Understanding Four-Row Cylindrical Roller Bearings: Specs, Uses, and Benefits

In-Depth Guide to Four-Row Cylindrical Roller Bearings: Design, Applications, and Advantages

Cylindrical roller bearings are a crucial component in the world of heavy machinery, known for their ability to handle high radial loads at high speeds. Among the various types, the four-row cylindrical roller bearing stands out as a powerhouse designed for the most demanding industrial applications. This blog post will provide a professional overview of their design, key applications, and the significant advantages they offer.

1. Design Features and Structure

Four-row cylindrical roller bearings are engineered to support extremely heavy radial loads. Their design is characterized by four rows of cylindrical rollers that run on a common outer ring raceway and two inner ring raceways.

• Internal Structure: As shown in the technical drawing below, the four rows of rollers are guided by cages (retainers), which are typically made from machined brass or steel to withstand high speeds and accelerations.

• Rings and Bore: These bearings are available with either a cylindrical or a tapered bore. The inner and outer rings are often separable, which greatly simplifies the mounting and dismounting process, especially when interference fits are required.

• Materials: To ensure durability and reliability under harsh conditions, they are manufactured from high-quality materials like case-hardened steel or high-carbon alloy steel.

• Lubrication: The outer rings are usually designed with lubrication holes and grooves to ensure an adequate supply of lubricant to the rolling elements, which is critical for heat dissipation and reducing friction.

2. Key Applications

Four-row cylindrical roller bearings are primarily used in heavy industrial applications where operating conditions are severe. Their ability to withstand immense radial loads and shock loads makes them indispensable in the following areas:

• Rolling Mills: This is the most common application. They are extensively used in the roll necks of rolling mill stands for ferrous and non-ferrous metals. In this environment, they support the backup rolls, enduring colossal radial forces and high speeds.

• Heavy Machinery: Beyond rolling mills, they are found in other heavy-duty equipment such as calenders in the paper and plastic industries, roller presses, and large crushers used in mining.

• Wind Turbines & Gearboxes: Their high load capacity and reliability also make them suitable for use in the main shafts and gearboxes of large wind turbines.

It is important to note that these bearings are designed to accommodate only radial loads. Any axial loads present in the application must be handled by separate thrust bearings, such as deep groove ball bearings, angular contact ball bearings, or tapered roller bearings.

The image below shows a steel rolling mill, the quintessential environment for these high-performance bearings.

3. Advantages

The unique design of four-row cylindrical roller bearings offers several significant advantages that make them the preferred choice for heavy-duty applications:

• Exceptional Radial Load Capacity: The primary benefit is their ability to carry extremely heavy radial loads due to the high number of rollers transferring the load.

• High Stiffness: The bearing's construction provides excellent radial stiffness, ensuring stability and precision under heavy loads.

• High-Speed Capability: When mounted with an interference fit on the roll neck, these bearings are well-suited for the high rolling speeds encountered in modern mills.

• Durability and Reliability: Designed with high-quality materials and robust cages, they offer a long service life even in harsh environments with shock loads, contamination, and high temperatures.

• Low Friction: Advanced designs with optimized roller and raceway profiles promote the formation of a lubricant film, reducing friction and heat generation.

• Compact Design: Their low cross-sectional height allows for relatively large roll neck diameters compared to the roll diameter, which is beneficial for the overall mill design.

• Ease of Maintenance: The separable components (inner and outer rings) are often interchangeable, facilitating easy mounting, dismounting, and inspection.

Conclusion

Four-row cylindrical roller bearings are critical components in the heavy industry sector, offering an unmatched combination of extremely high radial load capacity, high stiffness, and reliability. Their robust design makes them the ideal solution for the demanding environment of rolling mills and other heavy machinery. By understanding their design features and advantages, engineers and maintenance professionals can ensure the optimal performance and longevity of their equipment.