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Pelmar Engineering Ltd.:The
Model 720 Pressure Reducing Valve is an automatic control valve
designed to reduce a higher inlet pressure to a lower constant
outlet pressure regardless of fluctuating flow rates and/or
varying inlet pressure.
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 two-way control
principle, has varying pressure produced by the regulating pilot
and the pilot's internal upstream restriction needle valve.
The pressure regulating pilot senses downstream pressure and
modulates open or closed. This varies the pressure in the upper
control chamber causing the main valve to throttle thus maintaining
constant delivery pressure.
When the downstream pressure falls below the pilot setting,
the pilot opens, pressure in the upper control chamber decreases,
and the main valve modulates open to increase downstream pressure
and maintain pilot setting.
Should the downstream pressure rise above the pilot setting,
the pilot closes, pressure in the upper chamber increases and
the main valve throttles close to decrease downstream pressure
to the pilot setting.
The Pressure Reducing pilot has an adjusting screw to preset
the desired downstream pressure and an internal needle valve
to control the closing speed.
For easy identification the pressure reducing pilot is stamped
with the number "2" on the side of the pilot body
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Valve
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