1. The “Dryer Cylinder Dilemma“ of Bearing Replacement in the Pulp & Paper Industry

The pulp and paper industry is a classic example of continuous production. From pulping, stock preparation, forming, pressing and drying to winding and rewinding, the entire paper production line operates 24/7 without interruption. Bearings in dryer cylinders, press sections, conveyors, pulpers and other critical equipment operate year-round under extreme conditions of high temperature (above 100°C), high humidity, chemical corrosion and continuous heavy loads. Split spherical roller bearings are the ideal solution for equipment requiring regular maintenance, such as paper machine dryer cylinders, chemical reactor agitator shafts, and marine propulsion shafts. Split roller bearings can also accommodate a high degree of shaft misalignment, making them ideal for use in heavy applications such as those within paper mills. Application examples from the paper and pulp industry include blowers and fans, mixers and agitators, dryer cylinders, drive and transmission shafts, and conveyor equipment.

When bearings in these machines fail, maintenance teams face a far more complex “dryer cylinder dilemma“ than ordinary industrial equipment – traditional solid bearing replacement requires disassembly of shafts, couplings, gearboxes and numerous surrounding components, and paper mill dryer cylinders are often located in high-temperature, confined, hard-to-reach locations – the entire replacement cycle takes days or even weeks, with downtime losses reaching millions.

Taking a South African recycled fiber tissue paper mill‘s dryer cylinder bearings as an example: the dryer cylinders operate long-term in ambient temperatures constantly exceeding 100°C, originally using bronze-bush bearings that required frequent maintenance and replacement. Traditional solid roller bearing replacement requires removing gears, couplings, drive units and even the entire dryer cylinder shaft – extremely long downtime. Split roller bearings can be installed directly on-site without lifting the shaft or accessing the shaft ends, eliminating the need for expensive and awkward lifting equipment.

Typical pain points of traditional solid bearings in the pulp and paper industry:

High-temperature conditions accelerate bearing wear – Dryer cylinder bearings operate long-term at temperatures above 100°C. Under these conditions, ordinary bearing materials experience hardness decline and grease carbonization, significantly shortening bearing life. Traditional bronze-bush bearings wear rapidly at high temperatures, requiring frequent replacement.

High humidity and chemical corrosion – From the wet end to the dry end, paper production lines involve high humidity and chemical agents (sizing agents, bleaching agents, acid/alkali solutions). Ordinary bearing steel corrodes rapidly in humid and chemically corrosive environments, and seals age and fail.

Dryer cylinder shaft thermal expansion – Dryer cylinders experience significant thermal expansion during operation due to high temperatures. Traditional solid bearings cannot effectively accommodate shaft thermal expansion, often generating additional internal stresses that accelerate bearing failure.

Inaccessible equipment locations – Dryer cylinder bearings are located at both ends of cylinders, often enclosed within the dryer or between narrow frames. Lifting equipment cannot access these locations, and maintenance personnel working space is extremely limited.

Enormous disassembly workload – Traditional solid bearing replacement requires removing gears, couplings, drive units, dryer shaft seals and numerous other surrounding components – each maintenance session takes extremely long.

Downtime causes enormous losses – Paper production lines operate 24/7 continuously – one day of unplanned downtime can cost millions. For high-speed paper machines such as tissue machines, downtime losses are even greater.

2. NMT Split Bearings for the Pulp & Paper Industry: No Dryer Removal, No Shaft Removal, Quick Bearing Replacement

NMT split bearings for the pulp and paper industry perfectly combine the core advantage of split bearings – “no-shaft-removal installation“ – with the special requirements of paper mill equipment. The inner ring, outer ring, rolling elements and cage are all split along the axial direction – installation requires no removal of shafts, couplings, gearboxes or any other core components – assembly is completed directly on the shaft in situ.

More critically – NMT split bearings can be replaced without removing dryer cylinders, without moving shaft systems, without using large lifting equipment. The principle of split roller bearing design allows for complete bearing removal and replacement by simply supporting the shaft. There is no need to lift the shaft, or obtain access to the shaft ends, and therefore, expensive and awkward to handle lifting equipment is not required. This is like installing a “service door“ on paper mill equipment, enabling true “online“ maintenance. Compared to traditional solid bearings, split bearings can reduce maintenance time by over 80%.

▸ Full Split + High-Temperature Corrosion-Resistant Construction: Every Piece Can “Go in Separately, Rotate Together“ – Withstanding Paper Mill Conditions

Every component of an NMT split bearing for the pulp and paper industry is split – split inner ring, split outer ring, split cage with rolling elements, split seals. During installation, these half-ring components are assembled sequentially around the shaft. After being locked with high-strength stainless steel bolts, they form a precision transmission unit with performance fully equivalent to a solid bearing. Precision step-type mating or V-shaped split joint design at the split interfaces ensures load capacity and rotational precision equal to solid bearings.

In terms of materials, NMT offers a complete heat-resistant and corrosion-resistant steel system for paper industry high-temperature, high-humidity, chemical corrosion applications – carburized bearing steel with deep-case hardening achieves uniform surface hardness HRC60-64 while the core maintains sufficient toughness to absorb impact loads. For high-temperature applications such as dryer cylinders, heat-resistant steel and thermal stabilization treatment are available. For high-humidity and chemical environments in the wet end, stainless steel (304/316L) is available, resisting sizing agents, bleaching agents and acid/alkali solutions. Split bearings effectively block moisture, chemical splash and fiber dust intrusion in paper mills, protecting internal precision components. Some split roller bearings feature bored pocket machined brass cages as standard, outperforming designs with parallel rollers and weaker aluminum cages.

▸ Accommodating Dryer Cylinder Shaft Thermal Expansion: Inner Race and Rollers Move Freely Relative to the Outer Race

NMT split bearings are specifically designed to accommodate thermal expansion of dryer cylinder shafts under high-temperature conditions. Split roller bearings accommodate shaft thermal growth by the movement of the inner race and rollers relative to the outer race of the bearing. This arrangement permits a high degree of unrestricted axial movement within the bearing envelope, allowing for thermal expansion of the shaft whilst avoiding additional stresses within the bearing. Standard bearing operating temperatures up to 140°C are possible without problems.

▸ No-Shaft-Removal Installation: No Dryer Removal, No Coupling Removal, No Large Lifting Equipment

The core value of NMT split bearings for the pulp and paper industry is – bearing replacement without moving the shaft, without removing dryer cylinders and couplings, without using large lifting equipment. This means for dryer cylinder bearing replacement, the dryer stays in place, couplings stay in place, drive units stay in place. Maintenance personnel simply open the bearing housing, remove the old bearing halves, install the new bearing halves, and tighten the bolts – complete. No crane rental is required, no disassembly of the entire drive structure – significantly reducing maintenance labor and equipment lifting costs. The plant manager at Lothlorien‘s paper mill in South Africa commented: “To replace a typical solid roller bearing can take days, while split roller bearings can be replaced in just hours“. About 70% of the bearings supplied are for conversion applications where solid conventional roller bearings are being removed and the application converted to split roller bearings to save bearing fitting time and improve machine up-time and maintenance efficiency.

▸ Interchangeable with Standard Heavy-Duty Solid Bearings: Seamless Replacement, No Modifications

NMT split bearings for the pulp and paper industry are designed with full interchangeability with standard heavy-duty solid bearings in mind. In most cases, the outer diameter and outer ring width of split bearings are identical to standard spherical roller bearings (222, 230, 231, 239, 240, 241 series). Split spherical roller bearings can be installed in split plummer block housings without additional machining. This means paper mills can directly replace existing solid bearings in their equipment with NMT split bearings without any modifications to bearing housings.

3. Full Series Split Bearing Types for the Pulp & Paper Industry

NMT offers a complete split bearing product system covering multiple paper mill equipment applications:

▸ Pulp & Paper Split Spherical Roller Bearings

Split spherical roller bearings are the most widely used split bearing type in paper mills, capable of withstanding heavy loads (primarily radial loads with some axial load capacity) and impact loads, adapting to harsh conditions. NMT split spherical roller bearings are specifically designed for dryer cylinders, press sections, conveyors and other heavy-load applications – inner rings, outer rings and cages with rollers are all split in half. Spherical outer ring raceways and barrel-shaped rollers provide self-aligning capability, effectively compensating for shaft deflection and installation errors. Self-aligning performance is equivalent to solid spherical roller bearings, compensating for shaft deflection or installation errors and avoiding abnormal wear from misalignment. Widely used in paper mill dryer cylinders, press rolls, guide rolls, conveyors, pulpers and other critical equipment.

▸ Pulp & Paper Split Cylindrical Roller Bearings

Split cylindrical roller bearings use cylindrical rollers to carry high radial loads, with extremely strong radial load capacity, low friction coefficient and low operating temperature rise. Inner and outer rings each split in half, with one or two rows of cylindrical rollers in a split cage. Optimized profiled cylindrical rollers with bored pocket machined brass cages as standard provide high load capacity and long life. Suitable for various paper mill conveyors, roller tables, fans and other equipment. Split cylindrical roller bearings can accommodate a high degree of shaft misalignment, making them ideal for use in heavy applications such as those within paper mills.

▸ Pulp & Paper Split Tapered Roller Bearings

NMT split tapered roller bearings feature two rows of opposed tapered rollers, capable of simultaneously bearing radial and bidirectional axial loads, specifically designed for combined loads. Suitable for paper mill press sections, crushers and other bearing positions requiring combined loads.

▸ Split Housed Bearing Units

NMT offers split housed bearing units that integrate split bearings and housings as a complete assembly. Housings feature split design with upper and lower halves, including high-strength fastening bolts, seal caps, adjustment shims and other components. The housing can swivel around the shaft, ensuring that the seals always remain concentric to the shaft, thus further extending the potential life of the bearing, as contaminants are effectively excluded. Widely used in paper mill conveyors, fans, dryer cylinders and other equipment. Split roller bearings installed through split housed bearing units can significantly shorten downtime caused by replacing standard roller bearings in paper mill equipment.

4. Specialized Sealing and Lubrication Systems – Adapting to High Temperature, High Humidity and Chemical Splash Environments

Paper mill equipment operates year-round under harsh conditions of high temperature, high humidity, chemical splash and fiber dust. NMT split bearings for the pulp and paper industry feature customized sealing and lubrication systems:

▸ Heavy-Duty Labyrinth Seal Structure – Non-contact design using centrifugal force from rotation to expel moisture, fiber dust and chemical contaminants. Maintains reliable sealing in moisture-laden paper mill environments, effectively blocking steam, condensate, sizing agents and bleaching agents while preventing grease leakage.

▸ Contact Seal Upgrade – For high-humidity, high-contamination environments (wet end, press sections, pulpers), NMT offers contact seal upgrade options. Seals maintain elasticity at high temperatures without hardening or cracking. Paired with well-sealed bearing housings, they effectively prevent contaminant intrusion and grease leakage. Seals in split housed bearing units always remain concentric to the shaft, effectively excluding contaminants.

▸ High-Temperature Seal Materials – For dryer cylinder high-temperature radiation environments, NMT uses high-temperature seal materials that withstand continuous temperatures above 100°C and peak temperatures up to 140°C.

▸ Split Seals – Seals are also split for installation without shaft threading, assembled simultaneously with the bearing.

5. Installation and Maintenance – An Efficiency Revolution from “Days“ to “Hours“

Installation Time Comparison:

Traditional paper industry solid bearing: Shutdown → remove gears, couplings, drive units → move dryer shaft → slide bearing on → realign → reassemble → recommission. Typical time: days.

NMT split bearing: Shutdown → open bearing housing → remove old halves → install new halves → tighten bolts → complete. Typical time: just hours.

NMT split bearings for the pulp and paper industry can reduce bearing replacement downtime by over 80%. Taking the Lothlorien tissue paper mill dryer cylinder bearings in South Africa as an example: traditional solid roller bearing replacement takes days, while SRB split roller bearings can be replaced in just hours. Split roller bearing installation requires no lifting of the shaft or access to shaft ends – eliminating expensive and awkward lifting equipment. The mill‘s dryer cylinder bearings have successfully operated for over three years at ambient temperatures exceeding 100°C.

Maintenance Convenience:

No large lifting equipment required – Bearings are handled in sections – no large cranes needed. Only shaft support is required for replacement.

No dryer or coupling removal – Dryers and drive systems stay in place.

Inspect anytime – Bearing housing can be opened for inspection without disassembly.

Split handling – Bearings can be disassembled into smaller components, simplifying lifting and handling – especially suitable for confined spaces at dryer cylinder ends.

No on-site adjustment – Clearances are preset at the factory – no on-site adjustment or specialized tools required.

Accommodates shaft thermal expansion – Inner race and rollers move freely relative to the outer race, adapting to dryer cylinder high-temperature thermal expansion.

6. Quality Control – Triple Assurance of Split Precision, Heavy-Duty Heat Resistance and Seal Reliability

NMT implements a strict quality control system for pulp and paper industry split bearings:

Heavy-duty heat-resistant material certification – Each batch of bearing steel undergoes high-temperature hardness testing and impact load inspection to ensure performance meets paper mill high-temperature heavy-load requirements.

Precision split surface machining – High-precision wire cutting for inner and outer ring split surfaces, ensuring concentricity and strength after assembly.

High-strength locking system – High-strength steel clamp rings and multiple bolts ensure split surfaces remain secure during operation. In most split spherical roller bearings, the clamp ring is integrated into the inner ring.

Seal performance verification – Each batch undergoes high-temperature high-humidity environment seal testing to ensure sealing effectiveness under harsh paper mill conditions.

Post-assembly precision inspection – Each split bearing is inspected for radial clearance, rotational accuracy and vibration after assembly – ensuring performance equivalent to solid bearings.

7. Stock Availability + Customization – Rapid Response to Paper Mill Emergency Needs

Common paper industry split bearing models (split spherical roller bearings, split cylindrical roller bearings, split tapered roller bearings) kept in stock – Covering over 80% of split bearing needs for dryer cylinders, press sections, conveyors, pulpers and other applications. Emergency failures receive rapid response – minimizing unplanned downtime.

Custom solutions available – Special bore/OD/width (standard range 55mm to 630mm, expandable), custom heat-resistant and corrosion-resistant materials (carburized bearing steel/heat-resistant steel/stainless steel), special split configurations, custom sealing solutions (high-temperature labyrinth/Taconite seals/contact seals), custom clearance, split housed bearing units.

Rapid customization from samples or drawings – Provide old bearing samples or equipment drawings – NMT completes surveying and custom production quickly. About 70% of the bearings supplied are for conversion applications where solid conventional roller bearings are being replaced. Cost-effective replacement for imported brands (SKF Cooper, FAG, Timken, NSK) with significant procurement savings.

8. Lifecycle Cost Optimization – No Dryer Removal, No Shaft Removal, Save Millions in Downtime Losses

Unplanned downtime in the pulp and paper industry often costs tens of millions or even hundreds of millions of yuan. Taking dryer cylinder bearing replacement as an example: traditional solid bearing replacement requires days of downtime – paper production lines operate 24/7, with one day of downtime costing millions. After the Lothlorien tissue paper mill in South Africa replaced traditional bronze-bush bearings with split roller bearings, the dryer cylinder bearings have successfully operated for over three years at ambient temperatures exceeding 100°C. Split bearings can reduce replacement time from days to hours, significantly reducing downtime losses.

Hidden costs of cheap heavy-duty solid bearings:

Dryer cylinder replacement requires days of downtime – downtime losses are hundreds or even thousands of times the bearing price.

Disassembly of gears, couplings and drive units is time-consuming and may cause secondary damage.

Ordinary bearings have limited life at high temperatures – frequent replacement compounds the above losses.

Dryer cylinder shaft thermal expansion generates additional internal stresses in ordinary bearings, accelerating failure.

Lifting equipment cannot access confined spaces at dryer cylinder ends – hoisting costs and time increase significantly.

NMT split bearings for the pulp and paper industry deliver “no dryer removal, no shaft removal, quick bearing replacement without production stoppage“ in dryer cylinders, press sections, conveyors and pulpers:

Downtime reduced by over 80% – From days to hours – annual unplanned downtime losses dramatically reduced.

No dryer or coupling removal – Dryers and drive systems stay in place.

No large lifting equipment required – Bearings are handled in sections – only shaft support is required for replacement.

Heat-resistant steel withstands high temperatures and thermal expansion – Carburized bearing steel and deep hardening resist high temperatures – the split structure accommodates shaft thermal expansion through inner race and roller movement relative to the outer race.

Corrosion-resistant materials resist high humidity and chemical attack – Stainless steel or anti-corrosion coatings effectively resist sizing agents, bleaching agents, acid/alkali solutions and other corrosive environments.

Superior sealing for high-humidity high-dust environments – Effectively isolates moisture, fiber dust and chemical contaminants – protecting internal precision components.

Extended life of配套 equipment (gears, couplings, drive units) – Fewer disassembly cycles – longer overall equipment overhaul intervals.

For paper manufacturers, pulp mills, tissue producers and various paper product facility maintenance departments, the total cost of ownership with NMT split bearings for the pulp and paper industry is significantly lower than the repeated disassembly and replacement costs of traditional heavy-duty solid bearings – what you save is not bearing price difference, but the enormous operational risk of “replacing one bearing, shutting down an entire production line“ in paper equipment.