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Design and principle of operation
3.3.1
Actuator stem extends
When the signal pressure is reduced or the
control signal fails, the springs move the ac-
tuator stem downward and close the globe
valve. The valve opens when the signal pres-
sure is increased enough to overcome the
spring force.
3.3.2
Actuator stem retracts
When the signal pressure is reduced or the
control signal fails, the springs move the ac-
tuator stem upward and open a mounted
globe valve. The valve closes when the signal
pressure is increased enough to overcome
the spring force.
3-4
3.4 Mounting types
There are two types of mounting depending
on the valve/actuator combination: mount-
ing using a crossbeam or mounting using
rods (see Table 3-1).
When the actuator is mounted to the valve
using a crossbeam (form B, Fig. 3-3), the ac-
tuator is fastened to the valve bonnet using a
central nut.
When the actuator is mounted using rods
(form C, Fig. 3-4 and Fig. 3-5), the actuator
is connected to the valve bonnet using rods.
In this case, a crossbeam is not required for
mounting the actuator. A plate keeps the cor-
rect distance between rods in the 350 cm²
version.
Fig. 3-3: Form B: mounting using crossbeam
EB 8317 EN
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