Maintenance of forklift braking system

1、 Maintenance of master cylinder

1. Remove the master cylinder from the forklift, remove the brake pedal, clutch pedal return spring, two push rods and oil outlet pipe on the master cylinder, remove the fixing bolts on the master cylinder, and remove the master assembly of the brake master cylinder.

2. For the decomposition of the brake master cylinder, the hydraulic brake master cylinder produced in the early stage is integrated with the clutch hydraulic master cylinder. The parts in the two chambers should be placed separately during the decomposition to prevent the wrong installation.

A. Remove the dust cover clamp, remove the piston push rod and dust cover, clean the outside, unscrew the oil filler plug and drain the internal brake oil.

B. Remove the lock ring, take out the thrust washer, piston and cup, return spring and oil outlet valve; Remove the oil outlet and return valve from the return spring and remove the sealing ring from the piston.

C. Remove the pump cover and oil pipe joint, clean the internal parts with alcohol, and dredge the oil return hole, compensation hole, small hole on the piston head and vent hole on the refuelling plug.

3. Maintenance of master cylinder parts.

A. If the star valve plate on the piston is loose, it should be riveted tightly.

B. The degree of freedom of the positioning spring in the master cylinder is 107mm. Under the pressure of 53 -. 9-68.6n, the compression length shall not be less than 67mm. Otherwise, it shall be replaced.

C. Leather cup, sealing ring, dust cover and oil outlet and return valves shall be replaced with new parts.

4. Assembly and test of brake master cylinder.

A. All accessories shall be cleaned before assembly and then assembled in the reverse order of subsection. After reassembly, push the plug several times with the push rod to check whether the piston moves flexibly and freely in the cylinder barrel and whether there is card clamping. After loosening the pushrod, use a very thin steel wire to check whether the oil return hole and compensation hole are unblocked in the liquid storage chamber. If the oil return hole is closed by a leather cup, the washer at the back should be thinned to eliminate the fault. Otherwise, a braking seizure will occur or replace the return spring with a large elastic force.

B. For the test of a master cylinder, it is best to conduct a pressure test after reassembly. Check whether all parts are sealed, leaking oil and working usually. Otherwise, it shall be eliminated first and then loaded for use. For pressure test, fill the master cylinder with brake fluid, and then turn the handle to make the oil pressure reach 8820kpa for 3min. The master cylinder and wheel cylinder shall not leak oil, and the oil pressure drop shall not exceed 294kpa. Otherwise, it shall be reassembled.

2、 Maintenance of wheel cylinder.
The hydraulic brake wheel cylinder is installed on the wheel brake, and the maintenance method is the same as that of the master cylinder. The inner diameters of two wheel cylinders on the same wheel shall be the same, and the leather cup and sealing ring shall be replaced after removal. The free length of the spring in the wheel cylinder is 42mm. Under the pressure of 24.5-34.3N, the compression length should not be less than 17mm. Otherwise, it should be replaced. After reassembly, the pressure test shall be conducted with the master cylinder, and there shall be no oil leakage.