Product details

Origin:USA

Brand:bently

Product ID:3300/25

product description 

The 3300 XL 25 mm sensor system consists of a separate 25 mm probe, extension 

cable, and 3300 XL 25 mm preprocessor. The 0.787 V/mm(20 mV/mil) output gives 

the system a linear range of 12.7 mm(500 mil). Due to this linear range, the 3300 XL 25 mm 

sensor system is suitable for measuring differential expansion (DE) on medium to large 

steam turbine generators due to the different expansion rates of the turbine rotor and the 

machine stator (housing).

Differential expansion measurement

Differential expansion measurements are made by two eddy current sensors that measure 

the flange or bevel at a certain distance from the thrust bearing.

Typical sensor mounting methods include:

lBoth sensors measure the same side of the flange

lTwo compensated input sensors measure opposite sides of the flange, effectively 

doubling the DE range that can be measured

lAt least one of the two sensors measures a bevel of the rotor, and the other sensor 

measures a separate bevel or a different location on the rotor to compensate for radial 

movement.

This installation introduces some errors to the measurement, but allows the overall DE distance 

to be measured longer than the compensated measurement.

The installation needs to be based on the available target dimensions, the expected amount of 

rotor axial displacement, and the type of DE target inside the machine (flange versus bevel).

When the available flange height is sufficient, two sensors should be used to measure the same 

side of the flange.

Both sensors will provide measurements that are redundant to each other.