The LF910GD-17 (Globe) and LF910AD-17 (Angle) Series is a Pressure Reducing Control Valve with Return Flow Feature designed to automatically reduce a fluctuating higher upstream pressure to a constant lower downstream pressure regardless of varying flow rates, and open for return flow when downstream pressure exceeds inlet pressure. It is controlled by a normally open, pressure reducing pilot designed to: 1) Open (allowing fluid out of the main valve cover chamber) when downstream pressure is below the adjustable setpoint, and 2) Close (allowing fluid to fill the main valve cover chamber) when downstream pressure is above the adjustable setpoint. A decrease in downstream pressure causes the valve to modulate toward an open position, raising downstream pressure. An increase in downstream pressure causes the valve to modulate toward a closed position, lowering downstream pressure. If downstream pressure becomes greater than upstream pressure, the valve opens allowing the higher downstream pressure to return to the upstream pressure zone. Normal Pressure Reducing operation resumes when upstream pressure exceeds downstream pressure.