Natural gas pipeline ruptures

Between 1985 and 1991,1726 natural gas pipeline ruptures andleakages were reported in the United States. These incidents resulted in 634 injuries and 131 fatalities. Third-party damage was the most common cause of these incidents, followed by corrosion. The GAO believes that the corrosion-related incidents can be reduced with the use of smart pigs (46). U.S. DOT 1992 accident statistics showed that 52.5% of U.S. oil spills involving loss of at least 1590 m3 came from pipeline accidents, comparable to the worldwide statistic of 51.5%. The U.S. DOT regulated 344,575 km of liquids pipelines during the 10-yr study period and received reports on 1901 accidents during that time thus the number of failures per year per 1000 miles was 0.888, of which 27% was due to corrosion and 31% to outside forces (48). 

Commodity Pipeline Occurrence Report - Natural Gas Pipeline Rupture. Transportation Safety Board of Canada Report Number P94H0003, 1995-08-23. 

Natural Gas Pipeline Rupture and Fire Near Carlsbad, New Mexico, August 19, 2000, NTSB/PAR-03/01, National Transportation Safety Board, Washington, DC, 2003. 

FIGURE 4.4 Looking west at a portion of the crater created by the pipeline explosion near Carlsbad, New Mexico. The missing section of pipe between the arrows was ejected from the crater. (From the National Transportation Safety Board, Natural gas pipeline rupture and fire near Carlsbad, New Mexico, August 19, 2000. Pipeline Accident Report NTSB/PAR-03/01. National Transportation Safety Board, Washington, DC, 2003.)... 

In another incident a backhoe ruptured a 3-in. polyethylene natural gas pipeline fortunately the gas did not ignite. The drawings were complex and cluttered, and the contractor overlooked the pipeline. A metal detector was not used. This would have detected the pipe as a metal wire was fixed to it, a good practice. In a third incident a worker was hand-digging a trench, as an electric conduit was believed to be present. It was actually an old transfer line for radioactive waste, and he received a small dose of radioactivity. The planner had misread the drawing. 

Transportation of raw materials to depots and plants, by oil tankers, natural gas pipelines, barges, trains, and trucks, can create hazards. Another set of transportation hazards is posed by chemical intermediates (produced in one plant and transported to another plant for further processing) and industrial wastes. Sometimes, they travel past crowded urban areas, pristine beaches, and harbor tunnels. The hazards of oil spills on beaches by tankers are well known, and so are the instances of ruptures and breaks in oil and natural gas pipelines, which produce fire and pollution hazards. Trains and trucks can overturn in centers of habitation, and can lead to flames and explosions, as well as toxic hazards to the community. Toxic chemicals are barred from being trucked in tunnels under harbors and rivers. The storage of raw material and intermediates at plants or... 

Measures for reducing the probability of ruptures of high pressure natural gas pipelines... 

The depth of cover influences the rupture frequency of a natural gas pipeline. Increased depth of cover results in a decreased chance that the pipeline will be hit during digging activities. Combining for the entire transmission pipeline system, which includes about 12000 kilometer of pipelines, of N.V Nederlandse Gasunie (Dutch natural gas transmission company), the number of incidents in a pipeline depth class with the overall years of experience in a depth class the hit frequency (Eq. 2) could be derived (Jager et al. 2002). 

Several measures are discussed which can be used around high pressure natural gas pipelines for reducing the probability of pipeline rupmres. Because for namral gas pipelines external interference is the main cause of pipeline ruptures, the additional measures focus on this cause. For all measures the reduction of the probability of a pipeline rupture is estimated. 

Han and Weng (2011) consider that accidents caused by gas pipelines rupturing bring about major threats to public safety. Due to the physical and chemical characteristics of natural gas and the complexity of the topology of pipeline networks, the occurrence of accidents in pipelines are completely different from any other kind of industrial accident. 

The San Bruno pipeline explosion that occurred in a suburb of San Francisco in 2010 produced a ball of fire 1000 feet high due to the rupture of the natural gas pipeline and killed eight persons [12,18]. 

Hoff (1983) studied the effect of igniting natural gas after a simulated pipeline rupture by firing a bullet into the gas mixture. The tests were on a 10-cm diameter pipeline operating at an initial pressure of 60 bar and a gas throughput of 400,000 mVday. The openings created in the pipeline simulated full-bore ruptures. Maximum flame speeds of approximately 15 m/s, and maximum overpressures of 1.5 mbar were measured at a distance of 50 m. 

Hoff, A. B. M. 1983. An experimental study of the ignition of natural gas in a simulated pipeline rupture. Comb, and Flame. 49 51-58. 

This report is by Battelle Columbus Division to the Line Pipe Research Supervisory Committee of the American Gas Association. It presents an analysis of statistical data obtained from reports of lea)c or rupture (service) incidents and test failures in natural gas transmission and gathering lines over the 14.5 year period from 1970 through June, 1984. All gas transmission companies were required to notify the Office of Pipeline Safety Operations in the event of a "reportable" incident, as defined by the Code of Federal Regulations. The purpose of the study is to organize the reportable incident data into a meaningful format from which the safety record of the industry can be assessed. 

Pressure Development Overpressure in a UVCE results from turbulence that promotes a sudden release of energy. Tests in the open without obstacles or confining structures do not produce damaging overpressure. Nevertheless, combustion in a vapor cloud within a partially confined space or around turbulence-producing obstacles may generate damaging overpressure. Also, turbulence in a jet release, such as may occur with compressed natural gas discharged from a ruptured pipeline, may result in blast pressure. 

A natural gas high pressure pipeline with a diameter of 20" (508 mm), a wall thickness of 8 mm subject to a pressure of pi = 70 bar is planned in the vicinity of a residential area. For the section passing close by this residential area a risk assessment is to be performed. This is a so-caUed risk-based analysis, since the expected frequency of the undesired event (rupture of the pipeline and gas release) is directly taken from statistical material (actuarial approach) and not determined by a detailed analysis of the engineered systems involved. 

Hazard scenarios are defined taking into account some phenomena or aeeidents assoeiated with natural gas, due to gas pipeline leakages, operational failures, ete. The scenarios were based on hazard seenarios defined (Brito Ahneida, 2009). Hazards are the results of pimctures or ruptures oeeurring in gas pipelines, as per Figure 2. 

Acton M.R., Hankinson G., Ashworth B.P., Sanai M., Colton J.D. 2000. A Full Scale Experimental Study of Fires following the Rupture of Natural Gas Transmission Pipelines Proceedings of the International Pipeline Conference, Calgary, ASME International. 

National Transportation Safety Board, 2011. Pipeline Accident Report Pacific Gas and Electric Company Natural Gas Transmission Pipeline Rupture and Fire, San Bruno, California, September 9, 2010. Report No. NTSB/PAR-11/01. NTSB, Washington, DC, 153 h>. 

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