Thrust Collars for Integrally Geared Compressors


MAJOR APPLICATION: Cost effective axial load support in rotating machinery (typically integrally geared compressors)


Sponsor: Samsung Techwin (2012-2014)


OBJECTIVE: To evaluate the hydrodynamic pressure and force coefficients in the thin film between the thrust collar and bull gear taper.


Significance: Typically thrust collars are implemented in integrally geared compressors to absorb the axial load on the pinion shaft (see Fig. 1). This provides a cost effective and efficient means of balancing the thrust load created by the compressor or expander stages on either side of the pinion gear. These thrust collars (sometimes referred to as rider rings) act as hydrodynamic bearings transferring the axial load to the bull gear shaft, on which there is a large diameter thrust bearing to absorb the thrust in the compressor.


Fig. 2 shows a top view of the lubricated zone between the thrust collar and the bull gear. The lubricant in this region develops hydrodynamic pressure, governed by Reynolds equation. The thin film also has associated force coefficients (stiffness and damping).

Fig 1. Cut view of a four stage integrally geared compressor.


Fig. 2. Schematic view of the fluid film between the bull gear taper and the thrust collar.