Shaft Alignment Methods

Shaft Alignment Methods FSA Knowledge Series

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Abstract This Fluid Sealing Association Knowledge Series training provides an overview of equipment shaft alignment information, including:​

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Measuring misalignment

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Alignment methods

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Correlation between equipment alignment and machine life

Rotational Centers

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All shafts, whether they are straight or bent, rotate on an axis called the rotational center.

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The rotational center forms a straight line

Co-Axial Shafts ▪

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Two shafts are said to be co-axial when their respective rotational centers form a single axis.

Measuring Misalignment ▪

Machines are designated as stationary and movable.

Stationary Movable

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Measuring Misalignment ▪

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The rotational center of the stationary machine is a datum or reference line.

Measuring Misalignment ▪

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Misalignment is determined by finding the position of the movable rotational centerline in relation to the stationary centerline in two planes.

Measuring Misalignment

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Viewed from the top - Horizontal Misalignment

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Viewed from the side - Vertical Misalignment

Measuring Misalignment ▪

Lateral Misalignment (Parallel Offset)

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Angular Misalignment

Axial Misalignment

Alignment Methods ▪

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With all alignment methods - measurements are taken at the shaft ends or coupling hub.

Alignment Methods ▪

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Misalignment is corrected at the feet.

Alignment Methods ▪

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How far & where the feet move is calculated from measurements taken at the coupling or shaft ends

Different Ways of Aligning Shafts

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Mechanical Methods Straight edge / feeler gauge

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Radial misalignment ▪ Determine offset using straight ▪ edge & feeler gauges

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Angular misalignment ▪ Measure the gap 180° apart

Dial Indicator Methods

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Rim face method

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Reverse rim method

Rim Face Alignment Method

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Rim dial gauge measures radial misalignment (offset)

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Face dial measures angular misalignment

Reversed Rim Alignment Method

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Tradition method

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Both dials measure offset on the rim ○

Radial misalignment - difference between the 2 readings

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Angular misalignment - slope between the 2 readings

Laser Systems

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Single laser - single or double detectors

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Twin lasers - twin detectors

Machine Life (Years)

Comparative Analysis

Laser 0.001mm / 0.0004” Clocks 0.01mm / 0.004” Straight Edge 0.5mm / 0.020”

Method of Alignment 20

Three Stages of Alignment

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Pre-alignment ▪ Off site preparations - check machine specifications ▪ On site preparations - visual checks of machine ▪ On site actions - check condition of foundations’

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Rough-alignment ▪ Ensure the shafts are aligned “in-the-ballpark”

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Precision alignment ▪ Use laser alignment system ▪ Check for ‘Soft foot’ ▪ Three phases: Measure, Align and Document (MAD)

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