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The 3300 XL 25 mm Transducer System consists of a separate
25 mm probe, an extension cable, and a 3300 XL 25 mm
Proximitor Sensor. The 0.787 V/mm (20 mV/mil) output gives
this system a linear range of 12.7 mm (500 mils). Based on
this linear range, the 3300 XL 25 mm Transducer System is
suitable for measuring differential expansion (DE) on midsize to large steam turbine generators caused by the
difference in growth rates between the turbine rotor and the
machine stator (casing).
The Differential Expansion measurement is made by two
proximity transducers observing a collar or ramp some
distance from the thrust bearing. Typical transducer
mounting arrangements are:
l Two transducers observing the same side of a collar.
l Two complementary input transducers observing
opposite sides of a collar, effectively doubling the
measurable DE range.
Two transducers with at least one transducer viewing a ramp
on a rotor and the second transducer viewing either a
separate ramp or a different location on the rotor to
compensate for radial movement. This arrangement adds
some error to the measurement, but can measure a longer
total DE distance than the complementary measurement.
The criteria for selecting a mounting method are the size of
the available target, the expected amount of rotor axial
movement and the type of DE target that exists in the
machine (collar versus ramp). If sufficient collar height is
available, two transducers observing the same side of a
3300 XL Proximity Transducer System
Datasheet
163236 Rev. M
collar is the preferred configuration. These two
transducers provide redundant measurements.