Bearing insights

• The consistent issue of moisture contamination in lubricants and machinery poses a persistent challenge, potentially causing adverse impacts on equipment performance, life span and overall operational effectiveness.
• The infiltration of water can result in corrosion, wear and a disruption in lubrication, leading to expensive downtime and maintenance.

Bearings play a crucial role in various industrial applications, ensuring smooth and efficient machinery operation.

However, when exposed to humid or submerged environments, bearings face unique challenges that can compromise their performance and life span. In this article, we will explore effective strategies for managing bearings in such conditions to enhance durability and maintain optimal functionality.

Humid and submerged environments pose several challenges to bearings, including corrosion, lubrication breakdown and increased friction. Corrosion can lead to premature bearing failure and increased maintenance costs and down time. Therefore, it becomes imperative to adopt proactive measures to counteract these challenges.

Figure 1: Secondary clarifiers main gear drive bearing. Courtesy: Upper Occoquan Service Authority

Strategies for optimizing bearing performance in humid environments

Material selection: Choosing the right materials for bearings is a critical step in managing them in humid and submerged environments. Stainless steel and corrosion-resistant alloys are often preferred due to their ability to withstand the corrosive effects of moisture and water. These materials provide a protective barrier, reducing the likelihood of corrosion and enhancing the overall longevity of the bearings.

Sealing solutions: Effective sealing is essential to prevent water and moisture ingress into the bearing housing. Using high-quality seals and shields, such as labyrinth seals or rubber seals, creates a protective barrier that helps maintain the integrity of the bearing lubricant and prevents contaminants from entering. Regular inspection and replacement of seals are crucial to ensuring continued protection against environmental elements.

Lubricant selection and lubrication maintenance: Lubrication is a vital aspect of bearing management and it becomes even more crucial in humid and submerged environments. Specialized lubricants with water-resistant properties are recommended for such applications.

The capacity of lubricating grease to endure the introduction of water into the lubricant system without negative consequences is known as water resistance. This attribute generally consists of four components:

• Water washout resistance: This measures the grease’s ability to resist removal from a bearing when operating in the presence of water. Evaluation methods include ASTM D1264 or ISO 11009.

• Water absorption: This reflects how lubricating grease reacts when water is added to the system. Water absorption characteristics can be assessed through various tests, leading to three possible reactions:

  • Water soluble: The grease absorbs water, degrades to a semi-fluid consistency.

  • Water absorbent: The grease absorbs significant water quantities with minimal consistency change and no separate phase of free water.

  • Water resistant: The grease absorbs only small amounts of water, undergoes negligible consistency changes and most added water remains a separate second phase.

• Water corrosion resistance: This measures the grease’s ability to prevent metal surface corrosion in the presence of water. Evaluation methods include static tests or dynamic assessments involving bearings operated with water added to the lubricant reservoir, as in ASTM D1743, ASTM D5969, ASTM D6138 and ISO 11007.

• Water spray resistance: This assesses the grease’s resistance to displacement from a surface due to water spray impact. The testing method is detailed in ASTM D4049.

It’s important to note that lubricating greases for various applications may not require all these water resistance characteristics. These measures are not indicators of quality except in specific situations where water resistance is essential.

Regular monitoring of lubricant conditions and scheduled replenishment or replacement are essential to prevent lubrication breakdown and maintain optimal bearing performance.

In Ernest Rabinowicz’s book, “Friection and Wear of Materials,” he indicates that approximately 70% of equipment or machinery downtime can be attributed to surface degradation. Within this percentage, 20% of replacements are directly linked to corrosion, while the remaining 50% result from mechanical wear.

The primary culprits behind corrosion and wear are external factors such as dirt and moisture, collectively known as contamination. When lubricants or hydraulic fluids contain moisture, a cascade of adverse effects ensues. Moisture contributes to corrosion, leading to particulate contamination. Additionally, it can alter oil viscosity, deplete additives and prompt sludge formation.

Ways to combat moisture in bearings

Effectively combating these issues requires a comprehensive contamination control strategy. suppliers offering a wide range of contamination control equipment, including desiccant breathers, filters and other tools.

Desiccant breathers are intricate devices installed on machines preventing two critical contaminants: moisture and particles. To Understand what a desiccant breather is, it’s essential to understand the concept of a desiccant. A desiccant is a hygroscopic substance that attracts and retains water molecules, maintaining a dry environment. Common examples include silica gel found in packets.

Equipment such as gearboxes, pumps and reservoirs require proper “breathing” when air in the headspace expands and contracts due to temperature fluctuations or oil level changes in hydraulic systems. Each breath introduces dirt, debris and moisture, contaminating the lubricant and causing gradual equipment damage. Recognizing that a significant portion of lubricant contamination originates externally and given that machines are designed to “breathe,” it becomes imperative to intercept these contaminants at their source.

Figure 2: A desiccant filter installed on a gear drive breather at Upper Occoquan Service Authority. Courtesy: Upper Occoquan Service Authority

Proper installation: Correct installation and alignment are fundamental factors in the longevity of bearings, especially in challenging environments. Ensuring precise alignment of shafts and proper installation of bearings reduces the risk of misalignment-induced stress and wear. Properly aligned bearings operate more efficiently and are better equipped to handle environmental challenges.

Monitoring and maintenance: Regular monitoring of bearing and lubricant conditions is essential for identifying early signs of wear, misalignment or lubrication issues. Implementing a proactive maintenance schedule that includes inspections, lubrication checks and seal replacements can significantly extend the life of bearings in humid and submerged environments. Modern technologies, such as vibration analysis and temperature monitoring, can be employed to detect potential issues before they escalate.

If there is oil mixed with water, because water is denser than oil, it settles to the bottom where the drain is situated. Removing the water is a simple task of opening the drain until oil begins to emerge.

The frequency of water drainage may vary and can be determined by monitoring it regularly until you become familiar with your drive’s requirements. Adding a quarter-turn ball valve can be a convenient enhancement for effortless drainage.

Strategy implementation

Effectively managing bearings in humid and submerged environments requires a combination of material selection, sealing solutions, lubrication maintenance, proper installation and proactive monitoring. By implementing these strategies, industries can enhance the performance and longevity of bearings, reduce downtime and ultimately contribute to more reliable and efficient machinery operation in challenging environmental conditions.

Do you have experience and expertise with the topics mentioned in this content? You should consider contributing to our WTWH Media editorial team and getting the recognition you and your company deserve. Click here to start this process.