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Views: 0 Author: Site Editor Publish Time: 2026-10-15 Origin: Site
A scaffolding beam clamp — also known as a girder coupler, gravlock coupler, or C clamp — is a specialized structural fitting designed to securely lock scaffold tubes (typically Ø48.3mm) to steel or aluminum I-beams and H-beams. Unlike standard double couplers that connect tube-to-tube, beam clamps are engineered specifically to grip structural steel flanges without the need for drilling, welding, or permanent modification.
This makes them indispensable in steel-frame construction, industrial maintenance, and any project where scaffolding must be anchored to existing structural members rather than erected from the ground up.
keywords: girder clamp, gravlock clamp, scaffold beam coupler, beam clamp for scaffolding, I-beam tube clamp.
Choosing between fixed and swivel models is one of the most common decision points for buyers. Here's how they compare:
Feature | Fixed Beam Clamp | Swivel Beam Clamp |
|---|---|---|
Connection angle | Fixed 90° (right-angle) | Adjustable (any angle) |
Max flange thickness | Up to 44–45mm | Up to 44–45mm |
Material | Drop-forged steel | Drop-forged steel |
Safe working load (per pair) | 30kN (hanging/vertical) | 6.25–15kN (reduced due to swivel) |
Best applications | Standard I-beams, handrails, platforms, high-load hanging | Angled bracing, complex non-90° setups |
Must use in pairs? | Yes | Yes |
Key takeaway: Fixed clamps deliver higher load capacity and are the go-to choice for standard 90° installations. Swivel clamps offer flexibility for non-perpendicular connections but at a lower safe working load.
When sourcing scaffolding beam clamps, these are the critical parameters to confirm with your supplier:
Steel grade: Q235 or S235 is the industry standard for scaffold-grade beam clamps. Drop-forged construction is preferred over pressed steel for superior tensile strength and crack resistance.
T-bolt grade: Look for M12, Grade 8.8 bolts as a minimum.
Maximum load capacity: ≥30kN (typical for AS 1576-certified clamps).
Slippage under load: High-quality clamps maintain less than 6mm slippage under a 12.5kN load.
Safe working load: 30kN per pair for vertical hanging applications.
Standard | Max Flange Thickness |
|---|---|
AS 1576 (Australian) | 45mm |
JIS A 8951 / KSD 3501 (Japan/Korea) | 36mm |
EN 74 / BS 1139 (European/British) | Varies; typically up to 45mm |
Extension clamps | Up to 81mm for thicker flanges |
Electro-galvanized: Suitable for general outdoor use.
Hot-dip galvanized (HDG): Recommended for marine, coastal, or high-corrosion environments. HDG models typically exceed 5,000 hours of salt spray resistance.
Unlike standard scaffold couplers (which are governed by EN 74-1 for right-angle and swivel couplers), beam clamps do not yet have a dedicated British or European standard. This is a crucial point for procurement teams to understand.
Instead, most manufacturers test and certify beam clamps against:
AS 1576.2 (Australian Standard): The most widely referenced standard for girder/beam clamps. It specifies requirements for rigid and swiveling flange clamps, including slip tests along the flange.
EN 74-1: While EN 74-1 primarily covers right-angle, swivel, sleeve, and parallel couplers, some manufacturers also test beam clamps to the principles of this standard for quality assurance. EN 74-1 Class B represents the higher strength grade, with slip resistance of 9.1kN for right-angle couplers.
JIS A 8951 / KSD 3501: Japanese and Korean standards that specify a maximum flange thickness of 36mm for beam clamps.
BS 1139: A legacy British standard often cited alongside EN 74 for scaffold fittings.
