What is API 5L Standard

Definition of API 5L Standard

Grade classification of API 5L

Main changes and extensions of the 44th edition of API 5L standard

API 5L Line Pipe Steel Grade

Pipelines conveying Class A, B, or X fluids must be constructed of steel having an area under the stress-strain curve as specified in the material standard. The specified minimum yield strength and tensile strength represent points on the stress-strain curve.

Chemical Composition (for PSL1 Steel Pipes with t ≤ 25.0mm)

Steel Grade	C (max)	Mn (max)	P (max)	S (max)	V (max)	Nb (max)	Ti (max)
L175 or A25	0.21	0.6	0.03	0.03	-	-	-
L175P or A25P	0.21	0.6	0.045~0.080	0.03	-	-	-
L210 or A	0.22	0.9	0.03	0.03	-	-	-
L245 or B	0.28	1.2	0.03	0.03	c,d	c,d	d
L290 or X42	0.28	1.3	0.03	0.03	d	d	d
L320 or X46, L360 or X52, L390 or X56	0.28	1.4	0.03	0.03	d	d	d
L415 or X60, L450 or X65, L485 or X70	0.28	1.4	0.03	0.03	f	f	f

Welded Pipes

Steel Grade	C (max)	Mn (max)	P (max)	S (max)	V (max)	Nb (max)	Ti (max)
L175 or A25	0.21	0.6	0.03	0.03	-	-	-
L175P or A25P	0.21	0.6	0.045~0.080	0.03	-	-	-
L210 or A	0.22	0.9	0.03	0.03	-	-	-
L245 or B	0.26	1.2	0.03	0.03	c,d	c,d	d
L290 or X42	0.26	1.3	0.03	0.03	d	d	d
L320 or X46, L360 or X52, L390 or X56	0.26	1.4	0.03	0.03	d	d	d
L415 or X60	0.26	1.4	0.03	0.03	f	f	f
L450 or X65	0.26	1.45	0.03	0.03	f	f	f
L485 or X70	0.26	1.65	0.03	0.03	f	f	f

a) Cu≤0.50%; Ni≤0.50%; Cr≤0.50%; Mo≤0.15%. Cu, Cr and Ni shall not be intentionally added for grades L360/X52 and below.
b) For every 0.01% decrease in carbon content compared to the specified maximum carbon content, the manganese content is allowed to increase by 0.05% compared to the specified maximum manganese content, but for grades ≥L245 or B but ≤L360 or X52, it shall not exceed 1.65%; for grades L＞360 or X52 but c) Unless otherwise agreed, the sum of niobium content and vanadium content shall be ≤0.06%.
d) The sum of niobium, vanadium and titanium content shall be ≤0.15%.
e) Unless otherwise agreed.
f) Unless otherwise agreed, the sum of niobium, vanadium and titanium content shall be ≤ 0.15%

API 5L Seamless Steel Pipes

API 5L seamless steel pipes, also known as line pipe steel seamless pipes, include materials like GR.B, X42, X46, X52, X56, X60, X65, and X70. Line pipes are used to transport oil, gas, and water from the ground to petroleum and natural gas industry facilities. Line pipes include both seamless and welded steel pipes, and the ends can be plain, threaded, or coupled. Connection methods include welding, coupling, and socket connections.

API 5L Linepipe Testing and Inspection

Hydrostatic Test
The hydrostatic test checks for leaks in the pipe body or welds by filling the pipe with water and pressurizing it. If any leakage is detected, the pipe must be repaired or replaced. This test ensures pipeline integrity and safety.

Bend Test
The bend test evaluates weld soundness and steel strength by bending a pipe sample into a U-shape. The presence of cracks or defects results in rejection of the entire batch. A successful test confirms mechanical reliability.

Flattening Test
This test measures a pipe’s resistance to deformation and cracking under pressure. The pipe is compressed until deformation or fracture occurs. It helps determine the pipe’s ductility and structural integrity.

Charpy V-Notch (CVN) Impact Test
The CVN test assesses the pipe’s impact toughness at specific temperatures. It is performed on the base metal, weld, and heat-affected zone. It is a key requirement for ensuring performance under tough environmental conditions.

Drop Weight Tear Test (DWTT)
The DWTT evaluates the pipe’s resistance to brittle fracture by dropping a heavy weight on a notched sample. It is essential for confirming ductile fracture behavior, especially in large-diameter pipes used in high-stress environments.

API 5L steel pipe uses

API 5L steel pipe is widely used in the following aspects:

Long-distance oil pipeline

Natural gas transmission trunk pipeline

Pipeline connection from offshore platform to land

High-pressure and high-temperature transmission system

Urban gas transmission and distribution network

Especially in shale gas and deep-sea oil and gas development, the requirements for pipelines are higher, and API 5L steel pipe has become the preferred standard.

Importance of API 5L Certification

Manufacturers who obtain API 5L certification must have:

A sound quality management system (such as ISO 9001)

A complete material tracking system

Process control that meets API Q1 quality standards

Complete testing equipment and personnel qualifications

Therefore, API 5L certification is regarded as a "passport" to enter the international oil and gas market.

Comparison of API 5L with other standards

Standard	Application Field	Description / Key Features
API 5L	Transmission pipelines	Core standard for the oil and gas industry
API 5CT	Casing / Tubing	Used in downhole environments, offers stronger corrosion resistance
ASTM A106	High-temperature seamless pipes	Applied in chemical and boiler industries
ISO 3183	International equivalent	Highly consistent with API 5L

Summarize

The 44th edition of API 5L standard, based on the core specifications of the 43rd edition, puts forward stricter requirements on the performance of PSL2 grade pipeline steel pipes, and adds high-grade pipeline steels such as X90, X100, and X120, providing technical support for the transportation of oil and natural gas under high pressure and complex geological conditions.

As an engineering party or purchaser, in actual projects, API 5L steel pipe products should be reasonably selected in combination with PSL grade, steel grade, use environment, chemical composition and connection method to ensure efficient, safe and compliant operation of the project.

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