VAG Operating and Maintenance Instructions • 10
7 Trouble-shooting
For all repair and maintenance work, please observe the general
safety instructions described in Section 6.1
Problem
Cause
Remedial action
The knife does not move /
is jammed
Lateral seal is too tight
Evenly unfasten the screws of the thrust piece
Stem or stem nut is damaged
Check the stem for traces of jamming, clean and lubri-
cate the parts, replace the parts if
necessary!
Foreign particle is jammed in the seat
Open the valve (up to 10 - 30% of the stroke) and
close it again; repeat this action several times
Knife is blocked by hardened particles in the
medium
Unfasten the thrust piece by unfastening the screws
evenly, slightly hammer against the knife from above
and from the side with a rubber mallet, and try to ope-
rate the valve.
If this does not solve the problem: dismantle the valve,
dismantle the knife, clean it, lubricate it, replace dama-
ged parts.
See also Section 6.1!
High operating forces
Lateral seal is too tight
Evenly unfasten the screws of the thrust piece
See also Section 6.1!
Dirt sticks to the knife
Dry run of the knife
Open the valve, clean the knife, lubricate it
Stem and stem nut have run dry
Lubricate the parts
Leak at the knife passage
Foreign particle is jammed in the seat
Open the valve (up to 10 - 30% of the stroke) and
close it again, repeat this action several times, remove
jammed particle if possible
U profiled gasket is damaged
Replace U profiled gasket according to Section
6.3.3
Leak at the outlet of the
knife
Leaking lateral seal
Retighten the lateral seal according to Section
6.3.2
See also Section 6.1!
Damaged lateral seal
Replace the lateral seal according to Section
6.3.2
Clean the knife and lubricate it
See also Section 6.1!
Damaged lateral seal
Open the valve, remove the protection panel, clean the
knife and lubricate it
