With the development of bolt support technology, as the main mechanical equipment in the production process of bolt support, the bolt drilling rig has developed from the original single function, poor reliability, low technical content and poor safety to today's new drilling rig with high reliability, good safety and high degree of automation. At present, the use status of some mine bolting rigs is not very good. It is often that a new drilling rig needs to be repaired on the ground in less than two months, which seriously affects normal production. Whether the anchor drill can work normally and whether it can be eliminated accurately and timely after the failure is the key to improve the support effect, speed up the speed of roadway, reduce labor intensity, improve production efficiency and improve the utilization rate of equipment. Therefore, it is widely valued and adopted by coal-producing enterprises all over the country, which represents the main development direction of roadway support technology. Combined with his own practical work experience, the author puts forward the following views on the problems and maintenance methods in the use of pneumatic anchor drill, so as to facilitate peer exchange and reference. China has introduced Australian pneumatic bolting rigs since 1987. After more than 20 years of development, there are many models of pneumatic bolting rigs in China, ranging from MQT-50C to MQT-120C, and there are many manufacturers. Moreover, the performance of bolting rigs has reached the international level in the 1990 s. It is suitable for drilling roof bolting holes and bolting holes in roadway layers with rock firmness coefficient f≤ 8 in underground engineering such as coal mine roadways, it can integrate mixing, nut tightening and anchor rod installation, and has the characteristics of simple operation, multi-purpose machine and convenient maintenance.

 

1. Common faults and reasons of pneumatic anchor drill

 

1.1. Causes and troubleshooting of insufficient motor power

 

1.1.1. If the air source pressure is too low and the air volume is too small, check whether the air supply valve is fully opened and whether the air supply hose is damaged. The diameter of the intake pipe is too small to increase the diameter of the intake pipe. The air intake is soft. The pipe is too long, shorten the length of the intake hose; the oil cup is blocked, clean the oil cup to eliminate the fault; the air compressor is not working properly, solve the problem to make it work normally; the bearing is damaged, replace the bearing; whether the pressure reducing valve is in the closed position, the pressure reducing valve should be closed; air leakage at the joint, tighten the joint to ensure that the joint is in good condition; there are sundries in the motor reduction box, take out sundries. 1.1.2 The filter screen and silencer are blocked. Disassemble the filter and clean the filter screen; if the lubricating oil is excessive, disassemble and clean the filter and adjust the oil supply. The silencer is frozen, removed and cleaned. It is recommended to use antifreeze lubricant.

 

1.1.3 The wrench pressure is not in place to check the motor valve. If it cannot be fully opened, replace it with a new valve.

 

1.1.4 Check the "O" ring for air leakage at the tee shaft and replace the damaged "O" ring.

 

1.1.5 The motor drive torque is small. The gap between the motor rotor and the housing is too large, and the seal of the cylinder reversing valve is worn, resulting in a large amount of compressed air leakage. It makes the motor speed normal when idling, while the motor speed drops rapidly or loses speed after drilling, and stops when mixing the anchoring agent.

 

Cause analysis and troubleshooting of insufficient thrust of 1.2 outriggers:

 

① The compressed air pressure of the working face is low, which does not meet the requirements of the drilling rig. It is recommended to use the air pressure of 0.4- 0.65MPa;

 

The filter is blocked by pollutants, the pipeline pressure loss increases, the air pressure decreases, should be checked and cleaned;

 

③ The air supply valve is not fully opened, the air supply pipeline is damaged and leaking, the pipe joint is leaking, the air supply hose is folded, the ring is too much, the pipe diameter is too small, etc., which increases the pressure loss of the pipeline, resulting in the supply of compressed air to the cylinder Low pressure;

 

④ The oil injector is blocked, the pipeline pressure loss increases, and the air pressure decreases;

 

⑤ The seal of the cylinder reversing valve is worn, causing air leakage;

 

⑥ If the leg seal is damaged, replace it with a new one;

 

The leg of the oil too much, the resistance is too large; cleaning legs, proper amount of lubrication, reduce the resistance.

 

The reason for the slow falling speed of the 1.3 leg and the troubleshooting When the drilling rig is working, the telescopic pipe is bent due to the uneven force of the machine due to the unreasonable placement position. Dust entering the cylinder should be cleaned, lubricated properly, reduced resistance, and dust ring should be checked for damage. If damaged, replace it immediately. The inner wall of the steel outer sleeve rusts, which makes the rubber bowl ineffective and accelerates the wear of the rubber bowl. The exhaust valve is blocked and cleaned.

 

1.4 the causes of slow drilling speed and troubleshooting:

 

① Insufficient cylinder thrust: low working air pressure caused by pressure air pipeline exceeding rated load, pipeline leakage and valve wear, and insufficient cylinder thrust.

 

② Drill pipe specification is unqualified or has been bent and deformed: check whether the drill pipe is bent, if bent, repair it to be straight and then use it; check whether the drill bit specification is correct, and use a drill bit with appropriate specification. Check whether the drill bit is sharp, use a sharp drill bit; the center hole of the drill pipe is blocked, check and clean the center hole of the drill pipe.

 

Insufficient water supply: the water valve of the drilling rig cannot be fully opened, and the water flow is not smooth; the water source pressure is low, and the water pressure should be kept within the range of 0.6 ~ 1.2MPa; the water supply valve is not fully opened, the water supply pipe is blocked, the pipeline is damaged and the joint leaks, resulting in low water pressure and small flow.

 

2. Problems that should be paid attention to in the use of pneumatic anchor drill

 

2.1 work must have enough water pressure pneumatic anchor drill at work must have enough water pressure, should be maintained at 0.6MPa ~ 1.2MPa, and the water quality should be clean. In actual use, there are often cases where the water pressure is insufficient and the drilling rig continues to be used. In this way, between the output shaft and the water jacket and the seal, a large amount of heat is generated due to friction, which causes the water jacket and the seal to age quickly, causing the seal to be destroyed and the drill bit to be damaged prematurely. Therefore, in use, we must pay attention to the water supply before drilling, stop drilling when the water is stopped, and do not start drilling when the water pressure is insufficient. In addition, the drill sleeve sealing ring between the drill pipe and the drill sleeve should be replaced frequently. The water leakage at the connection between the downhole drill sleeve and the drill pipe is very serious, which is not only inconvenient for the operators, but also causes the pressure water to not fully flush the drill bit, and the cooling and chip removal are not sufficient.

 

The oil mist device of the 2.2 drilling rig shall not be short of oil, and the lubrication and cooling of the motor part of the anchor drilling rig shall be ensured to be sufficiently lubricated. High-pressure gas is used to bring oil into the motor through the oil mist device. If the oil mist device is short of oil, the pneumatic motor will not be lubricated, and the tooth surface temperature of the motor gear will rise rapidly, thus greatly reducing the efficiency of the pneumatic motor. If the motor is no longer lubricated and cooled, the burn area continues to expand, and the motor will soon be scrapped, making the anchor drill unable to work. Therefore, during the use of the pneumatic anchor drill, the oil mist must not be short of oil. In addition, before use, the drill pipe is coated with lubricating grease on the part inserted into the drill sleeve, which can prolong the service life of the drill pipe and the drill sleeve, and the assembly and disassembly of the drill pipe are also convenient.

 

Provide sufficient wind pressure and air volume when 2.3 anchor drilling rig is working. The normal control wind pressure of pneumatic anchor drilling rig is 0.4 ~ 0.63MP, and the diameter of pressure air pipeline is not less than Φ25. Only when the above conditions are met, the anchor drilling rig can be guaranteed to work under rated working conditions. When the air pressure is insufficient, it is forbidden to use the anchor drill, otherwise it will accelerate the damage of the parts of the drill. Be sure to keep the compressed air clean and dry. If the water content is too large, it will scour and destroy the oil film on the surface of the parts in the air motor, and make the silencer scale, block the exhaust duct, and make the drilling rig unable to operate normally.

 

2.4 Anchor drilling machine working torque and propulsion should match in the process of drilling, often appear the phenomenon of drilling rig plugging, greatly reducing the drilling efficiency. Therefore, in the selection, according to the average hardness of the mine's roof, due to the current promotion of the use of prestressed anchor, the selection of the anchor drilling machine will be more demanding. In the selection of anchor drilling machine, the hardness value of the top plate should be considered first, and secondly, the failure value of the nut stopper of the prestressed anchor rod used in this mine should be understood. The maximum torque of the selected anchor drilling machine must be greater than this value.

 

Pneumic anchor drill is one of the most widely used bolt support equipment in coal mines in China. Scientific management and maintenance and correct use of anchor drill are important factors to improve the efficiency and quality of bolt support, improve the accuracy of fault judgment of anchor drill, and improve the maintenance speed and quality of the drill. From the point of view of the development of high-yield and high-efficiency coal mine construction in China, the development of anchor drilling rig has hindered the pace of high-yield and high-efficiency coal mine construction in China, our country should be based on their own situation on the existing single anchor drilling rig to research, enhance the reliability of these anchor drilling rig, improve the output power, reduce weight, improve service life, to meet the needs of coal mine use.