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.
Bermad
Model 780 Brochure
