Line pipe grade designations come from API Spec 5L Specification for Line Pipe. Standard Line Pipe has grade designation A and B. Stronger grades have the designation X followed by the specified minimum yield strength of the pipe steel, measured in kilopounds per square inch (abbreviated ksi), e.g. X60 for pipe having a minimum yield strength of 60 ksi. See the table below for the standard available grades.

 Line Pipe Physical Properties

API 5L GradeYield Strength
min.
(ksi)
Tensile Strength
min.
(ksi)
Yield to Tensile Ratio
(max.)
Elongation
min.
%1
A30480.9328
B35600.9323
X4242600.9323
X4646630.9322
X5252660.9321
X5656710.9319
X6060750.9319
X6565770.9318
X7070820.9317
X8080900.9316
API 5L elongation figures vary with specimen dimensions. Values shown for 0.2 sq. in. specimen.

Line pipe mechanical testing usually omits Reduction of Area (RA) measurement reporting, and Charpy V-Notch (CVN) testing. This prevents use of this pipe as body material above 36 ksi yield strength for API Spec 6A equipment without retesting for Reduction of Area, and in the case of low temperature service, Charpy V-Notch testing as well.

CAUTION: Do not confuse pipe manufactured to meet ASTM A106 Grade A or B as interchangeable with API 5L Grade A or B without close observation of the mill test reports. The two pipe specifications overlap, but vary. Pipe may or may not meet both specs.

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