Machinery's Handbook, 31st Edition
2728 SHAFT ALIGNMENT The shims are omitted to visually explain why the motor will usually have a little less distance from the motor shaft centerline to the base than the pump has. This set up is desirable because with the motor shaft a little lower than the pump shaft, the motor can be shimmed up until both shafts share a common elevation. If the motor shaft is higher than the pump shaft, it can be very difficult to alter the position of the pump because of the rigidly connected piping.
Spool Piece
Moveable Unit
BASE
Fig. 12. Pump and Motor are to be Aligned The motor in Fig. 12 is in its approximate finished position about 8 inches (203.2 mm) from the pump. The spool piece shown in Fig. 12 is to be bolted between the motor and pump couplings after alignment is complete. The spool piece (not shown in Fig. 13) is 8 inches long and there is an 8 1 ⁄ 8 inch (206.4 mm) space between pump and motor couplings. Fig. 13 shows a viable mounting of dial indicators in the process of procuring readings from the zero setting at 12 o’clock (broken lines) to the 6 o’clock position (solid lines). Some calibrated eyeballing, a scale measure and some straight edging are used to align the motor initially to the pump.
face indicator
Moveable Unit
A
rim indicator
BASE
B
BASE
C
Fig. 13. Alignment Setup for Pump and Motor There are many ways to mount and adjust dial indicators to measure the remaining mis alignment between the two units. Several are correct and only a few are optimum. The mounting of the pair of dial indicators between the motor and pump shown in Fig. 13 is as good as any and commonly used. Many other arrangements are shown starting on page 2731. Although there seem to be four dial indicators in Fig. 13, there are only two. The two indicators with broken lines are drawn at the initial 12 o’clock position where they are zeroed with about half the indicator stems exposed, (both indicator pointers are shown at 12 o’clock). Then the motor and pump shafts are both turned 180 ° to the 6 o’clock position (those indicators are drawn with solid lines, and the pointers are shown set to the 3 o’clock and 9 o’clock positions in Fig. 13). In real life alignments, the pointers might be aimed anywhere on the dial face, but the dial face will rotate 360 ° , so the zero can be manually adjusted to align with the pointer no matter which direction the needle points.
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