Burkert 8681 - Safety Positions

154
Maintenance, troubleshooting
23.2 Safety positions
Safety positions of the solenoid valves after failure of the electrical or pneumatic auxiliary power:
Operating mode
Process valve
design
Safety positions
after failure of the auxiliary power
electrical pneumatic
up
down
single-acting
Control function A
•airopening
• spring closing
down down
up
down
single-acting
ControlfunctionB
• air closing
• spring opening
up up
up
down
double-acting
Control function I
•
air opening
• air closing
not dened for
both solenoid valves
NC*,but
_____________________
dened for
Solenoidvalve1NC*+
Solenoidvalve2NO**
notdened
BydefaultthecontrolheadisequippedwithsolenoidvalveswhichoperateinNC*mode,
thedesignfordouble-actingactuatorsisequippedwith1solenoidvalveNC*and1solenoidvalveNO**.
Ifprocessvalveswithseveralswitchingpositions(e.g.double-seatedvalves)areconnected,thesafety
positions of the individual actuators can be viewed according to the same logic as for a classical single-
seated valve.
Safety positions of the solenoid valves after failure of the bus communication:
AS interface:
IftheWatchdogisactivated(default),behaviouristhesameasafailureoftheaux-
iliaryelectricalpower,i.e.allsolenoidvalveoutputsaresetto„0“.
DeviceNet:
See chapter “13.12.1Congurationofthesafetypositionofsolenoidvalvesduringa
buserror”onpage71
IO-Link:
See chapter “14.7Safetypositionifthebusfails”onpage84
büS/CANopen:
See chapter „15.7Safetypositionifthebusfails“onpage90
__________________
* NC: 3/2-way valve; closed in rest position, output A unloaded,
** NO: 3/2-way valve; opened in rest position, output A pressurised.
english
Control Head Type 8681