The LF910GD-11 (Globe) and LF910AD-11 (Angle) Series is a combination Pressure Reducing and Surge Control Valve designed to automatically reduce a fluctuating higher upstream pressure to a constant lower downstream pressure, and will quickly modulate toward a closed position if downstream pressure suddenly becomes greater than the desired regulated setpoint. The quick closing action prevents possible damaging high inlet pressure from passing through the valve to downstream piping. Normal regulating action 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 suddenly becomes greater than the desired regulated setpoint, the normally closed surge control pilot opens and rapidly admits higher inlet pressure into the valve cover, increasing rate of valve closure. Normal pressure reducing operation resumes when downstream pressure decreases below the desired regulated setpoint.