Type 4 is a standard classification for heavy‑duty steel scaffolding tube, defined under BS 1139‑1.1 (UK) and EN 39 (European) standards. It refers specifically to a 48.3mm outside diameter, 4.0mm wall thickness galvanized steel tube for scaffolding tube.
| Parameter | Type 4 scaffold tube |
|
| Outside Diameter | 48.3 mm (nominal 48 mm) | |
| Wall Thickness | 4.0 mm (the defining "Type 4" mark) | |
| Inside Diameter | ~40.3 mm | |
| Material | Hot‑dipped galvanized carbon steel (S235JR / Q235 / STK400) | |
| Standard | BS 1139, EN 39 | |
| Unit Weight | 4.37 kg/m (nominal) | |
| Common Lengths | 0.5–6.4 m (standard 6 m / 20 ft) |
What it means vs Type 3
| Properties | Symbol | Type 3 tube | Type 4 tube |
| Cross-sectional area (cm2) | A | 4,53 | 5,57 |
| Second moment of area (cm4) | I | 11,6 | 13,8 |
| Elastic section modulus (cm3) | Wel | 4,80 | 5,70 |
| Plastic section modulus (cm3) | Wpl | 6,52 | 7,87 |
| Radius of gyration (cm) | i | 1,60 | 1,57 |
| Mass per metre (kg/m) | M | 3,56 | 4,37 |
| Modulus of elasticity (MPa) | E | 210 000 | 210 000 |
Type 3: 48.3 mm OD, 3.2 mm wall, lighter (3.56 kg/m), for general light‑to‑medium duty.
Type 4: 4.0 mm wall, thicker, heavier, higher load capacity, for heavy‑duty / high‑load / long‑span scaffolding, falsework, support structures.
Characteristics of Type 4 Scaffold Tube
Hot‑dipped galvanized for corrosion resistance (standard for outdoor construction).
ERW (Electric Resistance Welded) steel tube, precision‑sized for coupler compatibility.
Marked on the tube to identify Type 4, standard, and manufacturer for site compliance.
Typical Uses: Heavy construction scaffolding, support falsework, shoring, bridge access, industrial platforms, and high‑load temporary structures where extra strength is required.
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