10
EB 8393 EN
Design and principle of operation
3 Design and principle of oper-
ation
The Type 3755 Pneumatic Volume Booster is
used together with positioners to increase the
positioning speed of pneumatic actuators
with an effective area ≥ 1000 cm² or a
travel volume ≥ 6 l.
The pneumatic booster supplies the actuator
with an air flow output whose pressure
corresponds exactly to the signal pressure,
except that it has a much higher volume
output.
If the positioner signal to supply air to the
actuator increases, the pressure above the
diaphragm (1) increases. The differential
pressure at the diaphragm causes the supply
plug (2) to open, providing supply air up to
a maximum of 10 bar to the actuator.
In contrast, the signal to vent the actuator
causes the exhaust plug (3) to open. The
pressure in the actuator is relieved over the
exhaust port.
The bypass restriction screw (4) is used to
adjust the response of the pneumatic volume
booster to match the closed control loop
requirements. The setting of the bypass
restriction screw can be locked in position to
prevent it from being turned and can
additionally be lead-sealed.
Refer to section
on page
more details on how to adjust the bypass.
3.1 Safety function
The safety function of the Type 3755
Pneumatic Volume Booster is the emergency
venting on demand.