The Cla-Val Model CDHS-18 Differential Control Valve is a normally-open, spring-loaded, diaphragm-type pilot valve that operates hydraulically and is designed to close on a rising differential pressure. It provides accurate differential pressure control for rate of flow control by Cla-Val 40 Series Control Valves. 

When used as a pilot control with Cla-Val valves, it acts as a flow limiting control. The CDHS-18 pilot uses automatic hydraulic control of valve to assure system stability under all conditions. There is one inlet port and two outlet ports in the body for either straight or angle installation. The outlet port senses high pressure created by differential producing device in-stalled downstream of valve. The spring chamber above the diaphragm senses lower downstream pressure created by differential producing device.