API 5L Pipe Specification

API 5L Standard covers seamless steel pipe and welded steel pipe for use in conveying gas, water, and oil in the petroleum and natural gas industries. It includes various grades from Grade B to X70, with different product specification levels (PSL1 and PSL2) to meet different service requirements. 

This guide provides a complete overview of the API 5L specification, including PSL1 vs PSL2 differences, material grades, and key selection criteria to help you choose the right line pipe for your project.

API 5L Standard Grade Overview

API 5L Standard covers a range of steel grades with increasing strength levels. The most common grades include Grade B, X42, X46, X52, X56, X60, X65, and X70.

Higher X grades indicate higher strength and are typically specified for higher-pressure, long-distance pipelines. For example, Grade B is the most basic strength level, while X70 offers significantly higher strength for demanding long-distance transmission lines.

Beyond selecting the right grade, understanding the manufacturing process is also critical for your application.

API 5L Line Pipe Manufacturing Process:

● Seamless pipe: produced by hot rolling or cold drawing process, suitable for high pressure and small diameter pipes, but the cost is higher.

● Welded pipe: including high frequency electric resistance welding (ERW) and submerged arc welding (SAW), which dominates the field of large diameter (such as ≥24 inches) and has lower cost.

Once the grade and manufacturing type are determined, the next step is to choose the appropriate product specification level (PSL). Both PSL1 and PSL2 apply to all grades and manufacturing types listed above, but their requirements differ. The following section explains these differences.

Differences Between API 5L PSL1 and PSL2:

Understanding the difference between PSL1 and PSL2 is critical for proper material selection. The table below summarizes the core requirements:

Comparison Item	PSL1	PSL2
Quality Level	Standard quality for general applications	Higher quality for sour service, high-pressure, offshore, and other critical applications
Chemical Composition	Less restrictive	Stricter limits on carbon, sulfur, phosphorus, and other elements
Mechanical Properties	Only minimum yield and tensile strength	Minimum and maximum yield/tensile strength, with yield-to-tensile ratio ≤ 0.93
Impact Toughness (CVN)	Not required	Mandatory (Charpy V-notch impact test at 0°C)
Non-Destructive Testing (NDT)	Not required	Mandatory (ultrasonic or eddy current testing)
Carbon Equivalent (CE)	Not controlled	Strictly limited (CEIIW ≤ 0.43%, CEPcm ≤ 0.25%)
Hardness Requirements	Not required	Required for sour service (maximum hardness limits)
Hydrostatic Test	Performed (may be substituted by NDT per standard)	Performed on each pipe (cannot be substituted by NDT)
Typical Applications	General onshore pipelines, low-pressure transmission	High-pressure long-distance pipelines, sour service (H₂S), offshore, low-temperature service

Quick Selection Tip:

Choose PSL1 (Grade B-X52) for general, lower-risk applications such as standard onshore pipelines.
Choose PSL2 (X60-X80) for projects requiring higher toughness, stricter testing, and enhanced reliability, such as offshore pipelines, sour service (H₂S), and high-pressure applications.

API 5L Standard Mechanical Properties (PSL1 vs PSL2 ):

The following table provides a summary of the mechanical property requirements for API 5L line pipe under both PSL1 and PSL2.

For PSL1, the standard specifies minimum yield and tensile strength values for each grade. For PSL2, the requirements are more stringent, specifying both minimum and maximum limits for yield and tensile strength, along with a maximum yield-to-tensile ratio of 0.93. These stricter mechanical property controls ensure the higher reliability and toughness required for critical service applications such as sour service, offshore, and high-pressure long-distance pipelines.

Standard	Steel Grade	Yield Strength(MPa)	Tensile Strength(MPa)
API 5L	PSL1
	A25	172	310
	A	207	331
	B	241	414
	X42	290	414
	X46	317	434
	X52	359	455
	X56	386	490
	X60	414	517
	X65	448	531
	X70	483	565
	PSL2
		241-448	414-758
	B	290-496	414-758
	X42	317-524	434-758
	X46	359-531	455-758
	X52	386-544	490-758
	X56	414-565	517-758
	X60	448-600	531-758
	X65	483-621	565-758
	X70	552-690	621-827

Note: PSL2 grades have a maximum yield strength limit, which is not specified for PSL1. PSL2 also requires CVN impact testing.

Practical Selection Guide for API 5L Line Pipe:

Choosing the right API 5L line pipe for your project requires a clear understanding of your operating conditions. The following guidelines will help you make a practical decision based on pressure, environment, and budget.

Step 1: Select the Grade Based on Pressure and Distance

Comparison Item	PSL1	PSL2
Quality Level	Standard quality for general applications	Higher quality for sour service, high-pressure, offshore, and other critical applications
Chemical Composition	Less restrictive	Stricter limits on carbon, sulfur, phosphorus, and other elements
Mechanical Properties	Only minimum yield and tensile strength	Minimum and maximum yield/tensile strength, with yield-to-tensile ratio ≤ 0.93
Impact Toughness (CVN)	Not required	Mandatory (Charpy V-notch impact test at 0°C)
Non-Destructive Testing (NDT)	Not required	Mandatory (ultrasonic or eddy current testing)
Carbon Equivalent (CE)	Not controlled	Strictly limited (CEIIW ≤ 0.43%, CEPcm ≤ 0.25%)
Hardness Requirements	Not required	Required for sour service (maximum hardness limits)
Hydrostatic Test	Performed (may be substituted by NDT per standard)	Performed on each pipe (cannot be substituted by NDT)
Typical Applications	General onshore pipelines, low-pressure transmission	High-pressure long-distance pipelines, sour service (H₂S), offshore, low-temperature service

Step 2: Choose PSL1 or PSL2 Based on Service Conditions

Pressure Level	Pipeline Length	Recommended Grade	Reason
Low Pressure (e.g., ≤ 5 MPa)	Short to Medium	Grade B	Sufficient strength for basic applications; most economical.
Medium Pressure (e.g., 5 – 10 MPa)	Medium to Long	X42 – X52	Good balance of strength and cost; suitable for most onshore pipelines.
High Pressure (> 10 MPa)	Long Distance	X60 – X70	High strength reduces wall thickness and weight, saving material and transportation costs.
Ultra-High Pressure (e.g., > 15 MPa)	Ultra-Long Distance	X80 steel	Maximum strength for extreme conditions; requires careful welding and material handling.

Step 3: Select Pipe Type Based on Diameter and Application

Service Condition	Recommended PSL	Key Requirements
General onshore pipelines, standard temperature and pressure	PSL1	Meets basic mechanical and chemical requirements; lower cost and faster delivery.
High-pressure, long-distance, or safety-critical lines	PSL2	Stricter mechanical properties, mandatory impact testing, and tighter chemical composition controls.
Sour service (H₂S environment)	PSL2 (Sour Service)	Requires specific hardness limits and resistance to sulfide stress cracking (SSC); must comply with NACE MR0175.
Offshore or low-temperature environments	PSL2	Requires low-temperature impact toughness testing and stricter NDT for enhanced reliability.

Quick Selection Checklist:

Use this checklist to quickly define your project requirements before consulting a supplier:

Design Pressure: ______ MPa
Design Temperature: ______ °C
Pipeline Length: ______ km
Diameter: ______ mm (NPS)
Environment: Onshore / Offshore / Sour Service / Low Temperature
Grade Preference: B / X42 / X52 / X60 / X65 / X70 / X80
PSL Preference: PSL1 / PSL2
Pipe Type: Seamless / ERW / LSAW / SSAW

API 5L Pipe Delivery Condition:

PSL	Delivery Condition	Pipe Grade
PSL1	As-rolled, normalized, normalizing formed	A
	As-rolled, normalizing rolled, thermomechanical rolled, thermo-mechanical formed, normalizing formed, normalized, normalized and tempered or if agreed Q&T SMLS only	B
	As-rolled, normalizing rolled, thermomechanical rolled, thermo-mechanical formed, normalizing formed, normalized, normalized and tempered	X42, X46, X52, X56, X60, X65, X70
PSL 2	As-rolled	BR, X42R
	Normalizing rolled, normalizing formed, normalized or normalized and tempered	BN, X42N, X46N, X52N, X56N, X60N
	Quenched and tempered	BQ, X42Q, X46Q, X56Q, X60Q, X65Q, X70Q, X80Q, X90Q, X100Q
	Thermomechanical rolled or thermomechanical formed	BM, X42M, X46M, X56M, X60M, X65M, X70M, X80M
	Thermomechanical rolled	X90M, X100M, X120M
	The suffice (R, N, Q or M) for PSL2 grades, belongs to the steel grade

API 5L Pipe Chemical Requirements:

For detailed chemical composition limits for PSL1 and PSL2, please refer to the full API 5L specification below. Key requirements include:

Chemical Composition Highlights – PSL1 (t ≤ 0.984″):
● Carbon content: ≤ 0.28% (seamless) / ≤ 0.26% (welded) for Grade B-X70.
● Manganese content up to 1.65% (depending on grade).
● Phosphorus and sulfur limited to ≤ 0.030%.

Chemical Composition Highlights – PSL2 (t ≤ 0.984″):
● Stricter limits on carbon, phosphorus, and sulfur.
● Carbon equivalent (CEIIW) ≤ 0.43% (max) and CEPcm ≤ 0.25% (max) for most grades.
● No intentional addition of boron (B) is permitted, with residual B ≤ 0.001%.

Chemical Composition for PSL 1 pipe with t ≤ 0.984”

Steel Grade	Mass fraction, % based on heat and product analyses a,g
	C	Mn	P	S	V	Nb	Ti
	max b	max b	max	max	max	max	max
Seamless Pipe
A	0.22	0.9	0.3	0.3	–	–	–
B	0.28	1.2	0.3	0.3	c,d	c,d	d
X42	0.28	1.3	0.3	0.3	d	d	d
X46	0.28	1.4	0.3	0.3	d	d	d
X52	0.28	1.4	0.3	0.3	d	d	d
X56	0.28	1.4	0.3	0.3	d	d	d
X60	0.28 e	1.40 e	0.3	0.3	f	f	f
X65	0.28 e	1.40 e	0.3	0.3	f	f	f
X70	0.28 e	1.40 e	0.3	0.3	f	f	f
Welded Pipe
A	0.22	0.9	0.3	0.3	–	–	–
B	0.26	1.2	0.3	0.3	c,d	c,d	d
X42	0.26	1.3	0.3	0.3	d	d	d
X46	0.26	1.4	0.3	0.3	d	d	d
X52	0.26	1.4	0.3	0.3	d	d	d
X56	0.26	1.4	0.3	0.3	d	d	d
X60	0.26 e	1.40 e	0.3	0.3	f	f	f
X65	0.26 e	1.45 e	0.3	0.3	f	f	f
X70	0.26e	1.65 e	0.3	0.3	f	f	f
a. Cu ≤ = 0.50% Ni; ≤ 0.50%; Cr ≤ 0.50%; and Mo ≤ 0.15%, b. For each reduction of 0.01% below the specified maximum concentration for carbon, an increase of 0.05% above the specified maximum concentration for Mn is permissible, up to a maximum of 1.65% for grades ≥ L245 or B, but ≤ L360 or X52; up to a maximum of 1.75% for grades > L360 or X52, but < L485 or X70; and up to a maximum of 2.00% for grade L485 or X70., c. Unless otherwise agreed NB + V ≤ 0.06%, d. Nb + V + TI ≤ 0.15%, e. Unless otherwise agreed., f. Unless otherwise agreed, NB + V = Ti ≤ 0.15%, g. No deliberate addition of B is permitted and the residual B ≤ 0.001%

Chemical Composition for PSL 2 pipe with t ≤ 0.984”

Steel Grade	Mass fraction, % based on heat and product analyses																		Carbon Equiv a
	C		Si		Mn		P		S		V		Nb		Ti		Other		CE IIW		CE Pcm
	max b		max		max b		max		max		max		max		max				max		max
Seamless and Welded Pipe
BR	0.24		0.4		1.2		0.025		0.015		c		c		0.04		e,l		0.43		0.25
X42R	0.24		0.4		1.2		0.025		0.015		0.06		0.05		0.04		e,l		0.43		0.25
BN	0.24		0.4		1.2		0.025		0.015		c		c		0.04		e,l		0.43		0.25
X42N	0.24		0.4		1.2		0.025		0.015		0.06		0.05		0.04		e,l		0.43		0.25
X46N	0.24		0.4		1.4		0.025		0.015		0.07		0.05		0.04		d,e,l		0.43		0.25
X52N	0.24		0.45		1.4		0.025		0.015		0.1		0.05		0.04		d,e,l		0.43		0.25
X56N	0.24		0.45		1.4		0.025		0.015		0.10f		0.05		0.04		d,e,l		0.43		0.25
X60N	0.24f		0.45f		1.40f		0.025		0.015		0.10f		0.05f		0.04f		g,h,l		As agreed
BQ	0.18		0.45		1.4		0.025		0.015		0.05		0.05		0.04		e,l		0.43		0.25
X42Q	0.18		0.45		1.4		0.025		0.015		0.05		0.05		0.04		e,l		0.43		0.25
X46Q	0.18		0.45		1.4		0.025		0.015		0.05		0.05		0.04		e,l		0.43		0.25
X52Q	0.18		0.45		1.5		0.025		0.015		0.05		0.05		0.04		e,l		0.43		0.25
X56Q	0.18		0.45f		1.5		0.025		0.015		0.07		0.05		0.04		e,l		0.43		0.25
X60Q	0.18f		0.45f		1.70f		0.025		0.015		g		g		g		h,l		0.43		0.25
X65Q	0.18f		0.45f		1.70f		0.025		0.015		g		g		g		h,l		0.43		0.25
X70Q	0.18f		0.45f		1.80f		0.025		0.015		g		g		g		h,l		0.43		0.25
X80Q	0.18f		0.45f		1.90f		0.025		0.015		g		g		g		i,j		As agreed
X90Q	0.16f		0.45f		1.9		0.02		0.01		g		g		g		j,k		As agreed
X100Q	0.16f		0.45f		1.9		0.02		0.01		g		g		g		j,k		As agreed
Welded Pipe
BM		0.22		0.45		1.2		0.025		0.015		0.05		0.05		0.04		e,l		0.43	0.25
X42M		0.22		0.45		1.3		0.025		0.015		0.05		0.05		0.04		e,l		0.43	0.25
X46M		0.22		0.45		1.3		0.025		0.015		0.05		0.05		0.04		e,l		0.43	0.25
X52M		0.22		0.45		1.4		0.025		0.015		d		d		d		e,l		0.43	0.25
X56M		0.22		0.45f		1.4		0.025		0.015		d		d		d		e,l		0.43	0.25
X60M		0.12f		0.45f		1.60f		0.025		0.015		g		g		g		h,l		0.43	0.25
X65M		0.12f		0.45f		1.60f		0.025		0.015		g		g		g		h,l		0.43	0.25
X70M		0.12f		0.45f		1.70f		0.025		0.015		g		g		g		h,l		0.43	0.25
X80M		0.12f		0.45f		1.85f		0.025		0.015		g		g		g		i,j		.043f	0.25
X90M		0.1		0.55f		2.10f		0.02		0.01		g		g		g		i,j		–	0.25
X100M		0.1		0.55f		2.10f		0.02		0.01		g		g		g		i,j		–	0.25
a. SMLS t>0.787”, CE limits shall be as agreed. The CEIIW limits applied fi C > 0.12% and the CEPcm limits apply if C ≤ 0.12%, b. For each reduction of 0.01% below the specified maximum for C, an increase of 0.05% above the specified maximum for Mn is permissible, up to a maximum of 1.65% for grades ≥ L245 or B, but ≤ L360 or X52; up to a maximum of 1.75% for grades > L360 or X52, but < L485 or X70; up to a maximum of 2.00% for grades ≥ L485 or X70, but ≤ L555 or X80; and up to a maximum of 2.20% for grades > L555 or X80., c. Unless otherwise agreed Nb = V ≤ 0.06%, d. Nb = V = Ti ≤ 0.15%, e. Unless otherwise agreed, Cu ≤ 0.50%; Ni ≤ 0.30% Cr ≤ 0.30% and Mo ≤ 0.15%, f. Unless otherwise agreed, g. Unless otherwise agreed, Nb + V + Ti ≤ 0.15%, h. Unless otherwise agreed, Cu ≤ 0.50% Ni ≤ 0.50% Cr ≤ 0.50% and MO ≤ 0.50%, i. Unless otherwise agreed, Cu ≤ 0.50% Ni ≤ 1.00% Cr ≤ 0.50% and MO ≤ 0.50%, j. B ≤ 0.004%, k. Unless otherwise agreed, Cu ≤ 0.50% Ni ≤ 1.00% Cr ≤ 0.55% and MO ≤ 0.80%, l. For all PSL 2 pipe grades except those grades with footnotes j noted, the following applies. Unless otherwise agreed no intentional addition of B is permitted and residual B ≤ 0.001%. API 5L Pipe Mechanical Properties (Seamless and Welded):

Pipe Grade	Tensile Properties – Pipe Body of SMLS and Welded Pipes PSL 1			Seam of Welded Pipe
	Yield Strength a	Tensile Strength a	Elongation	Tensile Strength b
	Rt0,5 PSI Min	Rm PSI Min	(in 2in Af % min)	Rm PSI Min
A	30,500	48,600	c	48,600
B	35,500	60,200	c	60,200
X42	42,100	60,200	c	60,200
X46	46,400	63,100	c	63,100
X52	52,200	66,700	c	66,700
X56	56,600	71,100	c	71,100
X60	60,200	75,400	c	75,400
X65	65,300	77,500	c	77,500
X70	70,300	82,700	c	82,700
a. For intermediate grade, the difference between the specified minimum tensile strength and the specified minimum yield for the pipe body shall be as given for the next higher grade.
b. For the intermediate grades, the specified minimum tensile strength for the weld seam shall be the same as determined for the body using foot note a.
c. The specified minimum elongation, Af, expressed in percent and rounded to the nearest percent, shall be determined using the following equation:
Where C is 1 940 for calculation using Si units and 625 000 for calculation using USC units
Axc is the applicable tensile test piece cross-sectional area, expressed in square millimeters (square inches) , as follows
– For circular cross-section test pieces, 130mm2 (0.20 in2) for 12.7 mm (0.500 in) and 8.9 mm (.350 in) diameter test pieces; and 65 mm2 (0.10 in2) for 6.4 mm (0.250in) diameter test pieces.
– For full-section test pieces, the lesser of a) 485 mm2 (0.75 in2) and b) the cross-sectional area of the test piece, derived using the specified outside diameter and the specified wall thickness of the pipe, rounded to the nearest 10 mm2 (0.10in2)
– For strip test pieces, the lesser of a) 485 mm2 (0.75 in2) and b) the cross-sectional area of the test piece, derived using the specified width of the test piece and the specified wall thickness of the pipe, rounded to the nearest 10 mm2 (0.10in2)
U is the specified minimum tensile strength, expressed in megapascals (pounds per square inch)

Pipe Grade	Tensile Properties – Pipe Body of SMLS and Welded Pipes PSL 2						Seam of Welded Pipe
	Yield Strength a		Tensile Strength a		Ratio a,c	Elongation	Tensile Strength d
	Rt0,5 PSI Min		Rm PSI Min		R10,5IRm	(in 2in)	Rm (psi)
						Af %
	Minimum	Maximum	Minimum	Maximum	Maximum	Minimum	Minimum
BR, BN,BQ,BM	35,500	65,300	60,200	95,000	0.93	f	60,200
X42,X42R,X2Q,X42M	42,100	71,800	60,200	95,000	0.93	f	60,200
X46N,X46Q,X46M	46,400	76,100	63,100	95,000	0.93	f	63,100
X52N,X52Q,X52M	52,200	76,900	66,700	110,200	0.93	f	66,700
X56N,X56Q,X56M	56,600	79,000	71,100	110,200	0.93	f	71,100
X60N,X60Q,S60M	60,200	81,900	75,400	110,200	0.93	f	75,400
X65Q,X65M	65,300	87,000	77,600	110,200	0.93	f	76,600
X70Q,X65M	70,300	92,100	82,700	110,200	0.93	f	82,700
X80Q,X80M	80,.500	102,300	90,600	119,700	0.93	f	90,600
a. For intermediate grade, refer to the full API5L specification.
b. for grades > X90 refer to the full API5L specification.
c. This limit applies for pies with D> 12.750 in
d. For intermediate grades, the specified minimum tensile strength for the weld seam shall be the same value as was determined for the pipe body using foot a.
e. for pipe requiring longitudinal testing, the maximum yield strength shall be ≤ 71,800 psi
f. The specified minimum elongation, Af, expressed in percent and rounded to the nearest percent, shall be determined using the following equation:
Where C is 1 940 for calculation using Si units and 625 000 for calculation using USC units
Axc is the applicable tensile test piece cross-sectional area, expressed in square millimeters (square inches) , as follows
– For circular cross-section test pieces, 130mm2 (0.20 in2) for 12.7 mm (0.500 in) and 8.9 mm (.350 in) diameter test pieces; and 65 mm2 (0.10 in2) for 6.4 mm (0.250in) diameter test pieces.
– For full-section test pieces, the lesser of a) 485 mm2 (0.75 in2) and b) the cross-sectional area of the test piece, derived using the specified outside diameter and the specified wall thickness of the pipe, rounded to the nearest 10 mm2 (0.10in2)
– For strip test pieces, the lesser of a) 485 mm2 (0.75 in2) and b) the cross-sectional area of the test piece, derived using the specified width of the test piece and the specified wall thickness of the pipe, rounded to the nearest 10 mm2 (0.10in2)
U is the specified minimum tensile strength, expressed in megapascals (pounds per square inch
g. Lower values fo R10,5IRm may be specified by agreement
h. for grades > x90 refer to the full API5L specification.

API 5L Pipe Quality Inspection Standards:

Hydrostatic Test: 

Each pipe shall be subjected to a hydrostatic test with no leakage. No leakage in the weld or pipe body is permitted.

Bend Test: 

No cracks shall be present in any part of the test piece, and no openings shall be present in the weld.

Flattening Test: 

Acceptance criteria vary by pipe diameter-to-thickness ratio (D/t) and grade. For example, for ERW pipe with D<12.750 inches, the weld shall not open until the distance between the plates is less than 66% of the original outside diameter (for grades ≤ X60, t ≤ 0.500 inches).

CVN Impact Test (PSL2): 

Mandatory for PSL2 pipe. Seamless pipe is tested on the pipe body; welded pipe is tested on the pipe body, weld, and heat-affected zone (HAZ). Refer to the full API 5L specification for sizes and grades and a chart of required absorbed energy values.

FAQ:

1. How do I choose between PSL1 and PSL2?
A: Choose PSL1 for general onshore pipelines with standard pressure and temperature conditions. Choose PSL2 for critical applications requiring higher toughness, stricter testing, and enhanced reliability, such as offshore pipelines, sour service (H₂S), high-pressure, or low-temperature environments.

2. What is the difference between API 5L Grade B and X70?
A: Grade B has a minimum yield strength of 241 MPa, suitable for low-pressure, short-distance pipelines. X70 has a minimum yield strength of 483 MPa, offering nearly double the strength, making it ideal for high-pressure, long-distance transmission lines. Higher X grades provide higher strength but may also require stricter welding procedures and higher material costs.

3. Which pipe type is better for API 5L pipelines: seamless or welded?
A: Seamless pipes are preferred for high-pressure, small-diameter, or critical applications where safety and reliability are paramount. Welded pipes (ERW, LSAW, SSAW) are more cost-effective and suitable for large-diameter, moderate-pressure applications such as gathering lines and distribution networks.

4. What are the key mechanical property differences between PSL1 and PSL2?
A: PSL1 specifies only minimum yield and tensile strength values. PSL2 specifies both minimum and maximum limits for yield and tensile strength, with a maximum yield-to-tensile ratio of 0.93. PSL2 also requires mandatory impact testing (CVN) and stricter control of chemical composition and carbon equivalent.

5. What factors should I consider when selecting API 5L pipe grades?
A: Key factors include: design pressure (higher pressure → higher grade like X60-X70), pipeline length (longer distance → higher grade for cost efficiency), environmental conditions (sour service → PSL2 with hardness limits; low temperature → impact-tested PSL2), and budget (standard grades like B or X42 are more economical).

Read more: 

●  American Standard Seamless Steel Pipe 

●  API 5L ERW Standard line Pipe

●  ASTM A53 VS ASTM A106 VS API 5L

●  API 5L X70 vs. X80 Pipeline Steel