Troubleshooting Alignment Data - Pump Systems Problems, Pump Repair, Pump Installation, Pump Help & Resources

Troubleshooting Alignment Data

Written by David Zdrojewski, VibrAlign, Inc.

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The Laser Result

Angular Misalignment

The vertical slope relationship of the motor shaft to the pump shaft: 2-mils/1-in. The coupling icon indicates that the coupling gap is larger at the bottom. The red color guidance indicates this is condition is not satisfactory. Horizontally, we are reading zero.

Offset Misalignment

Vertically, the motor shaft is low 20-mils at axial plane of the coupling center. The data indicates the actual shaft misalignment not the total indicator value. Again, red means an unsatisfactory value. Horizontally, the offset misalignment is zero.

The Rim and Face Indicator Result

Angular Misalignment

We know the slope relationship = 2-mils/1-in sloping upward away from the coupling and that the face indicator is at a 6-in diameter. Therefore, if the face indicator is set to zero at 12:00 and rotated to 6:00, the dial will read +12

Offset Misalignment

Vertically, the motor shaft is low 16-mils at axial plane of the rim indicator. If the dial is set to zero at 12:00 and read at 6:00, the value will be +32.

Ending the Debate

In summary, the laser reports the angular misalignment as the slope relationship of the two shafts in mils/1-in. The face indicator measures coupling gap difference.

Face Reading / Diameter = Angular Misalignment

The laser reports the absolute shaft offset at the coupling center while the rim dial indicator reads twice the offset.

Rim Reading / 2 = Offset Misalignment

Other Differences to Consider

The rim indicator values will be slightly different because the laser is calculating the offset at the center of the coupling, while the indicator is measuring at the coupling hub. If the angular misalignment is not zero, measuring in different axial planes will cause small differences on final results.
The laser has no deflection due to gravitational forces. Consequently, you may see some differences in vertical values if you do not determine the amount of dial indicator bar sag.
You might note that the values at the feet are larger than those at the coupling. This is simply because even small angular misalignment will result in larger and larger values as you get further from the coupling.
In the final example the motor shaft is sloping downward away from the coupling. The shaft offset at the center of the coupling is 0.0. The distance from the center of the coupling to the front feet is 10.0-in. The front feet result is: (-.3*10) + 0 = -3.0. The distance from the center of the coupling to the rear feet is 25-in. The rear feet result is: (-.3*25) + 0 = -7.5.

David Zdrojewski is CEO of VibrAlign, Inc., 530G Southlake Blvd., Richmond, VA 23236, 800-394-3279, Fax: 804-379-0189, www.vibralign.com.

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