Failure Cause Analysis of Concrete Pump Truck Can not Pump

Concrete pump can not pump the cause of the malfunction Analysis: A SY5255 37m pump in the pump is completed, back to the mixing station car wash normal speed, positive and negative pump can not pump fault. Normal speed up instructions PLC can detect the speed of the transfer case signal, continue to check the pump control point Q2.0, Q2.1, lit normal Description of electronic control signal normal, should focus on checking the hydraulic control system. (1) DT1 / DT2 solenoid valve coil is shorted, open or solenoid valve to the PLC line is faulty. (2) DT1 solenoid valve is stuck, resulting in overflow pressure relief valve can not build up, DT2 solenoid valve spool if the card will cause a positive death, anti-pump out of control. (3) The main pump is faulty. Check found: (1) positive and negative pump observation pressure gauge, the pressure is 0, the system pressure. (2) Detection DT1 solenoid valve calls normal, manually after the top of its spool, the fault still. (3) suspected overflow valve spool stuck, remove the top cover remove the spool, valve spool, the next move flexible and normal; remove the spring, with 5 coins instead, fitted with spool cover, test machine fault remains the same, The relief valve is normal. (4) continue to test and found that the boom and piston retract all the functions are not normal, the speed can be automatically adjusted, and found that all three pressure gauges showed zero. Note that the fault should be in the main pump pressure output section. (5) analysis of pumping solenoid valve calls normal, you can explain driving, pumping position detection should be normal, but re-test: I2.5 light, transfer case position detection proximity switch lit, the car driving, pumping action with Cab operating action is normal, indicating that driving, pumping control circuit trouble-free. Engine speed is normal, and the system no pressure, position detection and no fault, so determine the fault transfer case internal shift fork problem. (6) Disassemble transfer case, check the third spindle spline and gear damage, replace the fault completely ruled out.