Type 9 Pressure Sustaining/Surplus Valve

The Type 9 pressure sustaining/surplus valves are designed to sustain and control the upstream pressure and pass surplus mediums into a zone where they can perform useful work or be recovered and conserved. The type 9 has a piston and lid of equal diameter, making the two areas balanced. This makes the valve suitable for applications where variable back pressures are present. Valves are supplied in sizes half inch to six inch and can be manufactured in Gunmetal, Cast Steel and Stainless Steel with ends screwed female BSP or flanged ends to customers requirements. The standard set pressure range of the Type 9 is 0.70 to 9.00 Bar g, although higher and lower set pressures can be accommodated. (Consult Broady Technical Sales Engineers for further information).

All valves are supplied with a nitrile diaphragm for air, gases, oils, etc. as standard, but other materials are available on request. Valves for steam service are supplied with a metallic diaphragm.

Pressure is admitted at the inlet and acts upon the area of the lid. To regulate the valve the spring is compressed an amount equal to the load acting against it, thus keeping the valve lid on its seat. As the pressure tends to increase above this setting, the extra load acting on the lid compresses the spring further and this allows it to leave its seat and excess pressure discharges to atmosphere or pump suction. Similarly when the pressure is decreased the spring overcomes the lighter load imposed on the lid and thus the valve closes. Compressing the spring increases the set pressure, relaxing the spring decreases the set pressure.

Surplus valves are not usually fitted in the main pipeline as in the case of reducing valves. They should be fitted in a branch line from the main, in a horizontal position with the spring uppermost and the flow indicated by the arrow cast on the body. It is most important that the pipe is clean and free from dirt, scale etc.

Type_9.pdf