Yuken hydraulic in a variety of unexpected conditions, try to change the triple gear pump into a double gear pump. Let's look at this case.

 

1 QY50 truck crane, the aluminum alloy shell of the third-stage pump (pump 3) was broken during work, and its function could not be repaired.

 

Causes the strut and the turn to have no movement. The three gear pump displacement installed in the hydraulic system of this machine is respectively 80mL/r, 63mL/r and 40mL/r, and the rated pressure is 25MPa.

 

Principle of hydraulic system

 

The hydraulic system of this crane is shown in FIG. 1. Pump 3 supplies oil to the air conditioning motor of the outrigger, rotary hydraulic system and lifting operation room, which is connected in series.

 

When the outrigger selector valve is in the middle position, the outrigger hydraulic system does not work. The pump supplies oil to the 3-way rotary hydraulic system and the air conditioning motor. When the outrigger working selector valve is not in the middle position,

 

The outrigger hydraulic system is in working condition, and the oil supply of the rotary hydraulic system and the air conditioning motor is cut off. Mainly supply oil to hydraulic system of boom telescopic and amplitude luffing mechanism, pump 1

 

It mainly supplies oil to the hydraulic system of main hook and auxiliary hook, and the pressure oil of pump 1 and pump 2 converges through the confluent valve set to jointly drive the working device. If the boom retracts and changes

 

When the amplitude handle (included in the boom telescopic and amplitude variable valve group, not specifically shown in FIG. 1) is in the middle position, the combined valve group will converge the pressure oil of pump 2 and pump 1, and work together to the main direction

 

Hook and auxiliary hook hydraulic system oil supply; If the main hook and secondary hook operating handles (included in the main hook and secondary hook control valve set, not specifically shown in FIG. 1) are in the middle, confluent

 

The valve assembly combines the pressure oil of pump 1 and pump 2 to supply oil to the hydraulic system of boom telescopic and amplitude variable mechanism. If pump 1 and pump 2 supply oil to their respective working devices, then no

 

Confluence; If all the four operating handles are in the middle position, pump 1 and pump 2 will be discharged, and the oil of pump 2 will go through boom expansion and amplitude variation valve group, d1-d2 oil pipe and oil cooler

 

Go back to the tank.

 

Modification methods

 

First, the breakdown of the three pump, welding pump 3 shell. Remove the transmission spline sleeve of pump 3, put pump 3 back in place, close the oil outlet of pump 3, and make it only play the role of sealing the end of the pump set.