what is line pipe

January 22, 2025

Tags: Seamless Pipe

What is line pipe
Line pipes were compiled and released by the American Petroleum Institute, and were transmitted to my country through various channels. Now there are such pipelines all over the world, which can be said to be universal. The main mode of operation of the line pipe is actually to transport the oil, natural gas or water pumped out of the ground to the oil and gas industry enterprises through this line pipe.

The main purpose
People mainly use it for transportation of gas, water and oil in the petroleum and natural gas industry. Because of its excellent bearing capacity and hardness, it can be trusted by people when it is used.

specification
The specification of the line pipe is API SPEC 5L-2011. It is mainly two kinds of seamless and welded pipes. The pipe ends of the line pipe are divided into flat ends, threaded ends and socket ends. There are also many connection methods, namely end Welding, collar connection, socket connection, etc. The main materials for making this kind of line pipe are L245, L360, L418, L480, X65, X70, X80 and other steel grades, and the steel grades of different materials have different functions.

The pipeline steel pipe products of Baotou Steel Pipe Co., Ltd. have supplied batches of steel grades below X65, and the products have been successfully exported to Germany, Canada, Brazil, Singapore, Egypt, South Korea, the United Arab Emirates and other countries; X70 steel grade pipeline steel pipes have been successfully industrialized; X52 steel Grade cryogenic pipeline steel pipe has completed laboratory research work. With the increasing consumption of hydrogen sulfide-resistant pipeline steel pipes, in recent years, Baotou Steel has been devoting itself to the development of hydrogen sulfide-resistant pipeline steel pipes and offshore service pipeline steel pipes, among which L290NS hydrogen sulfide-resistant pipeline steel pipes have passed the performance evaluation test of Xi’an Pipe Materials Research Institute , and batch supply; L360QS has completed laboratory development work. As the 159PQF unit and 460PQF unit have been put into operation, Baotou Steel already has the technological conditions to produce high-grade hydrogen sulfide corrosion-resistant pipeline steel pipes and offshore service pipeline steel pipes.

Mechanical properties:

Standard	Product Level	Steel grade	Yield Strength (min), Mpa	Tensile Strength(MPa)
API 5L GB/T9711.2	PSL 1	A or L210	210	335
		B or L245	245	415
		x42 or L290	290	415
		X46 or L320	320	435
		X52 or L360	360	460
		X56 or L390	390	490
		X60 or L415	415	520
		X70	483	565
	PSL 2	BR or L245R	245~450	415~760
		X42R or L290R	290~495	415~760
		BN or L245N	245~450	415~760
		X42N or L290N	290~495	415~760
		X46N or L320N	320~525	435~760
		X52N or L360N	360~530	460~760
		X56N or L390N	390~545	490~760
		X60N or L415N	415~565	520~760
		X65N or L450N	425~566	525~760
		X70 or L480	484~565	565~768
		X80	552~690	621~827

Differences between PSL1 and PSL2 pipes are as follows;

1.Chemical Properties
2.Mechanical Properties
3.Manufacturing Methods
4.Inspection and Defect Repair
5.Certification & Traceability

1.Chemical Properties

PARAMETER	PSL1	PSL2
Chemistry: Max C for Seamless pipe	0.28% for grades ≥ B	0.0024
Chemistry: Max C for Welded pipe	0.26% for grades ≥ B	0.0022
Chemistry: Max P	0.03% for grades ≥ A	0.0003
Chemistry: Max S	0.0003	0.0002
Carbon equivalent:	Only when purchaser specifies SR18	Maximum required for each grade

2.Mechanical Properties

PARAMETER	PSL1	PSL2
Yield strength, maximum	None	Maximum for each grade
UTS (Ultimate Tensile Strength) maximum	None	Maximum for each grade
Fracture toughness	None required	Required for all grades

For PSL2 pipe, there is a limit on Maximum Yield & Ultimate Tensile Strength, whereas for PSL1 pipe, meeting the minimum requirements is sufficient. The second requirement that is mandatory for the PSL2 pipe is Fracture toughness which is not required for the PSL1 pipe.

3.The difference between PSL1 & PSL2 Pipes Manufacturing

PARAMETER	PSL1	PSL2
Grade Range	A25 through X70	B through X80
Size range	0.405″ through 80″	4.5″ through 80″
Type of ends	Plain end, Threaded end,Bevelled end special coupling pipes	Plain end
Seam welding	All methods: continuous welding limited to A25	All methods: except continuous welding and laser welding
Electric welds: welder frequency	No minimum	kHz minimum 100
Heat treatment of electric welds	Required for grades >X42	Required for all grades (B through X80)

Here in this table, you can see the differences between PSL1 & PSL2 Pipes Manufacturing. PLS1 pipes are available in grades A25 through X70, whereas PSL2 pipes are available in Grade B through X80.

PSL1 pipes are available in sizes 0.405” to 80”, whereas the smallest diameter pipe available in PSL2 is 4.5” and the largest diameter is 80”.

4.Inspection and Defect Repair

PARAMETER	PSL1	PSL2
Non-destructive inspection of Seamless	Only when purchaser specifies SR4	SR4 mandatory
Repair by welding of pipe body plate, and skelp	Permitted	Prohibited
Repair by welding of weld seams without filler metal	Permitted by agreement	Prohibited

Non-destructive inspection of a seamless pipe is mandatory for PSL2 pipe, whereas for PLS1 pipe, it is a supplementary requirement.

Repair of pipe body plate and skelp by welding is not allowed in PSL2 pipes, whereas it is allowed in PSL1 pipes. Similarly, weld repair without filler metal is not allowed in PSL2 pipes, whereas it is allowed with the purchaser’s permission in PSL1 pipes.

5.Certification & Traceability

PARAMETER	PSL1	PSL2
Certification	Traceable only until all tests are passed	Certificates (SR15.1) mandatory
Traceability	Traceable only until all tests are passed unless SR15 is specified	Traceable after completion of tests (SR15.2) mandatory

For PSL1 pipes, Traceability & Certification is not required beyond the point it passes all the required tests whereas, for PSL2 pipes, Traceability & Certification is mandatory.

In short PSL1 pipes are standard quality pipes for normal services, and PSL2 pipes are higher quality pipes than PSL1.

Pipeline pipe chemical element table：

roduct Level	Steel grade	Chemical composition, %
roduct Level	Steel grade	C	Mn	P	S	Si	V	Nb	Ti	CEpcm
PSL 1	B or L245	≤0.28	≤1.20	≤0.030	≤0.030	–	–	–	–	–
	x42 or L290	≤0.28	≤1.30	≤0.030	≤0.030	–	–	–	–	–
	X46 or L320	≤0.28	≤1.40	≤0.030	≤0.030	–	–	–	–	–
	X52 or L360	≤0.28	≤1.40	≤0.030	≤0.030	–	–	–	–	–
	X56 or L390	≤0.28	≤1.40	≤0.030	≤0.030	–	–	–	–	–
	X60 or L415	≤0.28	≤1.40	≤0.030	≤0.030	–	–	–	–	–
	X70	≤0.28	≤1.40	≤0.030	≤0.030	–	–	–	–	–
PSL 2	BR or L245R	≤0.24	≤1.20	≤0.025	≤0.015	≤0.40	c	c	≤0.04	≤0.25
	X42R or L290R	≤0.24	≤1.20	≤0.025	≤0.015	≤0.40	≤0.06	≤0.05	≤0.04	≤0.25
	BN or L245N	≤0.24	≤1.20	≤0.025	≤0.015	≤0.40	c	c	≤0.04	≤0.25
	X42N or L290N	≤0.24	≤1.30	≤0.025	≤0.015	≤0.40	≤0.06	≤0.05	≤0.04	≤0.25
	X46N or L320N	≤0.24	≤1.40	≤0.025	≤0.015	≤0.40	≤0.07	≤0.05	≤0.04	≤0.25
	X52N or L360N	≤0.24	≤1.40	≤0.025	≤0.015	≤0.45	≤0.10	≤0.05	≤0.04	≤0.25
	X56N or L390N	≤0.24	≤1.40	≤0.025	≤0.015	≤0.45	≤0.10	≤0.05	≤0.04	≤0.25
	X60N or L415N	≤0.24	≤1.40	≤0.025	≤0.015	≤0.45	≤0.10	≤0.05	≤0.04	–
	X65N or L450N	≤0.24	≤1.40	≤0.025	≤0.015	≤0.45	≤0.10	≤0.05	≤0.04	–
	X70N	≤0.24	≤1.40	≤0.025	≤0.015	≤0.45	≤0.10	≤0.05	≤0.04	–
	X80	≤0.24	≤1.40	≤0.025	≤0.015	≤0.45	≤0.10	≤0.05	≤0.04	–

API 5L line pipe standard:

API SPEC 5L——American Petroleum Institute Standard

GB/T9711——China National Standard

There are two standards for API 5L line pipe: PSL1 and PSL2. Although the two standards have only one word

The difference is huge, and the content is also very different. PSL2 has a higher quality level than PSL1. Both standard levels have different levels of inspection requirements, chemical composition requirements, mechanical performance requirements, and mechanical performance requirements. When ordering according to the API 5L line pipe standard, the purchaser needs to indicate the standard level (PSL1 or PSL2) according to the basic contract terms such as product specification, steel grade, and order quantity. Under normal circumstances, if the contract does not mention the standard level, the manufacturer will produce according to the standard of PSL1.

PSL is the abbreviation of Product Specification Level. The product specification level of line pipe is divided into PSL1 and PSL2, and it can also be said that the quality level is divided into PSL1 and PSL2. PSL2 is higher than PSL1. These two specification levels are not only different in inspection requirements, but also in chemical composition and mechanical properties. Therefore, when ordering according to API 5L, the terms in the contract should not only indicate the usual indicators such as specifications and steel grades. , must also indicate the product specification level, that is, PSL1 or PSL2. PSL2 is stricter than PSL1 in terms of chemical composition, tensile properties, impact energy, non-destructive testing and other indicators.
PSL1 does not require impact performance. For all steel grades except x80 of PSL2, the average value of Akv at 0°C in the full size: longitudinal ≥ 41J, transverse ≥ 27J. X80 steel grade, full-scale 0℃ Akv average: longitudinal ≥ 101J, transverse ≥ 68J.
The line pipe should be subjected to hydrostatic test one by one, and the standard does not allow non-destructive substitution of water pressure, which is also a big difference between the API standard and the Chinese standard. PSL1 does not require non-destructive testing, and PSL2 should be non-destructive testing one by one.

American Petroleum Institute Standard (API SPEC 5L ) Line Pipe Specification Table


Nominal Size	Outside Diameter	Wall Thickness	Plain-end Weight
inch	mm	inch	mm	lb/ft	kg/m
0.405	0.405	10.29	0.095	2.4	0.31	0.47
0.54	0.54	13.72	0.088	2.2	0.43	0.62
0.54	13.72	0.119	3.0	0.54	0.79
0.675	0.675	17.15	0.091	2.3	0.57	0.84
0.675	17.15	0.126	3.2	0.74	1.10
0.84	0.84	21.34	0.109	2.8	0.85	1.28
0.84	21.34	0.147	3.7	1.09	1.61
1.05	1.05	26.67	0.113	2.9	1.13	1.70
1.05	26.67	0.154	3.9	1.48	2.19
1.315	1.315	33.4	0.133	3.4	1.68	2.52
1.315	33.4	0.179	4.6	2.17	3.21
1.660	1.660	42.2	0.145	3.7	2.72	3.43
1.660	42.2	0.191	4.9	3.00	4.51
1.900	1.660	42.2	0.382	9.7	5.22	7.77
1.900	48.3	0.145	3.7	2.72	4.07
1.900	48.3	0.200	5.1	3.63	5.43
1.900	48.3	0.400	10.2	6.41	9.58
2 3/8	2.375	60.3	0.109	2.8	2.64	3.97
2.375	60.3	0.125	3.2	3.00	4.51
2.375	60.3	0.141	3.6	6.36	5.03