1 Insufficient brake air pressure
Fault phenomenon:
Brake failure caused by insufficient air pressure is manifested as the air pressure gauge cannot reach the specified air pressure value (0.45-0.70Mpa), and the brake does not respond when the brake pedal is pressed.
Fault cause:
1) The pipeline leaks, the gas in the air tank has no pressure or the pressure is too low, which is not enough to push the booster pump group to generate braking force.
2) The air compressor is not working properly and cannot produce enough compressed air.
3) The one-way valve is rusted and stuck, resulting in the inability to enter the air tank or slow air intake.
4) The oil-water separator drain plug is not tightened, and the air leakage is serious.
5) The pressure regulating valve leaks seriously.
Troubleshooting:
First, check the pipeline leakage, and then check the working status of the air compressor. Remove the air compressor outlet pipe and press the air outlet with your thumb. If the exhaust pressure is low, it means that the air compressor is faulty. If the air compressor is in good working condition, check the oil-water separator drain plug or adjust the pressure to avoid bypass, and finally check the two one-way valves in the three-way joint. The one-way valve is stuck, which will cause the air to be unable to enter the air reservoir or the air to enter slowly.
2 Brake failure
Fault phenomenon:
The loader cannot slow down or stop when braking during driving
Fault cause:
1) Insufficient brake air pressure, unable to push the brake piston to move.
2) Brake valve failure, piston stuck or compensation hole and vent hole blocked, unable to generate sufficient air pressure
3) There is air in the brake oil pipe, causing oil pressure fluctuation or insufficient flow, unable to push the brake piston to move.
4) No brake fluid or insufficient brake fluid, resulting in insufficient amount of brake fluid entering the brake cylinder, low output power of the brake cylinder, unable to push the brake piston to move.
5) The brake oil pipe is broken or the oil pipe joint leaks oil, which reduces the amount and pressure of brake fluid entering the brake cylinder.
6) The booster cylinder piston is stuck or the sealing ring is damaged, and the output brake fluid volume and pressure are reduced.
7) The caliper disc brake cylinder has serious oil leakage, a large amount of pressure oil leaks, and the brake piston cannot be pushed to move.
8) The piston in the caliper disc brake cylinder is stuck and the piston cannot move.
9) The brake friction pad is greasy or severely worn, the friction coefficient is reduced or the brake clearance is increased, and the braking force is reduced. Fault diagnosis and elimination:
1) Check the brake air pressure, eliminate the fault of low brake air pressure, and ensure that the brake air pressure value is 0.45-0.70Mpa.
2) When the brake pedal is stepped on, the air pressure is normal but the brake pedal does not move, indicating that the brake control valve piston is stuck. Disassemble the brake valve, repair or replace.
3) When the brake pedal is stepped on, the pedal position is very low. When the pedal is stepped on again, the pedal gradually rises, but the brake pedal feels very weak and the braking effect is not good, indicating that there is air in the brake system, which should be eliminated.
4) When the brake pedal is pressed continuously, it feels heavy, but the pedal position gradually drops, indicating that the brake system is leaking oil. Inspection and maintenance should be carried out. If necessary, the brake should be disassembled for maintenance and maintenance, and the rectangular seal ring or brake piston should be replaced.
5) After the air in the oil pipe is removed, the brake pedal is still weak. Open the oil filler cap and find that the brake fluid is violently churning, indicating that the seal in the caliper disc brake is deformed or damaged. The damaged parts should be inspected and replaced.
6) The piston in the caliper disc brake cylinder is stuck, and the piston and seal should be inspected.
7) When the brake friction pad is worn to 1/3 of the original thickness, the friction pad should be replaced to prevent damage to the brake disc.
8) When the brake disc has deep grooves or is severely deformed, the brake disc should be repaired or replaced.
2.3 Braking failure
Fault phenomenon:
The loader cannot stop or decelerate quickly when the brake pedal is pressed to the bottom during driving.
Cause of failure:
1) There is air in the brake oil pipe or brake cylinder, causing oil pressure fluctuations or flow instability
2) The free travel of the brake pedal is too large.
3) The brake valve seal, booster cylinder seal, and brake cylinder seal are seriously worn, or the cylinder and piston are seriously worn, causing air and oil leakage.
4) The brake valve compensation hole or vent hole is plugged,
5) The brake oil pipe is broken or the oil pipe joint is leaking.
6) The gap between the brake disc and the friction plate is too large.
7) The friction plate surface is hardened, the rivets are exposed or there is oil stain.
8) The brake fluid quality is poor and it is easy to evaporate under heat.
9) The brake line is concave or blocked.
Fault judgment and elimination:
1) Check the brake air pressure, eliminate the fault of low brake air pressure, and ensure that the brake air pressure value is 0.45-0.70M.
2) The position is very low when the brake pedal is stepped on, and the pedal can gradually rise when the pedal is stepped on continuously, but the reaction force is small and the braking effect is not good, indicating that there is air in the brake oil pipe or brake cylinder, which should be eliminated.
3) One-foot braking is not effective, and the pedal position gradually rises when the brake pedal is stepped on continuously, The reaction force is large and the braking effect is good. This indicates that the free travel of the brake pedal is too large or the gap between the friction plate and the brake disc is too large. First check and adjust the free travel of the brake pedal, and then adjust the gap between the friction plate and the friction disc.
4) If you feel a heavy feeling when you step on the brake pedal continuously, but the brake pedal position gradually drops, it means that the brake system is leaking oil. You should check and repair it. If necessary, disassemble the brake for maintenance and replace the rectangular seal ring or brake piston.
5) After the air in the oil pipe is removed, the brake pedal is still weak. When you open the oil filler cap, you will find that the brake fluid is violently churning, indicating that the seal in the caliper disc brake is deformed or damaged. The damaged parts should be replaced.
6) When the brake pedal is stepped on, the pedal position is very low. When the brake pedal is stepped on continuously, the pedal position cannot be raised. Generally, the brake valve vent or compensation hole is blocked and should be unblocked.
7) When the brake pedal is stepped on, the pedal free travel and height meet the requirements, and it does not sink weakly, but the braking effect is not good. This is a fault of the caliper disc brake, which may be caused by friction. The reasons include hardening of the brake pads, exposed rivets, severe oil pollution, deformation of the brake disc, etc. At this time, the brakes should be inspected and the brake discs should be polished if necessary.
2.4 Braking deviation
Fault phenomenon:
During the driving process of the loader, the wheels on both sides cannot be braked at the same time, or one wheel brakes the other wheel to rotate, causing the vehicle to deviate to one side, causing the vehicle to be unable to drive in a straight line.
Fault cause:
1) The contact area and gap size between the left and right wheels and the brake pads are inconsistent.
2) The friction pads of some wheels are oily, hardened or exposed with rivets.
3) The friction pads of the left and right wheels are made of inconsistent materials.
4) There is air in some brake cylinders, the piston movement is blocked, or the oil pipe is blocked.
5) The tire pressure on the left and right sides is different.
6) Some brake discs are deformed.
The fundamental reason for the braking deviation is that the braking force of the wheels on both sides is unequal.
Fault judgment and elimination:
When the loader is driving, when the foot brake is used, the vehicle deviates to one side, which means that the wheel brake on the other side fails. After parking, check the drag marks of the wheels on both sides on the road surface. The wheel with a short or no drag mark is not braking properly. When it is determined that a wheel is not braking properly, check the deformation of the brake disc and remove the air in the brake cylinder. If it still does not work, disassemble the wheel brake, check the brake cylinder piston and seal, find out the fault location, and make necessary repairs.
2.5 Brake drag
Fault phenomenon:
After the loader brakes, lift the brake pedal, all or some wheels still produce braking effect, causing the brake disc to heat up and drive powerless, commonly known as "brake does not return"
Fault cause:
1) The free travel of the brake pedal is too small or the brake pedal returns poorly
2) The control valve piston return spring is too soft or broken, the piston is stuck, etc.!
3) The brake valve leather cup seal swells, making the return spring powerless.
4) The brake piston does not return, etc.
Fault diagnosis and troubleshooting:
1) After the loader has traveled a distance, touch the brake discs of each wheel by hand. If all brake discs are hot, it means that the fault is in the brake valve; if individual brake discs are hot, it means that the fault is in the brake of the wheel.
2) For the phenomenon that all brake discs are hot, the brake valve should be disassembled, and the working conditions of the seal, piston, vent hole, compensation hole, and return spring should be checked, and replaced if necessary.
3) For the phenomenon that individual brake discs are hot, the brake bleed screw should be loosened first during inspection. If the brake fluid sprays out rapidly and the piston returns to its position, it can be determined that the oil pipe is blocked and the brake line should be unblocked; if the brake piston still cannot return to its position, the brake should be removed for maintenance.
3 Maintenance of the brake system
To ensure that the brake system of the Changgong ZLM50E loader is always in good working condition, the following inspection and maintenance items should be noted during use:
1) Regularly check the connection and tightening of each part of the brake,
2) Regularly check whether there is leakage in the brake valve, brake cylinder, booster cylinder and pipeline. If there is oil leakage, it should be eliminated in time, and the oil on the friction plate should be cleaned in time.
3) Since the brake disc of the caliper disc brake is exposed to the outside, the dirt on it should be cleaned after the daily work task is completed.
4) Check the working condition of the brake pedal, whether there is any jamming when stepping on the brake pedal, and whether it can return to its position quickly when released.
5) Check whether there is air in the hydraulic system. If there is air, the pedal will feel soft and weak when stepping on it, and the braking effect will be reduced.
6) Check the amount of brake oil when necessary. The brake fluid level should be 15-20mm away from the edge of the refueling port.
7) The oil-water separator needs to be drained once every 50 hours of work, and it needs to be drained every day in winter.
8) After completing daily work tasks and maintenance, drain the air tank.