Introduction to L360 Steel Pipe
L360 steel pipe, also known as L360 Line Pipe, is a high-strength, low-alloy steel pipe specifically designed for pipeline transportation systems in the oil and gas industry. The "L" stands for "Line Pipe," and the "360" indicates its minimum specified yield strength of 360 MPa (or 52,000 psi).
It is one of the most common grades specified for onshore and offshore oil and gas transmission pipelines. According to the API 5L standard, L360 is equivalent to the API 5L Grade B (PSL 2) and historically known as X52 (where "X" stands for yield strength and "52" for 52,000 psi).
Key Characteristics:
High Strength: Suitable for high-pressure applications.
Good Toughness: Provides resistance to fracture propagation.
Excellent Weldability: Facilitates easy and reliable field welding.
Corrosion Resistance: Often used in conjunction with external coatings (FBE, 3LPE) and internal linings for corrosion protection.
Governing Standard: API 5L
L360 pipes are manufactured according to the API 5L (American Petroleum Institute Specification 5L) standard. This standard defines two Product Specification Levels:
API 5L PSL 1: Standard requirements for chemical composition and mechanical properties.
API 5L PSL 2: More stringent requirements, including enhanced control of chemical composition (e.g., maximum Carbon Equivalent for weldability), tougher Charpy V-Notch impact testing, stricter non-destructive testing (NDT), and higher hydrostatic test pressures. L360 is typically supplied as PSL 2.
Product Parameters & Technical Data
The following tables summarize the key parameters for L360 PSL 2 pipes as per API 5L.
Table 1: Chemical Composition (API 5L PSL 2 - Maximum Percent by Weight)
The composition is critical for ensuring weldability and mechanical properties. The Carbon Equivalent (CE) is a calculated value that must be controlled.
| Element | Standard Grade Max (%) | Alternative Grade Max (%) | Notes |
|---|---|---|---|
| Carbon (C) | 0.24 | 0.22 | Lower carbon improves weldability. |
| Manganese (Mn) | 1.40 | 1.40 | Increases strength. |
| Phosphorus (P) | 0.025 | 0.025 | Impurity, controlled to prevent brittleness. |
| Sulfur (S) | 0.015 | 0.015 | Impurity, controlled to improve toughness. |
| Carbon Equivalent (CE) | 0.43 | 0.43 | CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 |
Note: The standard and alternative grades have slight differences in permissible elements like Silicon, Niobium, Vanadium, etc., but the key limits above are consistent.
Table 2: Mechanical Properties (API 5L PSL 2)
These properties are verified through mechanical testing.
| Property | Requirement | Test Method |
|---|---|---|
| Yield Strength (Min) | 360 MPa (52,200 psi) | Tensile Test |
| Yield Strength (Max) | 530 MPa (76,900 psi) | Tensile Test |
| Tensile Strength (Min) | 460 MPa (66,700 psi) | Tensile Test |
| Elongation (Min) | Depends on sample size and tensile strength | Tensile Test |
| Charpy V-Notch Impact Test | Required | Absorbed energy must meet specified values at the design temperature. |
Table 3: Common Dimensions and Sizes
L360 pipe is available in a wide range of sizes as both Seamless (S) and Welded (EW, ERW, SAW).
| Type | Outer Diameter (OD) Range | Wall Thickness (WT) Range | Common Lengths |
|---|---|---|---|
| Seamless (S) | 10.3 mm to 1,219 mm (0.4" to 48") | Varies with diameter, e.g., 2.4mm to 100mm+ | Single Random: ~6m, Double Random: ~12m |
| Electric Resistance Welded (ERW) | 21.3 mm to 1,219 mm (0.84" to 48") | Varies with diameter | Single Random: ~6m, Double Random: ~12m |
| Submerged Arc Welded (SAW) | 406 mm to 2,540 mm (16" to 100") | 6.4 mm to 50 mm+ | Typically 12 meters or as required |
Types of L360 Pipes
L360 Seamless (L360 S): Manufactured without a weld seam. Ideal for high-pressure applications and critical services where weld integrity is a primary concern.
L360 ERW (Electric Resistance Welded): Formed from a rolled sheet and welded using electric resistance. Cost-effective for many standard pipeline applications.
L360 SAW (Submerged Arc Welded): Used for large-diameter pipes. The weld is made under a blanket of flux. Available as:
L360 SAWL (Longitudinally Welded): Weld seam runs parallel to the pipe length.
L360 SAWH (Helically Welded): Weld seam is spiral.
Typical Applications
Onshore and Offshore Gas Transmission Pipelines
Crude Oil Transmission Pipelines
Water Injection Lines in oil fields
Slurry and Process Piping in industrial plants
Structural Piling (in some cases)
Summary Table: L360 Quick Reference
| Feature | Specification |
|---|---|
| Standard | API 5L (PSL 1 or PSL 2) |
| Grade | L360 or X52 |
| Min. Yield Strength | 360 MPa / 52,200 psi |
| Min. Tensile Strength | 460 MPa / 66,700 psi |
| Key Characteristic | Excellent combination of strength and weldability |
| Common Types | Seamless (S), ERW, SAW (Longitudinal & Helical) |
| Primary Use | Oil and Gas Transmission Pipelines |
For specific project requirements, it is essential to consult the full API 5L standard and the manufacturer's technical data sheets to ensure all parameters (such as impact test temperature, hardness limits for sour service, etc.) are met.
