When two spinning pieces of equipment are joined by a shaft coupling, every effort should be made to reduce coupling and shaft misalignment.
Bearing, shaft, and coupling failures bearing and coupling temperature, vibration, and energy consumption will all be reduced with proper alignment.
One of the main characteristics of couplings is that they must fill a gap between shafts. Although it appears to be a straightforward process, not all couplings are capable of performing it.
Another reason for the gear coupling’s popularity is that it is extremely versatile. To account for design requirements, product line differences, variable motor frames, and maintenance needs, the distance between shaft ends of spinning machinery must vary. In a variety of ways, a gear coupling can suit those needs.
Furthermore, proper alignment will extend the life of equipment between scheduled maintenance intervals. Consider the alignment restrictions of all system components, not only the coupling, when determining how exact the alignment needs to be. Excessive misalignment is not excused by a flexible coupling.
To maintain the trouble-free mechanical functioning of a pump set and avoid damage to the transmission elements, coupling alignment is critical. It entails keeping the required spacing (a) between the coupling parts (see Shaft coupling).
See Figure 1. Alignment of coupling.
Figure 1: Flexible coupling alignment with a straightedge and a feeler gauge.
Furthermore, at the coupling, the shaft centerlines must be perfectly aligned, and any lateral, height or angular misalignment must be rectified. Figures 3, 4, and 5 Alignment of coupling
Figure 3: Misalignment of the coupling: Lateral or height misalignment
Figure 4: Angular misalignment in coupling alignment
The alignment should be examined using a straightedge and a feeler gauge, if possible. See Figure 1. Alignment of coupling
If a straight edge stretched across both coupling parts parallel to the shaft maintains the same distance from the shaft at all points around its circumference, the coupling is appropriately aligned. Furthermore, the axial distance between the connecting portions should be consistent along the circle.
Also read: How does gear coupling work?
Using an alignment jig, you may easily achieve accurate alignment. Coupling alignment (see Fig. 2)
Fig. 2 coupling alignment: Using an alignment jig to align flexible couplings.
The degree of coupling alignment accuracy required is mostly determined by the coupling type and rotating speed. When it comes to hot water pump connection alignment, it’s critical to follow the pump manufacturer’s specific guidelines for dealing with thermal deformations.
To prevent the pump set from shifting during operation, pin the pump, including the drive, to the baseplate or pump foundation after coupling alignment is complete.
Below is a table showing the relative ranking of different alignment methods.
| Methods | Ratings | Comments |
| Straight edge and caliper | Poor | The parallel misalignment is checked with a straight edge, and the angular misalignment is checked with a caliper. Coupling and \equipment life may be sacrificed using this method. This is not a good idea. |
| Straight edge with a feeler gauges and inside micrometer | Fair | Same as above. Not recommended |
| Laser Alignment or Reverse Dial Indicator | Best | The dial indicator is attached to one hub/ shaft and measures the rim of the other hub/ shaft. The dial indicator is then switched to the other shaft, and the processes are repeated. These measurements graphically show the extension of one shaft centerline in relation to the other shaft centerline, as well as the alignment modifications needed to bring the equipment shafts into alignment. Both shafts must be \rotated together. Recommended |
There are a few things to think about before you start aligning your equipment.
Soft foot: Occurs when a piece of equipment, such as a motor, is not level on its base or on rocks.
Tightening the hold-down bolts can halt the rocking, but it will put too much strain on the motor bearings, perhaps causing further vibration. Erroneous alignment readings might also be caused by a soft foot condition.
THERMAL GROWTH
When your equipment reaches operating speed and temperature, always evaluate if it will travel in any direction from the “cold” to the “hot” running condition.
If the growth is large, you must purposefully misalign your equipment while it is cold so that alignment is achieved once it is operational and up to temperature.
Shafts should be aligned to reduce deflection of the flexing parts to extend the coupling’s service life. In the axial, parallel, and angular axes, shaft alignment is necessary, with each of these values not exceeding the prescribed installation limits.
Laser Alignment, Reverse Dial Indicator, and Rim and Face are just a few of the known ways for measuring shaft alignment.
