Why arent distribution pipeline operators required to physically inspect their pipelines as are operators of other types of pipelines?
Distribution pipelines are generally complex, interconnected networks of smaller diameter pipe and branches, unlike other pipelines. In addition, approximately half of distribution pipelines are made of plastic, which is seldom used in other pipelines. The assessment techniques used on hazardous liquid and gas transmission pipelines (e.g., in-line inspection, pressure testing, direct assessment) cannot be used on smaller diameter and non-metallic pipe. In-line testing cannot be used to assess pipe with many branching connections, operating at relatively low pressures, typical of distribution pipelines. Pressure testing could be applied to distribution pipelines, but would require that service to customers be interrupted periodically, probably for many hours. Such interruptions are undesirable, especially when they are not needed. Since distribution pipelines operate at low pressures, they are not subject to the same forces as other pipelines and thus tend to leak rather than rupture. T
