LDCs Continue To Upgrade Gas Network

Gas Distribution Report
By Rita Tubb, Executive Editor | February 2014, Vol. 69 No. 2

Local distribution companies (LDC) remain the backbone of the nation’s natural gas distribution network. Natural gas utilities serve more than 71 million residential, commercial and industrial customers across the nation. Gas is delivered through a 2.4-million mile underground delivery system with an outstanding safety record.

The distribution network also includes measurement and pressure regulators, corrosion control equipment and valves and meters, all of which must be operated, maintained and upgraded by the local natural gas utility.

The more than 1,200 local natural gas utilities in the United States spend billions of dollars per year on safety programs to ensure the safety and reliability of the many miles of mains and service pipelines that are made up of steel, cast iron or copper, which are subject to corrosion.

Cast iron pipe, which exhibits brittle characteristics and is subject to cracking and breakage, sometimes as a result of ground movement in proximity to buried pipe, has been on the decline since the mid-1980s.

According to a recent American Gas Association (AGA) study, there has been a 46 percent decrease in the amount of cast iron main since 1985 and today, only 3 percent of the entire national gas distribution system is composed of cast iron mains. That figure that is continuously being reduced as pipeline operators implement accelerated pipeline replacement programs.

Also, the study stated that serious incidents involving cast iron mains have also declined – dropping by a difference of 86 percent between 1985 and 2012.

The LDC employs many techniques to reduce steel corrosion, including various pipe coatings and the replacement of leak-prone mains and service lines with medium- and high-density polyethylene (PE) plastic pipe that is the current industry standard for most distribution pipe sizes.

In the past decade, natural gas utilities have installed updated plastic lines at a rate of 30,000 miles per year, connecting new customers or replacing older pipeline infrastructure. Today, there are nearly 1.3 million miles of plastic pipe in the natural gas system, along with more than 1.1 million miles of cathodically-protected steel pipeline.

Moreover, while LDCs have made significant advances in modernizing pipeline infrastructure over the last two decades, industry estimates indicate it may easily take another three decades of effort to finish the job at the current pace of replacement.

The National Association of Corrosion Engineers (NACE) estimates the direct cost of corrosion for the natural gas distribution industry to be $5 billion annually.