Knife roller bearings: compact design for high radial loads in limited space

Introduction

Knife roller bearings are a critical component in rotating systems where high load capacity is required within a compact space. In production, especially in Ukraine, where the requirements for reliability and efficiency are high, these bearings are used in various mechanical units, from electric motors to transmissions. Improper selection or use of such bearings can lead to increased knock-out rates, reduced efficiency and increased repair costs. This article discusses the technical basis, standards, selection criteria, as well as practical recommendations for installing, preparing for operation and evaluating the reliability of knife roller bearings.

Fundamental principles

Knife roller bearings are a type of ball bearings that use cylindrical rollers instead of balls. This allows you to increase the bearing capacity at the same height, which is carried out due to a larger contact surface between the rollers and is equal to. They are made in a miniature form, which makes them ideal for use in compact units with high radial loads.

The main feature of such bearings is high bearing capacity at a relatively low height. This is achieved due to the distribution of the load on a larger number of rollers, which ensures an even distribution of the load, reducing jetting and endurance. Also, they are made of high-quality steel that meets ISO 6743-14 standards, which ensures durability and stability.

Technical parameters and standards

Knife roller bearings are manufactured in accordance with the following standards:

• ISO 281 — to determine the bearing capacity.
• ISO 76 — to determine the level of vibration and noise.
• ISO 492 — to determine the dimensions.
• DIN 51825 — for fulfillment and production requirements.
• IEC 60947-2 - for electrical units that use such bearings.

They also meet the requirements of CE and UkrSEPRO, which ensures their acceptability on the Ukrainian market. The use of such bearings ensures high reliability that meets production requirements.

Selection criteria and calculation

The choice of knife roller bearing depends on the following parameters:

• Radial load is determined by the formula: Fr = (P * K), where P is the nominal load, K is the safety factor (usually 1.2–1.5).
• The ratio of radial and axial load is determined by the formula Fr / Fa, which affects the choice of bearing type.
• Ambient temperature — affects the choice of material and lubrication.
• The rotation speed is determined by the formula n = (60 * f) / π * d, where f is the rotation frequency, d is the diameter.

Below is a table comparing the three types of knife roller bearings:

Practical recommendations for installation and preparation for operation

Correct installation and service preparation of knife roller bearings is critical to ensure their durability and efficiency.

• Surface cleaning - perform cleaning of inner and outer rings and bearing seats from dust, oil and other contaminants.
• Lubrication - Use high quality lubricants that meet the ISO 46 standard to reduce friction and wear.
• Installation - Install the bearings on the respective axles, ensuring proper bearing spacing and even load distribution.
• Preparation - check the temperature and vibration of the bearings after installation. Ensure correct operating temperature (no more than 60°C) and minimal vibration (no more than 1.5 mm/s).

Knockout trends and root cause analysis

Knife roller bearings can fail for various reasons:

• Roller wear is caused by high load or insufficient lubrication. An increase in noise and vibration is felt.
• Knockout rings - can occur due to insufficient clamping or high relative displacement. There is an increase in vibration and a decrease in speed.
• Surface damage - caused by poor quality material or improper installation. An increase in noise and vibration is felt.
• Insufficient lubrication - leads to increased friction and rapid wear. An increase in temperature and a decrease in service life are felt.

Service forecasting and condition monitoring

To ensure the durability and efficiency of knife roller bearings, the following control methods are used:

• Vibration measurement - vibration meters conforming to the ISO 76 standard are used to detect deviation from the normal level.
• Temperature control - bearing temperature should be within 60°C. Thermometers with high accuracy are used.
• Inspection and diagnostics - regular inspections of bearings allow participants to detect deviations from an early stage.
• Lifetime forecasting — data analysis methods are used to predict the life of bearings.

Comparison table

Below is a comparison of three types of knife roller bearings used in industrial systems:

Conclusion

Knife roller bearings are high-quality components that provide reliability and efficiency in industrial systems. Their choice and use have a decisive influence on the service life and cost-effectiveness of production. Use high-quality bearings from UNITEC-D that meet production requirements and ensure durability and stability.

Check out our catalog to find the best knife roller bearings for your project.

Sources

• ISO 281 — Determination of bearing capacity.
• DSTU 3765-2021 — Requirements for the production and operation of bearings.
• IEC 60947-2 - Electrical units.
• UNITEC-D Technical Whitepaper - Research and use of bearings in industrial systems.
• ISO 76 — Vibration and noise requirements.