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8 Malfunctions
8.1 Troubleshooting
Malfunction
Actuator and plug stem
does not move on
demand.
Jolting movement of the
actuator and plug stem
Actuator and plug stem
does not stroke through
the entire range.
Increased flow through
closed valve (seat
leakage)
Reduced flow rate
EB 8020 EN
Possible reasons
Actuator is blocked.
Diaphragm in the
actuator defective
Signal pressure too low Check the signal pressure.
Packing tightened too
far
Signal pressure too low Check the signal pressure.
Travel stop active
Incorrect setting of
valve accessories
Dirt or other foreign
particles deposited
between the seat and
plug.
Valve trim is worn out.
Strainer blocked
Recommended action
Check attachment.
Unblock the actuator.
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 fingers is possible
if they are inserted into the actuator or valve.
Before trying to unblock the actuator or plug stem,
disconnect and lock the pneumatic air supply as
well as the control signal. Before unblocking the
actuator and piston stem, release any stored energy
in the actuator (e.g. spring compression). See
associated actuator documentation.
See associated actuator documentation.
Check the signal pressure line for leakage.
Contact our after‑sales service.
Check the signal pressure line for leakage.
See associated actuator documentation.
Check the settings of the valve accessories.
Shut off the section of the pipeline and flush the
valve.
Contact our after‑sales service.
Clean strainer. See associated device
documentation.
Malfunctions
8-1
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