The Designation
API 5L Grade B PSL1 designates line pipe to the American Petroleum Institute specification, with Grade B indicating a specified minimum yield strength of 35,000 psi (241 MPa) and a specified minimum tensile strength of 60,000 psi (414 MPa). PSL1 is the basic product specification level, suitable for the majority of onshore service where the design does not demand the extra controls of PSL2. The pipe can be produced seamless or welded, including electric-resistance-welded and submerged-arc-welded forms, and it is used in oil and gas gathering and transmission lines, water lines, and general pipeline service.
Mechanical Properties and Chemistry
Grade B has a specified minimum yield strength of 241 MPa, a minimum tensile strength of 414 MPa, and an elongation calculated from the API 5L formula for the test piece. For PSL1, the maximum chemistry limits are about 0.28% carbon for seamless pipe and 0.26% for welded pipe, with manganese up to 1.20%, and phosphorus and sulphur at 0.030% maximum each. These are modest limits for a carbon-manganese steel, which makes the pipe economical to produce and readily weldable with standard procedures. The pipe is hydrostatically tested, and the weld seam of welded pipe is examined as required by the standard.
Typical Applications
Grade B PSL1 is the workhorse grade for low-to-medium-pressure service: onshore crude-oil and natural-gas gathering lines, product and water injection lines, water transmission mains, and general industrial pipeline service. It is also used for casing in some applications and for structural tubular products where the strength is adequate. The grade is chosen where the design pressure is moderate and where the project does not mandate the fracture-toughness controls of PSL2. For sour service, low-temperature duty, or critical gas transmission, a PSL2 grade with the appropriate supplementary requirements is required.
PSL1 vs PSL2
The difference between PSL1 and PSL2 is the level of assurance. PSL1 sets minimum strength and basic chemistry. PSL2 adds maximum yield and tensile strengths, a maximum yield-to-tensile ratio, mandatory Charpy impact testing for many sizes, tighter phosphorus and sulphur limits, and a maximum carbon equivalent for weldability. PSL2 steels are killed and fine grained, and the testing programme is more extensive. For a moderate-pressure water or product line, PSL1 is adequate and economical; for gas transmission or cold service, PSL2 is the standard choice.
Related Grades and Selection
For high-temperature service, the carbon-steel A106 Grade B or the alloy P11 (1.25Cr-0.5Mo) should be considered, because API 5L Grade B is a line-pipe grade without guaranteed elevated-temperature properties. Where the service fluid is corrosive, such as geothermal brines containing chlorides and CO2, carbon steel corrodes rapidly, and a corrosion-resistant alloy or a clad pipe is required. The specification should always be chosen from the service conditions and the governing code, not from habit.
Ordering Information
When ordering API 5L Grade B PSL1, state the standard and edition, the PSL level, the grade, the manufacturing route if specified, the outside diameter and wall thickness, the length, the end preparation, and the documentation. The mill test certificate reports the heat chemistry, the tensile results, and the hydrostatic data. For line pipe that will be welded in the field, confirm the carbon equivalent and the welding requirements with the project engineer.
Frequently Asked Questions
Q: What is API 5L Grade B PSL1?
Line pipe to API 5L with a minimum yield strength of 35,000 psi (241 MPa) and a minimum tensile strength of 60,000 psi (414 MPa), supplied at the basic PSL1 specification level.
Q: What is Grade B PSL1 pipe used for?
Oil and gas gathering and transmission lines at low to medium pressure, water lines, and general non-critical pipeline service.
Q: What is the difference between PSL1 and PSL2?
PSL2 adds maximum strength limits, yield-to-tensile ratio control, mandatory impact testing, tighter chemistry, and carbon-equivalent limits. PSL1 is the basic level.
Q: Is Grade B PSL1 suitable for sour service?
No. Sour service requires PSL2 with supplementary requirements for hardness, sulphur control, and hydrogen-induced cracking testing.
Q: Can Grade B PSL1 be used at elevated temperature?
It is a line-pipe grade without guaranteed elevated-temperature properties. For hot service, A106 Grade B or the Cr-Mo grades such as P11 should be used.
Q: What tests are required for PSL1?
Chemical analysis, tensile testing, hydrostatic testing, and the bend and flattening tests where applicable, with the results on the mill certificate.
