Elevated silicon content significantly enhances heat resistance in industrial environments, making ASTM/ASME A106/SA106 seamless carbon steel pipe a top choice for applications involving high heat. This includes process piping, boiling plants, compression stations, and refineries. The added silicon improves performance in high-temperature settings, such as steam lines and processing applications.
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A106 Comparative Specifications
- ASTM Specification A106 covers seamless carbon steel pipes for high-temperature service, ideal for bending, flanging, and similar operations.
- Pipes 1-1/2 NPS and under can be hot finished or cold drawn, while pipes 2 NPS and larger are hot finished unless specified otherwise.
- Surface finish standards are specified in the ASTM standards.
- Purchasers may opt for NDE instead of hydrostatic testing, or neither, with pipes usually furnished with plain ends.
MECHANICAL PROPERTIES – TENSILE REQUIREMENTS
| Grade A | Grade B | Grade C | |
|---|---|---|---|
| Tensile Strength, min, psi | 48,000 | 60,000 | 70,000 |
| Yield Strength, min, psi | 30,000 | 35,000 | 40,000 |
CHEMICAL REQUIREMENTS
| Element | Grade A | Grade B | Grade C |
|---|---|---|---|
| Carbon max. % | 0.25 | 0.30 | 0.35 |
| Manganese % | 0.27 – 0.93 | 0.29 – 1.06 | 0.29 – 1.06 |
| Phosphorus max % | 0.035 | 0.035 | 0.035 |
| Sulfur max % | 0.035 | 0.035 | 0.035 |
| Silicon, min % | 0.10 | 0.10 | 0.10 |
- Testing Requirements for seamless A106 carbon steel pipe
- Hydrostatic Testing: Inspection test pressures produce a stress in the pipe wall equal to 60% of specified minimum yield strength (SMYS) at room temperature. Maximum pressures are not to exceed 2,500 psi for NPS 3 and under, and 2,800 psi for the larger sizes. Pressure is maintained for no less than 5 seconds.
- Mechanical Tests:
- Tensile Test: Either transverse or longitudinal are acceptable for NPS 8 and larger
- Tensile tests smaller than NPS 8: Longitudinal testing only
- Flattening Test: NPS 2 and larger
- Bending Test (cold): NPS 2 and under
Degree of Bend Diameter of Mandrel For normal A106 uses 90 12x nominal diameter of pipe For close coiling 180 8x nominal diameter of pipe - Number of Tests: One tensile test per 200 lengths.
| NPS | On one length from each lot of: | |
|---|---|---|
| Tensile | 5 and smaller | 400 or less |
| 6 and larger | 200 or less | |
| Bending | 2 and smaller | 400 or less |
| Flattening | 2 through 5 | 400 or less |
| 6 and larger | 200 or less |
- Permissible Variations in Dimension
- Wall thickness: The minimum wall thickness at any point shall not be more than 12.5% under the nominal wall thickness specified.
- Weights per foot: The weight of any individual length shall not vary more than 10% over and 3.5% under that specified. NOTE – NPS 4 and smaller are weighed in lots. Larger sizes are weighted by individual length.
- Outside diameter: Shall not vary from standard specified below at any point.
| NPS | Over | Under |
|---|---|---|
| 1 ½ and smaller | +1/64” | -1/64” |
| 2-4 | +1/32” | -1/32” |
| 5-8 | +1/16” | -1/32” |
| 10-18 | +3/32” | -1/32” |
| Over 18 | +1/8” | -1/32” |
Lengths for A106 seamless carbon steel pipe must be defined upon order placement. In the absence of specific length requirements, the following standards apply:
- Single Random: Lengths vary between 16′ to 22′, with a 5% allowance for 12′ to 16′.
- Double Random: Minimum length of 22′, with an average of 35′. About 5% of these may range from 16′ to 22′.
Marking Requirements
- Rolled, die-stamped, or paint-stenciled, as per manufacturer’s discretion.
- Must include the manufacturer’s name, brand, or trademark.
- Designation as A106 A, B, or C.
- Hydrostatic test pressure and/or NDE, or NH if neither is specified.
- Size, length, weight per foot (for NPS 4 and larger).
- ANSI schedule number, weight class, or wall thickness.
- An additional “S” for pipes tested for supplementary requirements.