Flowserve NAF-Duball ball valves - Manual (Page 6)

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9.7 To change the upper stem seal with O-rings
If the stem seal is leaking, change the upper O-ring (10).
The valve need not be removed from the pipework for this
work. The entire stem bearing should be re-placed on the
next overhaul occasion as described in the next section.
Make sure that the valve is not under pressure.
1. Remove the actuator. Begin by removing the
plastic cover and the four bolts
securing the valve positioner,and then remove
the valve positioner. Then remove the nuts
securing the actuator from the underside to the
actuator mounting plate.
2. Remove the actuator. Remove the keys.
3. Remove the circlip (6) and backing ring (7)
- Fig. 4.
4. Back off the bolts (9), and remove the washer
(8) and the PTFE backing ring (10).
5. Fit a new upper O-ring (11). Coat the new O-ring
with silicone grease before fitting it.
6. Assemble in the reverse order.
9.8 To change the stem bearing and seal
Remove the valve from the pipework. Note the
instructions in sections 2 and 9.2 concerning lifting and
emptying of the valve.
1. Remove the actuator as described in item 1 and
2 in section 9.7.
2. Remove the circlip (6) and backing ring (7)
- Fig. 4.
3. Back off the bolts (9), and remove the washer
(8) and PTFE backing ring (10).
4. Remove the valve as described in section 9.2.
5. Press the stem down into the body and
remove it.
6. Remove the upper O-ring (11).
7. Press up the two bearing bushes (12) and the
O-ring (11) between them.
8. Grease the new bushes and O-rings with silicone
grease and fit them in position. Also fit a new
thrust washer (13) to the stem.
9. Fit the stem and other parts in the reverse order.
9.6 Valves incl. NAF Pocket ball with Stellite ball
and seat ring.
1. The instructions for these valves are the same as
those in section 9.5 above. If the sealing surfaces
are damaged, we recommend that the
valve is returned to NAF for overhaul. This applies
in particular if the ball must be ground before
lapping. Assemble the valve before dispatching it
to NAF.
2. The ball and seat rings can be temporarily over
hauled by lapping them together. This can be done
manually with a compound with grit size 200. Take
great care to ensure that the ball and seat rings do
not become oval.
3. New rings can be supplied grounded and lapped
together with a ”Master-ball”. Some following
machining of the rear side of the rings may be
necessary in order to keep the correct measure.
It is always recommended to order a complete
Ball set.
4. Balls in alloy 6 must be carefully cleaned and
greased before they are fitted. Use a suitable
solvent for cleaning. Then grease the ball with
Klüber Barrierta L55/3 H8 or similar. This coat of
grease must be very thin.