A Closer Look at Circular Hollow Section Standards and Dimensions

A Closer Look at Circular Hollow Section Standards and Dimensions

Circular Hollow Sections are widely used in structural and mechanical applications due to their uniform strength, aesthetic appeal, and efficient use of material. These steel tubes, characterized by their circular cross-section, provide a balance of strength, weight, and versatility that makes them a preferred choice across various industries including construction, infrastructure, transportation, and machinery.

In this article, we delve into the standards, dimensions, and practical aspects that define Circular Hollow Sections, offering engineers, architects, and builders a clear understanding of their specifications and use cases.

What Are Circular Hollow Sections?

Circular Hollow Sections (CHS) are tubular steel sections with a circular cross-section. They are part of a broader category known as Hollow Structural Sections (HSS), which also includes Rectangular (RHS) and Square Hollow Sections (SHS). CHS provide excellent strength-to-weight ratios and are ideal for load-bearing applications.

Their smooth, round profile also makes them suitable for aesthetic architectural features and structural frameworks that require uniform load distribution and resistance to torsion.

Material Grades and Manufacturing Standards

The production and use of Circular Hollow Sections are governed by national and international standards to ensure quality, performance, and consistency. The most commonly followed standards include:

1. IS 1161 (India)

This is the Indian Standard for steel tubes for structural purposes. It classifies CHS into various grades based on their chemical composition and mechanical properties such as:

·         YST 210

·         YST 240

·         YST 310

2. EN 10210 and EN 10219 (Europe)

·         EN 10210 covers hot-finished CHS.

·         EN 10219 deals with cold-formed welded CHS.

These standards specify tolerance levels, wall thickness, yield strength, and elongation limits.

3. ASTM A500 (USA)

Widely used in North America, ASTM A500 defines cold-formed welded and seamless carbon steel structural tubing in round, square, and rectangular shapes.

Each standard outlines tolerances in dimensions, welding quality, and performance criteria, ensuring that Circular Hollow Sections meet safety and durability requirements in engineering applications.

Common Dimensions and Sizes

Circular Hollow Sections come in a variety of diameters and wall thicknesses to accommodate different structural requirements. The dimensions are typically defined by:

·         Outer Diameter (OD)

·         Wall Thickness (WT)

·         Length (standard: 6m or 12m, but customizable)

Here’s an overview of some commonly used CHS sizes:

Outer Diameter: 21.3 mm
Wall Thickness: 2.6 mm
Approx. Weight: 1.37 kg/m

Outer Diameter: 33.7 mm
Wall Thickness: 3.2 mm
Approx. Weight: 2.80 kg/m

Outer Diameter: 60.3 mm
Wall Thickness: 4.0 mm
Approx. Weight: 6.81 kg/m

Outer Diameter: 114.3 mm
Wall Thickness: 6.3 mm
Approx. Weight: 17.90 kg/m

Outer Diameter: 168.3 mm
Wall Thickness: 8.0 mm
Approx. Weight: 33.53 kg/m

Note: The actual weight and strength capacity may vary depending on the grade of steel and manufacturing method.

Dimensional Tolerances

To maintain consistency and reliability, Circular Hollow Sections must adhere to strict tolerance guidelines. According to most global standards:

Outer Diameter Tolerance: ±1% with a minimum of ±0.5 mm

Wall Thickness Tolerance: ±10%

Length Tolerance: ±50 mm (for mill lengths)

Maintaining tight tolerances ensures that CHS can be accurately joined, machined, or fabricated without compromising structural integrity.

Advantages of Standardized Dimensions

Having standardized dimensions across Circular Hollow Sections provides several benefits:

Ease of Design: Engineers can refer to predefined sizes, allowing for efficient structural modeling.

Compatibility: CHS can be easily integrated with other structural elements such as beams, plates, and joints.

Reduced Waste: Predefined lengths and diameters minimize material wastage during cutting and fabrication.

Supply Chain Efficiency: Manufacturers, suppliers, and contractors operate on a unified sizing system, streamlining procurement and logistics.

Applications Based on Size and Wall Thickness

The dimension and thickness of Circular Hollow Sections determine their suitability for specific applications. Here’s a breakdown:

Lightweight CHS (OD < 50mm, WT < 2.5mm):

Ideal for furniture, railings, and non-load-bearing architectural features.

Medium CHS (OD 50–100mm, WT 3–5mm):

Common in small to medium building frames, fencing, and industrial sheds.

Heavy CHS (OD > 100mm, WT > 5mm):

Used in bridges, offshore platforms, towers, and heavy machinery structures.

Choosing the right CHS dimensions ensures optimum performance while minimizing material cost and installation complexity.

Structural Design Considerations

When incorporating Circular Hollow Sections into a design, several structural aspects must be evaluated:

Axial Load Capacity: CHS can bear axial loads effectively due to their symmetrical shape.

Bending Resistance: The circular cross-section offers uniform strength in all directions, unlike flat sections.

Torsional Strength: CHS perform well under twisting forces, which is essential in seismic or wind-exposed structures.

Connection Types: Can be bolted, welded, or joined using flanges. Accurate dimensions ensure secure and efficient connections.

Sustainable and Cost-Effective Construction

In modern construction, the use of Circular Hollow Sections is also driven by sustainability and cost-efficiency goals:

Material Efficiency: Reduced weight for similar strength compared to solid sections

Recyclability: Steel CHS are 100% recyclable without loss of quality

Lower Transportation Costs: Hollow sections weigh less, reducing freight charges

These benefits make CHS an eco-friendly choice for both public infrastructure and private development projects.

Conclusion

Understanding the standards and dimensions of Circular Hollow Sections is essential for selecting the right product for your structural or mechanical needs. With precise specifications defined by global and national standards, CHS offer uniformity, strength, and adaptability across a wide range of applications.

From light architectural frameworks to heavy-duty industrial structures, Circular Hollow Sections play a critical role in shaping modern infrastructure. By choosing the right size, thickness, and grade, professionals can ensure safety, efficiency, and long-term performance in every project.