I. Product Positioning: Self-Aligning Heavy-Load Impact Bearings

In heavy equipment such as mining crushers, vibrating screens, metallurgical rolling mills, paper machinery and large fans, bearings face extremely harsh operating conditions. Long shafts inevitably deflect under their own weight and heavy loads; alignment between shafts and housings is difficult to achieve during installation; crushers and vibrating screens endure severe impact and vibration—the of these three adverse factors causes raceway crushing, cage fracture and early fatigue spalling in ordinary bearings under heavy impact, making them a regular failure. Spherical roller bearings are precisely designed for these complex conditions, with spherical outer ring raceways providing self-aligning capability to compensate for coaxiality errors and shaft deflection.

Developed with Japanese heavy-duty bearing design experience, NMT spherical roller bearings focus on harsh conditions in mining, metallurgy and heavy machinery. With spherical raceways and barrel-shaped rollers as the core structure—the outer ring raceway is spherical and rollers are barrel-shaped—the bearing possesses excellent self-aligning capability, automatically compensating for shaft deflection and installation misalignment, maintaining normal operation even when inner and outer rings are relatively inclined within 0.5° to 2°.

The double-row roller structure enables the bearing to simultaneously withstand radial loads and bidirectional axial loads, with load capacity far exceeding other bearing types of the same size. The precise coordination of spherical raceways and barrel-shaped rollers ensures uniform contact stress distribution across the raceway surface, with crowned rollers effectively eliminating edge stress concentration and greatly extending service life under heavy loads and impacts.

II. Core Technology: Gradient Carburising and Labyrinth Seals

NMT has deeply cultivated materials and heat treatment processes, employing gradient carburising—carbon concentration decreases smoothly from the surface inward. This treatment provides extremely high spalling resistance on the contact surface while the core maintains excellent toughness for absorbing impacts. Modern spherical roller bearings generally adopt high-purity carburizing steel with advanced heat treatment processes, combined with optimised roller profile design and precision cages, significantly improving wear resistance and limiting speeds under high-speed heavy-load conditions. When heavy equipment undergoes millions of simulated acceleration and braking cycles, raceway wear depth curves are significantly smoother than ordinary bearings, with precision retention life notably extended.

By optimising the spherical radius of roller end faces, NMT forms a more stable contact geometry between rollers and rib flanges, enabling rollers to self-align under eccentric moments without leaving indentations on flange surfaces due to localised high pressure. This detail is particularly important in equipment such as crushers that endure frequent impacts—every impact-induced eccentric load is absorbed by the bearing's inherent geometric design rather than transmitted to adjacent structures.

In sealing structure design, NMT has shaped the outer edge of the cage into a labyrinthine曲折 channel, forming a dynamic barrier together with special grease. When the equipment rotates, centrifugal force throws grease toward the labyrinth exit, preventing external contaminants from entering the bearing interior. This adaptive sealing mechanism ensures bearing life is not significantly shortened by environmental factors when equipment operates in rugged, dusty mining environments.

EA high-capacity and EM general-purpose series are available in parallel. EA series maximises roller diameter and quantity for significantly increased rated load capacity with higher load capacity within the same installation space. EM series features one-piece solid brass cages offering balanced performance and wide applicability.

III. Installation and Clearance Adjustment: The Performance Key of Spherical Roller Bearings

The installation and clearance adjustment of spherical roller bearings directly determine bearing life and reliability under actual operating conditions. According to statistics, a considerable proportion of premature spherical roller bearing failures are caused by improper installation or incorrect use. The quality of installation conditions is often the primary factor affecting bearing life.

(1) Installation Environment and Preparation

Spherical roller bearings must be installed in dry, clean environmental conditions. Before installation, the fitting surfaces of shafts and housings, the end faces of shoulders, grooves and connecting surfaces should be carefully inspected for machining quality, and all fitting connecting surfaces must be thoroughly cleaned and burrs removed. Bearings should be cleaned with gasoline or kerosene and dried before use. For bearings that have been rust-prevented and packaged, do not open the packaging until immediately before installation.

(2) Installation Methods

Small and medium-sized bearings are mostly installed using cold mounting. During installation, uniform pressure must be applied on the circumference of the ring end face to press the ring into place. Hammers or similar tools must not be used to directly strike the bearing end face. The applied force should be steady and uniform without impact, and the resultant force should pass through the bearing axis as much as possible. Force must never be applied through the rolling elements—when mounting or dismounting the inner ring, force should be applied through the inner ring; when mounting or dismounting the outer ring, force should be applied through the outer ring.

When interference is large, oil bath heating or induction heating methods can be used for installation. The heating temperature range is generally 80°C-100°C, with a maximum not exceeding 120°C. Induction heating is currently the most commonly used method due to its controllability, efficiency and high safety. After heating installation, the bearing should be secured with nuts or other appropriate methods to prevent clearance between the ring and shaft shoulder caused by contraction in the width direction after cooling.

(3) Clearance Measurement and Adjustment

During spherical roller bearing installation, the reduction in radial clearance should be checked using feeler gauges. The clearance of both rows of rollers must be measured simultaneously, and the relative position of inner and outer rings must be adjusted to ensure the two values are approximately equal. After the radial clearance value of each row is qualified, the arithmetic mean of the two rows' clearance values is taken as the bearing's radial clearance value.

When installing large bearings on shafts, the outer ring may deform due to its own weight. If clearance is measured at the lowest point of the deformed bearing, the measured value may be greater than the actual clearance. In this case, half of the sum of clearances at two points on the horizontal line and the lowest point should be used as the installation clearance.

For tapered bore bearings, axial clearance can be adjusted through nuts, adjusting shims, threads in housing bores, or preload springs. The axial clearance size depends on the bearing arrangement during installation, the distance between bearings, and the materials of the shaft and housing, and can be determined according to operating conditions.

(4) Test Run

After bearing installation is completed, the specified lubricant should be added and a test run performed. Spherical roller bearings should not be started and accelerated to high speed under no-load conditions. A normally operating bearing will emit a uniform "growling" sound. During the test run, check for abnormal noise and whether bearing temperature is normal. It is normal for bearing temperature to rise immediately after start-up. With grease lubrication, the temperature will not drop until the grease is evenly distributed inside the bearing, after which it will reach equilibrium temperature. Abnormally high temperature or continuous large temperature rise indicates possible excessive lubricant, radial or axial deformation of the bearing, or insufficient clearance.

IV. Failure Modes and Root Cause Analysis

Failures of spherical roller bearings under harsh conditions often originate from the of multiple factors.

(1) Failures Due to Improper Installation

Improper installation is a significant cause of premature spherical roller bearing failure. Excessive or insufficient force during installation, uneven force application, force applied through rolling elements, or incomplete installation can all lead to abnormal stress states on bearing components, shortening service life.

(2) Failures Due to Improper Clearance

Insufficient bearing clearance is a common cause of failure. When bearing clearance is too small and the interference fit between shaft and housing is insufficient, the bearing is prone to overheating during operation. Under harsh conditions of heavy loads, high impact loads and heavy dust, bearing deflection during operation causes insufficient internal clearance, restricting rolling element movement space and affecting self-aligning function, leading to uneven load distribution and between rollers and raceways on one side. The friction between rollers and raceways generates  frictional heat that lubricating oil cannot remove, causing temperature rise that destroys the oil film and creates dry friction. The sharp temperature rise causes the subsurface layer of the inner ring raceway to exceed the austenitising temperature in a short time, resulting in secondary quenching. The temperature rise changes material structure and strength, and when stress exceeds the material's tensile strength, cracks form and eventually propagate to fracture.

(3) Failures Due to Material Defects

The presence of network carbides weakens the connection between metal matrix grains, reducing the mechanical properties of bearing steel, especially impact resistance. During forging, if overheating, overburning, internal cracking or network carbide formation occurs, the toughness and strength of rings will be reduced. As the severity of network carbides increases, both impact toughness and contact fatigue strength decrease.

(4) Failures Due to Poor Contact

Poor contact between the large end face of rollers and the large rib of the shaft ring can produce secondary quenching layers and high-temperature tempering layers at the poor contact area. The secondary quenched zone is in a compressive state, while the underlying high-temperature tempered zone material experiences maximum tensile stress, making it the most likely location for crack initiation.

(5) Cage Fracture

Cage fracture is one of the common failure modes of spherical roller bearings. When the axial displacement of the high-speed shaft of a reducer is large and the bearing outer ring has poor movement within the eccentric sleeve, the two rows of rolling elements experience uneven loading, and the rolling elements in the secondary loaded row impose additional impact loads on the cage, causing fatigue fracture. Another common cause of cage fracture is insufficient lubrication. Additionally, exceeding estimated loads, ineffective seals, and excessively small bearing clearance due to overly tight fits can also cause bearing damage.

V. Structural Classification and Functional Advantages

(1) EA Series High-Capacity Type

Optimised internal design and roller profiles with maximised roller diameter and quantity for significantly increased rated load capacity. Higher load capacity within the same installation space, suitable for heavy rolling mills, large crushers, ball mills and other equipment with extreme load capacity requirements.

(2) EM Series General-Purpose Type

Standard spherical roller bearings with one-piece solid brass cages, offering balanced performance and wide applicability, suitable for general mining equipment, conveying machinery, fans, paper machinery and other conventional heavy-load conditions.

(3) Sealed Spherical Roller Bearings

With sealing structure to effectively block dust, moisture and corrosive media intrusion. Labyrinth seal design combined with special grease forms a dynamic barrier, suitable for vibrating screens, crushers, outdoor conveyor equipment and other harsh environments with heavy dust and moisture.

(4) High-Temperature Spherical Roller Bearings

Special heat treatment and high-temperature grease adaptation for continuous operation at temperatures above 200°C. Suitable for hot rolling mills, drying equipment, sintering machines and other high-temperature conditions.

General advantages summary: Spherical raceways and barrel-shaped rollers provide self-aligning capability, compensating for shaft deflection and installation misalignment; double-row rollers carry radial and bidirectional axial combined loads; crowned rollers eliminate edge stress concentration; multiple cage options including machined brass, stamped steel and polyamide cages available.

VI. Two-Grade Material & Process Selection

Grade 1: Through-Hardened Bearing Steel (General Version)

Integral quenching and low-temperature stabilizing tempering achieve uniform overall hardness with consistent raceway and roller wear resistance. Suitable for general mining conveyor equipment, fans, paper machinery and other continuous stable heavy-load conditions, with outstanding cost performance for complete machine supporting.

Grade 2: Carburized Bearing Steel (Heavy-Duty Reinforced Version)

Inner rings, outer rings and rollers undergo deep carburizing quenching for hard wear-resistant surfaces with a tough impact-absorbing core. Applied to crushers, vibrating screens, hot rolling mills, ball mills and other impact-type heavy-load conditions, withstanding instantaneous peak loads to prevent raceway crushing and roller fracture, with significantly extended service life under extreme conditions.

VII. Japanese Precision Manufacturing Process

1. Vacuum degassing refining of high-purity special steel forging, controlling non-metallic inclusions to extremely low levels and eliminating fatigue crack initiation points;

2. Precision forging + gradient heat treatment, achieving uniform hardened layers on raceway surfaces with a strong tough core;

3. Spherical raceway ultra-precision grinding with precise spherical profile control, ensuring uniform load distribution between rollers and raceways across the full contact range;

4. Roller crowning machining—precise control of crowning profiles to optimise contact stress distribution and eliminate edge stress concentration;

5. Optimisation of roller end-face spherical radius—forming stable contact geometry between rollers and rib flanges, enabling self-alignment under eccentric moments;

6. Superfinishing grinding of inner and outer raceways for stable lubricating oil film formation;

7. Group matching of rollers with micron-level dimensional tolerance control for uniform load distribution;

8. Precision cage machining—EA series with stamped steel cages, EM series with machined brass cages;

9. Assembly in temperature-controlled dust-free workshops, with four full inspections before delivery: load test, vibration test, clearance test and temperature rise test.

All dimensions comply with national standards for direct interchange with mainstream spherical roller bearings. Clearance grades cover C0 to C5, and precision grades cover P0 to P2.

VIII. Seal Structure Matching for Working Conditions

1. Open Type : Maximum heat dissipation, suitable for high-speed fans, high-temperature rolling mills and other heavy-load applications requiring good cooling;

2. Single/Double-Sided Steel Dust Covers : Block large particle dust intrusion, suitable for mining conveyor equipment, general crushers and other dusty environments;

3. Labyrinth Seals (NMT Patent Design) : The outer edge of the cage is designed as a labyrinthine channel, forming a dynamic barrier with special grease. Centrifugal force throws grease toward the labyrinth exit, preventing external contaminants from entering. Suitable for vibrating screens, outdoor crushers, foundry and grinding workshops and other harsh environments.

IX. Technology Development Trends

Spherical roller bearing technology continues to evolve. With advancements in materials science and precision manufacturing, the life and reliability of spherical roller bearings have been significantly improved. In recent years, through optimisation of roller quantity and length and improved lubricant distribution,新一代 spherical roller bearings have achieved substantial increases in dynamic and static load ratings compared to traditional products.

Modern spherical roller bearings generally adopt high-purity carburizing steel with advanced heat treatment processes, combined with optimised roller profile design and precision cages, significantly improving wear resistance and limiting speeds under high-speed heavy-load conditions. High-performance bearings with long-life lubrication design and surface corrosion treatment have become core foundational components for ensuring continuous operation of critical industrial equipment and reducing maintenance costs.

With the development of high-end equipment manufacturing, spherical roller bearings will adopt more high-performance materials to increase load capacity and service life. With the application of IoT and smart sensing technology, spherical roller bearings will have self-monitoring and diagnostic capabilities, enabling remote monitoring and predictive maintenance to improve overall equipment operational efficiency.

X. Wide Application Fields

Mining Machinery: Cone crushers, jaw crusher main bearings, vibrating screens, ball mills, belt conveyor drums—withstanding enormous impact loads and severe vibration;

Metallurgical Equipment: Hot rolling mill work rolls and backup rolls, continuous casting machine roller tables, straighteners, sintering equipment—high-temperature heavy-load continuous operation;

Paper Machinery: Dryer cylinder bearings, press rolls, paper machine guide rolls—long-term reliable operation in high-temperature high-humidity environments;

Construction Machinery: Shield machine main bearings, large excavator slewing supports, concrete mixer trucks—heavy-load impact and harsh environments;

Fans & Ventilation Equipment: Large centrifugal fans, axial fans, high-temperature fan spindles—long-term continuous high-speed operation;

Cement & Building Materials Machinery: Vertical coal mills, rotary kilns, classifier spindles—dual challenges of heavy loads and high temperatures;

General Heavy Machinery: Large gearboxes, rubber and plastic machinery, marine propulsion systems.

XI. Brand Strength and Delivery Service

NMT has been dedicated to the research, development and manufacturing of precision bearings for over a decade. NMT continues to deepen its expertise in spherical roller bearings as a heavy-load category, optimising roller end-face spherical radius and rib flange contact geometry to enable self-alignment under eccentric moments. In sealing structure design, NMT shapes the outer edge of the cage into a labyrinthine channel, forming a dynamic barrier with special grease to adaptively prevent external contaminant intrusion. In heat treatment, NMT employs a differentiated heating strategy—raceway surfaces are rapidly heated to austenitising temperature and then quenched, while the core undergoes a relatively phase transformation, ultimately forming a uniform hardened layer with low retained austenite content.

NMT maintains sufficient spot inventory of mainstream spherical roller bearing specifications for urgent equipment repair and mass complete machine supporting with short lead time. Customisation services include special radial clearance (C0-C5), special precision grades (P0-P2), high/low temperature resistant materials, special sealing solutions (labyrinth seals/contact seals), special grease, non-standard sizes, EA high-capacity customisation, EM general-purpose configuration and more. Professional engineers provide targeted selection schemes based on equipment load spectrum, installation space, impact frequency and operating temperature to optimise bearing configuration, improve equipment reliability and durability under harsh conditions, extend maintenance intervals and cut the overall life cycle cost of equipment.