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8 Malfunctions
Read hazard statements, warnings and caution notes in the 'Safety instructions and mea-
sures' section.
8.1 Troubleshooting
Malfunction
Actuator stem does not
move on demand.
Actuator stem does not
stroke through its
complete travel range.
Note
Contact our after-sales service for malfunctions not listed in the table.
EB 8317 EN
Possible reasons
Actuator is blocked.
Insufficient signal
pressure
Signal pressure not
connected to the correct
diaphragm chamber.
Diaphragm in the
actuator defective
Insufficient signal
pressure
Incorrect setting of
valve accessories.
Recommended action
Check attachment.
Remove the blockage.
WARNING! A blocked actuator (e.g. due to seizing
up after remaining in the same position for a long
time) can suddenly start to move uncontrollably.
Injury to hands or fingers is possible if they are
inserted into the actuator or valve.
Before trying to unblock the actuator stem,
disconnect and lock the pneumatic air supply as
well as the control signal. Before unblocking the
actuator stem, release any stored energy in the
actuator (e.g. spring compression). See 'Relieving
the spring compression in the actuator' in the
'Removal' section.
Check the signal pressure.
Check the signal pressure line for leakage.
See 'Signal pressure routing' in the 'Design and
principle of operation' section.
See 'Replacing the diaphragm' in the 'Servicing'
section.
Check the signal pressure.
Check the signal pressure line for leakage.
Check the actuator without valve accessories.
Check the settings of the valve accessories.
Malfunctions
8-1
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