The Gas Circuit Is Damaged. Don'T Rush To Stop? It Will Be Easier To Do So

When a circuit in the braking system is damaged, we should drive to a nearby maintenance point for maintenance after confirming that other parts are undamaged. Why do you do this?

Let’s first understand the “protection device” four circuit protection valve in the braking system. After understanding, we will know why we are not in a hurry to stop when a circuit in the braking system is damaged!

● working principle of four circuit protection valve


According to different applications, the four circuits are connected in parallel, and the air pressure is charged at the same time, or circuits 1 and 2 are inflated before circuits 3 and 4. Some models of four circuit protection valves have a bypass hole in all circuits to ensure that if one circuit fails, the braking system will be inflated from 0bar.


The compressed air from the pressure regulating valve enters the four circuit protection valve through port 1, and enters the four circuits of the system through bypass holes (a, B, C, d) and check valves (h, J, Q, R). At the same time, the pressure is also established under the valve (g, K, P, s). When the set opening pressure (protection pressure) is reached, the valve opens and the diaphragm (F, I, O, t) overcomes the force of the spring (E, m, N, u) and bulges again. The compressed air flows into the air circuit 21, 2 and 24 of the brake cylinder through the ports of the brake cylinder 1, 2 and 4, and then into the air circuit 24. The 3-circuit supplies air to the emergency braking and parking braking system of the truck and also to the trailer. Circuit 4 supplies air to the auxiliary braking system.


The gas circuit is damaged. Don’t rush to stop? It will be easier to do so


The four circuit protection valve (hereinafter referred to as the four circuit protection valve) is composed of multiple pressure limiting check valves (usually four) arranged according to a certain relationship, and some of them are appropriately attached with other functional mechanisms, so as to realize the separate supply of air source in the braking system of commercial vehicles and ensure the independent and normal operation of each circuit


In the four circuit braking system, if one or more circuits fail, the braking air pressure of the intact circuit can be maintained.


If you see that the air pressure in the front axle circuit is low (air leakage), other circuits can still supply air. If you see that the air pressure in the rear axle circuit is gone, stop the vehicle in time and use the remaining braking efficiency to stop the vehicle in a safe area in a short time.


Warm tip: when the front axle of the four circuit protection valve is damaged, the brake pressure of 6.5 pressure can still be retained in other circuits, and the brake is still effective!