Natural Gas is Our Friend

Around 10:00 p.m., February 2^nd, a 22-year old male driver ran into a light pole in front of an apartment complex on FM 2094, or Marina Bay Drive, mid-way between League City and Kemah, knocking out power and television cable service to the complex. The young driver was arrested for DWI, and booked into county jail. At about 2:30 p.m., the next day, a crew from Texas-New Mexico Power was working to repair the pole, when they ruptured a six-inch natural gas pipeline. A Center Point Energy crew had to be rushed to the site, to repair the leak and stop the major release of explosive natural gas. Once an all-clear was given, the light crew completed the pole replacement and the restoration of power to the complex.

Since natural gas is looming ever larger in the nation's residential and commercial power supply because of: the reduction of coal-fired power plants; increased costs of electrical power and home heating oil; and, environmental concerns with carbon emissions; gas pipelines and supply grids are reaching ever further into urban areas. So, it's wise to have a good understanding of that system and the potential dangers presented when dealing with it, especially in an emergency situation like that in Friday's rupture. Natural gas is powerful stuff. It burns at the astonishing temperature of 3,632 degrees Fahrenheit; and, in concentrated quantities has the explosive power of dynamite. This especially matters in large pipeline ruptures because natural gas is a hydrocarbon derivative which is heavier that open air. It can settle in large quantities quickly, which can be easily ignited, and suffocate even if not burning. Thus, as with any powerful substance, it needs to be understood, respected and handled with care.

Natural gas is simply a combustible, gaseous mixture of simple hydrocarbon compounds, which are a fossil fuel. It is mostly methane, but also includes ethane, propane, butane and pentane. Slightly more than one-half of American homes use it for heating, cooking and certain other uses. It was first used to power street gas lamps in Baltimore, Maryland; but, since World War II, natural gas has steadily increased in usage, to become the nation's predominant fuel, for residential purposes. It is delivered to 170 million consumers, nationally, through a 1.5 million-mile network of underground pipelines; which are supplied from roughly 450,000 producing gas wells, with more coming on line every month. The country has 125 gas pipeline companies, and more than 1,200 local and regional distributing companies, which provide retail services in all fifty states.

This massive delivery system actually operates on a very basic principal of physics: gas moves from a higher pressure to a lower one. From the wells, gas naturally flows into "gathering lines", which are very like the branches of a tree. The smaller ones flow to ever larger ones on the way to central collection points. There, a gathering system uses large field compressors to move the gas to a large pipeline, or to a processing plant. The machinery of those pumps draw power from the gas. A considerable amount of gas requires no processing; which makes its relatively low delivery cost an attractive option to homeowners. But, some gas does require the removal of sulfur, carbon dioxide, water vapor, inert gases like helium, and other impurities.

From the gathering system, the gas moves into the transmission system of about 272,000 miles of high-gauge steel pipeline, ranging from 20"-42" in diameter. This system moves the gas where needed, literally all over the country, much like the Interstate Highway system does trucked cargos. The pressures in these enormous pipes range from 200 psi all the way up to 1,500 psi. Sometimes they are "looped", meaning that three or more will be laid side-by-side across a 100' right-of-way, to allow for expanded delivery capacity during peak-use times. Compressor stations are located every 50-60 miles, to maintain a constant flow pressure, and to allow access from maintenance and inspection. The gas is kept moving at a constant speed of about 30 mph. At any given time, a 50-mile stretch of 42" transmission line, operating at 1,000 psi, will contain about 200 million cubic feet of gas- enough to power a large kitchen stove for 2,000 years!

Once the gas reaches a local distribution company, like Center Point Energy, the gas moves into smaller distribution lines, like the six-inch one that ruptured Friday. These have a carrying pressure of 200 psi. Local handling facilities add a mal-odorant, butyl mercaptin, which gives the odorless gas the rotten egg smell most people associate with it, to make it safer by being readily detectible. Finally, the gas is dropped down to 2" customer distribution lines, which connect to meters. But, even at that level, it still carries a potent 60 psi pressure.

The most common cause of pipeline rupture is excavation, just as happened Friday. These accounted for 60% of all pipeline flow interruptions, between 1995-2004; according to statistics kept by the U.S. Department of Transportation. Other causes included fires, corrosion, explosion and other problems. Fortunately, these incidents are rare. But, when they happen, the potential for disaster is always present. If you ever need to dig, even on your own property, take the precaution of calling the 1-800 number provided by your gas supplier before you start. A ruptured line can cause a lethal fire or explosion. And, even absent that, you will pay a hefty price for the cost of the pipe repair and the emergency response team. Save your money and save your life. Check first!

For more information:  http://www.khou.com/news/neighborhood-news/Gas-line-rupture-closes-FM-2094-in-League-City-138641199.html