Editorial Technical Reference

Trunnion Ring

This page explains how Trunnion Ring is classified within Basic Metal Manufacturing. Technical values and manufacturer relationships are research references; confirm the current specification and supplier evidence for each order.

Technical Definition & Core Assembly

A heavy-duty structural ring that supports and enables the rotation of a Basic Oxygen Furnace vessel.

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Trunnion Ring in a manufacturing environment
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Product Specifications

Technical details and manufacturing context for Trunnion Ring

Definition
The trunnion ring is a critical load-bearing component of a Basic Oxygen Furnace (BOF) vessel assembly. It is a large, robust ring structure mounted to the vessel shell that interfaces with the trunnion pins or bearings on the furnace tilting mechanism. Its primary function is to transfer the immense weight of the vessel (including its refractory lining and molten metal charge) to the supporting structure while allowing the vessel to be tilted for charging, refining, and tapping operations. The ring is typically made of forged or cast alloy steel, with material grades such as ZG270-500 per GB/T 11352, offering tensile strength of 500–650 MPa and yield strength of 270–350 MPa. Key dimensions include bore diameter of 1500–3000 mm, outer diameter of 2000–4000 mm, thickness of 200–500 mm, and weight of 5000–20000 kg. Machining tolerance is ±0.05 mm (ISO 2768-m), surface roughness Ra 1.6–3.2 μm (ISO 1302), and operating temperature range -20 to 300°C. Non-destructive testing is 100% ultrasonic per GB/T 7233.1. The ring must withstand high static loads, dynamic stresses during tilting, and thermal stresses from the hot vessel. It is essential for the safe and efficient operation of the BOF, and its design and manufacturing require strict adherence to standards. Always verify model-specific values and standards with the legal manufacturer or supplier.
Working Principle
The trunnion ring is rigidly attached to the BOF vessel shell. It rotates on fixed trunnion pins or within large bearings that are part of the stationary furnace support structure. Hydraulic or electric drives apply torque to the ring (often via a gear attached to it), causing the entire vessel to tilt around its horizontal axis. The ring must withstand high static loads, dynamic stresses during tilting, and thermal stresses from the hot vessel. Its design ensures that the vessel can be tilted for charging, refining, and tapping operations while maintaining structural integrity.
Common Materials
Forged or Cast Alloy Steel
Technical Parameters
ParameterTypical rangeNotes & selection driver
Bore Diameter1500–3000 mmMatches BOF vessel trunnion shaft size
Outer Diameter2000–4000 mmDetermines bearing and housing interface
Thickness200–500 mmProvides structural rigidity
Weight5000–20000 kgAffects handling and installation
Material GradeZG270-500Cast steel with high strength and toughnessGB/T 11352
Tensile Strength500–650 MPaMinimum 500 MPa for structural integrityGB/T 11352
Yield Strength270–350 MPaEnsures elastic deformation under loadGB/T 11352
Hardness150–200 HBWBalances wear resistance and machinabilityGB/T 231.1
Machining Tolerance±0.05 mmCritical for bearing fitISO 2768-m
Surface RoughnessRa 1.6–3.2 μmSealing and fatigue lifeISO 1302
Operating Temperature-20–300 °CThermal expansion considered
Non-Destructive Testing100% UTUltrasonic testing for internal defectsGB/T 7233.1

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
  • Ring Body Part
    The main structural element, designed to handle bending moments and compressive loads.
    Material: Forged or Cast Alloy Steel
  • Mounting Flange Part
    The interface surface with bolt holes for attaching the ring to the BOF vessel shell.
    Material: Alloy Steel
  • Gear Teeth Segment (if applicable) Optional Part
    Machined teeth on the ring's outer circumference to engage with the drive pinion for tilting.
    Material: Hardened Alloy Steel
  • Bearing Surface Part
    The machined surface that contacts the trunnion pins or bearing pads, allowing rotation.
    Material: Hardened Alloy Steel

Application & selection

Application Fit & Sizing Matrix

Operational Limits
pressure: Atmospheric to 0.5 bar (7.25 psi) differential pressure
other spec: Max vessel weight: 300-500 metric tons, Rotation speed: 0.1-1.0 RPM, Slurry concentration: N/A (structural component)
temperature: Ambient to 400°C (752°F) continuous, 500°C (932°F) peak
Media Compatibility
✓ Molten steel/slag environment ✓ Industrial cooling water systems ✓ High-temperature lubricants (graphite-based)
Unsuitable: Chloride-rich environments (risk of stress corrosion cracking)
Sizing Data Required
  • Vessel weight and center of gravity
  • Required rotation angle and torque
  • Foundation/structural interface dimensions

Risk, maintenance & compliance

Reliability & Engineering Risk Analysis

Failure Mode & Root Cause
Fatigue cracking
Cause: Cyclic loading from rotational motion and uneven load distribution, exacerbated by stress concentrations at bolt holes or weld seams.
Wear and material loss
Cause: Fretting and abrasive wear at contact surfaces with rollers or bearings, often due to misalignment, inadequate lubrication, or contamination.
Maintenance Indicators
  • Visible cracks or spalling on the ring surface, especially near stress points
  • Abnormal noise (grinding, clicking) during rotation, indicating excessive clearance or contact issues
Engineering Tips
  • Implement regular alignment checks and laser alignment for trunnion support structures to minimize uneven loading and stress concentrations.
  • Establish a proactive lubrication schedule with high-temperature, extreme-pressure grease, and monitor for contamination to reduce wear at bearing contact surfaces.

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
ASTM A370 Standard Test Methods and Definitions for Mechanical Testing of Steel Products CE Marking (EU Machinery Directive 2006/42/EC)

Quoted from the published standard.

Manufacturing Precision
  • Bore Diameter: +/-0.025mm
  • Flatness: 0.05mm per 100mm diameter
Quality Inspection
  • Dye Penetrant Testing (PT) for surface defects
  • Ultrasonic Testing (UT) for internal discontinuities
Technical documentation
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Manufacturing capability
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Inspection readiness
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Supplier transparency
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Manufacturers of Trunnion Ring

Manufacturer profiles associated with Trunnion Ring.

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Frequently Asked Questions

What is the primary function of a trunnion ring?

The trunnion ring transfers the weight of the BOF vessel to the support structure while allowing tilting for charging, refining, and tapping.

What materials are commonly used for trunnion rings?

Forged or cast alloy steel, with grades like ZG270-500 per GB/T 11352, providing high strength and toughness.

What are typical dimensions of a trunnion ring?

Bore diameter 1500–3000 mm, outer diameter 2000–4000 mm, thickness 200–500 mm, and weight 5000–20000 kg, but these must be confirmed for specific applications.

What standards apply to trunnion ring manufacturing?

Material and testing standards include GB/T 11352, GB/T 231.1, ISO 2768-m, ISO 1302, and GB/T 7233.1. Always verify compliance with the manufacturer.

Data basis: editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Related equipment

Applied To / Applications

This component is essential for the following industrial systems and equipment:

Basic Oxygen Furnace Vessel
View system integration details

Industrial Ecosystem & Supply Chain Structure

Downstream Applications

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records.

Preliminary Technical Classification
This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review · Page last updated 13 October 2026

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