Burkert Type 2012 - Manual (Page 8)

8
Structureandfunction
Type 2012
6.2 function
Depending on the version, the seat of the valve is closed with or against
the medium flow.
Spring force (CFA) or pneumatic pilot pressure (CFB and CFI) gen-
erates the closing force on the swivel plate. The force is transferred
via a spindle which is connected to the actuator piston.
6.2.1 control functions (cf)
Warning!
for control function i – danger if pilot pressure fails!
For control function I control and resetting occur pneumatically. If
the pressure fails, no defined position is reached.
▶ To ensure a controlled restart, first pressurise the device with pilot
pressure, then switch on the medium.
a
(cfa)
P
A
Normally closed by spring action
B
(cfB)
P
B
Normally open by spring action
i
(cfi)
P
A
Actuating function via reciprocal
pressurisation
6.2.2 flow direction below seat
Depending on the version, the valve is closed against the medium
flow with spring force (control function A, CFA) or with pilot pressure
(control function B or I, CFB or CFI).
As the medium pressure is under the swivel plate, this pressure con-
tributes to the opening of the valve.
Warning!
medium may be discharged if minimum pilot pressure is too
low or medium pressure too high!
If the minimum pilot pressure is too low for CFB and CFI or the
permitted medium pressure is exceeded, leaks may occur.
▶ Observe minimum pilot pressure.
▶ Do not exceed medium pressure.
▶ See chapter entitled “7.4.2”.
CFA CFB /
CFI
Fig. 2: Flow direction below seat (closing against medium)
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