API 5L Pipe Specification Guide | PSL1 vs PSL2 | Grade Chart

What Is API 5L?

API 5L is the American Petroleum Institute's specification for line pipe — steel pipe used for conveying oil, gas, water, and other fluids in pipeline transportation systems. It is the most widely referenced international standard for line pipe, adopted by pipeline operators, engineering contractors, and regulatory bodies worldwide. The current edition is the 46th Edition (2018), which aligns with ISO 3183.

API 5L covers seamless and welded steel pipe (LSAW, SSAW, ERW) in diameters from 2-3/8 inch (60.3 mm) to 80 inch (2032 mm), with steel grades ranging from A25 through X120. The specification addresses chemical composition, mechanical properties, dimensions, testing, inspection, and marking requirements.

Key Point: API 5L is not a single-grade specification. It defines a family of steel grades (designated by minimum yield strength in ksi), two Product Specification Levels (PSL1 and PSL2), and covers both seamless and welded manufacturing processes. The appropriate grade and PSL selection depends on the pipeline design conditions — pressure, temperature, fluid composition, and environmental factors.

PSL1 vs PSL2 — Key Differences

API 5L defines two Product Specification Levels. PSL1 is the standard quality level suitable for most applications. PSL2 imposes additional mandatory requirements on chemical composition, mechanical properties, notch toughness, and non-destructive testing — making it mandatory for offshore, sour service, and critical onshore pipelines.

Requirement	PSL1	PSL2
Chemical Composition	Standard limits for C, Mn, P, S	Stricter limits; mandatory CE (Carbon Equivalent) control; CE_IIW max 0.43% (general) or 0.25% for C-Mn steel
Tensile Testing	One test per 100 pipes from same heat	One test per pipe (or per heat for small diameters)
Yield Strength	Minimum specified	Minimum AND maximum specified (prevents over-strength)
Notch Toughness (CVN)	Not required	Mandatory Charpy V-notch testing at specified temperature
NDT of Seam Weld	Optional (by agreement)	Mandatory 100% NDT (UT or RT) of seam weld for welded pipe
Hydrostatic Test	Required (or NDT alternative by agreement)	Mandatory hydrostatic test at specified pressure
Traceability	Heat-level traceability	Full traceability with certified MTR (Material Test Report)
Weld Repair	Weld repair permitted	Weld repair of pipe body NOT permitted; seam weld repair only by qualified procedure
Dimensional Tolerances	Standard tolerances	Tighter tolerances on diameter, wall thickness, and straightness
Fracture Toughness	Not addressed	DWTT (Drop Weight Tear Test) required for Grade X60 and higher, OD > 20"

API 5L Grade Chart — Chemical Composition

Grade	C max (%)	Mn max (%)	P max (%)	S max (%)	Other
A25	0.21	0.60	0.030	0.030	—
A	0.22	0.90	0.030	0.030	—
B	0.28	1.20	0.030	0.030	Nb/V/Ti optional
X42	0.28	1.30	0.030	0.030	Nb+V+Ti max 0.15%
X46	0.28	1.40	0.030	0.030	Nb+V+Ti max 0.15%
X52	0.28	1.40	0.030	0.030	Nb+V+Ti max 0.15%
X56	0.28	1.40	0.030	0.030	Nb+V+Ti max 0.15%
X60	0.28	1.40	0.030	0.030	Nb+V+Ti max 0.15%
X65	0.28	1.45	0.030	0.030	Nb+V+Ti max 0.15%
X70	0.28	1.65	0.030	0.030	Nb+V+Ti max 0.15%
X80	0.28	1.85	0.030	0.030	Nb+V+Ti+Cu+Ni+Cr+Mo

Note: Values shown are for PSL1. PSL2 imposes lower maximums for P (0.025%) and S (0.015%), plus CE limits. Actual composition may vary by manufacturer and wall thickness. Always refer to the current API 5L edition for complete requirements.

API 5L Mechanical Properties

Grade	Yield Strength min (ksi / MPa)	Tensile Strength min (ksi / MPa)	Elongation min (%)
A25	25 / 172	45 / 310	28
A	30 / 207	48 / 331	28
B	35 / 241	60 / 414	23
X42	42 / 290	60 / 414	23
X46	46 / 317	63 / 434	22
X52	52 / 359	66 / 455	21
X56	56 / 386	71 / 490	19
X60	60 / 414	75 / 517	18
X65	65 / 448	77 / 531	18
X70	70 / 483	82 / 565	17
X80	80 / 552	90 / 621	16

Dimensional Ranges

Manufacturing Process	Typical OD Range	Typical WT Range	Common Grades
Seamless	2-3/8" – 24" (60.3 – 610 mm)	3.0 – 100 mm	B, X42–X80
ERW (HFW)	2-3/8" – 24" (60.3 – 610 mm)	3.0 – 25 mm	B, X42–X70
LSAW (JCOE/UOE)	16" – 64" (406 – 1626 mm)	6.0 – 60 mm	B, X42–X80
SSAW (Spiral)	8" – 120" (219 – 3048 mm)	5.0 – 25 mm	B, X42–X80

Testing Requirements Summary

Chemical Analysis: Ladle analysis per heat; product analysis per test unit (PSL2)
Tensile Test: Yield strength (0.5% EUL), ultimate tensile strength, elongation
Charpy V-Notch (PSL2): Mandatory; test temperature specified by purchaser; minimum absorbed energy values per grade and wall thickness
DWTT (PSL2): Required for X60+ grades, OD > 20" (508 mm); minimum shear area 85% at test temperature
Hydrostatic Test: Minimum 60% SMYS for OD < 18"; 75% SMYS for OD 18-20"; 85% SMYS for OD > 20" (PSL2); hold time minimum 5 seconds; PSL2 allows test at 95% SMYS for special applications
NDT of Seam Weld (PSL2): 100% ultrasonic (UT) or radiographic (RT) inspection of full seam weld length
Dimensional Inspection: OD, WT, length, straightness, end squareness, and ovality
Visual Inspection: Surface condition, end finish, bevel geometry, marking verification

Typical Applications by Grade

Grade B: Low-pressure gathering lines, water injection, utility piping, structural
X42–X52: Medium-pressure onshore transmission, distribution systems, flowlines
X60–X65: High-pressure onshore transmission, offshore export pipelines
X70: High-pressure long-distance transmission, deep-water offshore
X80: Very high-pressure transmission, Arctic pipelines, reducing wall thickness/cost for large-diameter lines

API 5L Pipe Specification — Complete Guide