Created on:2021-07-22 14:10

Coal mine equipment_ Hoist hydraulic station failure

Coal mine equipment_ Hoist hydraulic station failure

Braking system is the key equipment of mine hoist, the key technical product of mechanical, hydraulic and electrical integration, and the fundamental guarantee of safe operation of mine hoist.

Hoist braking system is the product of hydraulic transmission and control technology. With the development of brake control theory and electronic technology, the hoist brake control technology has made great progress, and the hoist brake system has also made great progress.

(1) Function and working principle of hydraulic station

In the normal operation of the hoist, the oil pressure required for working braking is generated, so that the brake can produce braking torque, and realize working braking and speed control (for AC winch). In case of abnormality, it can make the brake return oil quickly, produce safe braking and realize secondary braking.

B159 hydraulic station is driven by the motor to rotate the hydraulic pump to generate high-pressure oil, which is regulated by the electro-hydraulic pressure regulating device to the hydraulic direction changing valve and supplied in three ways: one way goes to pipe a through solenoid valve G3 to the brake; One goes to pipe B through solenoid valve G4; There is another way to the accumulator through the pressure reducing valve and one-way valve. During normal operation, the solenoid valves G3, G4 and G5 are electrified and the oil circuit is connected. The driver controls the electro-hydraulic pressure regulating device to change the pressure of the hydraulic system, so as to make the winch operate normally; The third circuit does not work normally, only accumulates the pressure to the accumulator, and the oil pressure entering the accumulator after the pressure reducing valve is P1. When the hoist is in emergency braking and operation, the solenoid valves G3 and G4 are powered off, pipe a directly returns oil through G3, and pipe B partially returns oil through G4 and overflow valve, resulting in primary braking. Another part of high-pressure oil enters the accumulator and makes the oil pressure rise to P1. After a delay, the solenoid valve G5 is powered off and G6 is powered on, so that the third oil circuit is connected, and the system oil pressure all returns to zero, resulting in secondary braking.

(2) Fault and its treatment

① Hydraulic pump failure

a. The reason why the vane pump is not oiled is that the hydraulic pump has been stored for a long time. As long as the pipe is disassembled and oil is added from the pipe orifice to make it flow into the pump, the pump can be filled with oil.

b. Pumping air makes the oil pressure unstable. First of all, check whether the end cover of the pump is tightened or the sealing ring is missing. Tighten the screw and install the seal, but the tightening degree must make the main shaft of the pump rotate freely by hand. Secondly, check whether the pipeline is sealed.

c. If the pump is not pressurized, check whether the oil distribution plate has been grinded. If it has been grinded, polish it with a fine oilstone.

② Failure of electro hydraulic pressure regulator

a. The maximum clearance between the main valve core and the valve body of yf-b20b relief valve is 0.006mm. If the clearance between the valve core and the valve body is greater than 0.006mm, the upward pressure will be slow, so the valve can only be replaced. If the clearance is OK, but the relief valve doesn't work, the relief valve can be removed, the parts can be cleaned with gasoline, the dirt in the small holes can be removed, and the taper surface of the pilot valve can be checked to see if there are grooves, and the sealing rings are in good condition.

b. The two planes of the nozzle and the control rod are not flat. Screw the standard M12 gauge on the thread of the nozzle to expose the end face of the nozzle. Grind the end face of the nozzle carefully with a fine oilstone based on the plane of the gauge. If the end face of the guide rod is not flat, it can be machined on the lathe to make the original end face perpendicular to the axis of the guide rod. The end face can be turned, but it can only be leveled, not too much.

c. The pressure on the electro-hydraulic pressure regulator is slow. The reason is that the movable coil is not round after external force and rubs the magnetic steel when it moves up and down; When the control rod moves up and down, it rubs the center hole of the cross spring. The coil should be replaced or the control rod should be assembled in the center of the center hole of the cross spring so that it does not rub against the edge of the hole.

d. The residual pressure is large. There are two ways to reduce the residual pressure. First, the distance between the control rod and the nozzle can be adjusted to raise the rod, and the residual pressure can be reduced. The second is to remove the end cover of the filter under the pressure regulating device, find the copper damping ring, and hammer the ring tightly.

③ When the hydraulic directional valve is in fault, the two pumps should switch to each other when they are opened at the same time. If one pump does not supply oil, the main reason is that the two directional springs of the hydraulic directional valve are installed in the wrong position, and the two springs can be replaced.

④ The main reason why the secondary brake oil pressure can't be maintained is that the relief valve and pressure reducing valve don't work and there are dirty things stuck. Just remove and clean the parts and small holes with gasoline. If the valve is normal but the secondary braking is still not maintained, check whether there is leakage in the spring accumulator piston. If there is leakage, replace the sealing ring. If there is no leakage, clean the check valve. In a word, there should be no leakage in the pressure maintaining process of the secondary braking pressure maintaining system.

⑤ The reason is that the pressure regulating value of the relief valve is much higher than that of the pressure reducing valve. The main reason is that the method of adjusting P1 is wrong. When adjusting P1, the pressure regulating springs of the two valves should be loosened, and the pressure should be adjusted from low to high. First, the pressure reducing valve should be adjusted, and then the relief valve should be adjusted. If the relief valve is adjusted upward and then screwed back, and the pointer of the pressure gauge turns, the handle of the relief valve should be adjusted upward, which means that the two valves are adjusted at the same P1 value, However, the design requires that the relief valve should be turned slightly to make the oil pressure set by the relief valve 0.2 ~ 0.3MPa higher than that set by the pressure reducing valve.

⑥ The reasons for unstable oil pressure fluctuation are as follows: first, air is mixed in the system, and air must be discharged; Second, it is possible that the filtering of the 24 V, 0 ~ 250 ma current supplied to the KT coil is not good. There is often AC component in the DC current, which makes the coil vibrate up and down and causes unstable oil pressure. Therefore, the electrolytic capacitor is used to strengthen the filtering and remove the AC component.

⑦ The empty stroke of the brake handle on the operating platform is too large, that is, when the handle is just pushed, the oil pressure is too high, but the oil pressure of the last stroke of the handle does not change, and the brake cannot be held when the weight is lowered (for the AC winch). This is mainly due to the oil pressure and current following is not adjusted well. It only needs to increase the current value corresponding to the oil pressure from low to high.

(3) Matters needing attention in daily use and maintenance of hydraulic station

① Regularly clean the filter (replace the filter element if necessary), pipelines and valves to make the system smooth.

② The quality of hydraulic oil should be guaranteed. Before each oil change, hydraulic oil must be inspected, unqualified is strictly prohibited to use, and must use filter when refueling.

③ To ensure enough oil, always check the position of the liquid level, to ensure that the liquid level between the two scale lines.

④ The oil quality of the hydraulic station in use should be inspected regularly, and the unqualified oil should be replaced immediately.

⑤ Use two sets of brake devices correctly. It should be replaced regularly to ensure the normal operation of the standby pump and play a standby role when the other pump can not work.

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