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No need to rush to stop if the air pipe is damaged? Doing this would be more convenient.
When a circuit in the braking system is damaged, we should drive to the nearest maintenance point for repairs after confirming that the other components are intact. Why should we do this?Let's first understand the 'protective device' in the braking system, the four-circuit protection valve. After understanding this,
we will know why we do not need to rush to stop the vehicle when a circuit in the braking system is damaged!● Working principle of the four-circuit protection valveDepending on the application, the four circuits may be connected in parallel with air pressure supplied simultaneously, or circuits 1 and 2 may be pressurized before circuits 3 and 4. Some models of the four-circuit protection valve have a bypass hole in each circuit to ensure that if one circuit fails, the braking system can start pressurizing from 0 bar.Compressed air from the pressure-regulating valve enters the four-circuit protection valve through port 1 and passes through a bypass hole (a, b, c, d) and check valves (h, j, q, r) into the four circuits of the system. At the same time, pressure also builds up under the valves (g, k, p, s). When the set opening pressure (protection pressure) is reached, the valves open, and the diaphragms (f, i, o, t) overcome the spring forces (e, m, n, u) and bulge. Then, compressed air flows through ports 21 and 22 into the reservoirs of circuits 1 and 2 of the service brake system, and through ports 23 and 24 into circuits 3 and 4. Circuit 3 supplies air to the truck’s emergency brake and parking brake system and also provides air for the trailer. Circuit 4 supplies air to the auxiliary brake system.
The four-circuit protection valve (hereinafter referred to as the four-protection valve) consists of multiple pressure-limiting check valves (usually four) arranged in a certain manner, with some appropriately equipped with additional functional mechanisms, to ensure that the air supply in commercial vehicle brake systems is divided while maintaining independent and normal operation of each circuit.
In a four-circuit brake system, if one or more circuits fail, the braking air pressure of the remaining intact circuits can be maintained.
If you notice that the air pressure in the front axle circuit is low (leaking), the other circuits can still supply air. However, if the rear axle circuit air pressure is gone, you should stop promptly and use the remaining braking capability to bring the vehicle to a safe spot in a short period of time.
Friendly reminder: When the front axle of the four-circuit protection valve is damaged, the remaining circuits can still retain a braking air pressure of 6.5, and braking remains effective!
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