Centrifugal compressor alignment procedure

Centrifugal compressor alignment is a critical step to ensure efficient operation, minimize vibrations, and extend equipment life. Proper alignment ensures that the compressor shaft and the driver (e.g., motor or turbine) are collinear. Below is a step-by-step alignment procedure:

Download PDF: Training manual of shaft alignment

1. Preparation

A. Gather Tools and Equipment

• Dial indicators or laser alignment tools.
• Feeler gauges and straight edges (if required).
• Torque wrenches and shims for adjustments.
• Alignment software (if using advanced systems).

B. Inspect Components

• Ensure both the compressor and driver shafts are clean.
• Check for any visible damage or debris on coupling faces.
• Confirm that the base is level and the foundation bolts are secure.

C. Thermal Considerations

• Consider thermal growth of both the compressor and the driver.
• Refer to manufacturer-specified offsets for hot alignment (if applicable).

2. Initial Alignment

A. Rough Alignment

• Use a straight edge to visually align the shafts.
• Check for obvious misalignment before proceeding with precise measurements.

B. Coupling Check

• Ensure that the coupling type is correct and properly fitted.
• Leave the coupling bolts loose for adjustments.

Download PDF: Shaft alignment pdf document

3. Alignment Measurements

A. Axial (End Play) Alignment

• Measure the axial gap between coupling faces using feeler gauges.
• Adjust as per manufacturer-specified tolerances.

B. Radial (Offset) Alignment

• Use a dial indicator or laser alignment tool to measure radial offset.
• Position the dial indicator at four points (0°, 90°, 180°, and 270°).
• Record the readings to determine the amount of misalignment.

C. Angular (Face) Alignment

• Place the dial indicator on the coupling face.
• Rotate the shaft and take readings at the same four points.
• Calculate the angular misalignment based on the difference in readings.

4. Adjustments

A. Shim Adjustments

• Add or remove shims under the motor or compressor feet to correct vertical misalignment.
• Ensure the shims are clean, flat, and properly stacked.

B. Horizontal Adjustments

• Loosen the mounting bolts slightly and slide the machine horizontally.
• Use precise adjustments to achieve the required alignment tolerances.

Download PDF: Laser shaft alignment handbook

5. Final Checks

• Re-tighten all bolts to the specified torque values.
• Re-measure alignment to ensure it remains within tolerances after tightening.
• Check coupling alignment again with the coupling fully assembled.

6. Documentation and Verification

• Record all alignment readings and adjustments.
• Verify alignment meets the manufacturer’s specifications for axial, radial, and angular tolerances.
• Note any thermal growth adjustments applied.

7. Hot Alignment (if applicable)

• Run the machine under normal operating conditions to allow thermal expansion.
• Shut down safely and quickly measure alignment changes.
• Adjust as needed to account for thermal growth.

8. Alignment Tools

Dial Indicator Method

• Simple and effective for most setups.
• Requires manual calculations and interpretation.

Laser Alignment Tool

• Provides precise and quick measurements.
• Often includes software for automatic calculations and reporting.

Download PDF: Shaft alignment handbook

9. Common Issues and Solutions

A. Misalignment Post-Tightening

• Check for improper tightening sequence or uneven shimming.
• Ensure all bolts are tightened evenly and in steps.

B. Foundation Settling

• Inspect and re-level the foundation if alignment changes frequently.

C. Vibration After Alignment

• Verify that alignment tolerances are within specifications.
• Check for other issues like imbalance or coupling defects.

10. Maintenance Tips

• Regularly check alignment as part of preventive maintenance.
• Use alignment tools calibrated and in good condition.
• Document historical alignment data for troubleshooting and trends.

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