Proper Pump to Motor Alignment Techniques: Part 3 of 6
Proper Pump to Motor Alignment Techniques: Part 3 of 6
Correctly aligning the motor to a centrifugal pump is one of the most critical steps in the installation process. Performing this step well will set the foundation for many years of smooth pump and system operation. Failure to properly align a motor to the pump within the required tolerances can prove disastrous, resulting in high vibrations, increased shaft stress, high bearing temperatures, and possibly premature pump failure.
This multi-part guide aims to define the process as well as highlight some of the crucial steps that must be taken in order to achieve a successful alignment.
Alignment Precision
When aligning a high-energy centrifugal pump to its driver (typically a large electric motor or a steam turbine), many variables must be taken into account to determine the acceptable tolerance, including speed, rated power, coupling design, spacer length and the end-users expectation for service life. For the purposes of this article, assumptions will be made, yielding the table below that aims to establish alignment criteria based upon coupling type and pump speed in rotations per minute (RPM).
| Speed (RPM) | Misalignment (mils) | ||
| Acceptable | Excellent | ||
|---|---|---|---|
| Short, flexible type couplings Offset |
600 | 9.0 | 5.0 |
| 900 | 6.0 | 3.0 | |
 |
1200 | 4.0 | 2.5 |
| 1800 | 3.0 | 2.0 | |
| 3600 | 1.5 | 1.0 | |
| 7200 | 1.0 | 0.5 | |
| Speed (RPM) | Misalignment (mils) | ||
| Acceptable | Excellent | ||
|---|---|---|---|
| Short, flexible type couplings Offset |
600 | 15.0 | 10.0 |
| 900 | 10.0 | 7.0 | |
 |
1200 | 8.0 | 5.0 |
| 1800 | 5.0 | 3.0 | |
| 3600 | 3.0 | 2.0 | |
| 7200 | 2.0 | 1.0 | |