Direct strain measurements and failure pressure prediction in mechanically damaged and strained pipes

Overview

Main Objective

The objective of this project is to couple in-service measurements with predictive tools to determine the maximum safe operating pressure and Code margins of safety based on direct measurements of the strains in pipelines that have suffered mechanical damage, or have been subjected to bending, either intentionally in construction or unintentionally from the effects of ground movement.

Public Abstract

Maintaining the highest levels of safety, integrity and reliability regarding design, construction and operation of the Nation's pipeline infrastructure is of primary importance. Of particular importance is an accurate failure pressure prediction of the damaged pipelines which carry natural gas and oil throughout the country and world. In order to predict the remaining life of damaged pipes it is essential to accurately determine the strains and stresses in the damaged regions. Damaged sustained by ground movement from earthquakes or subsidence such as bending and kinking is especially important. To this end, we have been advancing ultrasonic measurements and shown the proof of concept to determine the effective strain in bent and wrinkled pipes utilizing Department of Energy and other funding. However, there is currently a significant technological gap inhibiting accurate diagnostics and prognostics for pipeline life assessment. Specifically a field portable tool to accurately measure the strains is needed for use on pipes damaged from unexpected earth movement and subsidence and for pipes that have been intentionally strained such as field bent pipes and catenary spans. In addition, this strain measurement method needs to have little or no reliance on laboratory calibrations. Furthermore, to fully realize the enhanced integrity and reliability that in-service tools can provide, they also need to predict the failure pressure of damaged pipes based on the current strains. This proposed work will take the next steps and develop methods to predict the failure pressure of line pipe based on direct measurements of the strains in pipes coupled with fracture mechanics models. We will specifically focus on developing field calibration methods with field portable equipment and will provide a roadmap for a handheld device that integrates the strain measurements with burst pressure prediction.

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