3.5 Special type with UVV safety interlock
For safety reasons, it is frequently necessary to install lockable
butterfly valves, i.e. the accidental opening of the valve or the
breaking of a shaft through the disk closing is prevented by lo-
cking the disk with an additional lock. Locking is carried out with
three bolts located on the circumference and at least one bolt is
movable. This locking system may also be double-sided, in which
case three more bolts are placed on the circumference. In this
case, we distinguish between fixed stops and movable bolts in
the body. Please refer to the illustration of the respective model
below for the secured side of the pipeline which is opened for ins-
pection and maintenance purposes while the operational pressure
of the medium is maintained on the opposite side of the disk.
The UVV lock is operated by pushing the movable bolts, when
required with a handwheel, radially in the direction of the pipe
centre behind the disk in the closed position. The position of the
Picture 6: VAG EKN
®
Butterfly Valve with UVV safety interlock
Type
Fixed
stops
Movable
bolts
Illustration
Single-sided
lock
0
3
side facing away from the shaft
side facing the shaft
1
2
side facing the shaft
side facing away from the shaft
2
1
side facing the shaft
side facing away from the shaft
(≥DN800)
3
3
side facing away from the shaft
side facing the shaft
Movable bolt
Fioxed stop
fixed
stop
fixed
stop
fixed
stop
secured
side
pressure side
pressure side
secured side
Fixed
stop
secured side / pressure side
pressure side
secured side
secured side / pressure side
Single-sided
lock
Single-sided
lock
Double-sided
lock
VAG Operation and Maintenance Instructions • 7
