Multi-circuit Safety Valve (4)
The multi-circuit safety valve is responsible for the distribution of the compressed air into the brake circuits independent of each other. In case of a failure, one or more circuits protect the functional circuits against drops in pressure. The four-circuit safety valve is a commonly used version (in the figure). The four brake circuits are divided into two service brake circuits: one circuit is responsible for the compressed-air supply of the emergency and parking brake system as well as of the trailer connection and one circuit for further accessories such as the control of the exhaust throttle brake (engine brake). In case of a failure of one brake circuit, the pressure drop leads to the closure of a non-return valve on the damaged circuit, such that a counter pressure of a magnitude which prevents the opening of the intact brake circuits can be maintained.