Slewing Ring Bearing

Product Specifications

Technical details and manufacturing context for Slewing Ring Bearing

Definition

A slewing ring bearing is a large-diameter rotational component used in machinery to support combined axial, radial, and tilting moment loads while allowing controlled rotation between a stationary and a rotating structure. It serves as the critical interface in rotational bearing assemblies, enabling 360-degree rotation with high load capacity. The bearing consists of inner and outer rings with raceways that contain rolling elements, typically balls or rollers. These elements reduce friction during rotation and transmit loads while maintaining precise alignment between connected components. Slewing ring bearings are commonly used in applications such as cranes, excavators, wind turbines, and medical equipment, where smooth, reliable rotation under heavy loads is essential. They are available in various designs, including single-row ball, double-row ball, and roller types, each suited to specific load and performance requirements. The materials used are typically alloy steel or bearing steel, chosen for their strength and wear resistance. Key parameters include outer diameter, inner diameter, axial load capacity, radial load capacity, tilting moment capacity, rotational speed, operating temperature, radial runout, axial runout, weight, ingress protection, and gear hardness. These parameters are provided as reference ranges and must be verified for the specific model and application. Standards such as ISO 76 for static load ratings and ISO 1101 for geometric tolerances are used as procurement references. It is essential to confirm model-specific values and standards with the legal manufacturer or supplier before selection.

Working Principle

The slewing ring bearing operates by using rolling elements, such as balls or rollers, arranged in raceways between the inner and outer rings. These elements reduce friction during rotation, allowing one structure to rotate relative to another with minimal resistance. The bearing transmits axial, radial, and moment loads through the rolling elements, which are designed to handle combined loads. The raceways are precisely machined to maintain alignment and distribute loads evenly. The bearing can accommodate continuous rotation or oscillation, depending on the application. The rolling elements are typically separated by a cage to prevent contact and ensure smooth operation. The bearing's design allows for high load capacity and durability, making it suitable for heavy-duty machinery.

Common Materials

Alloy Steel, Bearing Steel

Technical Parameters

Parameter	Typical range	Notes & selection driver
Outer Diameter	200–6000 mm	Standard range; larger sizes on request
Inner Diameter	100–5500 mm	Must be smaller than outer diameter
Axial Load Capacity	20–5000 kN	Static load ratingISO 76
Radial Load Capacity	15–3000 kN	Static load ratingISO 76
Tilting Moment Capacity	10–5000 kN·m	Static load ratingISO 76
Rotational Speed	0.5–10 rpm	For continuous rotation; higher for oscillation
Operating Temperature	-40–85 °C	Standard seals; extended range available
Radial Runout	0.05–0.5 mm	Depends on diameter and precision classISO 1101
Axial Runout	0.05–0.5 mm	Depends on diameter and precision classISO 1101
Weight	50–5000 kg	Approximate; varies with size and design
Ingress Protection	IP54–IP65	Higher IP available with special sealsIEC 60529
Gear Hardness	45–60 HRC	For slewing rings with gear teeth

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM

Inner Ring Part
Provides mounting surface for stationary structure and contains raceway for rolling elements

Material: Alloy Steel
Outer Ring Part
Provides mounting surface for rotating structure and contains raceway for rolling elements

Material: Alloy Steel
Rolling Elements Part
Balls or rollers that reduce friction between rings during rotation

Material: Bearing Steel
Cage/Spacer Part
Maintains proper spacing and alignment of rolling elements

Material: Steel or Polymer
Seals Part
Protect internal components from contamination and retain lubrication

Material: Rubber or Synthetic Polymer

Application & selection

Application Fit & Sizing Matrix

Operational Limits

pressure:	Max contact pressure: 4000-6000 MPa depending on material and design
other spec:	Max rotational speed: 0.5-5 rpm (varies with diameter), Load capacity: Axial: 100-10,000 kN, Radial: 50-5,000 kN, Moment: 100-20,000 kNm
temperature:	-40°C to +120°C (standard), up to +200°C with special materials

Media Compatibility

✓ Industrial machinery (cranes, excavators) ✓ Wind turbine yaw/pitch systems ✓ Solar tracking systems

Unsuitable: High-speed continuous rotation applications (>30 rpm)

Sizing Data Required

Maximum axial/radial/moment loads (kN/kNm)
Required rotational speed and duty cycle (rpm, intermittent/continuous)
Mounting dimensions and space constraints (bore diameter, overall height)

Risk, maintenance & compliance

Reliability & Engineering Risk Analysis

Failure Mode & Root Cause

Spalling and Pitting

Cause: Fatigue due to cyclic loading, improper preload, or contamination ingress leading to surface-initiated cracks and material flaking on raceways or rolling elements.

Corrosion and Fretting Wear

Cause: Exposure to moisture, corrosive environments, or inadequate sealing, combined with micro-movements under load, resulting in surface degradation and loss of material integrity.

Maintenance Indicators

Abnormal grinding or clicking noises during rotation, indicating potential damage to rolling elements or raceways.
Visible excessive play or wobble in the bearing assembly, suggesting wear, loss of preload, or structural issues.

Engineering Tips

Implement regular lubrication schedules with high-quality, environment-appropriate grease, ensuring proper sealing to prevent contamination and maintain film strength.
Conduct periodic alignment and preload checks to ensure even load distribution, reducing stress concentrations and preventing premature fatigue failures.

Indicative industry ranges for design and RFQ preparation. Confirm the exact figures and applicable standard with the manufacturer before specifying.

Compliance & Manufacturing Standards

Applicable Standards

ISO 1132-1:2000 - Rolling bearings - Tolerances - Part 1: Terms and definitions ANSI/ABMA 7:2015 - Shaft and Housing Fits for Metric Radial Ball and Roller Bearings DIN 5412-1:2016 - Rolling bearings - Tapered roller bearings - Boundary dimensions and series designations

Quoted from the published standard.

Manufacturing Precision

Bore diameter tolerance: H7 (+0.025mm to +0.000mm)
Raceway runout tolerance: 0.05mm maximum

Quality Inspection

Hardness testing (Rockwell C scale) for raceways and rolling elements
Ultrasonic testing for internal defects in forged components

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

Check the legal entity, factory address, ownership, certifications, and direct contacts.

Compare the published product scope and source details, then include your specifications and quantity in an enquiry.

Manufacturers of Slewing Ring Bearing

7 companies list this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.

XZWD Slewing Bearing Co., Ltd.

Xuzhou, Jiangsu (per official site), CN

The official single-row four-point contact ball slewing bearing page lists slewing bearings for tower cranes, replacement slewing bearings for excavators and truck crane slewing bearings with external gear; the production capacity page on the same site states XZWD Slewing Bearing has three plants (two operating, one under construction), diameters of 200–5000 mm, monthly output of 5,000 slewing bearings and over 230 employees. Confirm model dimensions, gearing and loads by drawing; customers and certifications are the company's own claims.