ASTM A106 Pipe | Grades, Specifications, Dimensions & Composition

ASTM A106 is a specification for seamless carbon steel pipe used in high-temperature service. It covers three grades—Grade A, Grade B, and Grade C—and is commonly applied to pressure piping in refineries, power plants, and process systems.

1. What Is ASTM A106?

ASTM A106 defines the requirements for seamless carbon steel pipe manufactured for high-temperature service. The specification covers material, manufacturing, dimensional, and inspection requirements for the finished pipe.

It includes three grades: Grade A, Grade B, and Grade C. These grades have different requirements for chemical composition and mechanical properties, resulting in different minimum strength levels.

2. ASTM A106 Grades A, B and C

The three ASTM A106 grades differ primarily in their chemical composition and minimum mechanical property requirements. These differences determine the minimum strength level of each grade and affect grade selection for specific service requirements.

2.1 ASTM A106 Grade A

Has the lowest strength requirements among the three grades. It may be specified where lower mechanical strength is sufficient and cold bending or forming requirements need to be considered.

2.2 ASTM A106 Grade B

Is the most commonly specified grade for general high-temperature and pressure piping. It provides higher minimum yield and tensile strength than Grade A.

For detailed Grade B properties, dimensions, applications, and material selection, see ASTM A106 Gr B Seamless Pipe Specification and Key Uses.

2.3 ASTM A106 Grade C

Provides the highest minimum tensile and yield strength among the three grades. It may be selected where higher mechanical strength is required.

3. ASTM A106 Pipe Specifications

ASTM A106 pipe specifications include nominal pipe size, outside diameter, wall thickness, pipe schedule, and length.

3.1 ASTM A106 Pipe Size Range

ASTM A106 pipe is specified by nominal pipe size (NPS). NPS identifies the nominal pipe size and does not directly equal the actual outside diameter. The outside diameter is determined by the applicable dimensional standard for the selected NPS.

Common ASTM A106 pipe sizes include NPS 1/2" through 24", with larger sizes available depending on the manufacturer's production range and applicable dimensional requirements.

Note: The outside diameters above follow standard pipe dimensions commonly used with ASTM A106 pipe. ASTM A106 itself specifies the pipe material and manufacturing requirements; dimensional requirements are governed by the applicable dimensional standard.

3.2 ASTM A106 Pipe Dimensions

ASTM A106 pipe dimensions are primarily specified by nominal pipe size (NPS), outside diameter (OD), and wall thickness (WT). The inside diameter (ID) is determined from the actual OD and wall thickness:

ID = OD − 2 × WT

For example, an NPS 4 pipe with an outside diameter of 114.3 mm and a wall thickness of 6.02 mm has a calculated inside diameter of 102.26 mm.

The actual inside diameter may vary with the specified wall thickness and manufacturing tolerances.

3.3 ASTM A106 Pipe Wall Thickness and Schedule

ASTM A106 pipe wall thickness varies according to NPS and the selected schedule. For the same NPS, a higher schedule generally indicates a greater nominal wall thickness.

Common schedules used for ASTM A106 seamless pipe include SCH 40, SCH 80, SCH 160, and XXS. The applicable wall thickness should be selected according to the required dimensions, design conditions, and applicable piping code.

Note: Pipe schedules and nominal wall thicknesses are based on applicable standard dimensional tables such as ASME B36.10M. For NPS 1, SCH 80 and SCH 160 both have a nominal wall thickness of 4.55 mm.

3.4 ASTM A106 Pipe Length

ASTM A106 pipe can be supplied in specified lengths or random lengths according to the applicable requirements and purchase specification.

Common supply arrangements include single random length (SRL), double random length (DRL), and specified or cut lengths. The required length should be confirmed when placing an order, together with the applicable dimensional and tolerance requirements.

4. ASTM A106 Chemical Composition

ASTM A106 chemical composition requirements specify the allowable content of carbon, manganese, phosphorus, sulfur, silicon, and residual alloying elements for Grade A, Grade B, and Grade C seamless carbon steel pipe.

* Manganese adjustment: The ASTM A106/A106M specification permits an increase in the manganese maximum when the carbon content is below the specified maximum, subject to the applicable footnote and maximum manganese limit for the grade. The exact allowance should be checked against the ASTM A106/A106M edition specified for the order.

5. ASTM A106 Manufacturing and Heat Treatment Requirements

ASTM A106 seamless pipe is manufactured by hot-finishing or cold-drawing. The required heat treatment depends on the manufacturing condition and the applicable pipe requirements.

5.1 Manufacturing Method

ASTM A106 pipe is manufactured as seamless pipe by hot-finishing or cold-drawing. The manufacturing method affects the dimensional condition and heat treatment requirements of the finished pipe.

5.2 Heat Treatment Requirements

Heat treatment requirements under ASTM A106 depend on the manufacturing condition and the applicable requirements of the specification. Hot-finished and cold-drawn pipe are subject to different heat treatment provisions. The applicable heat treatment condition should be confirmed against the ASTM A106/A106M edition and the purchase specification.

5.3 Dimensional and Surface Requirements

Finished ASTM A106 pipe must comply with the specified requirements for outside diameter, wall thickness, length, straightness, and surface condition. Dimensional tolerances are applied according to the applicable pipe dimensional standard and purchase requirements.

6. ASTM A106 Testing and Inspection Requirements

6.1 Chemical Analysis:

Verifies the chemical composition against the requirements for the selected grade.

6.2 Mechanical Tests:

Tensile Test: Verifies yield strength, tensile strength, and elongation.

Bend Test: Evaluates ductility during bending.

Flattening Test: Evaluates resistance to cracking or deformation.

6.3 Hydrostatic and Nondestructive Testing: 

Each length of pipe is subject to hydrostatic testing unless an applicable nondestructive electric test is performed in accordance with the specification.

6.4 Visual and Dimensional Inspection: 

Checks outside diameter, wall thickness, length, and surface condition against specified requirements.

6.5 Inspection Documentation: 

Inspection documentation may include chemical composition, mechanical test results, heat treatment information, dimensions, and applicable inspection results, depending on the purchase order. MTRs (Material Test Reports) may be provided when specified.

7. FAQs

Q1. What is ASTM A106 used for?

ASTM A106 is used for seamless carbon steel piping in high-temperature service, including pressure piping in refineries, power plants, and process systems.

Q2. What is the difference between ASTM A106 Grade A, Grade B, and Grade C?

The three grades differ mainly in their chemical composition and minimum mechanical property requirements. Grade A has the lowest strength requirements, Grade B provides an intermediate strength level, and Grade C has the highest strength requirements.

Q3. Is ASTM A106 seamless or welded?

ASTM A106 is a specification for seamless carbon steel pipe. It does not cover welded pipe.

Q4. What is the yield strength of ASTM A106 Grade B?

ASTM A106 Grade B has a minimum yield strength of 240 MPa (35 ksi) and a minimum tensile strength of 415 MPa (60 ksi).

Q5. What sizes are available for ASTM A106 pipe?

ASTM A106 pipe is commonly supplied in NPS 1/2 through NPS 24, with larger sizes available depending on the manufacturer's production range and applicable dimensional requirements.

Q6. Does ASTM A106 require heat treatment?

Heat treatment requirements depend on the manufacturing condition and applicable ASTM A106 requirements. Hot-finished and cold-drawn pipe may have different heat treatment requirements, which should be confirmed for the specified product condition.

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