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Maintenance, troubleshooting
19.2. Safety positions
Safety positions 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 (NC)
• air opening
• spring closing
down
down
up
down
single-acting
Control function B (NO)
• air closing
• spring opening
up
up
up
down
double-acting
Control function I
• air opening
• air closing
not defined
for both
solenoid valves NC, but
_____________________
defined
for
Solenoid valve 1 NC +
Solenoid valve 2 NO
not defined
By default the control head is equipped with solenoid valves which operate in NC mode,
the model 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 seat valves) are connected, the safety positions of
the individual actuators can be viewed according to the same logic as for a classical single seat valve.
Safety positions after failure of the bus communication:
AS interface:
If the Watchdog is activated (default), behavior is the same as a failure of the auxiliary electrical power, i.e. all
solenoid valve outputs are set to "0".
DeviceNet:
See chapter "12.12.1. Configuration of the safety position of solenoid valves if bus error".
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