The reasons for the weak lifting capacity of the paver and the failure of the hopper to close

1. The ironing board is too weak to lift or even cannot lift at all

After inspection, all components of the electrical part of this machine (fuses, relays) are working properly. There is no problem with the mechanical part either. Moreover, when the manual valve is placed in the ironing plate lifting position, the indicator lights of the anti-climbing solenoid valve and the anti-settling solenoid valve of the lifting cylinder are both on, indicating that the solenoid valves are also working normally. In addition, the pressure of the hydraulic circuit was inspected. The highest measured pressure was 20 MPa, indicating that the working pressure of the hydraulic system is also normal.

When we repeatedly pull the hopper control switch, if the hopper can freely open and close, it indicates that the oil circuit from the hydraulic pump to the hydraulic control valve is working normally. From the hydraulic system diagram of this machine, it can be seen that the hopper cylinder and the ironing plate lifting cylinder are supplied with oil by the same hydraulic pump. Therefore, it is suspected that there is a problem with the solenoid valves controlling the two lifting cylinders. To verify this judgment, we removed the anti-climbing solenoid valve and the anti-settling solenoid valve, and directly connected the oil pipe to the lifting cylinder. When the lifting switch was set to the lifting position, the ironing plate could be lifted but at a slow speed and could not reach the maximum height. Moreover, after 2 to 3 attempts to lift, the ironing plate could no longer move. It seems that the problem does not lie with the solenoid valve of the lifting cylinder.

Finally, we focused on the oil circuit of the hopper and the ironing plate control valve. The rated pressures of the two pilot relief valves in the oil circuit are 21 MPa and 3 MPa respectively, which are the rising and falling pressures of the ironing plate. The inability of the ironing plate to rise is very likely related to the low pressure of the pilot relief valve. The purpose of adjusting the pilot relief valve is to regulate the lifting pressure and lifting speed of the ironing plate (although there is a safety relief valve in the hydraulic system, adjusting the pilot relief valve will not affect the working safety pressure of the pump in the system).

When we turn the adjusting screw of the pilot relief valve inward by half a turn, the ironing plate can rise slowly. After turning it inward by another half a turn, the lifting of the ironing plate is basically the same as when it is working normally. Finally, just tighten the lock nut on it. At this point, the fault that the ironing plate could not be lifted has been eliminated.

2 The hopper cannot be closed

First, the mechanical part was inspected. No cases of the hopper being stuck or the locating pin of the hydraulic cylinder falling off were found, nor were any other mechanical faults discovered.

Secondly, all components of the electrical part are operating normally. No problems were found with fuses, relays, circuits, etc. After testing, the solenoid valve coil was also in good condition.

Finally, when checking the pressure of the hydraulic system, it was found that the pressure did not meet the working requirements. From the hydraulic system diagram of this machine, it can be seen that the hydraulic pump supplies oil to both the hopper cylinder and the ironing plate lifting cylinder simultaneously. The normal lifting of the ironing plate indicates that the hydraulic pump is working properly. So we suspected that the leakage was caused by severe wear of the hopper control valve. However, after replacing the valve, the fault persisted, indicating that the problem did not lie with the hopper control valve.

From the hydraulic system diagram of this machine, it can be seen that the hydraulic circuit of the hopper and that of the ironing plate are connected in parallel. Therefore, it is possible that there is a problem with the lifting control valve of the ironing plate, which affects the entire hydraulic circuit. Since the ironing plate can rise and fall normally, it indicates that the control valve is not leaking. When we pulled the manual control valve for the lifting of the ironing plate, the valve core only moved a little to the right and the hopper returned to its normal working state. Thus, it was determined that the cause of the fault was that the valve core of the manual control valve of the ironing plate was not in its working position. After adjusting the position of the valve core, the fault was eliminated.