DH Instruments ADCS-601, Operation And Maintenance Manual

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6. GENERAL MAINTENANCE AND ADJUSTMENTS
Page 115 © 2005 DH Instruments, Inc.
Tighten the first piston retaining pin.
Verify that both retaining pins are tight.
Verify that the silicon O-ring is in place on the upper mounting post (between the upper
and lower mounting post).
Attach the lower mounting post, aligning it with the cylinder.
Place a hand under the lower mounting post and firmly press up.
With the other hand, thread the mounting post nut mating the upper mounting post to the
lower mounting post.
Restart the FPG by pressing the [ON] button on the FPG Run Screen (see Section
4.3.6.2). Wait until the start up procedure is complete. NOTE: If this is the initial
FPG8601 start up, the
FPG Tools software is not running yet. Open the door on the
front of the Control Cabinet and set the FPG DRIVE regulator as specified in Section
6.13. Then return to Section 3.3.10.2.
Wait at least five minutes with the FPG at zero pressure. If the pressure (FPG8601 load
cell output <N> ) is noisy, the piston and cylinder may require lubrication restoration
procedure (see Section 6.3.7) or re-cleaning (see Section 6.3.4).
6.3.7 RESTORING PISTON-CYLINDER LUBRICATION AND
MOBILITY
6.3.7.1 OVERVIEW
For the FPG8601 piston-cylinder to operate properly, the piston must be well
centered in the cylinder so that it is free and mobile. The piston is lubricated and
centered by the flow of lubricating gas from the center of the piston-cylinder
through its upper and lower conical gaps (see Section 2.2.2). While the
lubricating gas flow can maintain the piston centered in the cylinder, for its action
to be effective, the piston must first be well lubricated with gas and centered in
the cylinder.
A piston-cylinder that has just been installed in the FPG8601 mounting post may
not be well enough centered and lubricated for the lubricating gas flow to center.
it. The piston centering may also be lost if the lubricating gas flow is interrupted.
The symptom of this condition is noisy output of the pressure even when the
pressure is stable, in particular when the FPG8601 is being zeroed or when the
lower mounting post has been removed.
When the FPG8601 output is noisy it often is not because the piston-cylinder is
dirty. It is because it is not well centered and lubricated.
The four procedures described in Section 6.3.7.2 should be used to center the
piston in the cylinder and lubricate it before applying the lubricating pressure.
If the centering methods do not reestablish stability, the piston-cylinder may need
to be cleaned (see Section 6.3.4).
It is not unusual to need to repeat the procedures multiple times.
6.3.7.2 PISTON CENTERING AND LUBRICATING METHODS
The four procedures below are used to prepare the piston-cylinder for application
of the lubrication pressure.
These procedures are used with the piston-clinder installed in the mounting post
but with the lower mounting post removed so that the piston-cylinder can be