SS Pipes & Fittings
Stainless Steel (SS) ERW Pipe
Stainless Steel (SS) ERW Pipes are produced by cold-forming stainless steel strips into a cylindrical shape and welding the longitudinal seam using high-frequency electric resistance. Unlike seamless pipes, which are extruded from solid billets, ERW pipes are cost-effective and highly accurate in wall thickness, making them ideal for water lines, structural supports, and food processing.
1. Primary Manufacturing Standards
The technical specifications for SS ERW pipes are primarily governed by international ASTM standards:
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ASTM A312: The standard for welded austenitic stainless steel pipes used for high-temperature and general corrosive service.
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ASTM A249: Specifically for welded austenitic steel boiler, superheater, heat exchanger, and condenser tubes.
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ASTM A554: Used for ornamental or structural applications where appearance and mechanical properties are more important than pressure ratings.
2. Technical Parameter Overview
Feature | Technical Specification |
|---|---|
Common Grades | TP304, TP304L, TP316, TP316L, TP321, TP310S |
Size Range (NB) | 1/8” NB to 36” NB |
Outer Diameter (OD) | 6.35 mm to 114.3 mm (for smaller range); up to 24" OD for standard ERW |
Wall Thickness | 0.5 mm to 12.7 mm (Schedules 5S, 10S, 40S, 80S) |
Length | Up to 12 Meters (Single or Double Random Length) |
Surface Finish | 2B (Mill finish), No.4 (Brushed), BA (Bright Annealed), 8K (Mirror) |
3. Material Properties (Grade 304 vs. 316)
These are the two most common grades you will likely deal with:
Property | SS 304 ERW (18/8) | SS 316 ERW (Chloride Resistant) |
|---|---|---|
Chemical Composition | 18% Cr, 8% Ni | 16% Cr, 10% Ni, 2% Mo |
Tensile Strength | 515 MPa (Min) | 515 MPa (Min) |
Yield Strength | 205 MPa (Min) | 205 MPa (Min) |
Max Temp Service | 870°C | 870°C |
Best Used For | Dairy, food, household, architecture | Marine, chemical, pharmaceutical |
4. Dimensional Chart (Standard Schedules)
For SS pipes, the schedules (thicknesses) are often denoted with an "S" (e.g., 40S).
Nominal Size (NB) | OD (mm) | Sch 10S (mm) | Sch 40S (mm) | Weight (kg/m - 40S) |
|---|---|---|---|---|
1/2" (15mm) | 21.34 | 2.11 | 2.77 | 1.29 |
1" (25mm) | 33.40 | 2.77 | 3.38 | 2.54 |
2" (50mm) | 60.33 | 2.77 | 3.91 | 5.52 |
4" (100mm) | 114.30 | 3.05 | 6.02 | 16.32 |
5. Quality & Testing
To ensure the integrity of the weld seam, ERW pipes undergo:
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100% Hydrostatic Test: To verify the pipe can handle specified pressures without leaking.
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Flattening & Flaring Tests: To check the ductility and strength of the weld zone.
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Eddy Current or Ultrasonic Testing: Non-destructive tests to find internal flaws in the longitudinal weld.
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Passivation: A chemical treatment to enhance the protective oxide layer and prevent rusting.
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.
Stainless Steel (SS) Seamless Pipe
Stainless Steel (SS) Seamless Pipes are high-performance tubes manufactured without any welding or joints. They are created by piercing a solid round steel billet, followed by rolling or cold drawing to achieve the final dimensions. Because they have no weld seam, they offer superior pressure-bearing capacity and corrosion resistance compared to ERW pipes.
1. Primary Technical Standards
Seamless SS pipes are usually manufactured to meet stringent international standards depending on the application:
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ASTM A312: The most common standard for seamless austenitic stainless steel pipes (high temperature/corrosive service).
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ASTM A213: Standard for seamless ferritic and austenitic alloy-steel boiler, superheater, and heat-exchanger tubes.
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ASTM A269: Standard for seamless tubing for general service.
2. Common Material Grades
Grade | Description | Key Properties |
|---|---|---|
TP 304/304L | Most versatile "18/8" stainless. | Excellent corrosion resistance and weldability. |
TP 321 | Titanium stabilized. | High resistance to intergranular corrosion at high temperatures. |
TP 316/316L | Molybdenum-bearing steel. | Superior resistance to chlorides and marine environments. |
TP 310S | High Chromium-Nickel alloy. | Outstanding heat resistance for furnaces and kilns. |
3. Dimensional Specifications (ASTM A312)
Seamless pipes use "Schedules" to define wall thickness. Below are the dimensions for the most common sizes:
Nominal Bore (NB) | Sch 10S (mm) | Outer Diameter (mm) | Sch 40S (mm) | Sch 80S (mm) |
|---|---|---|---|---|
1/2" (15mm) | 2.11 | 21.34 | 2.77 | 3.73 |
1" (25mm) | 2.77 | 33.40 | 3.38 | 4.55 |
2" (50mm) | 2.77 | 60.33 | 3.91 | 5.54 |
4" (100mm) | 3.05 | 114.30 | 6.02 | 8.56 |
6" (150mm) | 3.40 | 168.28 | 7.11 | 10.97 |
4. Technical Properties
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Finish: Usually supplied in Annealed & Pickled (AP), Bright Annealed (BA), or Polished (240/320/400/600 Grit).
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Mechanical Strength: * Tensile Strength: ≥ 515 MPa (Grade 304/316).
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Yield Strength: ≥ 205 MPa.
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Hydrostatic Pressure: Can typically withstand 20% to 50% higher pressure than welded pipes of the same size.
5. Essential Quality Tests
To ensure the integrity of a seamless pipe, the following tests are mandatory:
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Non-Destructive Testing (NDT): Eddy Current or Ultrasonic testing to find internal flaws or cracks.
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Hydrostatic Test: Every pipe is tested under water pressure to ensure no leakage.
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Mechanical Tests: Including Flaring, Flattening, and Hardness tests.
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IGC Test (Intergranular Corrosion): Specifically for 300-series pipes to ensure they won't corrode at the grain boundaries.
Applications
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Oil & Gas: High-pressure transport lines.
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Chemical/Pharma: Handling corrosive fluids where weld contamination must be avoided.
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Food Processing: Seamless interiors prevent bacterial growth in joints.
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Heat Exchangers: Used in boilers and condensers for efficient heat transfer.
Stainless Steel (SS) Seamless Pipe Fittings
Stainless Steel (SS) Seamless Pipe Fittings are high-integrity components manufactured from solid stainless steel bars or seamless pipes. Because they are forged or extruded without a weld seam, they provide maximum strength, uniform wall thickness, and zero risk of weld-related corrosion or failure, making them the standard for high-pressure, high-temperature, and sanitary applications.
1. Primary Technical Standards
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Material Standard: ASTM A403 (Standard Specification for 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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Marking: Seamless fittings are often marked with the suffix "-S" (e.g., WP304-S) to distinguish them from welded variants.
2. Common Material Grades
The choice of grade depends on the chemical environment of your project:
Grade | Prefix (WP) | Key Characteristic | Common Application |
|---|---|---|---|
SS 304 | WP304 | Standard 18% Cr, 8% Ni | General food/industrial use |
SS 304L | WP304L | carbon (prevents sensitization) | Heavy welding applications |
SS 316 | WP316 | 2-3% Molybdenum added | Marine & Chemical (Chloride resistance |
SS 316L | WP316L | Low carbon + Molybdenum | Pharmaceutical & Petrochemical |
SS 321 | WP321 | Titanium stabilized | High heat (Exhausts/Furnaces) |
3. Dimensional Data (ASME B16.9 - Seamless)
Seamless fittings match the Schedule (thickness) of the pipe they are connected to.
Nominal Size (NB) | Outer Dia (mm) | Sch 10S Wall (mm) | Sch 40S Wall (mm) | 90° Elbow (Center to End) |
|---|---|---|---|---|
1/2" (15mm) | 21.3 | 2.11 | 2.77 | 38 mm |
1" (25mm) | 33.4 | 2.77 | 3.38 | 38 mm |
2" (50mm) | 60.3 | 2.77 | 3.91 | 76 mm |
4" (100mm) | 114.3 | 3.05 | 6.02 | 152 mm |
6" (150mm) | 168.3 | 3.40 | 7.11 | 229 mm |
4. Technical Properties & Testing
Seamless fittings must undergo rigorous quality checks:
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Mechanical Strength: Tensile strength of $\geq 515$ MPa and Yield strength of $\geq 205$ MPa (for 304/316).
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Hydrostatic Test: Verified to withstand internal pressure without leakage (often tested at 1.5x the working pressure).
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Non-Destructive Testing (NDT): Ultrasonic (UT) or Magnetic Particle testing is performed to ensure no internal voids or cracks exist in the forged body.
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IGC Test: Intergranular Corrosion test (ASTM A262 Practice A or E) to ensure the steel remains corrosion-resistant after the forging process.
5. Surface Finish Options
For suppliers like Asma Enterprises, the finish is critical for specific industries:
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Annealed & Pickled (AP): Standard industrial finish.
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Sand Blasted: A matte, clean finish for structural use.
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Polished (Mirror/Satin): Essential for dairy, food processing, and pharmaceutical lines (Grit 180, 240, or 320).
Stainless Steel (SS) Pipe Flanges
Stainless Steel (SS) Pipe Flanges are used to create high-integrity, leak-proof connections in piping systems that require superior corrosion resistance and hygiene. Unlike MS flanges, SS flanges are used extensively in chemical plants, pharmaceutical labs, and food processing units where contamination and oxidation must be avoided.
1. Primary Technical Standards
SS flanges are manufactured to match global piping standards:
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ASTM A182: The standard for forged or rolled alloy and stainless steel pipe flanges for high-temperature service.
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ASME B16.5: Dimensional standard for flanges from 1/2" to 24" (Class 150 to 2500).
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MSS SP-43: Standard for lightweight, corrosion-resistant buttwelding fittings and flanges.
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EN 1092-1: European standard for steel flanges (PN ratings).
2. Common Material Grades
The grade of stainless steel determines the flange's resistance to specific chemicals and temperatures:
Grade | Common Name | Key Characteristics | Best Used For |
|---|---|---|---|
SS 304/L | 18/8 Stainless | High ductility, excellent corrosion resistance. | Food, dairy, and water treatment. |
SS 316/L | Marine Grade | Contains 2-3% Molybdenum; resists chlorides. | Marine, chemical, and pharma. |
SS 321 | Titanium Stabilized | Prevents carbide precipitation at high heat. | Exhausts and heat exchangers. |
SS 310S | Refractory Grade | High Chromium/Nickel for heat resistance. | Kilns, furnaces, and boiler parts. |
3. Technical Parameters (ASME B16.5)
Flanges are categorized by their pressure-temperature rating, known as "Class."
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Pressure Ratings: Class 150, 300, 400, 600, 900, 1500, and 2500.
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Facing Types: * Flat Face (FF): For low-pressure systems.
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Raised Face (RF): Most common; concentrates pressure on the gasket.
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Ring Type Joint (RTJ): Uses a metal ring for extremely high pressures.
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4. Dimensional Data (Class 150 - Standard)
The dimensions of an SS flange must precisely match the bolt-hole pattern of the equipment it connects to.
Nominal Size (NB) | Outside Dia (mm) | Thickness (mm) Copy | No of Holes | Bolt Circle Dia (mm) Copy |
|---|---|---|---|---|
1/2" (15mm) | 88.9 | 11.1 | 4 | 60.3 |
1" (25mm) | 108.0 | 14.3 | 4 | 79.4 |
2" (50mm) | 152.4 | 19.1 | 4 | 120.7 |
4" (100mm) | 228.6 | 23.9 | 8 | 190.5 |
6" (150mm) | 279.4 | 25.4 | 8 | 241.3 |
5. Surface Finishes
In the stainless steel industry, the finish is as important as the grade:
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Stock Finish: A continuous spiral groove (phonographic finish) for general industrial use.
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Smooth Finish: Used with metal gaskets.
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Mirror Polished: High-shine finish used in architectural and sanitary (food/pharma) applications.
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Serrated: Concentric or spiral grooves to "bite" into the gasket for a better seal.
6. Essential Quality Tests
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Positive Material Identification (PMI): To verify the exact chemical composition (e.g., ensuring 316 actually contains Molybdenum).
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Solution Annealing: Heating to 1000°C+ and quenching to ensure maximum corrosion resistance.
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Dye Penetrant Test (DP): Checking for surface cracks or porosity in the forged body.
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IGC Test: Testing for Intergranular Corrosion to ensure the flange won't fail at the weld zone.