Checking the health of the ZIL-131 pneumatic actuator
Before leaving, you must make sure that the pressure in the system is not lower than 4.5 kg / cm²
During the movement, the pressure in the pneumatic brake system should be in the range of 5.6-7.4 kg / cm²
Only short-term pressure drops can be tolerated with frequent repeated braking.
To avoid running out of air during frequent braking, it is strictly forbidden to stop the engine on long descents.
Increase in pressure above 7.4 kg/cm² indicates a malfunction of the pressure regulator or unloader; an increase in pressure of more than 10 kg/cm² also indicates a malfunction of the safety valve.
In this case, it is necessary to fix the problem immediately.
With a sharp full pressure on the brake pedal (with the engine off), the pressure in the cylinders should decrease slightly (upper scale of the pressure gauge), and the pressure in the brake chambers (lower scale of the pressure gauge) should become equal to the pressure in the cylinders.
After that, there should be no noticeable movement of the pressure gauge needles during the time while the pedal is depressed, a further decrease in pressure in this case indicates a violation of the tightness in the pneumatic system.
After the brake pedal is abruptly released, the time for the pressure drop in the brake chambers (on the lower scale of the pressure gauge) should not exceed 2 seconds.
When the brake pedal is in a free position with the engine off, the pressure drop in the brake system due to system leaks (according to the upper arrow of the pressure gauge) should not exceed 0.5 kg / cm² for 30 minutes.
A rapid drop in pressure in the pneumatic system when the engine is stopped indicates increased air leakage from the system.
The location of a large air leak can be determined by ear.
Small leaks can be detected with soapy emulsion, which should be moistened with possible leaks.
Air leakage through the connections is eliminated by stretching the connecting fittings.
You should periodically check if the hoses of the front brake chambers are touching the wheels that are turned to the left and right.
To ensure the normal operation of the brake system, it is necessary to open the drain valves in the air cylinders during technical inspections and drain the condensate.
It must be remembered that condensate can only be drained from cylinders if they contain compressed air.
A large amount of condensate should not be allowed to accumulate in cylinders, as this can lead to condensate entering the working devices of the brake system.
The amount of condensate depends on the condition of the compressor and the humidity of the surrounding air; therefore, in wet weather, it is necessary to drain the condensate daily, after finishing work.
A large amount of oil in the condensate indicates a compressor failure.
In winter, it is necessary to carefully monitor the draining of condensate from air cylinders in order to avoid freezing it in the piping system of the pneumatic brake drive.
If the condensate freezes, do not heat the cylinders with an open fire (torch, blowtorch, etc.).
Checking and adjusting the pneumatic drive of wheel brakes
It is necessary to periodically check the adjustment of the pneumatic brake drive and the stroke of the brake chamber rods.
The air pressure in the pneumatic brake system must be adjusted in the following order.
When the engine is idling, it is necessary to increase the air pressure in the pneumatic system to 7-7.4 kg / cm² (according to the upper scale of the pressure gauge on the instrument panel); in this case, the reading of the lower scale should be equal to the bullet (air pressure in the brake chambers).
Then you should press the brake pedal all the way down.
When an effort of 20-30 kg is applied to the end of the pedal, the air pressure in the brake chambers should equal the air pressure in the cylinders and the arrows on both pressure gauge scales should show the same values.
In this case, the end of the pedal should not reach the floor by 10-30 mm.
If the pedal rests on the floor or if the gap is not as specified, it is necessary to adjust the amount of brake pedal travel by changing the length of the rod connecting the brake valve lever to the intermediate drive lever using an adjusting fork screwed onto the threaded end of the rod.
If the brake valve drive is adjusted correctly, then in the presence of compressed air in the air cylinders, the free play of the end of the brake pedal should be within 40-60 mm.
In addition, it is necessary to check and adjust the air pressure in the connecting line of the pneumatic outlet for controlling the trailer brakes, to do this, connect a pressure gauge to the coupling head and open the release valve.
In the braked state, this pressure gauge should show a pressure in the range of 4.8-5.3 kg / cm².
If the reading on the pressure gauge does not match the specified value, you must adjust the valve section that controls the trailer brakes.
Adjustment should be done in this order:
- remove the housing 24 (see Fig. 1) of the brake valve levers, loosen the lock nut 22 of the rod guide and, by rotating the rod guide 6, set the air pressure supplied to the trailer line within 4.8-5.3 kg / cm².
Then, tighten the locknut and replace the lever housing (be sure to replace the gasket of the lever housing).
When you gently press the brake pedal, the pressure on the pressure gauge connected to the connecting head should gradually decrease and reach zero when you fully press the pedal.
Intermediate pedal positions must correspond to intermediate pressure gauge readings.
It is necessary to check the brake pneumatic system with the pressure control valve of the tire pressure control system closed.