Gear fixing screws::
Picture 25: Tightening torques of gear fixing screws
8 Trouble-shooting
For all repair and maintenance work, please observe
the general safety instructions described in Section
7.1!
Problem
Possible cause
Remedial action
Valve makes noise
Unfavourable installation posi-
tion causing unfavourable flow
around or inside the valve (e.g.
installed too closely downstream
of an elbow etc.)
Change installation position
Valve operating beyond its
design limits
Check design and/or operation data, change flow resistance
in the valve, if required, by using different internals
Valve cannot be operated
Foreign matter jammed in the
seat area
Flush valve, dismantle, if necessary, and remove foreign
matter
Gear blocked
Undo block
No electrical connection of elec-
tric actuator
Establish electrical connection
Unfavourable flow and impair-
ment of movement
Change installation position
Leaks in the body seat
Valve not completely closed yet
Close valve completely
Valve seal damaged or worn
Replace seal
Cavitation in valve
Valve operating beyond its
design limits
Butterfly valve not suitable for use as control valve. Replace
valve by a more suitable valve type.
Operational data changed
Leaks at the body
Deterioration of seals
Replace seals
High operating forces
Seat of the valve polluted by
deposits
Flush valve, dismantle, if necessary, and clean seat area
Valve is dry in pipeline, no medi-
um present
Valve can be operated more easily when wet
VAG Operation and Maintenance Instructions • 18
Gear fixing screws
M 10
M 12
M 16
M 20
M 24
M 30
M 36
36 Nm
60 Nm
150
Nm
290
Nm
500
Nm
950
Nm
1650
Nm
