Altitude Control Valve Bermad Model 780
The Model 780 Altitude Control Valve, One Way Flow is an automatic control valve designed to control the high water level in reservoirs and tanks without the need for external control devices such as floats, etc.
It is a pilot controlled, hydraulically operated, diaphragm actuated globe valve in either the oblique (Y) or angle pattern design. Valve differential pressure powers the diaphragm actuator open or closed.
The lower control chamber is connected through a fixed orifice to the downstream pressure, which serves to cushion the closing of the valve. The upper control chamber, which operates on a three-way control principle, has pressure applied from or pressure vented through the three-way altitude pilot.
The altitude pilot senses reservoir or tank pressure head. It closes at a pre-set pressure head and opens on decreasing pressure head.
The closing and opening of the pilot alternatively pressurizes or vents the pressure in the upper control chamber causing the main valve to close or open thus maintaining a constant pressure head in the reservoir or tank.
When the head pressure falls below the pilot setting the pilot
opens, pressure in the upper control chamber decreases and the
main valve opens to refill the reservoir or tank. When the head
reaches the set point of the pilot the pilot closes, pressure
in the upper chamber increases and the main valve closes to
stop flow into the tank or reservoir. The altitude pilot has
an adjusting screw to preset the desired head pressure.