Page 276 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

258 Major Process Equipment Maintenance and Repair

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Figure 6-30. Typical tooth contact pattern for spiral bevel gearing.

on one shaft, this rigid shaft alignment will be the most critical, and dow-
els should be installed under the rigid shaft.
A gear unit should be redoweled after any housing-to-foundation
change, no matter how slight. Proper location and installation of the
dowel pins are essential to maintaining the good alignment and satisfac-
tory operation of a gear unit.

Hot Alignment Check
After all components have run long enough to stabilize operating tem-
peratures, a hot alignment check should be made as quickly as possible.
The coupling halves should be separated, the alignment checked, indica-
tor readings recorded, and any necessary corrections made before the
shafts and machines cool down. After this initial hot alignment check is
made, the unit should be redoweled to the foundation if any corrections
were necessary. Then an additional hot alignment check should be made
to ensure as correct an alignment as is possible.