Shaft Alignment & Coupling
Alignment principles, angular and offset misalignment, dial indicators, laser alignment systems, and coupling types.
- Differentiate angular, offset, and combined misalignment
- Perform shaft alignment using dial indicators
- Operate laser alignment systems and interpret results
- Select and install rigid and flexible couplings
Lesson 1
Shaft Alignment Fundamentals
Why Alignment Matters
Shaft alignment is the process of positioning two or more shafts so their rotational centerlines are collinear (on the same line). Misalignment is the leading cause of premature failure in rotating equipment - it causes increased vibration, bearing wear, seal leakage, coupling failure, and excessive energy consumption.
Types of Misalignment
Angular Misalignment
Shaft centerlines intersect at an angle
The shafts are tilted relative to each other
Creates axial vibration at 1X running speed
Offset (Parallel) Misalignment
Shaft centerlines are parallel but not collinear
The shafts are displaced vertically or horizontally
Creates radial vibration at 2X running speed
In practice, most misalignment is a combination of angular and offset. Both must be corrected to achieve proper alignment.
Tolerance Standards
Alignment tolerances depend on operating speed:
| Speed (RPM) | Offset Tolerance | Angular Tolerance |
|---|---|---|
| 600-1200 | 0.10 mm | 0.10 mm per 100 mm |
| 1200-3600 | 0.05 mm | 0.05 mm per 100 mm |
| 3600+ | 0.025 mm | 0.025 mm per 100 mm |
Exam Tip
The exam may ask which vibration frequency indicates misalignment. Remember: angular misalignment = 1X axial vibration, offset misalignment = 2X radial vibration.
Misalignment causes 50% of rotating equipment failures. Angular misalignment creates 1X axial vibration; offset misalignment creates 2X radial vibration. Tighter tolerances are required at higher speeds.