11984 Rev 01
Page 2 of 4
5.1 Maintenance
5. Ensure the piston is free floating. Push down on the piston at point A on
Figure 5-1
and then let go (do not hold the piston down). If the piston and stepper motor work
together to return to set point, the piston is free floating.
In most cases, nothing will be found. After two months with no problems, the PM
schedule can be increased to once per quarter. Usually, after several quarters, the PM
schedule can be pushed up to once per year.
Progressive Technologies should be notified of any problems found, even if they can be
fixed internally. Progressive uses this information for product improvements and
customer notification of potential problem areas.
Recalibrate the Pressure Transducer
If the installation of the SENTRY 1510 relative to the furnace prohibits the use of the
standard length (5-15 feet) of process sense tubing then it will be necessary to
recalibrate the transducer to the new required length. Small modifications in length
resulting in a total length of 5 to 15 feet will not require recalibration.
Calibration is required due to the presence of the 0.1 liters/minute of nitrogen that is
used to maintain a purge in the line. The purge is used to prevent the migration of cor-
rosive process exhaust chemistries up the line, and to prevent the build up of con-
densation that could block the line. The purge flow causes a small pressure drop in the
sense tube that is proportional to the line's length.
Figure 5-2
: A) Nitrogen pressure regulator for the piston air bearing and
transducer purge; B) Nitrogen pressure regulator for piston bias flow
