Solenoid valves - Bürkert Fluid Control Systems

2.3.
Servo-assisted
solenoid valves
At high system pressures and with
large nominal diameters, it would also
be necessary to have higher magnetic
forces and electrical control power
values in direct-acting solenoid valves.
The larger solenoid coils required for
this would increase the overall weight
and overall size. Consequently, servoassisted
valves are used.
In the case of servo-assisted solenoid
valves, a main valve is controlled by a
solenoid-operated pilot valve with
smaller flow cross-sections and lower
electrical control power. This control
can comprise either a 2/2-way pilot
valve or a 3/2-way pilot valve. The main
valve uses a diaphragm or a piston as
a moving closure element for opening
and closing the fluid path.
The Bürkert valve range also includes
servo-assisted solenoid valves on which
the armature of the pilot valve is linked
to the piston or diaphragm of the main
valve (forced valve lifting). On these
valves (e.g. Bürkert Types 6213 and
290), a minimum pressure differential
is not required. Depending on the design,
a low pressure differential is required
to open the full cross-section.
This principle is used primarily with
2/2-way valves, both normally closed
and normally open. The valve can be
operated in only one flow direction.
The back-pressure tightness is very
low.
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