1. Removal and installation of the boom locking valve assembly
(1) Disassembly of the locking valve assembly of Hitachi excavating arm
Lower the working device to the ground and release the remaining pressure in the hydraulic circuit.
① Disassemble the tubes and hoses shown in Figure 4-203.
② As shown in Figure 4-204, remove the mounting bolts of the bracket, and then remove the bracket and the boom lock valve together.
(2) Installation of the boom locking valve assembly
The installation sequence and disassembly sequence of the boom lock valve assembly are opposite. After installation, add oil from the oil filler to the specified liquid level, run the engine to circulate the oil in the system, and then check the oil level to discharge air.
2. Removal and installation of boom cylinder assembly
(1) Removal of the boom cylinder assembly
Fully extend the stick and bucket to lower the working device to the ground, and place the safety lock lever in the locked position.
① Remove the lubrication hose.
② As shown in Figure 4-205. Hang the boom cylinder assembly and remove the locking bolt.
③ Remove the plate, and then remove the pin. Check the number and thickness of the installed gaskets and store them in a safe place.
④ Start the engine, retract the piston rod, and tie it with iron wire to prevent it from falling off. As shown in Figure 4-206, place the cylinder assembly on the bracket and adjust the position of the sliding surface to release the remaining pressure in the circuit.
⑤ Remove the hose.
⑥ Take off the plate, as shown in Figure 4-207, remove the pin with the pressure screw, and remove the boom cylinder assembly. Check the number and thickness of the installed gaskets and store them in a safe place.
(2) Installation of boom cylinder assembly
The installation sequence of the boom cylinder assembly is opposite to the removal sequence.
① As shown in Figure 4-208, tighten the lock nut so that the gap between the plate and the nut is 0.5~1.5 mm. When aligning the pin hole position, never put your fingers into the pin hole.
② Adjust the thickness of the gasket, as shown in Figure 4-209, so that the clearance force between the cylinder rod and the plate is VI mm. The standard thickness of the gasket is
0.8mm and 1.5mm. During installation and adjustment, when aligning the pin hole position, never put your fingers into the pin hole.
