Overflow and reduction valves
Relief valves are used for separating the individual circuits of the air system. In a motor vehicle, this function is performed by a four-circuit safety valve. There are three types of relief valves:
- Overflow valve with backflow
The passage of compressed air to the second air reservoir is not released until the design pressure of the brake system in the first air reservoir has been reached. In this way, greater readiness of the brake system is achieved. When the pressure in the first air reservoir drops, it is refilled with compressed air from the second air reservoir. - Overflow valve without backflow
The passage of the compressed air to auxiliary appliances (eg. door control, auxiliary brake circuit, parking brake, clutch booster, etc.) is only released when the design pressure of the brake system in the last air reservoir is reached.
- Overflow valve with limited backflow
The passage of compressed air to the trailer or to auxiliary appliances (eg. auxiliary brake circuit and parking brake) is only released when the design pressure of the brake system in the last air reservoir is reached. Furthermore, the pressure in the brake system of the motor vehicle is protected, even if the supply line to the trailer has been interrupted. When the pressure in the air reservoirs of the service brake system drops, there is a partial backflow of compressed air up to the value of the closing pressure depending on the overflow pressure.
Reduction valves are used to limit the output pressure to the set value. Their applications and uses may vary. For example, on a lifting axle, they can be used to reduce the pressure on the lifting bellows.
At Penax, we offer relief and reduction valves from leading manufacturers Wabco, Knorr-Bremse and Haldex.
