1. Standard pressure value of hydraulic system
The standard value of safety valve setting pressure of each working mechanism in the hydraulic system is shown in Table 4-13.
During the pressure adjustment process, the safety valve pressure changes as shown in Table 4-14.
2. Safety valve pressure adjustment
(1) Stop the excavator on level ground and turn off the flame.
(2) Relieve the pressure of the hydraulic system.
(3) Install a 4900kPa pressure gauge on the upper and lower pump pressure measuring joints
(4) Install a 490kPa pressure gauge on the power conversion connector.
(5) Start the engine and operate the stick control lever at full stroke to swing the stick cylinder in and out until the hydraulic oil temperature reaches 55°C.
(6) The power mode selection switch is in position Ⅲ, the engine throttle knob is in position 10, and the AEC switch is in the OFF position. Under no-load conditions, the engine speed is the rated speed, and note the engine rated speed.
(7) Adjust the safety valve pressure when the engine and main pump are working normally. If the pressure adjustment result is incorrect, check and adjust according to the characteristic curves of the engine and the main pump.
3. Adjustment of the main safety valve pressure
Adjust the pressure of the main safety valve in order to adjust the pressure of each working device and walking safety valve.
(1) Stop the excavator on level ground and turn off the flame
(2) Relieve the pressure of the hydraulic system
(3) Check the set pressure of the main safety valve, which should be (31400±490) kPa
(4) Tighten the lock nut and turn the adjustment bolt clockwise until it is fully tightened, and then tighten the lock nut
(5) Loosen the lock nut and turn the adjustment nut 1/4 turn clockwise, then tighten the adjustment nut.
4. Adjustment of the secondary safety valve
(1) Preparation: Enable the check method in the maintenance service program to keep the power conversion pressure at 2250kPa. This value can be displayed on the pressure gauge or monitor at the pressure measurement point. During the pressure period of the safety valve, do not stop the engine. This can prevent the power conversion pressure from changing.
(2) Using the pressure gauge on the pressure point of the upper pump, the opening pressure of the safety valve in the boom and bucket berth can be read out. Using the pressure gauge on the pressure point of the lower pump, the opening pressure of the safety valve in the stick oil circuit can be read out.
(3) Compare the opening pressure of the safety valve of the above working devices with the standard pressure, if it is inconsistent, adjust to the standard
(4) After adjusting the pressure of each safety valve, restore the opening pressure of the main safety valve to its original value.
The structure of the two-stage safety valve is shown in Figure 4101.
According to the above methods and steps, adjust the pressures of the arm cylinder safety valve, bucket cylinder safety valve, and boom cylinder safety valve to be consistent with the standard values in Table 4-13. After the pressure adjustment is completed, the verification method in the maintenance service program should be activated for verification.
5. Adjusting the pressure of the relief valve during walking
(1) Enable the check method in the maintenance service program and keep the power conversion pressure at 250kPa3
(2) During the calibration mode, in order to prevent the power conversion pressure from changing, do not stop the engine.
(3) Insert the track latch into the track drive wheel to prevent the drive wheel from rotating in the forward direction
(4) Slowly move the left walking joystick to the forward position, check the pressure gauge reading on the pressure point of the lower pump, that is, the opening pressure of the walking cross relief valve
(5) Move the left travel joystick back to the neutral position. At this time, you can adjust the pressure of the travel cross relief valve, loosen the lock nut and turn the adjustment bolt until the pressure gauge reads (36800±1470) kPa.
(6) Tighten the lock nut, the tightening torque is (44±5) N·m
(7) In the same way, adjust the pressure of the right travel cross relief valve
(8) Cancel the check method in the maintenance service program
6. Adjustment of pressure of rotary safety valve
The method of adjusting the pressure of the rotary safety valve is basically the same as the method of adjusting the pressure of the overflow valve. In the pressure measurement process, the excavator with a rotary lock pin is directly locked with the rotary lock pin to load the hydraulic system; for the excavator without the rotary lock pin, the rotary brake can be used to lock the rotary mechanism to load the hydraulic system .
