Shi Weiying Displacement Regulation of Concrete Pumps in Two Cases

1. Shi Weying KVM37 / P2023 concrete pump truck 1.1 Symptom Pump displacement can not be adjusted, has been maintained at maximum displacement (concrete output 96m3 / h, the number of strokes per minute: 19 times). Switching the displacement control valve block on the electronic / manual control switch, found that both electric control and manual control can not change the displacement. 1.2 Fault Diagnosis Process (1) Analysis of hydraulic system diagram found that the displacement control valve block built two exactly the same pressure reducing valve (pressure output range of 3.5 ~ 55bar), one of the pressure reducing valve is used to control the main pump The displacement of the control oil pressure, another relief valve is a buffer. The initial judgment is used to adjust the main oil pump pressure relief valve control circuit damage caused by the pressure can not be adjusted control circuit, and thus can not regulate the displacement of the main pump. (2) will adjust the main pump control circuit pressure relief valve removed, no abnormalities found after cleaning. (3) The two pressure reducing valve are removed to clean, and replace their position after installation, both the electric control or manual control to adjust the displacement back to normal. (4) Install the two pressure reducing valves back to the original position, and test the pressure of the MX1 port on the displacement buffer valve block (control the displacement of the oil pump) with the pressure gauge. When the displacement is adjusted, the pressure will be kept unchanged at 4 bar (Normal value should be in the range of 3.5 ~ 55bar), then further confirmed the main pump control oil pressure regulator pressure relief valve damage. (5) replace the valve after the test machine, truck everything is normal. 2. Schweitzer BP2800HDR type concrete pump 2.1 Symptoms Pump displacement can not be transferred to the maximum, has been maintained at 17 to 18 strokes / minute (standard maximum stroke of 31 to 32 beats / min). 2.2 Troubleshooting Process (1) test the main system pressure is 280bar, the system pressure is normal. (2) When the normal pumping stops, observe the piston rod does not retract phenomenon, ruled out the main cylinder leakage lead to the possibility of displacement. (3) with the pressure gauge test displacement buffer valve block on the MX1 port (oil pump displacement control) pressure, adjust the displacement found when the pressure changes in the range of 4 ~ 56bar, regulating the main oil pump control circuit Pressure relief valve is working properly. (4) Disassemble and clean the control spool valve spool on the main oil pump (remember the number of thread turns of the displacement adjusting knob before dismantling for restoration), clean the valve spool and reinstall it, and the fault still remains. (5) The displacement adjustment range knob into the test machine after two laps, the pump displacement increased, so adjust the displacement adjustment knob until the pump maximum stroke of 32 times / minute. Troubleshooting. 2.3 Analysis of the cause of the malfunction (1) valve return spring fatigue softening, or other reasons lead to loose spool spool control, making the spring without preload. (2) hydraulic oil contaminated, dirt into the control spool valve spool is stuck.