Table of Contents
Design and principle of operation
3 Design and principle of oper-
ation
Î See Fig. 3
The regulators are open when relieved of
pressure.
They close when the downstream pressure
rises above the adjusted set point.
The Type 44-2, Type 44-3 and Type 44-9
Pressure Reducing Valves mainly consist of
the valve body (30) with seat (35) and plug
(2) as well as the actuator with operating di-
aphragm (125), set point springs (70...78)
and set point adjuster (56).
The pressure reducing valve is used to main-
tain the pressure downstream of the valve to
an adjusted set point.
The process medium flows through the regu-
lator between seat and plug in the direction
indicated by the arrow on the body. The po-
sition of the valve plug determines the flow
rate and, as a result, the downstream pres-
sure.
The downstream pressure p
is transmitted over the control line (116) to
the operating diaphragm (125) where it is
converted into a positioning force. This force
is used to move the valve plug according to
the force of the set point springs (70...78).
The spring force is adjustable at the set point
adjuster (56).
12
to be controlled
2
The Type 44-3 Safety Shut-off Valve (SSV)
with integrated pressure reducing valve is
equipped with a second backup diaphragm
(126). Upon failure of the first operating dia-
phragm (125) the regulator continues to
function using the backup diaphragm
(126). In this case, the regulator functions as
a safety shut-off valve (SSV) with integrated
pressure reducing valve when the down-
stream pressure rises too far and closes the
valve. Diaphragm failure is indicated by a
red mark in the diaphragm rupture indicator
(12) (point of response at approx. 1.5 bar)
or medium escapes at the test connection.
The Type 44-9 Safety Shut-off Valve (SSV)
with integrated pressure reducing valve is
equipped with a second backup diaphragm
(126). Upon failure of the first operating dia-
phragm (125) the regulator is completely
closed. Diaphragm failure is indicated by a
red mark in the diaphragm rupture indicator
(12) (point of response at approx. 1.5 bar)
or medium escapes at the test connection.
EB 2623-1 EN
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