Much of the design, construction, and maintenance practices in the pipeline industry was established before the extensive use of modern control-rolled and microalloyed steels. These modern steels can behave differently from traditional hot-rolled and normalized steels. For instance, these modern steels tend to have a lower strain hardening capacity (higher Y/T ratio) than vintage hot-rolled and normalized steels. One of the observed trends is that modern steels could be qualified as higher grade due to the increase of yield strength (YS) while their ultimate tensile strength (UTS) remains at a...
Much of the design, construction, and maintenance practices in the pipeline industry was established before the extensive use of modern control-rolled and microalloyed steels. These modern steels can behave differently from traditional hot-rolled and normalized steels. For instance, these modern steels tend to have a lower strain hardening capacity (higher Y/T ratio) than vintage hot-rolled and normalized steels. One of the observed trends is that modern steels could be qualified as higher grade due to the increase of yield strength (YS) while their ultimate tensile strength (UTS) remains at a level close to the vintage lower grade steels. This would allow the pipelines built with modern steels to be operated at higher pressure when the design factor and other pipe dimensional parameters are the same.
Two representative linepipes are chosen from actual test data to examine the impact of the changes in the stress-strain behavior. One linepipe is a vintage X52; and the other is a modern X70. The UTS of those two pipes is very close. The vintage X52 pipe has a lower YS with a Y/T ratio of 0.73 and the modern X70 pipe has a higher YS with a Y/T ratio of 0.91.
The burst pressure of both pipes was analyzed under the following conditions: