Carbon Steel Scaffold Tube – BS 1139 / EN 39 Factory Direct | Huaxia-Steel
Carbon steel scaffold tube (also called scaffolding pipe or system scaffold tube) is the standardized structural tube for access scaffolding, shoring and temporary support structures on construction sites. Huaxia-Steel supplies factory-direct hot dip galvanized scaffold tube per BS 1139 (British standard) and EN 39 (European standard), in OD 48.3 mm with wall thickness 3.2 mm to 4.0 mm, in standard lengths 1.0 m, 1.5 m, 2.0 m, 3.0 m, 4.0 m, 5.0 m and 6.0 m. Material grades include S235GT (European), SG-A and SG-B (Japan), STK500 (JIS G3444), Q235B and Q345B. Each tube carries EN 10204 3.1 mill test certificate, hot dip galvanized coating per ASTM A53 / BS 1387 / ISO 1461, and a manufacturer’s mark on each piece for traceability.
1. Standards Mapping
| Standard | Title | Region |
|---|---|---|
| EN 39:2001 | Loose steel tubes for tube and coupler scaffolds – Technical delivery conditions | Europe (UK led) |
| BS 1139-2 | Metal scaffolding – Part 2: Steel couplers and loose steel tubes | United Kingdom |
| BS EN 10219 | Cold-formed welded structural hollow sections of non-alloy and fine grain steels | Europe (option) |
| JIS G3444 STK500 | Carbon Steel Tubes for General Structural Purposes | Japan |
| KS D 3566 | Carbon Steel Tubes for General Structural Purposes | Korea |
| AS 1576.1 | Scaffolding – General requirements | Australia |
| ASTM A53 Type E Gr.B | Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless | North America (where used) |
| GB/T 13793 | Welded steel pipes for low-pressure liquid delivery | China (local projects) |
| GB/T 3091 | Welded steel pipes for low-pressure fluid conveyance | China (option) |
EN 39 + BS 1139 is the dominant specification in global scaffolding export because it ties the tube to a well-defined coupler family that purchasers can source locally. JIS G3444 STK500 is the secondary specification for Japanese construction projects in South-East Asia.
2. Dimensional Specification
| Parameter | EN 39 / BS 1139 | JIS G3444 STK500 | China Q235B / Q345B |
|---|---|---|---|
| Outside diameter (mm) | 48.3 (plus or minus 0.5) | 48.6 (plus or minus 0.7) | 48.0 to 48.6 |
| Wall thickness (mm) | 3.2 or 4.0 (Type 4 only at 4.0) | 3.2 to 4.0 | 3.0 to 4.0 |
| Length tolerance | plus or minus 6 mm | plus or minus 5 mm | per GB/T |
| Straightness | 1:500 max deviation | 1:1000 max deviation | per GB/T |
| Surface | Hot dip galvanized per ISO 1461 | galvanized or black | galvanized or black |
| Coating weight | ISO 1461 average 105 microns (610 g/m2) | ISO 1461 or Z 275 (275 g/m2) | per buyer |
| Threading option | socket end + locking pin | plain end + pin | plain end + pin |
| Standard length (m) | 1.0 / 1.5 / 2.0 / 3.0 / 4.0 / 5.0 / 6.0 | same | same |
Most export orders are OD 48.3 mm x 3.2 mm wall x 6 m length, hot dip galvanized to ISO 1461 with 100 to 130 microns (average) zinc coating. The 4.0 mm wall is used in Asia and the Middle East where higher working loads are common. Outside-diameter 48.3 mm is the “magic number” because it fits the standard scaffolding couplers (right-angle / swivel / sleeve).
3. Available Grades and Properties
| Property | EN 39 / S235GT | STK500 | Q235B | Q345B |
|---|---|---|---|---|
| Yield strength min (MPa) | 235 | 355 | 235 | 345 |
| Tensile strength (MPa) | 340 to 520 | 500 min | 370 to 500 | 470 to 630 |
| Elongation min (percent) | 24 (50 mm) | 18 | 26 | 22 |
| Bending test | 90 deg bending, no crack | 90 deg bending | 90 deg | 90 deg |
| Flattening test | D/3, no crack | required | required | required |
| Charpy | not required | by agreement | by agreement | optional |
S235GT is the cost-effective grade for standard scaffolding. STK500 and Q345B are higher-strength grades used for shoring towers and high-rise load-bearing scaffold where the working stress is closer to yield.
4. Manufacturing Route
Scaffold tube is produced by:
- ERW (electric-resistance-weld) – the dominant route. Cold-rolled coil is slit to width, then formed into a tube and welded longitudinally by high-frequency induction. The weld seam is normalized by induction heating to maintain the structure.
- Hot finished seamless – occasionally used for OD 48.3 heavy wall applications, but more expensive.
The ERW route is dominant because the tube can be welded at high speed (10 to 30 m/min), the wall is uniform and the dimensional tolerance is tight. After welding, the tube is sized, cut to length, end-faced, and either left black or galvanized.
5. Hot Dip Galvanizing (ISO 1461 / EN ISO 1461)
Scaffolding tube is hot dip galvanized for corrosion protection. The process:
- Surface preparation: caustic degrease, water rinse, acid pickle (HCl or H2SO4), water rinse, flux (zinc ammonium chloride).
- Galvanizing bath: dipping in molten zinc at 445 to 465 deg C for 4 to 8 minutes (depending on wall).
- Withdrawal and cooling: tube is withdrawn at controlled speed, then water-quenched or air-cooled.
- Inspection: coating weight per ISO 1461 (sample test by magnetic or weigh-strip-weigh method).
ISO 1461 minimum local coating thickness for tube OD 48.3 mm is 85 microns (average 95) for “general” use and 105 microns (average 115) for “severe” environment. Most export orders specify the heavier coating for outdoor service life.
6. Common Accessories
Scaffold tube is half the system. The other half is the couplers and accessories:
- Right-angle coupler (double coupler) – connects two tubes at 90 degrees, BS EN 74 Class A
- Swivel coupler – allows variable angle
- Sleeve coupler (joint pin) – connects two tubes end-to-end in line, BS EN 74 Class B
- Putlog coupler – connects tube to putlog / board bearer
- Board retainer coupler – holds scaffold board in place
- Ladder coupler – clamped to ladder rungs
- Sleeve socket with internal peg – joins tubes end-to-end without pin
- Base jack / U-head jack – scaffold base adjustment
Huaxia-Steel can supply couplers forged from BS EN 10293 S235JR / S275JR steel and pressed steel board retainers. The complete scaffold system can be loaded in containers – tubes nested, couplers bagged, jacks skidded.
7. Common Applications
Carbon steel scaffold tube is used for:
- Building construction access scaffold – tube and coupler system, BS 1139
- Industrial plant maintenance scaffolding – chemical, petrochemical, power
- Birdcage shoring for slab pours
- Bridge inspection and painting platforms
- Building facade maintenance access
- Shoring towers for slab / beam propping – Q345B / STK500 heavy duty
- Cantilever scaffold for high-rise construction
- Suspended scaffold support frames
- Stage and event scaffolding – concert, grandstand
- Marine shipyard access scaffold
8. Specification Checklist for RFQ
- Standard – EN 39 / BS 1139 / JIS G3444 / AS 1576 / mixed
- Grade – S235GT / STK500 / Q235B / Q345B
- OD x wall (48.3 x 3.2 mm typical, 48.3 x 4.0 mm heavy)
- Length(s) – standard 1 to 6 m
- Surface – hot dip galvanized ISO 1461 average 105 microns minimum
- Coating weight check – ISO 1461 or customer specific
- End finish – plain end, swaged (socket) end, internally threaded, pin attached
- Stencil and marking – buyer’s specific mark on each tube
- MTC – EN 10204 3.1 mill certificate, bundle-tagged
- Third-party inspection – optional SGS / BV / Intertek
- Couplers – separate order or part of same shipment
- Bundle count – pieces per bundle (standard 91 pieces / 7 ft pile for 6 m)
- Container load – 20 ft or 40 ft, with bundling plan
9. Bundling and Shipping
Tubes are bundled in hexagonal or round stacks, strapped with steel banding at 1 to 2 m intervals:
- 6 m tubes in bundles of 91 (the “standard pack”) = 6.0 to 7.0 tonnes per bundle depending on grade and wall
- 3 m tubes in bundles of 100 to 150 pieces
- Luggage bands at each end and mid-span, plus lifting eyes
- Bundles stood upright in 20 ft open-top container (typically 6 to 8 bundles per 20 ft depending on length)
- Timber dunnage between bundles
- Shipping mark stenciled on bundle strap or on each tube end
A 20 ft open-top container holds about 23 to 27 tonnes of scaffold tube (3.2 mm wall). A 40 ft high-cube container holds about 26 to 28 tonnes.
10. Marking and Traceability
Each tube carries a watermark or stencil near one end:
- Manufacturer’s brand or logo
- “OD x wall” or equivalent (e.g. “48.3 x 3.2”)
- Steel grade (e.g. “S235GT”, “STK500”, “Q235B”)
- Heat number at intervals of 1 in 100 tubes per heat
- Coating class (where applicable)
The bundle strap tag carries bundle number, weight, quantity, batch reference and the MTC file identifier. Each bundle’s MTC is bundled inside or sent digitally to the buyer for traceability.
Request a Quotation
Huaxia-Steel is a factory-direct Chinese supplier of carbon steel scaffold tube per BS 1139 / EN 39 / JIS G3444, in OD 48.3 mm, wall 3.2 mm or 4.0 mm, length 1 to 6 m, hot dip galvanized to ISO 1461. We also supply EN 74 Class A and B couplers, base jacks and pressed steel accessories. Send your grade, tube size, length mix, accessory list and target port to [email protected] for a complete offer.
