Because safety is the natural gas industry's top priority, the industry spends more than $6 billion each year to maintain the system's excellent safety record. Serious accidents on the natural gas delivery system are rare, but the natural gas industry is dedicated to making them obsolete.
Because nearly 60 percent of the incidents on utility distribution pipelines are due to excavation damage, the most important part of the safety program for most natural gas utilities is the operation of a "call-before-you-dig" or a utility-locator service for excavators.
In 1998, with the support and encouragement of the natural gas industry, Congress enacted a law establishing a national "call before you dig" safety program, known as One-Call. The One-Call program is aimed at developing a variety of best practice procedures to prevent excavation damage to underground facilities.
"Call-Before-You-Dig" and “Dig Safely” Programs
When all local utilities – not only the local gas company -- participate in a comprehensive system, excavators can call one telephone number to arrange for marking or other identification of all underground facilities, including gas, water, telephone, electric and cable television lines. To further expand awareness of Call Before You Dig and One-Call programs, natural gas utilities participate in the “Dig Safely” public education campaign, designed to inform the public about safe digging practices through printed materials, direct contact, advertising and other avenues. AGA estimates that national one-call efforts may save as much as $58 million per year through reduced damage to the environment, public safety and property loss. In 2005, the Federal Communications Commission designated 811 as a Nationwide 3-Digit Phone Number for contractors and others to call before conducting excavation activities. Implementation of the 811 number will begin in late-2006 or 2007.
In addition, pipelines and utilities install above-ground markers to indicate the location of buried gas lines. The markers were developed by the gas industry and later incorporated into the federal regulations for the industry. At a minimum, line markers are placed at each crossing of a public road, except in very urban areas where utility-locator services are available. The natural gas industry is cooperating with other utilities to standardize temporary marking of underground utilities to further enhance public safety.
Gas companies regularly perform visual inspections of their systems to identify potential problems. The patrols vary according to population density and individual company policy, but all transmission lines are patrolled at least once per year. The inspectors look for construction activity, signs of leakage, such as dried-out vegetation, or conditions that could affect the pipeline, such as soil erosion. Inspections are done on foot, in vehicles and, for major transmission companies, by low-flying airplanes or helicopters.
Stringent industry standards exist for every component of the gas delivery system. For example, careful inspections are conducted by pipeline representatives at steel mills producing large-diameter transmission pipe, to ensure that the pipe meets the high standards of the industry and the federal government.
The same care applies to construction techniques. For example, because large transmission pipelines are all welded steel, only persons who have proven through qualification programs and testing that they can create high-quality welds are permitted to work on pipeline construction. Then x-rays, ultrasonic and other nondestructive tests are used to check the welds as an additional safeguard. As a final step where appropriate, many pipelines are subjected to hydro-static testing, where water is injected into the pipeline and pressurized to exceed the pressure level that will be created by the amount of gas the pipe will carry.
Similarly, utilities have rigid requirements for qualification and inspection of construction techniques for the types of piping used or maintained in their systems.
Corrosion and Damage Control and Inspection
Metal gas lines are installed with special corrosion-control coatings on the outside surface, and state-of-the-art technology is used to protect any areas where the coatings may become damaged. In addition, highly trained personnel use sophisticated tools to evaluate gas line conditions, so that defects are identified before they become a problem. Such equipment includes external devices such as ultrasonics, internal devices such as "smart pigs," and equipment to measure levels of cathodic protection.
In addition, government regulations require surveys of pipelines with leak detectors at specified intervals, with the frequency depending on whether the pipe is located in a populated area or a rural region.
Smart pigs are self-contained electronic devices that are pushed through the gas system by the pressure of the gas while recording detailed data about the condition of the line. Generally, pigs can be used only on certain large-diameter transmission lines that have been specially designed to accommodate pigs.
All regulator stations, pressure relief valves and other valves that are used to control the pressure or flow of gas are also tested at least once each calendar year, at intervals not longer than 15 months. In addition, all gas companies have stringent training and testing programs for employees involved in any aspect of operations, maintenance or repair.
Industry and Peer Education Programs
Through technical conferences and seminars, members of the natural gas industry share information and experiences on all aspects of operating a gas system with others in the industry. At the American Gas Association's annual Operations Conference, for example, more than 200 technical papers are presented and made available to the industry. These papers cover topics ranging from pattern analysis software for system mapping to the use of trenchless technology for renovating or repairing gas pipelines. Industry trade associations also publish numerous manuals, books, pamphlets and studies on delivery system operations and "best-practices" programs.
Public Education Programs
The natural gas industry conducts a wide range of information and education programs on natural gas safety, primarily focusing on the potential danger of digging into buried lines. Almost all major media are employed in these programs, including television, radio and print messages; direct mail; public presentations; and school materials. Natural gas utilities have joined together with other industries through the Common Ground Alliance to determine the best methods to improve safety around all buried facilities. The industry participates in the Dig Safely campaign, a joint government-industry public education campaign to alert the public to the importance of good safety practices around buried pipelines. In addition, gas companies work with local emergency response agencies, such as police and fire departments, to coordinate responses in the unlikely event of a pipeline accident and to educate them on pipeline operations.
* By law, pipeline incidents are reportable if they involve a death, a personal injury resulting in hospitalization or estimated property damage of $50,000 or more, which includes the value of the lost gas.