Double Row Self-aligning Ball Bearing

I. Product Overview​

Double-Row Self-Aligning Ball Bearings (abbreviated as DRSABB) are a core category in the self-aligning ball bearing family, designed specifically for heavy-load scenarios with significant shaft system misalignment. Upgraded from single-row self-aligning ball bearings, they feature a "double-row steel balls + shared spherical raceway" structure, with core advantages of dual characteristics: "high radial load-carrying capacity + strong self-aligning capability". They can automatically compensate for angular deviations of 1°-3° (up to 3.5° for some large-sized models) caused by installation errors, shaft bending, or misaligned bearing housings in the shaft system. Meanwhile, their radial load-carrying capacity is 60%-100% higher than that of single-row self-aligning ball bearings of the same size, making them key transmission components for complex working conditions requiring "heavy loads + poor alignment".​

The outer diameter of these bearings typically ranges from 20mm to 500mm, and the inner diameter covers 10mm to 250mm, with a basic dynamic load rating of 8kN-350kN-far exceeding that of single-row models. Structurally, they adopt a design of "inner ring with double-row spherical raceways + outer ring with single spherical raceway + double-row steel balls". Primarily intended to bear radial loads, they can also withstand small bidirectional axial loads (axial rated load is approximately 20%-35% of the radial rated load). They are suitable for harsh scenarios such as heavy-duty motors, mining machinery, and metallurgical equipment, where both heavy-load transmission and shaft system misalignment exist.​

Compared with single-row self-aligning ball bearings, double-row models have a slightly lower limiting speed (grease-lubricated limiting speed: 6,000-15,000 r/min). However, through the coordinated load-bearing of double-row steel balls, their impact resistance is improved by over 40%, enabling stable operation under working conditions with frequent start-stops and large load fluctuations. This effectively solves the problem of overload failure of single-row models in heavy-load scenarios, reducing the equipment downtime failure rate by more than 50%.​

II. Core Structure and Design Features​

1. Precision Structural Composition​

The four core components of double-row self-aligning ball bearings are optimized to meet the triple requirements of "heavy-load bearing, self-alignment, and impact resistance", ensuring reliable operation under complex working conditions:​

Inner Ring: Adopts a double-row symmetrical spherical raceway structure. Two parallel spherical arc raceways are machined on the outer surface of the inner ring to provide precise guidance for the double-row steel balls. The inner bore of the inner ring is a cylindrical surface (some models have a tapered bore, suffix K, suitable for installation with adapter sleeves), connected to the shaft via an interference fit. The preferred material is SUJ2 high-carbon chromium bearing steel, which undergoes "integral forging + carburizing and quenching + ultra-precision grinding" processes. The surface hardness reaches HRC 62-65, and the raceway surface roughness is Ra ≤ 0.08μm, ensuring uniform force distribution on the double-row steel balls. For large-sized heavy-load models (outer diameter ≥ 300mm), 20CrNiMo alloy carburized steel is used, which increases core toughness by 35% and significantly enhances impact resistance.​

Outer Ring: The inner surface of the outer ring is a shared spherical raceway, with the center of the spherical curvature coinciding with the bearing axis. This provides a unified "swinging space" for the double-row steel balls and serves as the core structure for realizing the self-aligning function. The wall thickness of the outer ring is 25%-30% thicker than that of single-row models, greatly improving deformation resistance and preventing outer ring cracking under heavy loads. Some models are equipped with an annular lubrication groove and 3-5 oil holes (suffix /W33) on the outer ring, facilitating grease replenishment via high-pressure lubrication systems and extending the maintenance interval. For extreme heavy-load models, the outer ring adopts a "thickened wall + enhanced forging" process, increasing radial stiffness by 20% compared to ordinary double-row models.​

Rolling Elements (Double-Row Steel Balls): Feature a symmetrical configuration of high-purity double-row steel balls. The diameter of the steel balls is 10%-20% larger than that of single-row models of the same size, and the quantity is 1.8-2 times that of single-row models. Through coordinated load-bearing of the double rows, radial loads are distributed to reduce the force on individual steel balls. The material used is GCr15SiMn ultra-fine grain bearing steel, processed through "vacuum degassing + precision forging + nano-level polishing". The roundness error is ≤ 0.15μm, and the surface hardness is HRC 62-64, ensuring uniform contact with the spherical raceways. For high-corrosion scenarios (e.g., chemical equipment), silicon nitride ceramic balls are optional, which improve acid and alkali corrosion resistance by 90% and are suitable for harsh environments.​

Cage: Classified into two types based on speed and load requirements:​

For medium-low speed heavy-load scenarios (rotational speed ≤ 10,000 r/min), solid brass cages (HPb59-1) are used, offering excellent wear resistance, heat dissipation, and impact load resistance;​

For medium-high speed scenarios (rotational speed ≤ 15,000 r/min), reinforced nylon cages (PA66 + 30% glass fiber) are used, which are 40% lighter than brass cages and have a friction coefficient as low as 0.002-0.003.​

The cage pockets adopt a "double-row symmetrical design", with the clearance between the cage and steel balls controlled at 0.15mm-0.25mm to avoid noise caused by steel ball movement during high-speed operation, with no-load noise ≤ 52dB.​

2. Key Design Characteristics​

High Radial Load-Carrying Capacity and Impact Resistance: With coordinated load-bearing of double-row steel balls, the radial basic dynamic load rating is 60%-100% higher than that of single-row self-aligning ball bearings of the same size (e.g., Model 2220 (100mm inner diameter, 180mm outer diameter) has a basic dynamic load rating of 195kN, while the same-sized single-row Model 1220 only has 105kN). It can withstand instantaneous impact loads up to 5-7 times the rated load, making it suitable for heavy-load equipment such as mining crushers and metallurgical rolling mills.​

Wide-Range Self-Aligning Capability: The shared spherical raceway design of the outer ring allows angular deviations of 1°-3° in the shaft system (up to 3.5° for large-sized models with outer diameter ≥ 400mm). It can compensate for misalignment issues caused by misaligned bearing housing installation (coaxiality error ≤ 0.3mm) and shaft bending after long-term operation (deflection ≤ 0.2mm/m), avoiding local overload wear on the raceways.​

Adaptability to Harsh Installation Conditions: It has low requirements for installation accuracy. Even with a bearing housing parallelism error of ≤ 0.15mm/m and surface roughness Ra ≤ 3.2μm, it can still operate normally. It is suitable for heavy-duty equipment with limited processing accuracy, such as cast bearing housings and welded frames, reducing equipment manufacturing and installation costs.​

Long-Term Stable Operation: The double-row steel balls ensure uniform force distribution, resulting in low vibration (vibration acceleration ≤ 4m/s²)-30% lower than that of single-row models. Some sealed models (double-sided steel dust covers 2Z, double-sided contact seals 2RS) can block dust and impurities, achieving a maintenance-free period of 15,000-25,000 hours under normal working conditions and reducing equipment downtime for maintenance.​

III. Main Product Models and Classification​

1. Classification by Size and Load Rating​

Based on outer diameter and load-carrying capacity, double-row self-aligning ball bearings can be categorized as follows to accurately match different heavy-load scenarios:

2. Classification by Installation and Seal Method​

Double-Row Self-Aligning Ball Bearings with Cylindrical Bore (No Suffix): The inner ring has a standard cylindrical bore, directly connected to the shaft via an interference fit. Suitable for scenarios with high shaft diameter accuracy (e.g., precision heavy-duty motors).​

Double-Row Self-Aligning Ball Bearings with Tapered Bore (Suffix K/K30): The inner ring has a 1:12 (K) or 1:30 (K30) tapered bore, requiring installation with adapter sleeves (H) or withdrawal sleeves (AH) to facilitate adjustment of bearing clearance. Suitable for scenarios with large shaft diameters and limited installation space (e.g., drive shafts of mining crushers).​

Sealed Double-Row Self-Aligning Ball Bearings (Suffix 2Z/2RS): Suffix 2Z (double-sided steel dust covers) is suitable for dry and clean environments (e.g., machine tool spindles); suffix 2RS (double-sided nitrile rubber seals) has an IP54 dust and water resistance rating, suitable for humid, low-dust scenarios (e.g., water pumps, printing and dyeing machines).​

Double-Row Self-Aligning Ball Bearings with Lubrication Grooves (Suffix /W33): Equipped with an annular lubrication groove and multiple oil holes on the outer ring, suitable for long-term continuous operation scenarios requiring regular grease replenishment (e.g., conveyor rollers, rolls of metallurgical rolling mills).​

IV. Applicable Industries and Typical Applications​

With core advantages of "high radial load-carrying capacity + strong self-aligning capability", double-row self-aligning ball bearings are widely used in industrial fields with heavy loads and significant shaft system misalignment. Typical applications include:​

Mining Machinery Industry: Spindles of mining crushers (e.g., jaw crushers, suitable for Model 22324K with adapter sleeve installation), drive shafts of ball mills (suitable for Model 22330/W33, resistant to heavy loads and dust), and support shafts of vibrating screens (suitable for Model 22218, adaptable to high-frequency vibration and shaft system misalignment), ensuring continuous heavy-load operation of mining equipment.​

Metallurgical Industry: Rolls of metallurgical rolling mills (e.g., backup rolls of hot rolling mills, suitable for Model 22328, high-temperature and impact resistant), bearings of ladle turrets (suitable for Model 22340, withstanding extreme radial loads), and conveyor rolls of continuous casting machines (suitable for Model 22224/W33, adaptable to high temperatures and shaft deformation), meeting the high-temperature, heavy-load, and high-dust working conditions of the metallurgical industry.​

General Heavy Machinery Industry: Heavy-duty motors (e.g., asynchronous motors above 200kW, suitable for Model 22220, high radial load-carrying capacity), large centrifugal pumps (e.g., chemical process pumps, suitable for Model 2218K, tapered bore for easy installation), and output shafts of reducers (e.g., planetary gear reducers, suitable for Model 22216, impact load resistant), addressing heavy-load transmission and shaft system misalignment issues.​

Construction Machinery Industry: Auxiliary bearings for slewing rings of small excavators (suitable for Model 22222, vibration and impact resistant), gearbox shafts of loaders (suitable for Model 22214, load fluctuation resistant), and drive shafts of road rollers (suitable for Model 22318, high radial load-carrying capacity), adapting to complex outdoor working conditions of construction machinery.​

Other Heavy-Load Fields: Support rolls of large cement rotary kilns (suitable for Model 22344, extreme heavy loads), coal mills of heavy thermal power units (suitable for Model 22332/W33, high-dust environment), and drive shafts of port portal cranes (suitable for Model 22326K, tapered bore for easy maintenance), providing transmission support for heavy-load equipment in various industries.​

V. Summary of Product Advantages​

Outstanding High Radial Load-Carrying Capacity: Coordinated load-bearing of double-row steel balls significantly increases the radial rated dynamic load compared to single-row models, meeting the core transmission needs of heavy-load equipment, avoiding early bearing failure due to insufficient load-carrying capacity, and extending equipment service life.​

Strong Self-Aligning and Deviation Resistance: The shared spherical raceway design of the outer ring can compensate for 1°-3.5° angular deviations in the shaft system, adapting to working conditions with limited installation accuracy and easily deformable shafts, reducing reliance on equipment processing and installation accuracy, and lowering overall costs.​

Excellent Impact Resistance and Stability: Thickened outer rings, high-toughness materials, and double-row steel ball configuration improve impact resistance by over 40% compared to single-row models, enabling stable operation under conditions with large load fluctuations and frequent start-stops, with a failure rate controlled below 0.3%.​

Balanced Adaptability and Economy: Diversified installation methods (cylindrical bore/tapered bore), sealing solutions (2Z/2RS), and lubrication designs (/W33) can accurately match different heavy-load scenarios. Although the unit cost is higher than that of single-row models, there is no need for additional auxiliary bearings, reducing the overall transmission cost of equipment by 25%-30% and providing significant cost-effectiveness.

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