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2021
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09
Faults and Solutions of Heavy Truck Brake Relay Valve
Heavy trucks, as long-distance transport vehicles, have very important brakes, which are also components that can easily malfunction. 1. The function and structure of the relay valve.
Heavy trucks, as long-distance transport vehicles, have very important brakes, which are also components that are prone to failure.
1. Function and Structure of the Relay Valve
1. The function of the relay valve: it can shorten the time for the pressure in the brake chamber to build up; quickly release the air pressure in the chamber when braking is released; reduce the airflow of control valves (main pump, hand valve); improve the reliability of the valve.
2. The relay valve has a total of 4 ports: Port 1 = Inlet Port, Port 2 = Outlet Port, Port 3 = Exhaust Port, Port 4 = Control Port
2. Common Fault Modes
a. Air leakage at the exhaust port b. Slow release of brakes
3. Inspection Tool: Pressure Gauge
4. Fault Diagnosis: (Ensure the vehicle pressure reaches the rated working pressure of above 0.8MPa) For the current fault modes:
a. Detection method for air leakage at the exhaust port: Apply soapy water at the exhaust port of the relay valve.
① Turn the manual valve handle to the driving position, keep the brake pedal in place, apply soapy water at the exhaust port of the relay valve, and observe if bubbles are produced. If no bubbles are produced, the relay valve is normal. If bubbles are produced, disconnect the outlet pipe of the relay valve (this step is to eliminate the influence of air leakage from the brake chamber), and observe if there is gas discharged from the outlet of the relay valve. If gas is discharged, the relay valve needs to be replaced (this phenomenon indicates that the inlet of the relay valve is in a constant open state). If no gas is discharged, there is no need to replace the relay valve.
② Press the brake pedal all the way down and hold it, apply soapy water at the exhaust port of the relay valve, and observe if bubbles are produced. If bubbles are produced, it indicates air leakage at the exhaust port, and the relay valve should be replaced.
b. Detection method for slow release of brakes: Remove the air pipe at the outlet of the relay valve, then connect the pressure gauge from the inspection tool to the outlet of the relay valve, press the brake pedal all the way down and quickly release it, and observe the reading on the pressure gauge.
Judgment method: Check if the reading on the pressure gauge drops to zero quickly.
Handling method: If the reading on the pressure gauge does not drop to zero quickly, the relay valve should be replaced; otherwise, there is no need to replace the relay valve.
Braking, replacement, relay valve,, brake valve
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