How to Solve the Problem of Excessive Bearing Wear in Paper Machines: A Practical Guide with Lubricant Optimization

Photo: Isis França / Unsplash

In the paper industry, bearings are among the most stressed components. High speeds, constant vibrations, and humidity create extreme conditions that accelerate wear. If bearings begin to overheat or produce unusual noises, it is a sign that the lubricant is not performing its function. However, the problem often lies not only in the quality of the lubricant but also in its incorrect application or selection. In this article, we will explore how to proceed with diagnostics and how to choose a lubricant that will withstand even the demanding operating conditions of a paper machine.

1. Problem Diagnosis: How to Identify the Causes of Excessive Bearing Wear

Excessive bearing wear in paper machines typically manifests as increased noise, vibrations, or localised heating. The first step is a visual inspection of the bearings and their surroundings – look for traces of metal shavings, colour changes (e.g., blue or black discolouration indicating overheating), or unusual deposits. It is also important to measure the bearing temperature during operation; if it exceeds 80 °C, this is a clear sign of lubrication issues or overload.

For more accurate diagnostics, oil analyses are used to detect the presence of metal particles, water contamination, or foreign substances. For example, spectrometric analysis can identify elements such as iron, copper, or chromium, which helps determine whether wear is occurring in the bearing itself, the cage, or surrounding components. It is also advisable to check the condition of the seals and filtration system, as the ingress of contaminants is a common cause of premature wear.

2. Selecting the Right Lubricant: Key Parameters for Paper Machines

In the paper industry, bearings are exposed to extreme conditions – high temperatures, humidity, and mechanical stress. The lubricant must meet several criteria: high resistance to oxidation (to prevent deposit formation), good adhesion to surfaces (to resist water washout), and stable viscosity across a wide temperature range. For these applications, synthetic oils based on polyalphaolefins (PAO) or esters are often used, as they offer better performance than mineral oils.

Another important factor is the compatibility of the lubricant with bearing and seal materials. For example, some synthetic oils can cause elastomers to swell, leading to lubricant leaks. Before changing the lubricant, it is therefore necessary to verify that the new product is compatible with the existing system. In high humidity conditions, lubricants with anti-corrosion additives and emulsifiers, which prevent the separation of water and oil, are recommended.

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3. Optimizing the Lubrication Process: Frequency, Quantity, and Application Methods

Incorrect frequency or amount of lubricant is a common cause of bearing failures. Over-lubrication leads to overheating and increased wear, while insufficient lubrication causes dry running and seizing. For paper machines, it is recommended to follow the bearing manufacturer's instructions and adjust intervals according to real operating conditions – for example, at high temperatures or humidity, lubrication intervals may need to be halved.

Modern methods such as automatic lubrication systems ensure even lubricant dosing and minimize the risk of human error. These systems can be programmed for precise quantities and intervals, which extends bearing life and reduces lubricant consumption. For manual lubrication, it is crucial to follow the correct technique – the lubricant should be applied gradually to distribute evenly across the entire bearing, always while the machine is rotating to prevent local overload.

4. Preventive Maintenance and Monitoring: How to Prevent Future Problems

Regular monitoring of bearing and lubricant condition is the foundation of long-term reliability for paper machines. It is recommended to implement a predictive maintenance system that includes regular oil analyses, vibration measurements, and thermographic inspections. These methods allow early detection of problems and help avoid costly downtime.

In addition to technical measures, staff training is crucial – operators should be able to recognize warning signs such as changes in noise or temperature and respond appropriately. Bearing replacement should follow a schedule, not wait until failure occurs. Furthermore, it is advisable to maintain records of all maintenance interventions, which helps identify recurring issues and optimize the entire lubrication and maintenance process.

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Lubricant contamination analysis: How to identify and eliminate harmful impurities

Excessive bearing wear in paper machines is often linked to contamination of the lubricant with solid particles, water, or chemical impurities. Solid particles such as dust, cellulose fibers, or metal shavings act as abrasives and accelerate abrasive wear. Water in the lubricant reduces its viscosity and lubricating properties, leading to insufficient separation of friction surfaces. Chemical contaminants, such as residues of process fluids or acidic oil aging products, can cause corrosion or degradation of the lubricant.

Standard analytical methods such as spectroscopy, ferrography, or water content tests are used to identify contamination. In practice, regular lubricant sampling and laboratory evaluation have proven effective. If analysis reveals a high level of impurities, the lubricant must be replaced, and the source of contamination identified. Installing effective filters, sealing bearing housings, or adjusting lubricant storage to minimize the risk of contamination ingress often helps.

Impact of Temperature and Operating Conditions on Bearing and Lubricant Lifespan

Temperature is one of the most critical factors affecting the lifespan of bearings and lubricants. In paper machines, local overheating often occurs due to high speeds, friction, or insufficient cooling. At temperatures above 80 °C, lubricant oxidation accelerates significantly, leading to deposit formation and loss of lubricating properties. Conversely, excessively low temperatures increase lubricant viscosity, which can result in inadequate lubrication and increased friction.

To optimize temperature conditions, it is crucial to monitor bearing temperatures using thermocouples or infrared cameras. In case of overheating, adjusting operational parameters such as reducing speed or improving cooling can be considered. It is also important to select a lubricant with a suitable temperature range and stability. For example, synthetic oils with anti-oxidation additives are suitable for high temperatures, while low-viscosity lubricants are better suited for cooler operating conditions.

Practical Tips for Lubricant Replacement and Storage in Paper Mill Operations

Proper lubricant replacement and storage are often underestimated factors that can significantly impact bearing lifespan. When replacing lubricant, it is essential to thoroughly clean the bearing housing of old lubricant residues and contaminants to prevent contamination of the new lubricant. It is recommended to use special cleaning agents that are compatible with bearing and seal materials. After cleaning, it is advisable to gradually fill the bearing with new lubricant to ensure even distribution and eliminate air bubbles.

Lubricant storage requires adherence to several basic rules. Lubricants should be stored in sealed containers in a dry and cool place to minimize the risk of contamination or degradation. It is important to observe the recommended shelf life and regularly check the condition of lubricants before use. In paper mill operations, where large volumes of lubricants are often handled, it is advisable to implement a batch labeling and tracking system to avoid using expired or substandard products.

Need help choosing a lubricant?

Every operation has its specific requirements. GCG Group provides technical data sheets and safety data sheets (SDS) for all lubricants and industrial oils and will advise you on selecting the optimal solution for your specific conditions. Contact us – or browse our catalogue of over 1,300 products right away.