The concrete pump is a constuction machinery with high mechanical and electrical integration. Its hydraulic system can be divided into closed and open type. According to the distributing valve, it can be divided into rotary valve, gate valve and S valve. On electrical equipment, PLC (programmable logic controller) is now introduced into the concrete pump, which greatly improving the reliability of the electrical system. But no matter what kind of concrete pump, its implementation components are the same, including the main delivery cylinder, distribution valve, swing cylinder and mixing motor, etc., and the reversing of the cylinder is controlled by the corresponding solenoid valve on-off and stroke switch (or proximity switch). Although there are different forms in failure, they usually be analyzed from three aspects: mechanical, hydraulic and electrical.
1. The main motor can not reach the specified speed, according to the main motor start button, the motor can run, but can not reach the specified speed, and from star connection method to triangle connection when the automatic stop
First check the power supply voltage is normal, transformer capacity adequacy (transformer capacity is generally 1.15 times the computational load), through the calculation and measurement of starting voltage supply line diameter meets the requirements, ensure the voltage drop in the specified range (line allowable voltage drop less than 5%), if the starting voltage drop is too large, it may be appropriate to increase the line size. Improper operation and malfunction of hydraulic system will cause difficulty in starting. Before starting, check whether the pump and motor motor handle is in the middle or not, whether the pump button is closed or not. If you can not start, you must check the control of the main oil pump solenoid valve is normal, to ensure that the start of the main oil pump in the state of unloading.
2. according to the pumping button, concrete conveying cylinder does not work or work weakness
①. check whether the hydraulic oil level is normal, insufficient to the specified position; restart the motor to observe whether the vacuum meter readings are within the normal range, to determine whether the need to replace the filter.
②. shutdown, open the main power supply, by pumping button, carefully inspected whether the electromagnetic valve to control the pump action, can also be used multimeter to measure the electromagnetic valve on-off state, if not normal should further determine the fault line, or solenoid valve damage or spool stuck. If normal, it should check the action of the hydraulic reversing valve.
③. if the main cylinder is not in the reverse position, it is likely that the switch has a problem.
④. check the main pump system pressure (pumping operation), if not reach the specified value, you should check the overflow valve and the main oil pump. For closed system, under normal circumstances, motor start, repair pump work, pressure display should be about 2.5MPa, if the pressure is not enough, adjust the oil pump safety valve and check the wear of the oil pump.
⑤. oil temperature is too high, leading to leakage increase, oil pressure drop, work powerless. The heat dissipation system should be checked to ensure the good heat dissipation effect.
3. Common faults and troubleshooting methods of reversing system
①. main cylinder non reversing
Fault: lack of hydraulic oil, fuse blows, the reverse button to poor contact, the reverse relay socket connection loose, damaged electrical control box delay relays, light emitting diode light-emitting diode does not flash, permanent flashing, hydraulic valve spool due to dirt stuck, solenoid valve coil burning.
Troubleshooting: add the hydraulic oil to the required position, replacing the fuse, repair or replace the reverse button to remove loose wiring, replacing the delay relay, replacing the light emitting diode, the switch seated, remove the dirt in the valve spool, the valve core can move freely, repair or replace solenoid valve.
②. distribution valve can not automatically change
Failure reason: accumulator oil circuit is not full pressure, distribution valve reverse switch damage or poor contact, S tube swing area accumulated aggregate or aggregate deposition in the hopper, hinder reversing.
Exclusion method: check accumulator pressure, turn off the accumulator unloading valve, repair or replace the reverse switch, use repeated reversing and reverse pumping method to pump out the aggregate in the S pipe area, and open the hopper discharge port to remove the aggregate sediment if necessary. The pumping concrete should meet the requirements of pumping capacity.
4. Distribution valve swing weakness
Distribution valve swing weakness is generally due to insufficient oil pressure caused by, and the lack of oil pressure is caused by abnormal leakage. The specific steps are as follows:
①. check the appearance, see the oil pipe, connector, valve body, oil pump, cylinder whether there is leakage phenomenon.
②. check whether the hydraulic oil level is normal, the oil filter is too dirty, otherwise it may cause poor oil intake. Under normal circumstances, the filter plug will be accompanied by noise increases and oil temperature rise phenomenon, and the reverse pressure is insufficient, sometimes without, and therefore should be replaced in time, otherwise it will accelerate the wear of the oil pump and other hydraulic components.
③. adjust the relief valve to see whether the pressure rise, if not rising, you should check the relief valve, see whether the spring damage, stuck, the valve is seriously worn.
④. check accumulator pressure. It can be checked by pressure gauge at shutdown, generally 110MPa, and also can be judged by observing the decline of pressure meter reading when the machine is running. Under normal circumstances, the pressure drops 3MPa ~ 4MPa. when reversing, if the accumulator does not meet the specified value, the accumulator bladder may be damaged and need to be replaced.
⑤. check whether the distributing valve is pulled and worn seriously, resulting in insufficient pressure.
⑥. for the distribution system of constant flow pump (pump distribution system and some concrete delivery and share a main oil pump). After the above steps are completed, the pressure of the pump should be checked, and the pressure should be adjusted when the pressure is insufficient