Solution for Enhancing Performance and Reliability of Tandem Axial Bearings in Extruder Gearboxes

The efficient performance of extruder gearboxes is pivotal in industries like plastics and petrochemicals. Tandem axial bearings of series T.AR, designed specifically for these applications, play a critical role in maintaining the operational reliability and high output of extruder systems. This solution outlines the advanced design features, material improvements, and lubrication strategies that enhance the performance and durability of these bearings.

Design and Material Innovations

1. Structural Design: 

Tandem axial bearings of series T.AR consist of multiple axial cylindrical roller bearings arranged in line, separated by sleeves. This configuration ensures uniform load distribution across the bearings. The use of cylindrical rollers guided by brass, aluminum, or polyamide cages, and bearing washers and sleeves made from hardened steel, provides robustness. For high-performance variants, high-performance steel is used for the bearing washers.

2. High-Performance Materials:

·Cromadur: This through-hardened steel offers a 30% higher basic dynamic load rating due to a special heat treatment that enhances toughness.

·Mancrodur: A case-hardening steel, particularly suitable for carbonitriding, provides a tough core and a nitrided surface layer, increasing overrolling resistance and dynamic load capacity by 30%.

These material enhancements allow for higher bearing loads, extended fatigue life, and reduced system downtimes.

The improved materials also enable the development of new, higher-performance extruders without redesigning the gearbox, or alternatively, the downsizing of gearboxes to economize on footprint, weight, and costs.

Lubrication and Maintenance

1. Circulating Oil Lubrication: To ensure adequate heat dissipation and lubrication, tandem axial bearings operate with circulating oil systems equipped with filters and cooling facilities. Maintaining the correct oil viscosity, temperature, and speed is crucial for forming a separating EHD lubricant film, essential for long bearing life without wear-induced failures.

2. Anti-Wear Coatings: Under unfavorable conditions, anti-wear protection is achieved using coating systems like Durotect B and Triondur C. These coatings significantly reduce wear and extend the bearing's operational life.

Installation and Fit

1.  Mounting Fit:

For optimal performance, tandem axial bearings require a precise mounting fit. Recommendations include:

·Shaft: f6 fit

·Housing Bore: F7 fit

Ensuring tilt-free bearings after fitting and adhering to tight geometrical tolerances of the adjacent construction is vital for uniform load distribution.

2.  Preload:

A preload of 1% of the basic dynamic load rating is essential to avoid slippage damage during load-free operation and to maintain the linearity of the deflection characteristic curve.

Application Example

In large gearboxes for counter-rotating twin screw extruders used in plastic granulate production, the following INA series bearings are utilized:

·81128: Axial cylindrical roller bearing

·SL185026: Semi-locating bearing, double row full complement cylindrical roller set

·T8AR: Tandem axial bearing, performance-enhanced variant in Mancrodur

·SL185024: Semi-locating bearing, double row full complement cylindrical roller set

·T2AR: Tandem axial bearing, performance-enhanced variant in Mancrodur

These components ensure high output and operational reliability, reducing costly production stoppages.

Conclusion

Tandem axial bearings of series T.AR, with their advanced design, high-performance materials, and robust lubrication systems, provide a reliable solution for enhancing the performance and durability of extruder gearboxes. By implementing these innovations, industries can achieve higher operational efficiency, reduced maintenance costs, and extended equipment lifespans.