Review the Intent and Safety Impact of Hoop Stress and Percentage of Specified Minimum Yield Stress Boundaries on Natural Gas Transmission and Distribution Pipelines

Overview

Main Objective

To complete a knowledge-based study to: investigate definitions for natural gas transmission and distribution lines in 49 CFR 192; complete a literature review; establish safety considerations for new vs. existing systems related to DIMP and TIMP; identify safety/integrity implications from (re)classifying transmission-to-distribution; and document in-service history/incidents and system attributes. Emphasis will be placed on 20% - 30% SMYS segments and include leak vs. rupture considerations.

Public Abstract

This project addresses the topic, "Review the Intent and Safety Impact of Hoop Stress and Percentage of Specified Minimum Yield Strength (SMYS) Boundaries on Natural Gas Transmission and Distribution Pipelines" listed in the General Knowledge section of the Other - Materials research area of the DOT RA 693JK3191RA01. This topic is closely connected to pipeline safety considerations regarding Class Location, Maximum Allowable Operating Pressure (MAOP), and whether a natural gas pipeline is defined as a transmission or distribution pipeline. The objective of this project is to complete a knowledge-based study to: investigate definitions for natural gas transmission and distribution lines in 49 CFR 192; complete an in-depth literature review; establish safety considerations for new vs. existing systems related to DIMP and TIMP; identify safety/integrity implications from (re)classifying transmission-to-distribution; and document in-service history/incidents and system attributes. Additional emphasis will be placed on 20% - 30% SMYS segments and include leak vs. rupture considerations and effects on failure modes and related risk consequences. This project will focus on low strain steel pipe, specifically to determine whether specific pipe segments operating between 20% - 30% SMYS are safely operating as distribution lines under DIMP (49 CFR Part 192, Subpart P), or should be reclassified as transmission lines and be operated under 49 CFR 192 Subpart O. Likewise, the study will indicate, if proven safe, steel transmission lines operating between 20-30% SMYS can be safely transferred into the distribution classification and safely operated under DIMP. Finally the project will provide information to help ensure the criteria for transition between DIMP and TIMP management programs maintains a consistent level of safety. If appropriate, the outcomes can also be considered for new/updated language in the ASME B31.8 family of standards.

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