GB/T 3091 covers welded steel pipe — black and hot-dip galvanized, DN15–DN200 (21.3–219.1 mm OD), Q235B — the fencing, plumbing and structural pipe of the Chinese system. GB/T 8162 covers seamless structural pipe (20#, 45# steel); GB/T 8163 is its fluid-transport twin. Supplied threaded, grooved or plain from 5 tons.
Two standards cover nearly every pipe order from China: GB/T 3091 for welded (the fencing and plumbing workhorse, usually galvanized) and GB/T 8162/8163 for seamless (structural and fluid). Here is what each standard delivers and the size ladder.
GB/T 3091 — Welded Pipe (Black & Galvanized)
| DN | OD (mm) | Common Walls (mm) | Application |
|---|---|---|---|
| DN15 (½") | 21.3 | 2.0–2.8 | Water lines, conduit |
| DN25 (1") | 33.7 | 2.8–3.2 | Plumbing branch lines |
| DN40 (1½") | 48.3 | 3.2–3.5 | Fencing rails, handrails |
| DN50 (2") | 60.3 | 3.2–3.8 | Greenhouse structure, plumbing risers |
| DN80 (3") | 88.9 | 3.5–4.0 | Fire lines, industrial water |
| DN100 (4") | 114.3 | 3.8–4.5 | Fire mains, piling sleeves |
| DN150 (6") | 168.3 | 4.0–5.4 | Yard piping, structural columns |
| DN200 (8") | 219.1 | 4.5–6.0 | Transmission, heavy structure |
- Steel: Q195/Q215 for light conduit; Q235B structural and plumbing duty.
- Finish: black (oiled), pre-galvanized, or hot-dip galvanized after fabrication (+25–40%) — coating comparison →
- Ends: plain, threaded + coupling, or grooved for mechanical couplings.
GB/T 8162 / 8163 — Seamless Pipe
- GB/T 8162 (structural): 20# steel (≈ 1020/C22E) and 45# (≈ 1045) — machinery frames, cylinders, booms.
- GB/T 8163 (fluid): the transport twin for pressurized water/oil lines — hydro-tested per standard.
- OD 32–426 mm, wall 3–40 mm; hydraulic test certificates included.
How GB Pipe Maps to Other Systems
- DN sizes follow ISO — the same DN15–DN200 ladder used by EN and ASTM NPS sizing, so schedules cross-reference easily: schedule guide →.
- Q235B pipe ≈ ASTM A53 GrB / EN 10255 class in application terms.
- For coating choices by application (fence/greenhouse/water): galvanized vs black pipe →
Supply from Foshan
Welded and seamless, black/galvanized/primed, threaded-grooved-plain ends, 6 m standard lengths or cut-to-size. EN 10204 3.1 MTC naming GB/T 3091 or GB/T 8162 with heat chemistry. MOQ 5 t; 40GP takes 26–27 t ≈ 2,700–3,300 pcs of 6 m DN40 depending on wall. Square/rectangular tube options: tube size table →
DN sizes, walls, finish — quoted in one sheet
Pipe list to [email protected] or WhatsApp +86 191 5745 8011 — GB/T 3091 and GB/T 8162 quoted with black/pre-galv/HDG options, MOQ 5 tons.
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