EB 8091 EN 8-1
Malfunctions
8 Malfunctions
Read hazard statements, warnings and caution notes in the 'Safety instructions and mea-
sures' section.
8.1 Troubleshooting
Malfunction Possible reasons Recommended action
Actuator and plug stem
does not move on de-
mand.
Actuator is blocked. Check attachment.
Remove the blockage.
WARNING! A blocked actuator or plug stem
(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 n-
gers is possible if they are inserted into the actu-
ator or valve.
Before trying to unblock the actuator or plug
stem, disconnect and lock the pneumatic air sup-
ply as well as the control signal. Before unblock-
ing the actuator, release any stored energy in the
actuator (e.g. spring compression). See associat-
ed actuator documentation.
Diaphragm in the actuator
defective
See associated actuator documentation.
Signal pressure too low Check the signal pressure.
Check the signal pressure line for leakage.
Jolting movement of the
actuator and plug stem
Packing tightened too far Tighten the packing correctly (see information
under 'Adjusting the packing' in the 'Testing the
installed valve' section).
Actuator and plug stem
does not stroke through
the entire range.
Signal pressure too low Check the signal pressure.
Check the signal pressure line for leakage.
Travel stop active See associated actuator documentation.
Incorrect setting of valve
accessories
Check the settings of the valve accessories.
Increased ow through
closed valve (seat leak-
age)
Dirt or other foreign parti-
cles deposited between the
seat and plug.
Shut off the section of the pipeline and ush the
valve.
Valve trim, particularly
with soft seat, is worn.
Replace seat and plug (see the 'Servicing' sec-
tion) or contact our after-sales service.
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