ROTARY DRILLING RIG AND DEVICE CONTROLLING MAIN HOIST LOWERING SPEED THEREFOR

摘要

Disclosed is a rotary drilling rig and a device controlling the main hoist lowering speed therefor. The device controlling the main hoist lowering speed comprises: a sensor (1), a controller (3), and a reversing valve apparatus, wherein the sensor (1) is for sensing in real-time the relative distance between a drill rod and a unit head shock cushioning apparatus and when the relative distance is equal to a predetermined distance, sending a trigger signal; the controller (3) is for sending a voltage signal to the reversing valve apparatus after receiving the trigger signal; an oil supply port of main pump negative feedback ports is connected to the main pump negative feedback ports (71, 73) via the reversing valve apparatus, and when the reversing valve apparatus receives the voltage signal and the main hoist is in a lowering state, the oil supply port supplies oil to the main pump negative feedback ports (71, 73). The rotary drilling rig can control the negative feedback pressure of the main pump, altering the delivery of the main pump, and during the process of the drill rod lowering, can thereby effectively reduce the main hoist lowering speed, preventing violent collisions between the drill rod and the unit head, increasing the service life of the unit head and improving the reliability of the whole machine.