Assessment & Validation of TFI-Identified Anomalies Criteria for Repair and Available Repair Methods

Project Categories

Click on any category to see other projects in this category.

• Onshore Transmission Pipeline
• In-Line Inspection/Pigging
• Non-destructive Testing/Evaluation
• Weld/Fabrication Defects

Main Objective

To develop a repair tool kit that will assist pipeline operators in determining available repair methods while defining anomalies in seam welds.

Public Abstract

The objectives of this project are to (1) compile and evaluate the unique properties of early generation pipeline weld seams, (2) compile a catalog of defect types, and (3) develop methods for evaluating seam weld defects to determine whether pipeline integrity has been compromised.

.

Following this methodology, the proposed work will provide an understanding of the types of defects and mechanical properties of early generation seam welds, and will describe methods for evaluating the severity of seam weld defects. The results will expand the options to use the emerging seam weld inspection technologies.

.

Seam weld defects are some of the integrity threats that are considered by pipeline operators in the development of integrity management plans. In particular, some early generation seam welds (e.g., prior to about 1970) can be more susceptible to failures because of poor mechanical properties (e.g., low toughness) that result in relatively small tolerable defect sizes (depth and length).

.

Pipeline operators have typically managed the integrity of early generation seam welds through hydrostatic testing. More recently, in-line inspection (ILI) technologies, especially transverse field inspection (TFI) tools, have emerged as another option to identify seam weld defects that could affect pipeline integrity. However, the methods for evaluating the severity of seam weld defects are still evolving. The current industry practice is to repair any 'crack-like' seam weld defect, rather than following a protocol with formal assessment criteria. This practice has likely resulted in the unnecessary repair of numerous seam weld defects.

.

Many pipeline operators have difficulty with the interpretation of results presented by ILI vendors. Without a consistent classification method and assessment protocol, the assessment is a very time consuming task. The proposed work will provide an understanding of the types of defects and mechanical properties of early generation seam welds, and will describe methods for evaluating the severity of seam weld defects.

.

Status History

Seam weld defects are some of the integrity threats that are considered by pipeline operators in the development of integrity management plans. In particular, some early generation seam welds (e.g., prior to about 1970) can be more susceptible to failures because of poor mechanical properties.

.

Therefore, the U.S. Department of Transportation (DOT) Pipeline and Hazardous Materials Safety Administration (PHMSA) contracted with CC Technologies Services, Inc. to research the unique properties of early generation seam welds, describe seam weld defect types, and develop a defect assessment protocol. Principal funding for this work is provided by the Pipeline Research Council International (PRCI).

.

The project started in February of 2003, and major milestones have already been achieved. Pipeline operators were contacted to anonymously make seam property and defect type information available for this project. Seam property data and defect type data was collected from past reports for these operators, and from PRCI-funded research and from the open literature. Common formats for the presentation of the information were defined.

.

A total of approximately 40 pipe samples were identified and acquired from pipeline operators and other sources. The samples contained several different grades of pipe material, contained a variety of defects material, were produced by several manufacturers.

.

Material property testing is being performed to characterize the samples. This testing includes: chemical analyses, mechanical property tests for tensile and yield strength, and Charpy V-notch impact testing.

.

The results of this project will provide an understanding of the types of defects and mechanical properties of early generation seam welds, and will describe methods for evaluating the severity of seam weld defects.