BS 1387
- Size range 1/8″~4″ (6.35~114.3mm)
- Wall Thickness Grading: Light: 0.8~2.35mm / Medium: 1.2~2.65mm / Heavy: 1.6~4.05mm
- Working Pressure Light Grade 12bar / Medium Grade 16bar / Heavy Grade 25bar
- Chemical Composition: C≤0.25%, Mn≤1.0%, P≤0.05%, S≤0.05%
- Galvanized layer: average zinc layer≥610g/m², local≥480g/m².
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BS 1387, as the British standard galvanized welded steel pipe, is manufactured by ERW process, with double anti-corrosion protection through hot dip galvanizing. Its Light/Medium/Heavy three-level classification meets different pressure requirements, and the threaded interface is compatible with the BS 21 standard, which is mainly used in the scenarios of building fire-fighting system and water supply and drainage engineering. The fittings can maintain stable mechanical properties below 300℃, and the galvanized layer can slow down the heating rate of the steel pipe in the early stage of fire.
BS 1387 Steel Pipe Specification
Chemical Composition Analysis
- Carbon (C) ≤0.25
- Manganese (Mn) ≤1.00
- Phosphorus (P) ≤0.05
- Sulphur (S) ≤0.05
The total amount of chromium (Cr), nickel (Ni), molybdenum (Mo) and other alloying elements should be <0.60% to avoid unintentional addition of alloying.
Comparison of carbon equivalents of ASTM A135 and BS 1387
BS 1387: CE=0.38%, Cr, Ni, Mo alloy content below 0.6%, low alloy design reduces welding cold crack sensitivity.
ASTM A135: CE = 0.42% (C ≤ 0.30%, Mn ≤ 1.2%), higher carbon content leads to poor grain boundary stability at high temperatures.(Carbon equivalent online calculator)
Carbon Equivalent (CE): CE=C+Mn/6
BS 1387 physical property
- Data based on measured values for Heavy wall pipe.
- Blue brittleness occurs above 200°C.
BS 1387 Size Charts
| NPS | OD tolerance | Light | Medium | Heavy | |||
| Thickness | Weight | Thickness | Weight | Thickness | Weight | ||
| 15 mm | ±0.5 mm | 2.0 mm | 0.62 kg/m | 2.5 mm | 0.77 kg/m | 2.8 mm | 0.85 kg/m |
| 20 mm | ±0.5 mm | 2.0 mm | 0.87 kg/m | 2.5 mm | 1.08 kg/m | 3.2 mm | 1.32 kg/m |
| 25 mm | ±0.5 mm | 2.3 mm | 1.27 kg/m | 2.8 mm | 1.52 kg/m | 3.6 mm | 1.89 kg/m |
| 32 mm | ±0.6 mm | 2.3 mm | 1.67 kg/m | 2.9 mm | 2.07 kg/m | 4.05 mm | 2.75 kg/m |
| 40 mm | ±0.6 mm | 2.6 mm | 2.37 kg/m | 3.2 mm | 2.88 kg/m | 3.95 mm | 3.45 kg/m |
| 50 mm | ±0.8 mm | 2.6 mm | 3.01 kg/m | 3.6 mm | 4.05 kg/m | 4.50 mm | 4.95 kg/m |
| 65 mm | ±0.8 mm | 2.9 mm | 4.35 kg/m | 3.6 mm | 5.35 kg/m | 5.10 mm | 7.30 kg/m |
| 80 mm | ±1.0 mm | 3.2 mm | 6.00 kg/m | 4.0 mm | 7.42 kg/m | 5.60 mm | 10.10 kg/m |
| 100 mm | ±1.0 mm | 3.6 mm | 8.50 kg/m | 4.5 mm | 10.50 kg/m | 6.30 mm | 14.20 kg/m |
Wall thickness tolerance: Light/medium tubes: ±10%; Heavy tubes: +15%/-10%
BS 1387 Steel Pipe Process & Quality
BS 1387 Pipe Fire-Resistance
1. Fire resistance of galvanized coatings
Since the BS 1387 standard places greater emphasis on the ductility of steel, it relies more heavily on the galvanized coating for fire resistance. The galvanized coating effectively enhances the fire resistance of steel; however, the melting point of zinc is 419°C. Therefore, above 300°C, the fire resistance of the galvanized coating begins to diminish, and the molten zinc may accelerate corrosion of the steel.
2. Improvement Methods
Composite protection technology is a widely adopted technique. Applying a 2.8mm-thick fire-resistant coating (with a fire resistance rating of 1.84 hours) followed by galvanization can increase the strength retention rate at 600°C to 35%.