ARI Armaturen STEVI 446 EN - Manual (Page 12)

Page 12 Rev. 0040301000 0410
Operating and installation instructions
Str. thr. control valves - STEVI
®
440 / 441, 445 / 446
7.0 Care and maintenance
Maintenance and maintenance intervals have to be defined by the operator according to
the service conditions.
7.1 Replacement of stem sealings
7.1.1 PTFE V-ring unit design
PTFE V-ring unit (pos. 12) consisting of:
1 backing ring
4 sealing rings
1 cover ring
Owing to the installed compression spring (pos. 15), this
stem packing is self-adjusting. If the stem starts leaking,
the ring pack is worn out and must be replaced.
Replacement of PTFE V-ring units:
- Remove actuator.
(Refer to operating instructions for actuator!)
- When replacing PTFE V-ring unit (pos. 12), make sure
that the parts are installed in the correct order and
positions (refer to Fig. 18).
- Gasket (pos. 17) must be replaced.
Damaged stems must also be replaced (refer to item 7.2
for instructions) since a new ring pack will soon start
leaking again if the stem is damaged.
ATTENTION !
Refer to item 10.0 and 11.0 before
dismantling the valve.
Fig. 18:
V-ring unit DN15-150