Carbon Steel Pipe: Grades, Sizes, Standards & Supplier Guide
Carbon steel pipe is the most widely used piping material in the world. From oil and gas pipelines in Nigeria to power plant steam lines in Saudi Arabia to water distribution networks in Kenya — carbon steel pipe moves fluids across every industry in every country.
It is strong, cost-effective, available in every size from 1/2 inch to over 60 inches, and can be manufactured seamless or welded to suit virtually any pressure, temperature, and service condition. But not all carbon steel pipe is the same. Different grades, manufacturing methods, and standards exist for different applications — and specifying the wrong one can mean failed inspections, project delays, and rejected material.
This guide covers the grades, sizes, manufacturing methods, standards, and selection criteria that procurement engineers and project managers need to know when sourcing carbon steel pipe for industrial projects.
Carbon Steel Pipe Grades: Which One Do You Need?
ASTM A106 — Seamless Pipe for High-Temperature Service
ASTM A106 is the standard specification for seamless carbon steel pipe intended for high-temperature service. It is the most commonly specified pipe in refineries, power plants, and petrochemical facilities worldwide.
Grades and mechanical properties:
Property | Grade A | Grade B | Grade C |
|---|---|---|---|
Min. Tensile Strength | 330 MPa (48,000 psi) | 415 MPa (60,000 psi) | 485 MPa (70,000 psi) |
Min. Yield Strength | 205 MPa (30,000 psi) | 240 MPa (35,000 psi) | 275 MPa (40,000 psi) |
Max. Carbon Content | 0.25% | 0.30% | 0.35% |
Manganese Range | 0.27–0.93% | 0.29–1.06% | 0.29–1.06% |
Grade B is what you need in 90% of cases. It is the industry default for process piping in refineries, power plants, and petrochemical facilities. When a piping specification says "carbon steel pipe" without more detail, it means A106 Grade B. It is equivalent to ASME SA106 Grade B (for ASME code applications), ASTM A53 Grade B, and API 5L Grade B in chemical and mechanical properties.
Additional chemical requirements (all grades): Phosphorus max 0.035%, Sulfur max 0.035%, Silicon min 0.10%. Total of Cr, Cu, Mo, Ni, V shall not exceed 1.0%. For each 0.01% reduction below the maximum carbon content, an increase of 0.06% manganese is permitted, up to a maximum of 1.35%.
Temperature range: Suitable for continuous service temperatures up to approximately 425°C (800°F). Above this, alloy steel pipe (ASTM A335 grades P11, P22, P91) with chromium-molybdenum content is required to maintain strength and resist creep.
Sizes: NPS 1/8" (DN 6) through NPS 48" (DN 1200). Standard wall thickness per ASME B36.10 schedules (SCH 10 through SCH 160, plus STD, XS, and XXS). NPS 1-1/2" and under may be hot-finished or cold-drawn. NPS 2" and larger shall be hot-finished unless otherwise specified.
Standard lengths: Single random 5.0–7.3m (17'–24'), double random 10.7–13.4m (36'–44'). Fixed lengths (6m / 20ft or 12m / 40ft) available on request.
Required testing: Every heat must undergo tensile testing, flattening test (NPS 2-1/2" and larger), bend test (NPS 2" and smaller), and hydrostatic test. The hydrostatic test pressure produces a stress in the pipe wall equal to 60% of specified minimum yield strength.
Applications: Refinery process piping, boiler feedwater and steam lines, power plant piping, petrochemical plants, heat exchanger connections, and pressure vessel nozzles. Suitable for bending, flanging, and similar forming operations.
ASTM A53 — Welded and Seamless Pipe for General Service
ASTM A53 covers both seamless and welded carbon steel pipe for general mechanical, structural, and low-pressure fluid service. It is less stringent than A106 and is commonly used for non-critical applications.
Types and Grades:
Type S (Seamless) — Grade A (330 MPa tensile) and Grade B (415 MPa tensile)
Type E (ERW — Electric Resistance Welded) — Grade A and Grade B
Type F (Furnace-welded / continuous weld) — Grade A only. Lower quality, declining in use.
Key difference from A106: A53 allows both seamless and welded manufacturing. A53 Type S is often substituted for A106 Grade B in non-critical service because it is interchangeable in many applications. However, A106 requires stricter testing (including mandatory tensile and flattening tests on every heat) and is the preferred specification for process piping.
Applications: General-purpose piping, structural supports, water lines, fire sprinkler systems, fencing, piling, and low-pressure mechanical service.
API 5L — Line Pipe for Oil & Gas Pipelines
API 5L is the American Petroleum Institute specification for steel line pipe used in pipeline transportation systems — crude oil, natural gas, petroleum products, and water. This is the standard for any pipeline project.
Grades — the "X" number indicates minimum yield strength in thousands of psi:
Grade | ISO 3183 | Min. Yield Strength | Min. Tensile Strength | Typical Application |
|---|---|---|---|---|
Grade B | L245 | 241 MPa (35,000 psi) | 415 MPa (60,000 psi) | General pipeline, water transmission |
X42 | L290 | 290 MPa (42,000 psi) | 415 MPa (60,000 psi) | Low-medium pressure oil & gas |
X46 | L320 | 320 MPa (46,000 psi) | 435 MPa (63,000 psi) | Medium pressure pipelines |
X52 | L360 | 359 MPa (52,000 psi) | 455 MPa (66,000 psi) | Most common O&G transmission grade |
X56 | L390 | 390 MPa (56,000 psi) | 490 MPa (71,000 psi) | Medium-high pressure |
X60 | L415 | 414 MPa (60,000 psi) | 517 MPa (75,000 psi) | Higher-pressure gas transmission |
X65 | L450 | 448 MPa (65,000 psi) | 531 MPa (77,000 psi) | High-pressure gas, offshore |
X70 | L485 | 483 MPa (70,000 psi) | 565 MPa (82,000 psi) | Long-distance high-pressure pipelines |
X80 | L555 | 552 MPa (80,000 psi) | 621 MPa (90,000 psi) | Ultra-high pressure, deepwater |
Which grade to choose: For most onshore oil and gas transmission pipelines in Africa and the Middle East, X52 is the standard. It offers the best balance of strength, weldability, and cost. X65 and X70 are specified for high-pressure, long-distance gas pipelines where wall thickness reduction (and therefore material savings) is critical. Grade B and X42 are used for lower-pressure distribution networks and water transmission.
PSL Levels — this is critical for your project:
PSL 1 (Product Specification Level 1) — standard quality level. Basic chemical, mechanical, and testing requirements. No mandatory impact testing. Suitable for most general pipeline applications.
PSL 2 — stricter chemical composition limits (lower carbon, phosphorus, sulfur), mandatory Charpy V-notch (CVN) impact testing, maximum yield strength cap (not just minimum), and mandatory non-destructive examination (NDE). Required for sour service (H2S environments per NACE MR0175/ISO 15156), offshore projects, and any application where higher reliability is mandated by the project specification or national oil company.
Delivery conditions for PSL2: The suffix letter indicates the manufacturing route — R (as-rolled), N (normalized), Q (quenched and tempered), M (thermomechanical controlled rolling). Add "S" for sour service. Example: API 5L X52 QS = Grade X52, quenched and tempered, sour service.
Sizes: NPS 1/4" to NPS 80" (DN 6 to DN 2000). Seamless available up to approximately NPS 26". ERW up to NPS 24". Large-diameter pipe above NPS 16" is manufactured LSAW or SSAW.
Applications: Crude oil pipelines, natural gas transmission and distribution, water pipelines, petroleum product transport, and offshore risers.
ASTM A333 — Low-Temperature Service Pipe
ASTM A333 covers seamless and welded carbon and alloy steel pipe for low-temperature service applications.
Key grades:
A333 Grade 6 — the most common low-temperature carbon steel pipe. Charpy impact tested at -45°C. Used in LNG facilities, cryogenic systems, and cold-climate pipelines.
A333 Grade 3 — nickel alloy steel for even lower temperature service down to -100°C.
Applications: LNG processing plants, cold storage facilities, cryogenic piping systems, and any application where the operating temperature drops below -29°C (the lower limit of standard A106).
Seamless vs Welded: Manufacturing Methods
Seamless pipe is manufactured by piercing a solid steel billet to form a hollow tube. No weld seam exists, which means the pipe has uniform strength around its entire circumference. Seamless pipe is required for high-pressure, high-temperature, and critical service applications.
ERW (Electric Resistance Welded) pipe is formed from steel coil and welded longitudinally. Modern high-frequency ERW produces a narrow heat-affected zone and reliable weld quality. Used for structural, low-to-moderate pressure, and general service applications up to approximately NPS 24".
LSAW (Longitudinal Submerged Arc Welded) pipe is formed from steel plate and welded longitudinally using the submerged arc welding process. Used for large-diameter pipeline applications (typically NPS 16" to NPS 60"+).
SSAW (Spiral Submerged Arc Welded) pipe is formed by spirally winding steel coil and welding the helical seam. Cost-effective for large-diameter, lower-pressure applications such as water transmission, piling, and structural use.
Which to choose: Seamless for high-pressure process piping, boiler tubes, and critical service. ERW for general service, structural, and moderate-pressure applications. LSAW for large-diameter, high-pressure pipelines. SSAW for large-diameter, lower-pressure and structural applications.
Pipe Sizes and Schedules
Carbon steel pipe sizes are specified by Nominal Pipe Size (NPS) in inches or Nominal Diameter (DN) in millimeters. The actual outside diameter (OD) is standardized per ASME B36.10.
Wall thickness is specified by Schedule Number. Higher schedule numbers mean thicker walls and higher pressure ratings.
Common schedules:
SCH 10 / SCH 10S — thin wall, low-pressure service
SCH 40 / STD (Standard Weight) — the most commonly ordered schedule for general industrial piping. Note: SCH 40 and STD are identical up to NPS 10". Above NPS 10", SCH 40 is heavier.
SCH 80 / XS (Extra Strong) — thicker wall for higher-pressure service. SCH 80 and XS are identical up to NPS 8". Above NPS 8", SCH 80 is heavier.
SCH 120 / SCH 160 — heavy wall for high-pressure applications
XXS (Double Extra Strong) — maximum standard wall thickness
Quick reference — common sizes and weights (SCH 40):
NPS | DN | OD (mm) | Wall (mm) | Weight (kg/m) |
|---|---|---|---|---|
2" | 50 | 60.3 | 3.91 | 5.44 |
3" | 80 | 88.9 | 5.49 | 11.29 |
4" | 100 | 114.3 | 6.02 | 16.07 |
6" | 150 | 168.3 | 7.11 | 28.26 |
8" | 200 | 219.1 | 8.18 | 42.55 |
10" | 250 | 273.1 | 9.27 | 60.31 |
12" | 300 | 323.9 | 10.31 | 79.73 |
16" | 400 | 406.4 | 12.70 | 123.30 |
20" | 500 | 508.0 | 12.70 | 155.12 |
24" | 600 | 609.6 | 14.27 | 209.64 |
The outside diameter stays constant for a given NPS — only the wall thickness (and therefore the inside diameter and weight) changes between schedules. This is a critical point that procurement teams new to pipe specification sometimes overlook.
Key Standards and Specifications
Standard | Scope | Common Use |
|---|---|---|
ASTM A106 | Seamless CS pipe for high-temperature | Refinery, power plant, petrochemical |
ASTM A53 | Seamless and welded CS pipe | General service, structural, mechanical |
API 5L | Line pipe for pipeline systems | Oil & gas pipelines, water transmission |
ASTM A333 | CS and alloy pipe for low-temperature | LNG, cryogenic, cold-climate |
ASME B36.10 | Pipe dimensions (OD, wall, weight) | Size and schedule reference |
ASME B16.25 | Butt-welding end preparation | Weld end bevel dimensions |
ASME B31.1 | Power piping code | Power plant piping design |
ASME B31.3 | Process piping code | Refinery and chemical plant piping |
NACE MR0175 | Materials for sour service (H2S) | Oil & gas (sour environments) |
What Documentation to Request from Your Supplier
When sourcing carbon steel pipe for projects in Africa, the Middle East, or any international market, always request the following documentation to ensure material quality and project compliance:
Material Test Report (MTR) / Mill Test Certificate (MTC) — EN 10204 Type 3.1 inspection certificate showing chemical composition and mechanical properties of each heat. This is the minimum requirement for any serious project.
Hydrostatic Test Certificate — confirmation that each pipe has been hydrostatically tested per the applicable standard (ASTM or API).
Dimensional Inspection Report — verification of outside diameter, wall thickness, length, straightness, and end preparation (bevel angle for butt-weld ends).
Third-Party Inspection (TPI) — for critical projects, independent inspection by agencies such as Bureau Veritas, SGS, TÜV, or Lloyd's Register. Many EPC contractors and national oil companies (ADNOC, Saudi Aramco, KNPC, NNPC) require TPI as standard.
NDT Reports — non-destructive testing (ultrasonic, radiographic, or eddy current) per the applicable standard, particularly for seamless pipe and weld seams.
How to Select the Right Carbon Steel Pipe
Step 1 — Define the service conditions. What fluid? What pressure and temperature? What is the design life? Is there any corrosion concern (H2S, CO2, seawater)?
Step 2 — Choose the specification. High-temperature process piping → ASTM A106. Pipeline → API 5L. General service → ASTM A53. Low temperature → ASTM A333.
Step 3 — Select the grade. Match the minimum yield and tensile strength to the design requirements. For API 5L, the grade determines the allowable operating pressure for a given diameter and wall thickness.
Step 4 — Specify seamless or welded. Critical and high-pressure service → seamless. General and structural → ERW. Large-diameter pipeline → LSAW or SSAW.
Step 5 — Determine size and schedule. Use the applicable piping code (ASME B31.1 or B31.3) and pressure-temperature tables to calculate the required wall thickness, then select the corresponding schedule.
Step 6 — Specify end connections. Plain end (PE), beveled end (BE) for butt welding, or threaded end (TE). Most industrial pipe is supplied with beveled ends per ASME B16.25.
Step 7 — Specify documentation. MTR 3.1 minimum. Add TPI, NDT, and coating requirements as the project demands.
Coatings and Linings
For pipeline and buried applications, external coatings protect against soil corrosion:
3LPE (3-Layer Polyethylene) — the most common pipeline coating for onshore buried pipe. Operating temperature -40°C to +80°C.
3LPP (3-Layer Polypropylene) — for higher operating temperatures up to +110°C.
FBE (Fusion Bonded Epoxy) — single-layer epoxy coating for moderate corrosion protection. Also used as internal lining.
Coal Tar Enamel / Asphalt Enamel — traditional coatings still used in some regions but declining.
Concrete Weight Coating (CWC) — for offshore and river crossing pipe to provide negative buoyancy.
Internal linings (cement mortar, epoxy, polyethylene) are specified for water transmission pipelines to protect against corrosion and maintain water quality.
Supply from Kasko Makine
Kasko Makine supplies the full range of carbon steel pipe — ASTM A106 Grade B seamless, ASTM A53 ERW, API 5L line pipe in grades from Grade B through X70, and ASTM A333 Grade 6 for low-temperature service. Available in sizes from NPS 1/2" to large-diameter LSAW and SSAW up to NPS 60"+.
We supply complete piping packages including pipe, flanges, fittings, fasteners, and gaskets — reducing your procurement complexity to a single source.
All pipe supplied with EN 10204 Type 3.1 material test reports. Third-party inspection available on request. We deliver to project sites across Africa, the Middle East, Central Asia, South Asia, and Southeast Asia.
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Q: What is the most common carbon steel pipe grade?
A: ASTM A106 Grade B is the most widely specified carbon steel pipe for industrial process piping. For pipeline applications, API 5L X52 is the most commonly used grade. For general service and structural use, ASTM A53 Grade B is standard.
Q: What is the difference between ASTM A106 and A53 pipe?
A: Both cover carbon steel pipe, but A106 is specifically for seamless pipe in high-temperature service with stricter testing requirements. A53 covers both seamless and welded pipe for general service. A106 Grade B and A53 Type S Grade B have similar mechanical properties but A106 is preferred for process piping.
Q: What does API 5L PSL1 vs PSL2 mean?
A: PSL stands for Product Specification Level. PSL 1 is the standard quality level. PSL 2 has stricter requirements for chemical composition, mechanical testing, and traceability. PSL 2 is required for sour service (H2S environments), offshore projects, and critical pipeline applications.
Q: What is the difference between seamless and welded pipe?
A: Seamless pipe is made from a solid billet with no weld seam, providing uniform strength. Welded pipe (ERW, LSAW, SSAW) is formed from plate or coil and welded. Seamless is required for high-pressure and critical service. Welded is more cost-effective for general, structural, and large-diameter applications.
Q: What documentation should I request when buying carbon steel pipe?
A: At minimum, request an EN 10204 Type 3.1 Material Test Report (MTR) showing chemical composition and mechanical properties. For critical projects, also request hydrostatic test certificates, dimensional inspection reports, and third-party inspection (TPI) certificates from agencies like Bureau Veritas, SGS, or TÜV.
Q: What pipe coating is used for buried pipelines?
A: 3LPE (3-Layer Polyethylene) is the most common external coating for buried carbon steel pipelines. 3LPP is used for higher temperatures. FBE (Fusion Bonded Epoxy) provides moderate protection. For offshore pipe, concrete weight coating (CWC) provides negative buoyancy.
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Request pricing for your project — contact us via WhatsApp at +90 (537) 521 1399 or email info@kaskomakine.com with your pipe specification, sizes, quantities, and delivery location. We respond to inquiries within 24 hours.