Scaffold tube
The 48.3 mm steel or aluminium tube that fills every gap a system part cannot – as brace, rail, tie member or complete tube-and-fitting scaffold.
Also called: steel tube, aluminium tube, 48.3 tube, scaffold pole, tube and fitting tube
When a scaffolder says "we'll stick a tube on it", that is rarely wrong. The scaffold tube is the most versatile part on site and is used wherever system components do not fit: as a diagonal next to compensation frames, as plan bracing on a lattice girder, as part of a scaffold tie, as a strut under a bracket, as a rail at an oblique corner or as a runner to which other parts are clamped. Together with right-angle and swivel couplers it can build almost any shape – a traditional tube-and-fitting scaffold consists of nothing else. In the UK such scaffolds are designed to NASC guidance TG20.
In a system scaffold, tube supplements the system but does not replace it. Where a tube is to carry load or brace, the instructions or a structural calculation must provide for it.
Dimensions and weights
The common denominator is the outside diameter of 48.3 mm (1.9 in), to which couplers and most standards are designed. Steel scaffold tubes are covered by EN 39. Material and wall thickness differ:
- Galvanised steel: usually 3.2 mm wall, less often about 4 mm. One metre weighs around 3.6 kg (about 2.4 lb/ft), a 6 m tube therefore just over 21 kg.
- Aluminium: mostly 4.0 mm wall and only about 1.5 kg per metre. Pleasantly light, but not approved for every structural task.
- Lengths: 1 to 6 m in one-metre steps, plus intermediate lengths.
Tube is not just tube: a structural or pipeline tube of similar diameter is no scaffold tube.
Fixing tube properly
- Clarify the job: barrier only, or load-bearing and bracing? That decides length, coupler type and connection point.
- Choose the length so the tube projects beyond the coupler at both ends; an end that barely sits in the coupler is a fault.
- Place couplers close to the nodes of the uprights so the force enters without a lever arm.
- Tighten with the scaffold spanner, usually to about 50 Nm.
- Join tubes with sleeve couplers or joint pins instead of improvising with parallel clamping.
- Check all joints and mark or cap projecting ends in walkways.
When dismantling, release couplers only when someone is holding the tube – and pass tubes down lift by lift, never throw them.
What to check on used tube
- Straightness: sight along the full length. Bent tubes are scrapped, not bent back.
- Ends: crushed, split or flared ends no longer fit couplers and connectors.
- Corrosion: white deposits on zinc are harmless; pitting, flaking or noticeably thin spots are not.
- Steel or aluminium: no aluminium tube in a structure designed for steel – the weight gives it away at once.
- No anchor point at an open end: a fall-arrest karabiner can slide off.
Straight, cleanly galvanised tubes without deep corrosion are a very sound used purchase. Lengths and weights are listed under scaffold tubes; for transport loads see scaffolding weight.