Proper alignment of a centrifugal pump with its driver (motor, turbine, or engine) is crucial to prevent vibration, bearing failure, shaft damage, and energy loss. Misalignment can lead to premature wear and costly downtime. The two main types of misalignment are:
Parallel (Offset) Misalignment – Shafts are parallel but not concentric.
Angular (Gap) Misalignment – Shafts are at an angle to each other.
Before starting alignment, ensure:
✔ Foundation is rigid (no soft foot).
✔ Pump & driver are properly leveled.
✔ Piping strain is eliminated (use expansion joints if needed).
✔ Coupling is clean and undamaged.
✔ Shafts can rotate freely.
Used for initial checks before precision alignment.
Steps:
Place a straightedge across coupling halves (check parallel misalignment).
Use a feeler gauge to measure gaps between coupling faces (check angular misalignment).
Adjust motor/pump position with shims as needed.
Uses dial indicators to measure misalignment accurately.
Equipment Needed:
Dial indicators (magnetic base)
Micrometer or shims
Adjustable spanners
Mount Dial Indicators:
One on the rim (measures parallel misalignment).
One on the face (measures angular misalignment).
Rotate Shafts Together (360°):
Record readings at 12, 3, 6, and 9 o'clock positions.
Calculate Misalignment:
Difference between top/bottom and side/side face readings.
Average vertical & horizontal rim readings.
Parallel Misalignment (Offset):
Angular Misalignment (Gap):
Adjust Motor Position:
Use shims under motor feet for vertical correction.
Adjust motor bolts horizontally for side-to-side alignment.
Recheck Alignment:
Repeat until within tolerance (typically < 0.05mm for precision pumps).
Modern laser alignment tools provide real-time feedback.
Steps:
Attach laser emitters & sensors to both shafts.
Rotate shafts and follow software-guided adjustments.
System calculates required shim thickness & horizontal moves.
| Pump Type | Maximum Allowable Misalignment |
|---|---|
| General-purpose | ≤ 0.10 mm (0.004 in) |
| High-speed (>3000 RPM) | ≤ 0.05 mm (0.002 in) |
| Critical service (API 610) | ≤ 0.025 mm (0.001 in) |
✔ Run the pump & monitor vibration (should be < 2.5 mm/s RMS).
✔ Check bearing temperatures (< 70°C).
✔ Recheck alignment after 24–48 hours (settling may occur).
❌ Ignoring soft foot (motor feet not properly seated).
❌ Forcing piping connections (causes strain misalignment).
❌ Using too many shims (can lead to instability).
❌ Skipping thermal growth considerations (hot alignment vs. cold alignment).
Proper pump alignment extends equipment life, reduces energy consumption, and minimizes downtime. For critical applications, laser alignment is recommended, while dial indicators work well for most industrial pumps. Always follow manufacturer tolerances and recheck alignment after operation.
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