Choose an Alignment Method
Method 1 - Face and Periphery
The face and periphery method is the oldest and most widely used dial indicator method. Figure 2 illustrates the correct setup for this method, which is good for large-diameter hubs with a short distance between shaft ends.
Advantages:
- The end user only needs to rotate one shaft.
- Visualizing shaft positions is easier compared to other methods.
Disadvantages:
- It is difficult to obtain face readings if there is any axial float.
- An end user typically has to remove the coupling.
- It is more complicated to make the graphical calculations compared with other methods.
- Any out-of-roundness in the hub periphery or out-of-squareness in the hub face—meaning the hub flange is not round or flat and square relative to the shaft—will affect the readings.
Method 2 - Reverse Periphery (Indicator) Method
The reverse periphery (indicator) method is becoming increasingly popular and is the optimal method for most alignments. Figure 3 illustrates the correct setup for this method.
Advantages:
- It is generally more accurate than the face and periphery methods.
- Axial float, or out-of-roundness or out-of-squareness in the hub, does not affect the readings.
- It is easier to plot graphically compared with other methods.
- It is possible to make measurements with the coupling in place.
Disadvantages:
- End users must rotate both shafts.
- It is not accurate for close-coupled shafts.
Method 3 - The Laser System
The modern laser system (see Figure 4) consists of either two laser/detector units or one laser and one mirror/prism reflector unit. One unit is attached to each shaft, and the laser/detectors are connected to a keyboard/display unit by a cable or via a wireless Bluetooth system. The system operates using the principles of reverse periphery, detecting the movement of the laser beams as a measure of the misalignment.
Advantages:
- The system fits a variety of shafts.
- End users do not have to remove the coupling.
- End users can measure long spans with no sagging issues.
- It is not affected by axial float.
- The system detects the soft foot condition easily.
Disadvantages:
- The system is not suitable for couplings with backlash.
- Heat or steam can affect its accuracy.
- The system is expensive.
