8
EB 8547 EN
Design and principle of operation
3 Design and principle of oper-
ation
The quick exhaust valve is mounted between
the positioner or solenoid valve and the
actuator. It is used to vent the actuator more
quickly. When a control pressure (SIG) is
applied, the diaphragm plate (1) rests on the
seat (2), closing the valve. The check valve
allows the air to flow through the output
(OUT) to the actuator while the control
pressure rises. No air is vented.
The check valve (3) closes when the control
pressure decreases. After the actuator
pressure and control pressure reach a certain
differential pressure, the diaphragm plate (1)
releases the seat of the exhaust port (EXH),
causing the actuator to be vented quickly.
The adjustable restriction screw (4) prevents
the air from being exhausted quickly during
normal control mode and is used to set the
venting characteristic. The access to the
restriction screw is secured by a cotter pin
inserted into the hole (5).
4
3
1
2
5
SIG
EXH
OUT
1
Diaphragm plate
2
Seat
3
Check valve
4
Restriction screw
5
Hole for cotter pin
Threaded connections:
SIG
G
3
/
8
OUT
G ¾
EXH G ¾
Fig. 1:
Sectional drawing of Type 3711 Quick Exhaust Valve including ports
