ArchitecturalHandrails & Staircases
Smooth round profile for safe grip and clean architectural finish.
IS 3601 | SRMB Realfabrica
Circular Hollow Section Manufacturer in India: IS 3601
If you're sourcing a round pipe, ERW pipe, CHS pipe, round steel pipe, or circular hollow section for a structural, mechanical, or architectural project, this page covers what you need to specify one correctly: size range, grade, applicable IS code, and where a circular profile fits best on a project. SRMB Realfabrica manufactures circular hollow sections at SRMB Srijan's integrated steel plant in Durgapur, West Bengal, rolling our own hot rolled coil into finished circular sections on Cold Formed ERW lines, under IS 3601.
IS 3601
CHS Standard
YST 240
Top Grade
89mm
Max OD
Durgapur
Integrated Plant
Circular Hollow Section — At a Glance
IS 3601
Standard
YST 240
Top Grade
89mm
Max Outer Diameter
ERW
Cold Formed Process
Product Description
Circular Hollow Section — CHS
A circular hollow section provides equal strength and stiffness in all directions — ideal for columns, curved structures, and applications where the section is seen and the profile matters. The circular form gives the best strength-to-weight ratio for axial and torsional loads.
SRMB Realfabrica manufactures CHS at our integrated plant in Durgapur — from rolled coil we produce ourselves, through Cold-Formed ERW lines, to IS 1161 and IS 3601 certified finished section. Every batch is tested for mechanical and chemical compliance before despatch.
IS 3601 / IS 1161YST 210 & YST 240Up to 80mm NB / 89mm OD1.8–5.4 mm thick6–7 m lengths
IS 1161 / IS 3601
Circular hollow sections for structural and general use
YST Grades
YST 210 / YST 240 — structural grades
CF ERW Process
Cold-Formed Electric Resistance Welded
IMS Certified
Integrated Management System certified plant
Batch-Level Testing
Mechanical and chemical testing per batch before despatch
Primary Steel Producer
Integrated plant — coil to finished section
| Specification | Detail |
|---|---|
| Product standard | IS 3601 (Steel tubes for mechanical and general engineering purposes) |
| Size range | 15mm NB to 80mm NB |
| Thickness range | 1.8mm to 5.4mm |
| Grade (tube designation) | WT 160, WT 210, WT 240, WT 310 |
| Standard length | 6 metres to 7 metres, custom cutting available on request |
| Surface finish | Black, smooth, consistent finish |
| Input material | Hot rolled coil conforming to IS 10748 |
| Forming process | Cold Formed ERW (Electric Resistance Welded) |
Not every nominal bore size is available in every grade, so for a specific size and grade combination, our technical team can confirm current availability and share a formal specification sheet.
| Tube Designation | Min Tensile Strength (MPa) | Min Yield Strength (MPa) | Elongation, up to 33.7mm OD | Elongation, above 33.7mm OD |
|---|---|---|---|---|
| WT 160 | 310 | 160 | 15.0% | 22.0% |
| WT 210 | 330 | 210 | 12.0% | 20.0% |
| WT 240 | 410 | 240 | 10.0% | 15.0% |
| WT 310 | 450 | 310 | 6.0% | 10.0% |
As with our square and rectangular range, these figures are minimum guaranteed values. Higher grades beyond WT 310 are also manufactured on request for projects with more demanding strength requirements. Outside diameter and thickness for each grade are confirmed against the specification you provide, since IS 3601 allows a range of OD and thickness combinations within each tube designation.
SRMB Realfabrica circular hollow sections are manufactured to hold outside diameter and wall thickness within the tolerances specified under IS 3601 for the selected tube designation. Because exact tolerance figures vary by size and grade combination, our technical team can share the specific tolerance data sheet for whichever size and grade you're specifying, alongside a formal quotation.
Where Circular Hollow Sections Are Used
Architectural
OutdoorPergola Columns
Upright round columns for outdoor pergola and canopy structures.
IndustrialPipe Racks
Industrial pipe support frames and overhead distribution networks.
SecurityGate Frames
Residential and commercial entry gates with round tube framing.
InfrastructureSpace Frames
Long-span 3D truss structures for roofs, canopies, and stadia.
MechanicalMechanical Shafts
Rotating and torsional drive components in machinery and conveyors.
Why Circular Hollow Sections Are Specified
1
Equal Torsional Strength
Round profile resists twisting from all directions — ideal for poles, railings, and shafts.
2
Easy to Bend & Curve
Uniform cross section bends cleanly with standard tooling — no corner cracking.
3
Clean Exposed Finish
No flat faces or corners — preferred for visible architectural and public-facing applications.
4
IS 3601 / IS 1161 Certified
Manufactured to IS standards with batch-level testing and on-product traceability.
Handling and Site Considerations
Weldability
SRMB Realfabrica circular hollow sections can be welded using standard MS electrodes without preheating, allowing straightforward fabrication and site jointing.
Open Ends
Sections are supplied with open ends. We recommend sealing exposed ends with a welded end plate on site to prevent moisture ingress and internal corrosion over the working life of the structure.
Packaging
Sections are bundled and strapped for transit to minimise surface damage, with bundle-level identification for easy tracking on site and at stockyards.
Frequently Asked Questions
A circular hollow section is a structural steel tube with a round cross section and hollow core. It's also called round pipe, ERW pipe, CHS pipe, round steel pipe, or circular steel tube.
We manufacture circular hollow sections from 15mm NB to 80mm NB in 1.8mm to 5.4mm wall thickness, under IS 3601. Not every size is available in every thickness, so please confirm with our technical team.
SRMB Realfabrica circular hollow sections conform to IS 3601, which covers steel tubes for mechanical and general engineering purposes.
We manufacture circular hollow sections in four IS 3601 tube designations: WT 160, WT 210, WT 240, and WT 310, classified by minimum tensile and yield strength.
WT 310 has a higher minimum yield strength (310 MPa) and tensile strength (450 MPa) than WT 160 (160 MPa yield, 310 MPa tensile), making it suited to more demanding structural applications.
Standard supply length is 6 metres to 7 metres. Custom cut lengths can be arranged on request for specific project requirements.
Circular hollow sections are used for flag poles, handrails, balustrades, wind exposed structural supports, mechanical torsional applications, architectural elements, and conveyor systems.
Yes, in practice. ERW (Electric Resistance Welded) pipe and circular hollow section both describe the same welded round steel tube, formed on the same manufacturing process.
Circular sections handle torsional and rotational load, wind resistance, and pressure containment better than square or rectangular sections, which are optimised for axial and one-directional bending load instead.
Controlled chemistry and a smooth surface finish support good corrosion resistance. Sealing all open ends with a welded end plate further protects against internal corrosion over the section's working life.
Yes. SRMB Realfabrica circular hollow sections can be welded using standard MS electrodes without any preheating required beforehand.
For outside diameter and thickness tolerance, along with weight per length for your selected size and grade, please contact our technical team or download our product brochure for current data.
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