Pipeline operators are always monitoring their pipelines. In addition to a 24/7 control-room computer system that monitors the pressure of the line, operators send out foot and aerial patrols to monitor the pipeline route. Crews are looking for dead vegetation, sinkholes or unexpected construction work along the right away, which the operator will investigate further.
In 2002, Congress directed the Pipeline and Hazardous Materials Safety Administration, the Department of Transportation agency that regulates pipeline safety, to develop a more comprehensive inspection program targeted at High Consequence Areas, which for interstate natural gas pipelines, means densely populated areas.
PHMSA regulations require inspections every seven years using one of four methods: an internal, in-line inspection device (or a “smart pig”); hydrostatic pressure testing (filling the pipe with water and pressurizing it well above operating pressures to verify a safety margin); direct assessment (digging up and visually inspecting sections of pipe selected based on various electronic measurements and other characteristics), or “other alternative methods that the Secretary of Transportation determines would provide an equal or greater level of safety.”
PHMSA requires pipeline operator to repair all potentially dangerous imperfections and adjust operation and maintenance practices to minimize the chance of an incident.
Pipeline operators primarily use internal inspection devices/smart pigs to assess the integrity of natural gas transmission pipelines because they are versatile and efficient. They use the other assessment methods generally when pig technology is impossible for example, if the pipeline bends or narrows or if the terrain is particularly steep or sloping.
PHMSA is looking to expand its Integrity Management Program for natural gas transmission lines to include pipeline segments located in less populated areas.
In its first 15 years, this federal program has helped significantly lower the number of corrosion-related incidents on pipelines.