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Installation, Operation and Maintenance Manual
MAN 564 Rev. 6
June 2020
Maintenance
Section 5: Maintenance
To replace the piston seal ring (9) and the O-ring (19) proceed as follows:
1.
Remove the existing Teflon seal ring (9) and the O-ring (19) from their groove.
2.
Clean the groove carefully and lubricate it with a protective oil film.
3.
Assemble the new O-ring into its groove and lubricate it with a protective oil film.
4.
Assemble the new Teflon seal ring (9) on its rubber O-ring (19) by introducing
one side of it into the groove and then enlarge it with your fingers so as to
introduce it into the groove: take care to enlarge it uniformly without any tools
which could possibly damage it. The elastic memory of the kind of Teflon type the
seal ring is made of allows the ring to shrink back to its previous dimension after a
short time.
If the O-ring (17) has to be replaced, measure the protrusion of the stop screw (11) with
reference to the end flange (13) surface, so as to be able to easily restore the setting of the
actuator mechanical stop in the open valve position, once the maintenance procedures
have been completed.
5.
Loosen the stop setting screw cover (14) and unscrew the stop screw (11).
6.
Remove the O-ring (17) from the stop screw (11). Carefully clean and lubricate the
stop screw thread and the surface of the end flange area, on which the O-ring works.
7.
Screw the new O-ring onto the stop screw until it touches the cover (14).
8.
Screw the stop screw into the threaded hole of the end flange until it reaches its
original position (the same protrusion with reference to the flange surface).
9.
Check that the O-ring (17) is inside the groove into the end flange and in contact
with the groove bottom surface.
