Automatically reduces a higher inlet pressure to constant lower outlet pressure. The valve consists of a main valve and a  pressure reducing control pilot. Slight changes in downstream pressure acts on topside of control diaphragm causing main Valve to counteract pressure changes and hold a constant outlet pressure.
The regulator will reduce the upstream pressure to a constant
downstream pressure regardless of the change in flow rotes/or inlet pressure. The pilot is a Normally - Open valve that senses the downstream pressure.