Watson McDaniel Company Back Pressure Relief Valve 1 1/2" R Series 75-300

The R Series & 10691 Series Back Pressure Relief Valves are used in the following applications: Water pump bypass for Irrigation, sprinkler systems on golf courses, fountains, and fire protection systems Fuel oil pump bypass on commercial systems or large residential systems The Relief Valve is actuated by the system pressure on the inlet side of the valve. Valve loading is provided by a spring. The adjustment is done by removing the cap and rotating the screw clockwise or counter-clockwise. Spring load tends to close the main valve against the opening force of the upstream (or relief) pressure. Valve will be open at the slightest increase in pressure above the spring set point, and closes when the excess pressure has been relieved. The higher the system pressure is above the relief set point pressure, the more flow the valve will pass. It is therefore typical to specify the maximum capacity of a back pressure relief valve at 10% & 20% over set pressure.