ARI Armaturen STEVI 426 EN - Manual (Page 11)

Rev. 0040314001 0410 Page 11
Operating and installation instructions
Straight through control valves - STEVI
®
425 / 426
7.1.3 Bellows seal design
If the stem leaks, the bellows seal (pos. 20.3) is defective. The leak can initially be stopped
by tightening the stuffing box gland with nuts (pos. 20.29).
Stem and bellows (pos. 20.3) can only be replaced together.
Replacement of bellows seals:
- Remove actuator.
(Refer to operating instructions for actuator!)
- Loose nuts (pos. 11).
- Detach bellows assembly (pos. 20) .
- Slacken nuts (pos. 20.29) by about 2-3 turns.
- Extract stem-bellows unit (pos. 20.3) from the
bellows housing (pos. 20.1).
- Drive pin (pos. 4) out with a drift.
- Unscrew stem-/bellows unit (pos. 20.3) and plug
(pos. 3).
- Bolt new parts together, drill and pin them.
- Replace 2 gaskets (pos. 20.19, 9).
- Assemble in reverse order.
- Secure with nuts (pos. 11) and tighten them
crosswise.
(For tightening torques refer to item 7.3.1)
- Tighten nuts (pos. 20.29) gradually up to
tightness of the stuffing box packing
(pos. 20.10).
ATTENTION !
Refer to item 10.0 and 11.0 before dismantling the valve.
Fig. 10: Series 426