INTRODUCTION
1. Front end of rock drill
1. Front end of rock drill
The front end of the rock drill is mainly composed of shell, guide sleeve, flushing head, thrust ring, hydraulic plate and other parts. It has two main functions. One is to guide and support the rotation of the drill tail; the other is to introduce water from the water pump into the drill tail and provide it to the drill pipe.
1.1 Wear of guide sleeve and thrust ring
The copper guide sleeve is generally not easy to wear when lubricated with drill tail oil. If the guide sleeve wears repeatedly in a short period of time (which needs to be judged based on the actual situation), you need to check whether the drill tail lubricating oil channel of the rock drill is blocked. If it is blocked, The rock drill needs to be disassembled and repaired.
When the rock drill drills holes upward, rock debris will also flow into the front end of the rock drill along the drill pipe, accelerating the wear of the guide sleeve. The medium-deep hole rock drilling rig used in a mine has a lot of upward drilling operations, so the guide sleeve wears much faster than the horizontal excavation rig. Installing a waterproof cover at the drill tail can better prevent debris from entering and extend the service life of the guide sleeve.
The thrust ring bears the axial impact force and radial friction force of Shank Adapter. If the wear degree at the contact position between the thrust ring and the drill tail spline exceeds 1mm, it needs to be replaced. The thrust ring is also lubricated with lubricating oil. If it is replaced frequently in a short period of time, you need to pay attention to whether the lubricating oil channel is blocked.
1.2 Water leakage from front end of rock drill
Worn front water seal can cause water leakage. The water seal is a 4-way Y-shaped seal, which not only prevents water leakage, but also prevents debris from entering. If water leakage occurs, the water seal should be replaced immediately, otherwise the front end of the rock drill will be damaged and the eye entry speed will be affected.
A cracked flush head can also cause water leakage from the front. There are two main reasons for the rupture of the flushing head. First, the operator has been dry drilling for a long time. When the operator cannot unload the drill pipe, he will start the impact vibration drill pipe. At this time, the drill pipe does not push against the rock, and most of the force is concentrated on the flushing head. Doing this for a long time will cause the flushing head to break; the second is caused by corrosion.
2. Gear box
The gearbox consists of a transmission shaft, a driving gear, a driven gear, a beating sleeve, a driving sleeve, a gearbox cover and a bearing. Its function is to transmit the power of the oil motor to the drill bit.
2.1 Drive sleeve wear
Under normal circumstances, the splines of the drive sleeve will be worn. When the spline exceeds 2mm, the drive sleeve needs to be replaced. The larger the diameter of the drill bit used, the faster the drive sleeve will wear. Excessive drill diameter will increase the load on the rock drill and cause the drive sleeve to rupture.
In the case of improper use, the drive sleeve will show abnormal wear. This is caused by a lack of grease in the gearbox or deterioration of the grease. Grease has the function of dissipating heat. If the temperature of the gearbox is too high, the copper bushing in the driven gear will rise above the step due to thermal expansion, and the drive sleeve will also rub against the thrust ring at the front end of the rock drill, eventually causing the end face of the drive sleeve to wear and tear. Debris generated by the friction of the drive sleeve will enter the inside of the rock drill, block the oil passage and even wear the cylinder part of the rock drill. Therefore, the grease in the gearbox needs to be resistant to high temperatures and should be replaced once a week.
2.2 The condom broke after being beaten
The beating sleeve is located at the end of the drill tail and the front end of the buffer piston, and transmits the recoil force of the drill tail to the buffer piston. Under normal circumstances, the contact position between the beating sleeve and the end of the drill tail needs to be replaced if the wear exceeds 1mm.
During an impact, the energy of the impact piston is transmitted to the drill tail. The drill tail transmits the energy to the back of the rock through the drill pipe, and the remaining energy is transmitted to the buffer piston through the beating sleeve. Frequent dry driving or oil leakage from the buffer piston seal may cause the beating sleeve to rupture. If the pressure gauge shows normal pressure but the rock drill enters the hole slowly, you need to disassemble the front end and check whether the beating sleeve is damaged.
2.3 Rotary pressure is too high when idling
When the rock drill is idling, the pressure is generally below 5MPa. If the pressure is high, there are two reasons if the pressure regulating valve is normal. First, there is no grease in the gear box, which is prone to wear of the drive sleeve; second, during the installation of the gear box, the preload force of the cylindrical roller bearing in the gear box is not grasped, and the adjustment pad is placed too much, which presses the bearing. If it is too tight, the problem of excessive pressure during idling will also occur. When assembling the gear box, special tools should be used to tighten the gear box cover. The tightening torque of the tool is 200N·m. Use a feeler gauge to measure the gap between the gearbox cover and the gearbox, and control the gap to 0.15~0.20mm by increasing or decreasing the adjustment pad. Only then can the gearbox be considered correctly installed.
3. Intermediate body and cylinder
The intermediate body and cylinder body are mainly composed of buffer piston, impact piston, front guide sleeve, rear guide sleeve, reversing valve and other parts. Both the intermediate body and the cylinder block can be understood as a form of oil cylinder.
3.1 Wear of buffer piston and intermediate inner cavity
The buffer piston also moves axially in the rock drill, and its surface will be worn by the two seals. When the wear degree exceeds 0.1mm, it needs to be replaced. If the buffer piston is severely worn and is not replaced, the buffer piston and the inner cavity of the intermediate body will rub against each other. At this time, the entire intermediate body will be scrapped, causing huge losses, as shown in Figure 3. When assembling the buffer piston, the intermediate body should be placed horizontally, apply hydraulic oil to the intermediate body cavity and the surface of the buffer piston, and press the buffer piston vertically. If you encounter large resistance or there is obvious rebound force when knocking, you should stop pressing immediately and check whether the buffer piston is placed vertically to avoid damage to the intermediate cavity.
3.2 Impact piston breaks
A broken impact piston is a very serious problem. In actual use, the operator cannot immediately judge after the piston breaks. If the impact continues, the broken piston and debris may wear the cylinder, causing the rock drill cylinder to be scrapped. Therefore, in daily maintenance, we should try our best to avoid this situation.
There are two main reasons for the fracture of the impact piston. One is the uneven wear of the two guide sleeves at the front and rear ends of the cylinder; the other is the different tightening torques of the three fixing bolts of the rock drill. When the gap between the guide sleeve and the piston exceeds 0.06mm, it needs to be replaced. It is important to note that the order should also be paid attention to when removing and assembling the impact piston. When dismantling the rock drill, you should first remove the impact piston, and then remove the fixing bolts of the rock drill. When assembling the rock drill, the three fixing bolts should be tightened to a torque of 300N·m, apply hydraulic oil to the piston, and slowly screw it in from the rear end. If resistance is encountered, the installation should be stopped immediately and the cause should be found. This is to ensure that the impact There will be no eccentricity after the piston is installed.
3.3 Impact piston cavitation
During an impact, if the hydraulic oil cannot be replenished, the vacuum generated by the cylinder will suck out the air mixed in the hydraulic oil, forming bubbles. The bubbles burst under high temperature and pressure and eroded the surface of the impact piston, causing cavitation. When cavitation occurs in the impact piston, its rough surface will accelerate the damage of the seal during the friction process with the seal, thereby causing oil leakage in the rock drill.
Regularly checking the accumulator pressure can effectively prevent cavitation of the impact piston. The two accumulators of the COP1238K rock drill are connected to the high-pressure oil circuit. When one of them fails to work, the other can still play a certain role. When it is found that the main oil return pipe of the rock drill is beating abnormally, it is necessary to add nitrogen or replace the accumulator. The nitrogen charging pressures of the two accumulators are 8 to 10 MPa respectively.
4. Precautions for use and maintenance
The rock drill is a precision core component of the rock drilling rig. The following points should be noted during use and maintenance:
(1) Make sure the hydraulic oil is clean and replace the hydraulic oil filter element regularly. When replacing the oil pipe and adding hydraulic oil, you should also be careful not to mix mud, gravel, etc.;
(2) Wearing parts such as the guide sleeve and water seal at the front end of the rock drill must be replaced in time;
(3) Regularly check the accumulator pressure and lubricating oil passage, regularly add grease and tighten the fixing bolts according to the torque requirements;
(4) After dismantling the rock drill, focus on checking the wear degree of the beating sleeve, drive sleeve, buffer piston, driven gear and other parts, and check the matching clearance between the impact piston and the front and rear end guide sleeves;
(5) When assembling the rock drill, attention should be paid to the installation sequence of the impact piston, the pretightening force of the gear box, and the tightening torque of each bolt of the rock drill.
5. CONCLUSION
By analyzing the causes of various failures of the COP1238K rock drill, suggestions for use and maintenance were put forward respectively, which provided theoretical support for preventing operators from improperly using rock drills and improving the skill level of maintenance personnel.
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