SS Pipes & Fittings
Stainless Steel (SS) ERW Pipe Fittings
Stainless Steel (SS) ERW Fittings (Electric Resistance Welded) are manufactured by forming stainless steel plates or strips into the desired shape and welding the seam using high-frequency electric current. These fittings are highly cost-effective and are the standard choice for low-to-medium pressure applications in water treatment, food and beverage, and architectural industries
1. Primary Technical Standards
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Material Standard: ASTM A403 (Wrought Austenitic Stainless Steel Piping Fittings).
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Dimensional Standard: ASME B16.9 (Factory-Made Wrought Buttwelding Fittings) or MSS SP-43 (Light Weight Corrosion Resistant Fittings).
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Welding Process: Manufactured using High-Frequency Induction (HFI) or Electric Resistance Welding (ERW).
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Marking: These are typically marked with the suffix "-W" (e.g., WP304-W) to indicate a welded construction.
2. Common Material Grades & Chemical Composition
Grade | Carbon (C) | Chromium (Cr) | Nickel (Ni) | Molybdenum (Mo) |
|---|---|---|---|---|
SS 304 | 0.08% Max | 18–20% | 8–10.5% | — |
SS 304L | 0.03% Max | 18–20% | 8–12% | — |
SS 316 | 0.08% Max | 16–18% | 10–14% | 2–3% |
SS 316L | 0.03% Max | 16–18% | 10–14% | 2–3% |
3. Dimensional Data (Reference for ERW/Welded Fittings)
ERW fittings are often used in "S" schedules (Stainless Steel schedules).
Nominal Size (NB) | Outer Dia (mm) | Sch 10S Wall (mm) | Sch 40S Wall (mm) | Standard 90° Elbow Weight (kg) |
|---|---|---|---|---|
1/2" (15mm) | 21.34 | 2.11 | 2.77 | 0.08 |
1" (25mm) | 33.40 | 2.77 | 3.38 | 0.20 |
2" (50mm) | 60.33 | 2.77 | 3.91 | 0.70 |
4" (100mm) | 114.30 | 3.05 | 6.02 | 3.10 |
6" (150mm) | 168.28 | 3.40 | 7.11 | 7.70 |
4. Technical Mechanical Properties
For the most common grades (304/316):
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Tensile Strength: $\geq 515$ MPa ($75$ ksi)
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Yield Strength: $\geq 205$ MPa ($30$ ksi)
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Elongation: Minimum 28% to 35% depending on the specific grade.
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Hardness: Maximum 187 HB (Brinell Hardness) or 90 HRB (Rockwell Hardness).
5. Quality Control & Testing
To ensure the weld seam is as strong as the base metal, ERW fittings undergo:
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X-Ray/Radiography: Often performed on the weld seam (especially for Class 1 fittings) to detect internal defects.
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Pneumatic/Hydrostatic Test: To verify that the weld is leak-proof under pressure.
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Solution Annealing: The fittings are heated and rapidly cooled to restore corrosion resistance and ductility lost during the welding process.
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Pickling & Passivation: Removal of surface impurities to ensure the "passive" chromium oxide layer remains intact.
6. Key Advantages
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Cost: Significantly cheaper than seamless fittings for large diameter projects.
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Accuracy: Extremely consistent wall thickness throughout the body of the fitting.
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Availability: Faster production times for standard industrial sizes.