The Fig. A71 Surplus/Sustaining valve is a single-seated, diaphragm-controlled, spring-regulated valve.

System pressure acting on the diaphragm provides sensitive and stable control of the valve opening in accordance with the regulating spring setting.

This design makes the valve well suited to installations where a direct spring-loaded valve would be too insensitive to changes in pressure or flow.

The Fig. A71 is commonly used to:

• Protect systems from overpressure

• Monitor and control pump discharge pressure

It is suitable for use on water, air, gas, oil, and compatible chemical services.