Transmission Line Condition Assessment

pipeline and excavator

How Best Practices Discussed in ASCE’s MOP 134 Are Essential to Both Condition Assessment and Asset Management Personnel

By George Ruchti

In the early morning hours of August 19, 2000, a natural gas transmission pipeline ruptured and ignited in New Mexico killing 12 people camping nearby. The rupture was determined to be the result of internal corrosion of the pipeline. The loss of life and property makes such pipeline condition assessment a critical need with remediation essential. The primary concern in the petroleum industry is electrically continuous butt-welded steel pipe. Inspection devices like smart pigs, with ultrasonic wall thickness testing capability, make it possible to determine the extent of pipe wall corrosion, if any, thus allowing for rehabilitation and future protection. Superior pipeline coatings and the application of cathodic protection have also been advantageous in providing successful asset management programs in that industry.

Unfortunately, the same integrity management systems do not hold true for water pipelines. These are composed of many different materials with different design and installation procedures and different modes of failure. Historically, pipe materials have included wood, wood stave, cast iron, ductile iron, steel, concrete (with 6 different varieties and properties), polyvinyl chloride (PVC), high density polyethylene (HDPE), fiberglass and asbestos cement. Fortunately, water line failures rarely cause fatalities, although this may be due to luck rather than potential. To demonstrate that potential, a 200 lb. chunk of concrete from a concrete pipe rupture in Cleveland, was reported to have broken through a window on the second floor of a nearby office building.

Asset Management personnel look to Condition Assessment personnel to provide them with an understanding of the condition of a water pipeline and Condition Assessment looks to Asset Management for an understanding of the finances available for the task.

One resource that is available to both organizations is the ASCE Manual of Practice (MOP) No. 134 on Water Pipeline Condition Assessment. A look at how this manual was developed, along with some of the key findings, underscores how knowledge of best practices and approaches to water transmission line condition assessment can benefit both condition assessment and asset management personnel.

In the past, papers were written about various aspects of water pipeline condition assessment, but there was nothing in the manner of a comprehensive approach or document. This was recognized by the Underground Pipeline Asset Management Technical Committee of the Pipeline Division of the American Society of Civil Engineers (ASCE). To address the issue, the Water Pipeline Condition Assessment Task Committee was formed. The express purpose of the task committee was to provide a Manual of Practice for all primary pipe materials in current operation and capable of having their condition assessed.

Members were recruited by the appointed chair of the committee through personal relationships and through general notices in various pipeline magazines. The response was remarkable, largely due to the recognition of the importance of the water pipeline condition assessment issue to our water industry. The committee met for the first time at the 2010 ASCE Pipelines Conference. The group was comprised of consulting engineers, pipe suppliers, utility personnel, corrosion engineers, pipeline testing personnel, and academics, many of whom were noted experts in their field.

At that first meeting, the committee defined the structure of the manual. Since there was no predecessor manual or other condition assessment document to emulate, the committee needed to break new ground. It was determined there were four essential sections: planning, records keeping, pipe materials and testing.

Chapters and sub-committees were formed for each section. It was decided that a single chapter encompassing all pipe materials would be too inclusive and needed further refinement. Reiterating the materials previously mentioned; they included wood, wood stave, cast iron, ductile iron, steel, concrete, PVC, HDPE, fiberglass and asbestos cement.

Within the original direction of the committee requiring that the pipe materials be present in current operations and capable of being assessed, three of the products were eliminated from consideration:

  • Wood pipelines were produced in colonial times and demonstrated the importance of water conveyance back then. They were made in short lengths (6 foot +/-) and small diameter (4” +/-) from shaved tree trunks with the interior hollowed out using a hot poker. The ends were formed with tongue and groove joints which, by filling the pipe with water, the tongue would swell into the groove. Most, if not all, such pipelines are no longer in service.

  • Wood stave pipe is another early pipe product. It was produced by curving thin wood sheets with small tongue and groove edges and joints. These sheets were produced to specific radii and circumferential lengths, so that when assembled and strapped together with iron or steel straps, they formed a specific diameter pipe. This author witnessed a 60” hydroelectric wood stave penstock being replaced with steel pipe in the 1990s in Virginia. Like wood pipelines, wood stave is largely a thing of the past.

  • High density polyethylene Pipe (HDPE) was considered, then rejected, due to its primary use, at least at the time, in directional drilling operations, or as inserted liner pipe. Neither of these uses lend themselves to condition assessment practices.

After separating the material chapters and adding Introduction and Case Studies to the list, 12 chapters for the manual were developed.

Introduction

The introduction addresses costing practices for utility assets, the concept of condition assessment, and establishes that the manual is for transmission lines and not the distribution system piping. The Introduction explains the function of each chapter and the general information included in each. It provides a list of pertinent websites, related documents and acronyms used throughout the manual.

Data Collection & Management

Data Collection and Management addresses the type of information helpful to the planning of a condition assessment effort. The chapter also explains that even problems that require exposing a pipeline for repair or modification can provide important localized information, such as water table level, soil type encountered, reason for problem, pipe condition, etc., that is beneficial during the planning process.

Planning

Planning addresses the gathering of information to initiate the condition assessment process. It provides information on prioritizing based on function or risk-based concepts. These concepts can assist the large utility with substantial pipeline assets or a smaller utility with only one such asset. It can address issues such as age of the pipeline(s), pipe material and failure mode, critical nature of the line, history of a line’s problems, terrain conditions, future planned pipeline modification, etc.

Pipe Materials

The manual consists of six chapters detailing various pipe materials and a history of each product; thereby acquainting the assessor with an understanding of the pipe properties at the time of the original installation. The materials discussed are: Cast Iron and Ductile Iron; Concrete, including Prestressed Concrete Lined Cylinder, Prestressed Concrete Embedded Cylinder, Reinforced Concrete Cylinder, Bar Wrapped Concrete Cylinder (formerly Pretensioned Cylinder), Reinforced Concrete Non-Cylinder, Prestressed Concrete Non-Cylinder; Steel; Fiberglass; Polyvinyl Chloride; and Asbestos Cement. Internal and external condition issues are addressed, jointing methods described, and condition assessment techniques presented. Finally, though not part of condition assessment but essential in asset management, each chapter provides information on repair, rehabilitation or replacement procedures.

Pipe Inspection Tools

Pipe inspection tools is a balanced chapter thoroughly describing every practical tool available at the time of the manual writing. It addresses low-risk, medium-risk and high-risk pipeline techniques and the individual tools associated with each. It addresses each tool describing what it does and what it cannot do. In general, the level of risk also describes the level of cost. One of the Blue Ribbon Committee members, tasked with the review of the manual stated, “I don’t know what the price of this manual will be, but this chapter alone would be worth it.”

Condition Assessment

The condition assessment portion addresses the life cycle of a pipeline; i.e., the design service life and the effective service life. It provides data and structural analyses and risk ranking procedures. This chapter also incorporates alternatives analysis and economic assessment.

Case Studies

Finally, a case studies section provides seven projects from around the country; projects that included most of the pipe materials in the manual.

The utilization of MOP 134 can now provide the basis for the Condition Assessment personnel to formulate a planned approach to a project and allow Asset Management personnel to recognize the options available for that analysis.


George Ruchti, M.ASCE, is a senior technical advisor with Lockwood, Andrews & Newnam, Inc. Ruchti served as chair of the Task Committee and editor of the ASCE’s Manual of Practice 134. Among his many career accolades, in 2020, Ruchti was the recipient of ASCE’s Stephen D. Bechtel Pipeline Engineering Award, honoring him for his many contributions in the field of pipeline engineering.

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