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 The
Model 730 Pressure Relief / Sustaining Valve is an automatic
control valve designed to relieve excess pressure or sustain
a minimum upstream backpressure.
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 pilots internal upstream restriction
needle valve.
 The
pressure regulating pilot senses upstream pressure and modulates
open or closed. This varies the pressure in the upper control
chamber causing the main valve to throttle thus maintaining
constant upstream pressure.
When the upstream pressure rises above the pilot setting the
pilot opens, pressure in the upper control chamber decreases
and the main valve modulates open to relieve upstream pressure
and maintain pilot setting.
Should the upstream pressure fall below the pilot setting the
pilot closes, pressure in the upper chamber increases and the
main valve throttles closed to maintain the preset pilot setting.
The pressure relief/sustaining pilot has an adjusting screw
to preset the desired upstream pressure and an internal needle
valve to control the closing speed. For easy identification
the pressure relief/sustaining pilot is stamped with the number
"3" on the side of the pilot body.
Back to 700 Series Control
Valve Line Up
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