Now that you understand pipe coatings and protection methods, let’s dive into the most important steel pipe standards used worldwide: API (American Petroleum Institute) and ASTM (American Society for Testing and Materials).
1. Why Are Pipe Standards Important?
Steel pipes are manufactured according to strict standards to ensure quality, performance, and safety across different industries.
🔹 API Standards → Used in oil & gas, petroleum pipelines, and OCTG (Oil Country Tubular Goods)
🔹 ASTM Standards → Used in general industrial piping, mechanical, and structural applications
🔹 ASME (American Society of Mechanical Engineers) → Used in boilers, pressure piping, and high-temperature applications
2. API Pipe Standards (Oil & Gas Industry)
API standards are used in oil and gas transmission pipelines, casing, tubing, and line pipes.
(1) API 5L – Line Pipe Standard
- Covers seamless and welded steel pipes used for transporting oil, gas, and water.
- Available in two product specification levels (PSL1 and PSL2).
| Grade | Yield Strength (ksi/MPa) | Tensile Strength (ksi/MPa) | Application |
|---|---|---|---|
| X42 | 42 ksi (290 MPa) | 60 ksi (415 MPa) | Low-pressure oil & gas pipelines |
| X52 | 52 ksi (360 MPa) | 66 ksi (455 MPa) | General transmission pipelines |
| X60 | 60 ksi (415 MPa) | 75 ksi (520 MPa) | Medium-pressure gas pipelines |
| X70 | 70 ksi (485 MPa) | 82 ksi (565 MPa) | High-pressure long-distance pipelines |
| X80 | 80 ksi (550 MPa) | 90 ksi (620 MPa) | High-strength, large-diameter pipelines |
✅ PSL2 pipes have stricter chemical composition and mechanical properties than PSL1.
(2) API 5CT – OCTG (Casing & Tubing) Standard
- Used for casing (protecting boreholes) and tubing (oil & gas production lines).
- Includes seamless pipes only (no welded pipes).
| Grade | Minimum Yield Strength (MPa) | Application |
|---|---|---|
| J55 | 379 MPa | Shallow wells, low-pressure applications |
| K55 | 379 MPa | Similar to J55 but with better toughness |
| N80 | 552 MPa | Deep wells, medium-strength applications |
| L80 | 552 MPa | Corrosion-resistant applications |
| P110 | 758 MPa | High-pressure deep drilling operations |
✅ For deep wells and extreme conditions, L80 and P110 grades are preferred.
(3) API 5DP – Drill Pipe Standard
- Covers drill pipes used in oil and gas drilling operations.
- Grades: E, X95, G105, S135 (higher grades for deeper drilling).
3. ASTM Pipe Standards (General & Industrial Applications)
ASTM standards cover structural, mechanical, and industrial piping applications.
(1) ASTM A53 – General Piping Standard
- Covers seamless and welded steel pipes.
- Used in water pipelines, steam, and air piping.
- Grades:
- Grade A → Lower strength, higher ductility
- Grade B → Higher strength, commonly used in pressure applications
✅ ASTM A53 is widely used for low-pressure applications.
(2) ASTM A106 – High-Temperature Carbon Steel Pipe
- Covers seamless pipes used in high-temperature applications.
- Used in boilers, refineries, power plants, and process piping.
- Grades:
- Grade A → Lower strength
- Grade B → Most commonly used
- Grade C → Highest strength
✅ ASTM A106 Grade B is commonly used for high-temperature piping systems.
(3) ASTM A333 – Low-Temperature Service Pipe
- Covers seamless and welded pipes for low-temperature applications.
- Used in cryogenic systems, LNG plants, and cold environments.
- Grades:
- Grade 1, 6 → Most commonly used
- Grade 8, 9, 10 → Higher alloy content for extreme cold environments
✅ ASTM A333 is used for pipelines operating at sub-zero temperatures.
(4) ASTM A335 – High-Temperature Alloy Steel Pipe
- Covers seamless alloy steel pipes for power plants and high-pressure systems.
- Contains Cr-Mo (Chromium-Molybdenum) for strength and heat resistance.
- Grades:
- P5, P9, P11, P22, P91 → Used in boilers, heat exchangers, and power plants
✅ P91 is widely used in high-pressure steam pipelines.
4. API vs. ASTM Pipe Standards – Key Differences
| Feature | API (Oil & Gas) | ASTM (Industrial & Mechanical) |
|---|---|---|
| Primary Use | Oil & gas transmission, OCTG | General piping, boilers, structures |
| Material Types | Carbon steel, alloy steel, corrosion-resistant | Carbon steel, stainless steel, alloy steel |
| Strength Grades | X42 to X80, J55 to P110 | Grade A, B, C, P5, P91 |
| Seamless & Welded | Both, but API 5CT is only seamless | Both, depending on application |
| Temperature Range | Normal to extreme high-pressure & corrosion conditions | Low-temperature to high-temperature applications |
✅ API pipes are designed for high-pressure and harsh environments, while ASTM pipes are used in general industrial applications.
5. Pipe Standard Marking & Labeling
Steel pipes must be marked with standard specifications, grade, size, and manufacturing details.
Example:
🔹 API 5L X52 PSL2 12” SCH 40 → Oil & gas transmission pipeline
🔹 ASTM A106 Gr. B 8” SCH 80 → High-temperature industrial piping
🔹 API 5CT L80 9-5/8” BTC → Casing pipe for oil wells
✅ Understanding markings is essential for selecting the right pipe for the job.
🔹 Summary of Lesson 5
- API standards (5L, 5CT, 5DP) are used in oil & gas transmission, casing, and drilling.
- ASTM standards (A53, A106, A333, A335) are used in industrial piping, boilers, and mechanical applications.
- API pipes focus on high-pressure, corrosion-resistant environments, while ASTM pipes serve general industrial needs.
- Pipe markings include standard, grade, size, and wall thickness, which must be understood for proper selection.
