How Are Pipelines Replaced?

Nearly 50% of the U.S. pipeline system is 40 years old or older. As recently as 2016, the federal Department of Transportation (DOT) estimated 30,000 miles of cast-iron pipe still carried gas in the United States, with the highest percentage of these mains located in older eastern cities such as New York City, Philadelphia, Boston, Baltimore, and Washington, D.C.

There is an effort underway to replace this aging infrastructure. Here’s a brief overview of some of the rehab work. DOT data show that replacement work, while steady, is far from complete:

• In 2015, there were still 27,771 miles of wrought- and cast-iron gas distribution lines in service in the U.S., down from 39,342 miles since 2005, a decrease of almost 30%.
• About 97% of natural gas distribution pipelines in the U.S. were made of plastic or steel at the end of 2017.
• The remaining 3% is mostly iron pipe.
• During the period 2004-13, distribution companies replaced 17,000 miles of bare-steel mains, leaving about 56,000 miles of bare-steel still in operation.

The data show 250 oil and gas companies ranging in size from 6 million to 1,300 customers are currently building pipelines throughout the U.S. and Canada. Much of that is to rehab miles and miles of older pipelines. Here’s a look at what’s involved with replacing older lines:

• Before rehabilitation of a pipeline, its condition must be assessed by intelligent pigging, cathodic-protection surveys, and coating surveys.
• Pipeline rehabilitation is normally more cost-effective than replacement if most of the work consists of recoating.
• For recoating costs of more than $200,000/km, it is probably not worth rehabilitating typical pipelines smaller than 18-in. OD if more than 70% of the pipeline length requires recoating.
• If safety concerns require pipeline shutdown for rehabilitation, the resulting production losses, if crude transfer rates are high, will often make this approach uneconomic.

The cost effectiveness of rehabilitation compared to new construction will depend on several factors. These include length of pipeline requiring replacement, length of pipeline requiring recoating, rehabilitation coating specification, feasibility of carrying out rehabilitation on live lines, and production losses during rehabilitation.

Each case must be treated separately, and each company must decide if the cost of rehabilitation is worth the work. To learn how Submar can help your pipeline project bring the entire line up-to-date, visit our services page.