How to ensure the correct alignment of bearings and improve the key process of equipment life and operating efficiency

In the precision world of mechanical equipment, bearings are the rotating "heart", while alignment is the "nerve center" that ensures the health and smooth beating of this heart. Poor shaft alignment is one of the main causes of equipment vibration, early bearing failure, seal damage, increased energy consumption, and even production interruption. According to statistics, over 50% of equipment failures are related to alignment issues. Therefore, mastering the methods to ensure the correct alignment of bearings is a core skill essential for every equipment maintenance engineer.

1、 What is right? Why is it so important?
Alignment refers to the process of aligning the rotational center lines of the driving shaft (such as the motor shaft) and the driven shaft (such as the pump or fan shaft) on the same straight line during installation and commissioning. In an ideal state, the two axes should be completely aligned, but in practical engineering, we strive to control their deviation within the allowable tolerance range.

Serious consequences of adverse reactions:

Premature bearing damage: Misalignment can generate additional bending moments and radial forces, leading to uneven stress distribution inside the bearing, exacerbating fatigue and wear, and significantly reducing its lifespan.

Abnormal vibration and noise: are the most intuitive manifestations of centering, which can damage the equipment foundation and other adjacent components.

Shaft seal failure: A skewed shaft will continuously squeeze the seal, causing leakage, polluting the environment, and increasing lubricant consumption.

Increased energy consumption: The additional friction will be directly converted into higher operating current, resulting in energy waste.

Coupling damage: Especially for rigid couplings, poor alignment can subject them to significant stress, leading to fracture.

2、 Main types of alignment and tolerance standards
There are two main types of centering errors:

Offset/Parallel Misalignment: Two axis centerlines are parallel but not on the same straight line.

Angular/Gap Misalignment: The intersection of two axis centerlines forms a certain angle.

In practical operation, these two types of deviations often coexist. The goal of alignment is to control both types of errors within the tolerance range recommended by equipment manufacturers or international standards such as ISO 10816. Usually, the tolerance value depends on the rotational speed (RPM), and the higher the RPM, the higher the required alignment accuracy. Modern laser alignment instruments automatically calculate and display whether they are within the allowable tolerance range.

3、 Ensure correct alignment of core steps and methods
Method 1: Laser alignment with French (preferred, modern industrial standard)
This is currently the most accurate, efficient, and reliable method, strongly recommended for all critical equipment.

Preparation: Clean the shaft end and coupling to ensure that the installation surface of the measuring frame is clean and free of burrs. Install the laser emitter (S) and receiver (M) on the main and driven shafts respectively.

Coarse alignment: Use a ruler or dial gauge for initial alignment to ensure that the laser point is within the measurement range of the receiver.

Measurement and Calculation:

The turning wheel rotates the shaft (usually at one point every 90 degrees), and the laser system automatically collects data from multiple positions (usually at three or more points).

The built-in software will calculate and display the current horizontal and vertical parallel and angular deviations in real time.

Adjustment: Based on the real-time data displayed by the device, gradually correct the error value to the green tolerance zone by adjusting the gasket under the foot of the driven equipment (usually the motor) (adjusting the vertical deviation) and the top screw or levering equipment (adjusting the horizontal deviation).

Tightening and review: After adjusting in place, tighten the anchor bolts in diagonal order. The crucial step is to measure the alignment data again after tightening, as the tightening process may cause slight changes in the position of the equipment. If the deviation exceeds the tolerance, it needs to be readjusted.

Method 2: Percentage table method (traditional method)
Suitable for situations with low requirements or when lacking laser alignment instruments, requiring high operational experience.

Radial table: measure parallel deviation.

Axial table: measure angular deviation.
By reading the runout value of the dial gauge during the synchronous rotation of the two axes, and then calculating the deviation and the required shim thickness through the formula. This method takes a long time and is susceptible to factors such as shaft end jumping and table frame deflection, resulting in lower accuracy compared to laser methods.

4、 Best practices and precautions
Following the principle of "cold to center": The centering operation should be carried out when the equipment is at ambient temperature (cold state). It is necessary to consider the impact of thermal expansion during equipment operation (thermal compensation). For example, when equipment such as fans and pumps are running, the temperature of the pump body increases, and the shaft center will rise. Therefore, it is necessary to consciously set the motor shaft center slightly lower when it is cold. Equipment manuals usually provide thermal compensation values.

Ensure a solid foundation: The equipment foundation must be flat and stable. Soft foot is the enemy of centering, which refers to poor contact between the equipment foundation and the base. When tightening bolts, it can cause deformation of the machine base. Soft feet must be eliminated first: check the gap under each foot with a feeler gauge, and eliminate the gap by adding shims under loose feet to ensure that all feet are firmly in contact with the foundation.

Correct installation and fastening sequence: When installing measuring tools, ensure that the clamping is firm to avoid loosening or bending deformation of the gauge frame. When tightening the anchor bolts, they must be tightened step by step and evenly according to the manufacturer's recommended sequence (usually diagonal sequence).

Recording and archiving: After each alignment, the final alignment data, date, equipment number, and operator should be recorded, and an equipment alignment file should be established for future trend analysis and preventive maintenance.

Conclusion
The correct alignment of bearings is not an optional "rough job", but a rigorous and precise "precision process". From traditional dial indicators to modern laser alignment instruments, tools are advancing, but the core spirit of pursuing accuracy and detail has never changed. Investing in a laser alignment instrument and training employees to master it will yield immediate returns: longer bearing and equipment lifespan, lower maintenance costs, fewer unexpected shutdowns, and higher energy efficiency. Ensuring that every alignment is accurate and error free is the most solid foundation for the long-term stable operation of the equipment.