ARI Armaturen STEVI 426 EN - Manual (Page 12)

Page 12 Rev. 0040314001 0410
Operating and installation instructions
Straight through control valves - STEVI
®
425 / 426
7.2 Replacement of internal parts
7.2.1 Replacement of plug and stem
- Remove actuator. (Refer to operating instructions for actuator!)
Series 425:
- Loose nuts (pos. 11).
- Detach stuffing box housing (pos. 7).
- Slacken nuts (pos. 18) by about 2-3 turns.
- Extract plug (pos. 3) and stem (pos. 5).
- Drive pin (pos. 4) out with a drift.
- Unscrew stem (pos. 5) and plug (pos. 3).
Note:
In some designs the stem is locked by a spot
weld, which has to be removed with a grinding
machine.
- Bolt new parts together, drill and pin them.
- Replace gasket (pos. 9).
- Assemble in reverse order.
- Secure with nuts (pos. 11) and tighten them crosswise.
(For tightening torques refer to item 7.3.1)
Series 426:
For replacement of plug and stem with bellows sealing (Series 426) refer to item 7.1.3.
7.2.2 Replacement of seals of pressure balanced plugs
- Remove actuator.
(Refer to operating instructions for actuator!)
- Remove plug as described in item 7.2.1.
- Prise worn piston seal (pos. 30) out of groove in
plug with suitable tool (e.g. screwdriver).
- Insert new piston seal (pos. 30), taking care that
it is in the correct position (refer to Fig. 12).
- Replace guide ring (pos. 29).
- Clean sliding surface of guide bush (pos. 28);
smooth with fine abrasive if necessary.
- Replace 2 gaskets (pos. 9).
- Assemble in reverse order.
- Secure with nuts (pos. 11) and tighten them crosswise.
(For tightening torques refer to item 7.3.1.)
ATTENTION !
Refer to item 10.0 and 11.0 before dismantling the valve.
ATTENTION !
Refer to item 10.0 and 11.0 before dismantling the valve.
Fig. 11
Fig. 12: Pressure balanced plug