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API 5L is a specification for seamless and welded steel pipes designed for pipeline transportation systems in the petroleum and natural gas industries. The standard covers two product specification levels (PSL1 and PSL2), each catering to different requirements, including impact toughness and testing. It is particularly relevant in regions where projects are funded or insured by U.S.-based organizations, making it a critical specification in international pipeline construction.
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This specification mandates rigorous manufacturing requirements and includes a monogram license for manufacturers, ensuring that the mills meet the stringent requirements set by the API. Additionally, API 5L requires non-destructive testing (NDT) and hydrotesting, particularly in legal contexts, where these tests cannot be waived by either the end user or the manufacturer. Special annexes address specific needs for sour service and offshore applications.
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The API 5L specification uses ASME B36.10 for nominal pipe dimensions, making it compatible with ASTM A53, A106, and A333 grades. While API 5L is often used for pressure piping (as per ASME B31.X), it is not typically accepted for pressure vessels under the ASME BPVC, unless exceeding the design requirements and approved by local authorities.
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API 5L also has clear limits on dimensional deviations such as end squareness, straightness, and pipe flare, which are often seen as more definitive than those in ASTM standards. For this reason, API 5L is frequently adopted as the baseline for mill tolerances, regardless of whether it is explicitly stated in the purchase order.
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Basic Product Properties:
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Grade L175 / A25:​​
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Yield Strength (YS): 175 MPa (25.4 ksi)
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Ultimate Tensile Strength (UTS): 310 MPa (45.0 ksi)
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Grade L210 / A:
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YS: 210 MPa (30.5 ksi)
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UTS: 335 MPa (48.6 ksi)
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Grade L245 / B:
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YS: 245 MPa (35.5 ksi)
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UTS: 415 MPa (60.2 ksi)
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Grade L290 / X42:
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YS: 290 MPa (42.1 ksi)
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UTS: 415 MPa (60.2 ksi)
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Grade L320 / X46:
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YS: 320 MPa (46.4 ksi)
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UTS: 435 MPa (63.1 ksi)
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Grade L360 / X52:
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YS: 360 MPa (52.2 ksi)
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UTS: 460 MPa (66.7 ksi)
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Grade L390 / X56:
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YS: 390 MPa (56.6 ksi)
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UTS: 490 MPa (71.1 ksi)
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Grade L415 / X60:
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YS: 415 MPa (60.2 ksi)
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UTS: 520 MPa (75.4 ksi)
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Grade L450 / X65:
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YS: 450 MPa (65.3 ksi)
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UTS: 535 MPa (77.6 ksi)
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Grade L485 / X70:
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YS: 485 MPa (70.3 ksi)
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UTS: 570 MPa (82.7 ksi)
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Product Specification Levels (PSL):
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PSL1: Standard specification; not impact tested.
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PSL2: For grades ≤ L415 / X60; impact tested at 0°C (32°F) to meet a minimum 27J (20 ft-lb) for pipe ≤ 762mm OD (NPS 30), or minimum 40J (30 ft-lb) for pipes > 762mm OD (NPS 30).
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API 5L also ensures that the weld metal and heat-affected zone (HAZ) meet the required impact toughness, with a minimum of 27J (20 ft-lb) for pipes < 1422mm OD (NPS 56).
API 5L is a crucial specification for ensuring the safety, performance, and reliability of pipeline systems used in harsh and high-pressure environments such as the petroleum and natural gas industries.