Shaft alignment is the single most impactful maintenance activity for any coupled drivetrain. A flange coupling perfectly selected and carefully installed will still fail prematurely if the shafts it connects are not accurately aligned. Yet shaft alignment is also one of the most frequently skipped or inadequately performed procedures in Australian industrial maintenance. This guide covers the complete alignment procedure from initial preparation through to final documentation.
Understanding the Two Types of Shaft Misalignment
Angular Misalignment
The shaft centrelines are not parallel — they intersect at an angle. Think of a V-shape when viewed from the side. Corrected by shimming or adjusting motor feet differentially — raising or lowering one end relative to the other.
↔️
Parallel (Offset) Misalignment
The shaft centrelines are parallel to each other but laterally offset — they run in the same direction but not on the same line. Corrected by moving the motor bodily sideways (horizontal) or shimming all feet equally (vertical).
↕️
Axial Misalignment
The shaft faces are too close together or too far apart along the axis. Corrected by moving the motor or pump axially. The DBSE specification on the coupling drawing defines the correct axial shaft separation.
Laser Alignment: The Current Industry Standard
Laser shaft alignment systems have replaced dial indicator methods as the standard tool for flange coupling alignment in Australian industrial maintenance. The entire procedure takes 20–40 minutes for a typical pump drive, compared to 2–3 hours for a skilled dial indicator alignment.
1
Mount the Alignment HeadsFit the laser emitter to one coupling hub and the detector to the other using the magnetic mounts. Ensure both heads are secured firmly — any movement during the rotation sweep will invalidate the readings.
2
Enter Machine DimensionsInput the motor foot positions relative to the measurement plane and the distance between feet into the alignment software. Incorrect dimensions are a common source of alignment correction errors — measure carefully.
3
Perform the Rotation SweepRotate both shafts through the software-specified arc while the system records laser beam position. Observe the display for any readings flagged as unreliable — these indicate shaft movement or target obstruction during the sweep.
4
Correct Vertical Alignment FirstApply the calculated shim changes at each motor foot. Use precision ground stainless steel shim stock. After shimming, re-check the reading to confirm vertical alignment is within target before moving to horizontal correction.
5
Correct Horizontal AlignmentLoosen the motor hold-down bolts and use jack screws or a soft mallet to move the motor laterally in the amount indicated. Re-check and repeat until horizontal alignment is within target.
6
Final Torque and Re-checkTorque all hold-down bolts to the specified value in a cross-pattern. Re-run the laser alignment measurement to confirm the final reading — bolt tightening can shift the motor position slightly. Record final figures in the equipment file.
Alignment Tolerances by Coupling Type
Coupling Type
Angular Tolerance (°)
Parallel Tolerance (mm)
Notes
Rigid Flange Coupling
≤ 0.05°
≤ 0.05 mm
Zero tolerance for dynamic misalignment — verify hot alignment
Flexible Tyre Coupling
≤ 0.1° cold
≤ 0.1 mm cold
Coupling accommodates up to 4° in service — cold alignment sets the margin
Disc Coupling
≤ 0.05°
≤ 0.05 mm
Low damping — tight alignment prolongs disc pack life
Spacer Coupling (flexible ends)
≤ 0.15° per flex plane
≤ 0.15 mm
Two flex planes allows more total system misalignment
Frequently Asked Questions
How do I know if my flange coupling is misaligned?+
Common symptoms include: vibration that increases after the machine warms up, unusual noise at the coupling during deceleration, premature motor bearing failure, rapid elastomeric spider wear, and mechanical seal failures occurring more frequently than expected. Confirm misalignment using laser alignment or dial indicator measurement.
How often should flange coupling alignment be checked?+
For critical rotating machinery, alignment should be checked annually as a minimum, and any time a connected machine is dismantled for maintenance. Always check alignment after any motor or pump replacement, after significant vibration events, and after concrete grouting of baseplates.
What is the difference between angular and parallel misalignment?+
Angular misalignment occurs when shaft centrelines intersect at an angle and is corrected by shimming motor feet differentially. Parallel misalignment occurs when shaft centrelines are parallel but laterally offset and is corrected by moving the motor bodily sideways or shimming all feet equally. In practice, both types are usually present simultaneously.
Can I use a straight edge to align a flange coupling?+
A straight edge provides only a rough alignment check — sufficient for very low-speed, low-power drives where precision is not critical. For any motor above 5 kW or speed above 500 RPM, laser alignment or dial indicator reverse indicator method is required for the accuracy needed for reliable service.
What is thermal growth compensation in coupling alignment?+
Thermal growth compensation involves intentionally introducing a calculated cold misalignment offset that will be eliminated by differential thermal expansion at operating temperature. Without thermal compensation, machines aligned perfectly at cold start develop significant misalignment under operating conditions.
Need Expert Coupling Advice?
Our engineering team in Condell Park NSW is ready to help — free of charge.
