API 5L PIPES FOR PIPELINES


In this article, we give a quick overview of API 5L pipes for pipelines. We describe their typical applications (transportation of oil & gas), the chemical and mechanical properties of low-yield and high-yield API grades (both in PSL1 and PSL2), the differences between PSL1 and PSL (and the difference between grade API 5L and ASTM A53), manufacturing tolerances.


API 5L PIPES APPLICATIONS

API 5L pipes for pipelines

The API 5L/ISO 3183 specification sets standards for seamless and welded pipes to convey oil, gas, water in the natural oil & gas and petrochemical industries. The specification covers seamless and welded steel line pipes in various grades of carbon steel (from Gr. B to grade X100). API 5L foresees plain (PE), threaded (THD), and beveled (BE) pipe ends, as well as through-the-flowline (TFL) pipe, and pipe with ends prepared to be joined to special types of couplings.

Even if in some cases suppliers quote A106 and A53 pipes as alternatives to API 5L requests, there is no full interchangeability with API 5L as the mechanical and chemical requirements of API 5L pipes are actually more strict. When an API 5L pipe is required, rolled grades are not accepted and rework is not allowed. Furthermore, specific attention shall be given to the toughness requirements and toughness tests for sour services and higher pressure and temperature ratings.

The main applications and advantages of API 5L pipes are:

  • Pipes are resistant to cracking forces that may propagate in long pipelines
  • Sour service suitability
  • Rather inexpensive/long service life pipes

API 5L pipes can be supplied with different surface finish: black, varnish paint, anti-rust oil, hot galvanized, cold galvanized, 3PE (coated pipes)

The size range of API 5L pipes conforms to ASME B36.10. Diameters range from 2 to 28″ for seamless pipes and up to 80″ for welded pipes (larger API pipes are available with LSAW execution).

 


API 5L PIPES CHEMICAL AND MECHANICAL PROPERTIES

API 5L carbon steel pipes have several material grades designations. The yield strength of API 5L pipes is specified with the number that follows the X in the material grade specification (in kilopounds per square inch – i.e. KSI). So, for instance, an API 5L X52 pipe has a minimum yield strength of 52 KSI. The yield strengths of the various API 5L material grades are summarized in the below table (strengths in min KSI). Carbon steel grades for API 5L range from A to X100 (highest tensile and yield strength):

The table shows the chemical composition of API 5L PSL1 and PSL2 pipes for grades from A to X70, as well as their mechanical properties.

PIPES API 5L PSL 1

GRADE

Chemical Composition

Mechanical Property

C (Max)

Mn (Max)

P (Max)

S (Max)

TENSILE ( Min )

YIELD ( Min )

Psi X 1000

Mpa

Psi X 1000

Mpa

A25

CL I

0.21

0.60

0.030

0.030

45

310

25

172

CL II

0.21

0.60

0.030

0.030

A

0.22

0.90

0.030

0.030

48

331

30

207

B

0.26

1.20

0.030

0.030

60

414

35

241

X42

0.26

1.30

0.030

0.030

60

414

42

290

X46

0.26

1.40

0.030

0.030

63

434

46

317

X52

0.26

1.40

0.030

0.030

66

455

52

359

X56

0.26

1.40

0.030

0.030

71

490

56

386

X60

0.26

1.40

0.030

0.030

75

517

60

414

X65

0.26

1.45

0.030

0.030

77

531

65

448

X70

0.26

1.65

0.030

0.030

82

565

70

483

 

PIPES API 5L PSL 2

GRADE

Chemical Composition

Mechanical Property

C
(Max)

Mn
(Max)

P
(Max)

S
(Max)

Tensile

Yield

C. E. IMPACT ENERGY

Psi x 1000

Mpa

Psi x 1000

Mpa

PCM

IIW

J

FT/LB

B

0.22

1.20

0.025

0.015

60 – 110

414 – 758

35 – 65

241 – 448

0.25

0.43

T/L 27/41

T/L 20/30

X42

0.22

1.30

0.025

0.015

60 – 110

414 – 758

42 – 72

290 – 496

0.25

0.43

T/L 27/41

T/L 20/30

X46

0.22

1.40

0.025

0.015

63 – 110

434 – 758

46 – 76

317 – 524

0.25

0.43

T/L 27/41

T/L 20/30

X52

0.22

1.40

0.025

0.015

66 – 110

455 – 758

52 – 77

359 – 531

0.25

0.43

T/L 27/41

T/L 20/30

X56

0.22

1.40

0.025

0.015

71 – 110

490 – 758

56 – 79

386 – 544

0.25

0.43

T/L 27/41

T/L 20/30

X60

0.22

1.40

0.025

0.015

75 – 110

517 – 758

60 – 82

414 – 565

0.25

0.43

T/L 27/41

T/L 20/30

X65

0.22

1.45

0.025

0.015

77 – 110

531 – 758

65 – 82

448 – 565

0.25

0.43

T/L 27/41

T/L 20/30

X70

0.22

1.65

0.025

0.015

82 – 110

565 – 758

70 – 82

483 – 565

0.25

0.43

T/L 27/41

T/L 20/30

X80

0.22

1.90

0.025

0.015

90 – 120

621 – 827

80 – 102

552 – 705

0.25

0.43

T/L 27/41

T/L 20/30

 


DIFFERENCE PSL1 PSL2 API 5L PIPES

PSL 1 is a standard quality for API 5L pipes. PSL 2 is a higher quality that has additional chemical, mechanical and testing requirements. PSL1 and PSL 2 should be seen as two pipes specification levels. Example of difference between PSL 1 and PSL 2 chemical composition for the API 5L X42 grade:

PSL

C, a

  Mn a

P

 S

 Si

V

Nb

Ti

Other

CEIIW

CEpcm

1

0.24

1.40

0.025

0.015

0.45

0.10

0.05

0.04

b,c

.043

0.025

2

0.28

1.40

0.03

0.03

b

b

b

In terms of testing requirements for PSL1 vs PSL2, the following table summarizes the differences:

 

Test type PSL1 PSL2
Charpy test None required Required for all grades
Seamless NDT test Only if purchaser specifies SR4 SR4 mandatory
Certification Certificates when specified per SR15 Certificates (SR 15.1) mandatory
Traceability Traceable only until all tests are passed, unless SR15 is specified Traceable after completion of tests (SR 15.2) mandatory
Hydrostatic Test Required Required

 


TOLERANCES FOR API 5L PIPES

DIAMETER TOLERANCE API 5L

Specified outside
diameter D mm (in)

Diameter tolerances mm (in)

Out-of-roundness tolerances mm (in)

Pipe except at end a

Pipe end a,b,c

Pipe except at end a

Pipe end a,b,c

SMLS pipe

Welded pipe

SMLS pipe

Welded pipe

< 60.3 (2.375)

– 0.8 (0.031 ) to + 0.4 (0.016)

– 0.4 (0.016) to + 1.6 (0.063)

d

≥ 60.3 (2.375)
to
≤ 168.3 (6.625)

± 0.007 5 D

0.020 D

0.015 D

≥ 168.3 (6.625)
to
≤ 610 (24.00)

± 0.007 5 D

± 0.007 5 D

but maximum

of + 3.2 (0.125)

± 0.005 D,

but maximum of ± 1.6 (0.063)

> 610 (24.000)
to
≤ 1 422 (56.00)

± 0.01 D

± 0.005 D,

but maximum

of + 4.0 (0.160)

± 2.0 (0.079)

± 1.6 (0.063)

0.015 D

0.01 D,

but maximum of
15 (0.6),

but maximum of 13 (0.5),

for d / ts ≤ 75

for d / ts ≤ 75

by agreement

by agreement

for d / ts > 75

for d / ts > 75

> 1 422 (56 000)

as agreed

a — Pipe end includes a length of 100 mm (4.0 in) for each side
b — For SMLS pipe, the tolerances apply for 25.0 mm (0.984 in); tolerances for thicker pipes have to be as agreed.
c — For pipe with D219,1 mm (8.625 in) the diameter tolerance and the out-of-roundness tolerance may be determined by using the calculated inside diameter (the specified outside diameter minus two times the specified wall thickness) or measured inside diameter rather than the specified outside diameter
d — Included in the tolerance of the diameter

 

WALL THICKNESS TOLERANCE API 5L

wall thickness
t
mm (in)

Tolerances a
mm (in) mm (in)

SMLS pipe b

≤ 4,0 ( 0.157)

+ 0,6 (0.024)
– 0,5 (0.020)

> 4,0 ( 0.157) to < 25,0 (0.984)

+ 0,150
– 0,125

≥ 25,0 (0.984)

+3,7 (0.146) or + 0,1 t whichever is the greater
– 3,0 (0.120) or – 0,1 t whichever is the greater

Welded pipe c, d

≤ 5,0 (0.197)

± 0,5 (0.020)

> 5,0 (0.197) to <15,0 (0.591 )

± 0, 1 t

 ≥ 15,0 (0.591)

±1,5 (0.060)

a — if the purchase order specifies a minus tolerance for wall thickness smaller than the applicable value given in this table, the plus tolerance for wall thickness shall be increased by an amount sufficient to maintain the applicable tolerance range.
b — for pipe with D ≥ 355,6 mm (14.000 in) and t ≥ 25,0 mm (0.984 in) the wall thickness tolerance locally may exceed the plus tolerance for wall thickness by an additional 0,05 t, provided that the plus tolerance for mass (see 9.14) is not exceeded.
c — The plus tolerance for wall thickness does not apply to the weld area.
d — See 9.13.2 for additional restrictions.


WHAT IS THE API 5L MONOGRAM?

Manufacturers of steel pipes may request API an audit to assess their capabilities to comply with the API 5L standard. Pipe mills that pass the API audit successfully are awarded an API monogram. API lists in a composite index the names of the factories that have passed the audit successfully. The monogram has an expiration date. The API monogram is therefore similar to franchising scheme, however, API does not have any financial benefit from the certification of pipe mills, nor does it take any liability and the performance of the certified mills and products.

 


HOW TO ORDER API 5L PIPES?

Parameter Order Specification
Qty Feet or lengths
Size NPS (Outside Diameter) and Schedule Number (Average Wall Thickness)
PSL PSL 1 or PSL 2
Material Grade A, B, X42, X46, X52, X60, X70, X80, etc
Execution Seamless or Welded
Surface finish Bare, Black, FBE, etc
Manufacturer Approved Manufacturer List (AML), or Country of Origin restrictions
Sour service Yes / No