Pressure Sequence Valve
An important feature of all pressure sequence valves is a separate drain connection from the spring chamber. This is because, unlike a conventional relief valve, a high pressure can occur in the output port during the normal course of operation. Should it be internally drained, any pressure in the output port will be reflected back into the spring chamber causing a malfunction. In fact a sequence valve may be used as a relief valve in any circuit "here excessive back pressures are encountered in the return line. The independently drained pilot makes sequence valves insensitive to downstream back pressure.