Machinery's Handbook, 31st Edition
SHAFT ALIGNMENT 2729 Solution for Vertical Alignment: Once a motor has been aligned with straight edges and such, it is probably close enough to use dial indicators. The dials most often used have a stem range of just over 0.200 inch (roughly 7 ⁄ 32 inch). These dial indicators (usually two) are positioned with the buttons of the indicators against the rim and face of the pump cou- pling respectively, as shown in Fig. 13. The seasoned millwright/mechanic will adjust the indicator jig/bracket in such manner that the stem on each of the indicators has freedom to travel inward or outward about 0.100 inch. This adjustment is made at the 12 o’clock position, shown by broken lines in Fig. 13. A good arrangement is for the rim indicator in Fig. 13 to register a minus r reading at the 6 o’clock position and the face indicator to register a plus f reading (see bottom right of Fig. 1b on page 2732). Readings on both indicators show that the motor needs to be raised, involving the simple task of determining how much shim material to add under each foot. For the indicator arrangement in Fig. 13, the required shim thickness can be determined by using the equations below. F r A f B 2 ! ! # = − + and R r A f C 2 ! ! # = − + where F = ± change in shim thickness needed under the front feet R = ± change in shim thickness needed under the rear feet The equations use the gathered data to calculate the correct shim placement. With either equation, a positive solution indicates that shims equal to the calculated value are added, and a negative solution indicates that shims equal to the calculated value are removed. The rim and face indicator setup depicted in Fig. 13 is one of the sixteen arrangements described in the material that follows. Each of these formats has its own similar but unique formula; just plug the variables into the formulas that matches the current indicator format and calculate the shims required. Solution for Horizontal Alignment: Fig. 14 shows a top view of the motor in Fig. 13, with indicators in the reading positions for horizontal alignment. The rim and face indicators are zeroed at the position 180 ° opposed to that shown in Fig. 14. The directions corresponding to horizontal movement of the motor in Fig. 14 are indi cated by east and west arrows. Magnetic-mount dial indicators (not shown) may be set up to monitor the horizontal movements. The dimensions B and C represent the distances from the rim indicator path to the locations of the monitoring indicators or jackbolts. If jackbolts (or monitor indicators) are positioned on the west side as indicated in Fig. 14, the B and C dimensions are used in the equations. If jackbolts (or monitor indicators) are positioned at a different location on the east side (for example, jackbolts shown by dashed lines in Fig. 14), the east-side set of dimensions, B ′ and C ′ , are used in the equations. The equations are the same as previously used in the vertical alignment procedure. Per the indicator arrangement in Fig. 14, a positive solution demands a move eastward, and a negative solution requires a westward move. F = ± east-west movement needed at the front monitoring location R = ± east-west movement needed at the rear monitoring location r = plus or minus rim indicator reading f = plus or minus face indicator reading A = diameter of face indicator path on coupling B = distance from rim indicator path to front feet C = distance from rim indicator path to rear feet
r = plus or minus rim indicator reading f = plus or minus face indicator reading A = diameter of face indicator path
B = distance from rim indicator path to front monitoring location C = distance from rim indicator path to rear monitoring location
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