Bypass valve part
The bypass valve is composed of valve body, valve sleeve, valve core and spring. Under pressure, the valve core slides in the valve sleeve. The movement of the valve core changes the flow direction of the liquid, so that the bypass valve can be bypassed and closed. Two states: During the drilling and drilling operations, the valve sleeve and the valve body through hole are not closed, and the bypass valve is in the bypass state, so that the mud in the drill string bypasses the motor and enters the annulus; when the mud flow and pressure reach the standard When the value is set, the valve core moves down to close the bypass valve hole. At this time, the mud flows through the motor and converts the pressure energy into mechanical energy. When the mud flow value is too small or the pump is stopped, the spring pushes up the spool, and the bypass valve hole is in the open position-in the bypass state.
The motor consists of a stator and a rotor. The stator is made by injecting a rubber bushing on the inner wall of a steel pipe, and its inner hole is a spiral with certain geometric parameters; the rotor is a screw with a hard layer. The rotor and the stator mesh with each other, and the lead difference between the two forms a spiral sealed cavity to complete the energy conversion. The helix of the motor rotor can be divided into single-end and multi-end. The fewer the number of rotor heads, the higher the speed, and the smaller the torque; the more heads, the lower the speed, and the greater the torque.
Introduction to Cardan Shaft
The function of the cardan shaft is to convert the planetary motion of the motor into the fixed shaft rotation of the drive shaft, and transmit the torque and speed generated by the motor to the drive shaft to the drill bit. The universal joint shaft mostly adopts the flexible shaft type.
Axis of rotation
The function of the DTH Bit drive shaft is to transmit the rotational power of the motor to the drill bit, and at the same time bear the axial and radial loads generated by the weight-on-bit. Therefore, the drive shaft requires high hardness, wear resistance and service life. At this time, quenching heat treatment can greatly increase the service life of the drive shaft.