Pipeline Condition Assessment by Physical Evaluation

Abstract

This paper discusses the requirements and techniques used to evaluate the condition of water and wastewater pipelines. Asset management practices have recently focused attention on the condition of existing pipelines. The assessment of these pipelines, including the logistical challenges involved in performing assessment, is becoming a critical issue for pipeline operators. External and internal evaluations are often required to provide an accurate assessment of pipeline condition, and to determine the remaining useful life. External evaluations may involve identifying locations of corrosive soils, known leaks, pipe settlement and recent construction in the area of the pipeline, among others. Excavation and in-situ testing of the pipeline allows direct measurement and documentation of the exterior condition. Reliable information on the condition of the pipeline interior often requires confined space entry into the pipe. The parameters that can be measured and their relative importance in evaluating the condition of the pipeline and establishing remaining useful life are discussed. Safety issues associated with confined space entry over 1,000 feet into a pipeline are also addressed. Today we are shifting from a mentality of building and operating assets to managing them. The goal of condition assessment, as a part of asset management, is to document existing facilities and address long term life cycle costs rather than the day-to-day issues related to meeting service level goals. Desktop studies are useful, particularly in Phase One of an effective condition assessment approach, but by themselves fall short of accomplishing the goals of effective asset management. Asset deterioration curves, for example, don't take into account manufacturing variability, site specific conditions, design parameters, methods of installation or operational conditions. These curves attempt to simplify what is a very complex operational system. The design for many of these systems is based on very specific design parameters, which may or may not actually be experienced during the actual operation of the systems. The condition assessment plan should consider as many of these variables as possible, and be performed on a case by case basis with some level of physical observation to determine actual operational conditions. Without the actual physical observations multimillion dollar decisions are being made on desk top estimates. Condition assessment of pipelines can be broken down into 3 phases. Phase 1 involves developing a work plan. Phase 2 is where the field work is completed and data is collected on the condition of the pipeline. Phase 3 develops repair and rehabilitation alternatives. This paper addresses Phases 1 and 2.