Solenoid valves - Bürkert Fluid Control Systems

2.3.4. Servo-assisted solenoid
valves with 3/2-way pilot
A pivoted-armature or rocker valve
with isolating diaphragm is used as
the pilot valve. The essential difference
with respect to the 2-way pilot is that
a medium does not flow through the
pilot in an open switch position and
thus there is a much slighter risk of
clogged control bores due to dirty
media. In addition, a diaphragm protects
the solenoid armature against
harmful influences.
The chief field of application of this
functional principle (e.g.: Type 142
and Type 5282) therefore obviously
relates to both dirty media and aggressive
media.
Advantages:
■ No small control bores in the diaphragm
and thus less sensitive to
dirty media
■ Solenoid chamber protected by
isolating diaphragm
■ Only a small quantity of medium
flows through the pilot valve for
opening or closing
■ No medium flow through the pilot
valve in open condition! This is a
crucial advantage over valves with
2-way pilot.
■ Response times adjustable with
adjusting screws
■ NC and NO function, possible simply
by turning the pilot
■ Extremely high functional reliability
■ Also available as explosion-proof
version.
Potential disadvantages:
■ Cost-intensive
■ Cannot be used in all circuits, since
the system requires pressure
differential for opening.
Figure 8:
Media-separated servo-assisted solenoid valve with diaphragm
and 3/2-way pilot solenoid
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