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SS Pipes & Fittings

Stainless Steel (SS) Seamless Pipe

Stainless-Seamless

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:

  • ASTM A312: The most common standard for seamless austenitic stainless steel pipes (high temperature/corrosive service).

  • ASTM A213: Standard for seamless ferritic and austenitic alloy-steel boiler, superheater, and heat-exchanger tubes.

  • 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

  • Finish: Usually supplied in Annealed & Pickled (AP), Bright Annealed (BA), or Polished (240/320/400/600 Grit).

  • Mechanical Strength: * Tensile Strength: ≥ 515 MPa (Grade 304/316).

    • Yield Strength: ≥ 205 MPa.

  • 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:

  1. Non-Destructive Testing (NDT): Eddy Current or Ultrasonic testing to find internal flaws or cracks.

  2. Hydrostatic Test: Every pipe is tested under water pressure to ensure no leakage.

  3. Mechanical Tests: Including Flaring, Flattening, and Hardness tests.

  4. IGC Test (Intergranular Corrosion): Specifically for 300-series pipes to ensure they won't corrode at the grain boundaries.

Applications

  • Oil & Gas: High-pressure transport lines.

  • Chemical/Pharma: Handling corrosive fluids where weld contamination must be avoided.

  • Food Processing: Seamless interiors prevent bacterial growth in joints.

  • Heat Exchangers: Used in boilers and condensers for efficient heat transfer.

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