July 2020
Installation, Operation and Maintenance Manual
MAN 575 Rev. 4
26
Maintenance
Section 5: Maintenance
5.3
Lubrication of Mechanism
For normal duty the rack and pinion mechanism of the actuator is lubricated "for life".
In case of high load and high frequency of operation it may be necessary to periodically
restore lubrication: it is advisable to apply a generous coating of grease on the contact
surfaces of moving parts, especially on the surface of the rack in contact with the thrust
bearing sliding block and on the teeth of the rack and pinion.
For this operation proceed as follows:
1.
Disassemble the actuator from the valve.
2.
Measure the protrusion of the stop screw (30) with reference to the end
flange surface (4), to be able to easily restore its setting once the maintenance
procedures have been completed.
3.
Loosen the lock nut and unscrew the stop screw until it is removed.
4.
Remove the nuts (25) from the tie rod (14) at the end flange side: they must be
gradually unscrewed all at the same time so as to release the thrust of the spring
against the flange.
5.
Slide off the end flange (4) and the cylinder tube (13).
6.
Measure the protrusion of the thrust- bearing screw (15), with reference to the
housing surface, so as to be able to restore the right working position of the thrust
bearing sliding block with reference to the rack once the maintenance procedures
have been completed.
7.
Remove from the actuator the complete spring module, the main components
of which are the piston (3), the spring (16), the rack spacer rod (12), the spring
retainer disk (11) and the rack (5).
8.
Remove the spacer tube (33).
9.
Lubricate abundantly the teeth of the rack and pinion and the surface of the rack in
contact with the thrust bearing sliding block. Use recommended grease.
Prior to reassemble:
1.
Check that the actuator components are in good conditions and clean.
2.
Substitute the gaskets and the O-Rings if worn or damaged.
3.
Assemble all the components, taking care not to damage the seals.
