Self-aligning roller bearings are widely used in paper-making machinery, primarily to support the rotation of rollers. They are suitable for high-temperature and high-humidity environments such as the wet section, dry section and finishing section, and offer the benefits of long-term lubrication and stable operation. Their specific applications and advantages are as follows:
Key Applications
Wet End Equipment
Headbox: Agitators and distributors require high-precision, low-friction bearings to ensure uniform pulp distribution. Self-aligning roller bearings reduce friction and improve agitation efficiency by optimising the contact angle between the rollers and the raceway.
Wire Rollers: Chest rolls, press rolls and other components support the forming wire and bear the tension of the paper sheet and wire fabric. The line-contact design of self-aligning roller bearings (such as cylindrical roller bearings) can withstand high radial loads, preventing roller deformation and ensuring the quality of pulp dewatering and forming.
Vacuum headbox: The rotating suction roll operates under high-vacuum conditions, placing extremely high demands on bearing sealing and wear resistance. Self-aligning roller bearings utilise special sealing structures (such as labyrinth seals) and hardened raceways to prevent the ingress of air and impurities, thereby extending service life.
Press Section Equipment
Press rolls: These rotate in pairs to compress the paper sheet for dewatering and to enhance strength, withstanding immense pressure and friction. Self-aligning roller bearings, with their special roller configurations (such as barrel-shaped rollers) and reinforced cages, can withstand radial loads of tens of tonnes and automatically self-align in the event of minor shaft misalignment, thereby preventing uneven pressing.
Drying Cylinders: Hollow cylinders made of cast iron, through which steam is passed to heat and dry the paper sheet. Drying cylinder bearings must withstand high temperatures (up to 200°C) and high rotational speeds (approximately 250–300 r/min). Self-aligning roller bearings achieve dimensional stability at high temperatures and reduce the risk of inner ring cracking through the use of special steels (such as vacuum-melted carburised steel) and surface hardening treatments, whilst employing a centralised oil lubrication system (such as CLP 150 lubricant) to lower operating temperatures.
Guide and pressure rolls: These assist in paper sheet transport and require bearings with both rotational flexibility and load-bearing capacity. A combination of self-aligning roller bearings and cylindrical roller bearings is used, with the former handling radial loads and the latter providing axial positioning, ensuring stable paper sheet transport and preventing creasing or paper breaks.
Finishing section equipment
Calender: Multiple sets of calender rolls enhance sheet smoothness and gloss through high-pressure compression. Self-aligning roller bearings optimise the contact angle between the rollers and raceways, withstanding combined axial and radial loads to ensure the parallelism and coaxiality of the calender rolls, thereby achieving uniform pressure application.
Winding machine: The winding rollers require uniform tension control. Self-aligning roller bearings (such as flanged spherical roller bearings) can compensate for installation errors or shaft deflection. When combined with high-precision tension control roller bearings, they prevent paper creasing or breakage.
二、Technical Advantages
High Load Capacity
Self-aligning roller bearings feature a double-row roller design, capable of withstanding both radial and bidirectional axial loads. They are suitable for heavy-duty applications (e.g. press roll loads up to 300 kN).
Self-aligning Capability
Allows for angular misalignment between the shaft and bearing housing of up to 1°–2.5°, compensating for shaft deflection or installation misalignment, preventing edge stress concentration and extending bearing service life.
High-Temperature and Corrosion Resistance
Through the use of special steels (such as Inconel 718) and surface treatments (such as carbonitriding), dimensional stability is maintained at temperatures up to 200°C, making them suitable for high-temperature environments such as drying cylinders.
Long-term Lubrication and Sealing Design
Filled with solid lubricants (such as special greases) to ensure long-term lubrication, combined with sealing structures (such as double-labyrinth seals) to prevent the ingress of water and contaminants, thereby reducing maintenance frequency.
Adaptation to Complex Operating Conditions
For environments involving high speeds (e.g. guide rollers up to 750 r/min), high humidity (relative humidity in the wet section exceeding 80%) or impact loads (e.g. wood chip extruders), the cage material (e.g. turned brass cages) and roller structure are optimised to enhance impact resistance.
