Reliability in Pulping & Preparation Equipment: High-Performance Bearing Solutions
Pulping and Preparation is the “heart” of the paper-making process. Its goal is simple: turn wood, recycled paper, or other fibers into clean, high-quality pulp. Key equipment in this stage includes Chippers, Pulpers, Digesters, Pressure Screens, and Bleaching Towers.
This stage has the harshest conditions in the entire mill. Bearings here face extreme threats: heavy shock loads in Chippers, extreme heat in Digesters, and constant water and chemicals in Washing and Bleaching lines. If a bearing fails here, the whole production line stops.
Standard bearings often fail quickly in these conditions. TFL Bearings offers engineered solutions designed specifically for pulp processing. We use special steel, high-temperature treatments, and advanced sealing technologies to handle these tough environments.
By switching to TFL solutions, mills can reduce unexpected breakdowns, extend the time between repairs (MTBF), and lower the total cost of producing each ton of pulp.
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Common Bearing Problems in Pulping
Why do bearings fail in the pulping process? Here are the most common reasons.
Common Problems List
| Failure Mode | What Happens? | Primary Causes |
| Corrosion & Rust | Rust spots on raceway; watery grease. | Water, acids, and chemicals get inside and destroy the steel. |
| Impact Damage | Dents or cracks in rings/rollers. | Sudden, heavy shocks from hitting hard wood or trash. |
| Contamination | Noisy operation; fast wear. | Fibers and dirt get past seals and act like sandpaper. |
| Heat Seizing | Bearing locks up; metal turns blue. | Heat over 150°C causes metal expansion, removing clearance. |
Application Analysis: Proven Solutions
We have specific bearing solutions for every critical machine in the pulping line.
Application 1: Chippers (Disc Shaft)
The Challenge:
The Chipper knife disc spins fast and hits wood logs hard. This creates massive shock loads and vibration. Standard bearings can crack or suffer from fatigue very quickly.
TFL Solution: Heavy-Duty Cylindrical Roller Bearings
- Tough Steel: Made from premium alloy steel with special heat treatment to resist cracking.
- Line Contact: The rollers make “line contact” with the raceway. This spreads the shock load over a larger area, making the bearing much stronger against impacts.
Application 2: Pulpers (Rotor & Impeller)
The Challenge:
Pulpers work in a wet, dirty soup of recycled paper and trash. The biggest threat is water and fiber ingress (getting inside the bearing) and irregular impacts from waste bales.
TFL Solution: Sealed & Hardened Bearings
- For Horizontal Pulpers: We use Stainless Steel Deep Groove Ball Bearings with high-performance seals (like triple-lip seals) to keep water out.
- For Secondary Pulpers: We use Heavy-Duty Tapered Roller Bearings with surface-hardened raceways. This resists wear from dirt and handles the heavy push-and-pull forces.
Application 3: Digesters (Agitators)
The Challenge:
Inside the Digester, it is hot (over 150°C) and pressurized. Metal expands when hot. If a standard bearing is used, it will expand, run out of room to move, and lock up (seize).
TFL Solution: High-Temp Spherical Roller Bearings
- C4 Clearance: We use bearings with “C4” internal clearance. This provides extra room for thermal expansion, so the bearing runs smoothly even when hot.
- Special Cages: We use stamped steel cages that do not melt or deform under high heat.
Application 4: Bleaching & De-inking
The Challenge:
Machines here sit in chemicals like ink, chlorine, and peroxide. These chemicals eat away at standard steel bearings.
TFL Solution: Ceramic Hybrid & Coated Bearings
- Ceramic Balls: We use Silicon Nitride (Ceramic) balls. They are harder than steel, create less friction, and never rust.
- Anti-Corrosion Coating: For shafts exposed to bleach fumes, we apply a special coating to the steel rings to stop chemical corrosion.
Application 5: Washers & Screens
The Challenge:
Filters and screens are constantly wet. Regular grease washes away easily, leading to metal-on-metal contact.
TFL Solution: Solid Lube Technology
- Maintenance-Free: We fill the bearing with a polymer matrix containing oil (Solid Lube). It cannot be washed out by water. This means you don’t need to re-grease, and the bearing is protected from moisture.
Product Overview: Quick Reference Guide
| Application Part | Bearing Type | Common Part Numbers (Examples) | Key Features |
| Chipper(Disc Shaft) | Cylindrical Roller Bearing | NU 2328 ECJ | NU: Handles expansion. EC: Extra capacity rollers. P/J: Tough cage for shocks. |
| Pulper (Rotor Drive) | Stainless Ball Bearing | SS-6316-2RS, SS-6220-2RS | SS: Stainless Steel body. 2RS: Rubber seals on both sides to stop water.. |
| Sec. Pulper (Impeller) | Tapered Roller Bearing | 32315 B, | 323xx: Steep angle for heavy combined loads. B: Optimized contact angle. |
| Digester (Agitator) | Spherical Roller Bearings | 22324 CC/W33 C4, 22232 CC/W33 C4 | C4: Large internal clearance for high heat (150°C+). CC: Steel cage suitable for heat. |
| De-inking (Flotation) | Ceramic Hybrid Bearings | 6212-2RS/HC5, 6310-2RS/HC5 | HC5: Ceramic balls (Non-corrosive). 2RS: Sealed against ink particles. |
| Bleach Tower (Agitator Shaft) | Self-Aligning Ball Bearings | 2210-2RS1, 2312-2RS1 | 22xx: Adjusts to shaft misalignment. 2RS1: Advanced sealing. |
| Pressure Screen (Rotor) | Precision Cylindrical Bearings | NN 3020 K/P5, N 1016 K/P4 | P5/P4: High precision for smooth spinning. K: Tapered bore for precise fit. |
| Washer (Filter Drum) | Solid Lube Spherical Bearings | 22222 E/W64, 23036 CC/W64 | W64: Solid Oil filling (Waterproof & Maintenance-free). |
Note: Final bearing selection depends on specific load, speed, and dimensional requirements. Please consult a TFL application engineer for a precise recommendation.
Investing in Reliability is an Investment in Productivity
The Pulping stage sets the quality for your entire paper mill. Using the wrong bearing in a Chipper or Digester might save a few dollars today, but it risks days of lost production tomorrow. TFL bearings are engineered to handle the heat, shock, and chemicals of the pulping process. Choose TFL for longer uptime and lower maintenance costs.