A single protective valve maintains pressure in the receivers of the tractor vehicle in case of an emergency decrease in pressure in the trailer supply line, and also prevents compressed air from escaping from its line when pressure drops in the brake drive of the tractor vehicle, preventing automatic self-braking of the trailer.
The valve is adjusted to bypass air and from port I to port II when pressure reaches 550 kPa in port I.
Compressed air through outlet I enters cavity A under membrane 3.
After reaching a pressure of 550 kPa, compressed air, overcoming the force of springs 6 and 7, lifts the membrane 3 and passes into the sub-valve cavity B, from where it flows through the check valve 2 to terminal II of the trailer supply line.
When the pressure in outlet I is below 545 kPa, the membrane 3, under the action of springs 6 and 7, falls onto the saddle and disconnects outlets I and II; at the same time, check valve 2 closes and prevents the reverse flow of compressed air from port II to port I.
The opening pressure of the valve is set by adjusting screw 8.
When screwing it in, the valve opening pressure increases, when turning it out, it decreases.
Replacing the single safety valve
The single safety valve is replaceable in case of the following faults:
- - violation of the tightness of the valve. An external sign is air leakage through the terminals and in the places where the cover is attached to the valve body;
- - mechanical damage to the valve body, cover and membrane, disrupting its normal operation
Tools will be required: keys 22x24, 27x30
Removing the 28 single safety valve
We prepare the car and release air from the receivers 19 of the parking brake circuit
Unscrew the union nut of the pipeline coming from the receiver 19 from the fitting of the single protective valve 28 and disconnect the pipeline from the valve
Unscrew the safety valve 28 from the tee connecting the safety valve control valve 27
Installing a single safety valve 28
We wind the protective valve 28 onto the valve tee 27
Note: The airflow direction arrow on the body of the single safety valve must point towards valve 27
Connect the pipeline from the receiver 19 to the safety valve and tighten the union nut
Removing single safety valve 10
We release air from the receiver 19 of the parking brake system
Unscrew the union nuts of the inlet and outlet pipelines from the fittings of the single protective valve 10
Disconnect the pipelines from the valve and remove the valve
Installing a single safety valve 10
Connect the pipelines to the safety valve 10 and tighten the union nuts of the pipelines
Note: The arrow of the single safety valve must point in the direction of the compressed air flow from the compressor
We start the engine and create pressure in the pneumatic brake actuator. We check the tightness of pipelines and protective valves. Air leakage is not allowed
Disassembly and assembly of a single safety valve
You will need tools: a vice, soft jaws, a 12x13 wrench, a 10 socket wrench, a screwdriver, special pliers I801.23.000-01, dishes for fuel and lubricants, a brush
Single Safety Valve Disassembly
Installing the valve in a vise
Using keys 13, a socket wrench 10, we unscrew the adjusting screw 15 and the lock nut 14
With a screwdriver, unscrew the screws 13 fastening with washers 12 of the cover
Remove cover 11, spring plate 10, spring 9, piston 8, membrane 7
Remove thrust ring 1, bushing 2, spring 3, valve body 4, valve ring 5
Remove the body from the vise
Promwe wash the valve parts in diesel fuel, blow them with compressed air and check their technical condition
We install valve ring 5, valve body 4, spring 3, bushing 2 and thrust ring 1 into body 6
We install the membrane 7, the piston 8, the spring 9, the plate 10 of the spring into the body 6
Note: coat the spring with Ciatim-221 lubricant
We install the cover 11 on the valve body 6, insert the fastening screws 13 with spring washers into the holes of the cover 11 and the body
We screw in the fastening screws 13 with spring washers 12 and screw the adjusting screw 15 into the cover, tighten the locknut 14
Remove the valve from the vise and test the valve
Connect the device according to the scheme
Open the tap 7. Set the pressure reducer on the pressure gauge 1 to 539 kPa (5.5 kgf / cm2).
We achieve the position with the adjusting screw 3 so that the receiver 6 begins to fill. Close faucet 7 and open faucet 5.
We close the valve 5 and open the valve 7. Using the reducer 8, we set the pressure of 736 kPa (7.5 kgf / cm2) on the pressure gauge 1. Gauges 1 and 4 should show equal pressures.
During the test, device 2 should not show a decrease in pressure
Secondary check the adjustment, as mentioned above, and correct the adjustment, if necessary