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PRCI Report 168
- Yield Tensile Ratio Effect on Line Pipe Behavior
- Report / Survey by Pipeline Research Council International, 08/01/1988
- Publisher: PRCI
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L51562e
Battelle Memorial Institute
Need: Considerable research has been conducted to define the significance of the yield-to-tensile (Y/T) ratio for line-pipe steels. In the late 1960s and early 1970s, a study was completed in which a series of burst tests was conducted on 41 pipes ranging from 8 to 42 inches in diameter and representing API Specification 5L Grades A through X65. In this study, only 2 of the 41 materials studied had a yield-to-tensile ratio greater than 0.9, and these were artificially created. With the advent of the X70 and X80 steels, higher yield-to-tensile ratios have developed as the yield strength increased. A re-examination of this question in terms of the higher strength materials is presented herein.
Benefit: The objective of this research is to determine if the high yield-to-tensile ratio of X70 and X80 line-pipe steels in any way restricts such operating practices as hydrostatic testing, operating stress level, and flaw behavior.
Result: The conclusion from this study is that there appears to be no reason why high yield-to-tensile pipe should not be used for line pipe. The advent of new steel making and rolling practices can produce pipe with the fracture toughness and fracture propagation transition temperatures that are required for fracture control. Because the higher yield-to-tensile pipe has a higher yield stress than the specified minimum yield stress, it is less likely to yield in a hydrostatic test taken to the specified minimum yield stress than is lower yield-to-tensile pipe.
Battelle Memorial Institute
Need: Considerable research has been conducted to define the significance of the yield-to-tensile (Y/T) ratio for line-pipe steels. In the late 1960s and early 1970s, a study was completed in which a series of burst tests was conducted on 41 pipes ranging from 8 to 42 inches in diameter and representing API Specification 5L Grades A through X65. In this study, only 2 of the 41 materials studied had a yield-to-tensile ratio greater than 0.9, and these were artificially created. With the advent of the X70 and X80 steels, higher yield-to-tensile ratios have developed as the yield strength increased. A re-examination of this question in terms of the higher strength materials is presented herein.
Benefit: The objective of this research is to determine if the high yield-to-tensile ratio of X70 and X80 line-pipe steels in any way restricts such operating practices as hydrostatic testing, operating stress level, and flaw behavior.
Result: The conclusion from this study is that there appears to be no reason why high yield-to-tensile pipe should not be used for line pipe. The advent of new steel making and rolling practices can produce pipe with the fracture toughness and fracture propagation transition temperatures that are required for fracture control. Because the higher yield-to-tensile pipe has a higher yield stress than the specified minimum yield stress, it is less likely to yield in a hydrostatic test taken to the specified minimum yield stress than is lower yield-to-tensile pipe.
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