Natural Gas Pipeline Safety Research Articles

Study on the natural gas pipeline safety monitoring technique and the time-frequency signal analysis method

Hydrate plugging and leakage in natural gas pipelines have been big issues for the industry with the globally increasing demand for natural gas. A natural gas pipeline safety monitoring technique is studied in this paper, which is based on acoustic excitation. In this technique hydrate plugging and leakage can be monitored online at multiple locations and distinguished by “energy-pattern” method based on the wavelet packet analysis. The position of a hydrate plugging or leakage can be achieved by correlation algorithm. The results of experiments and modeling work show that the technique can locate hydrate plugging or leakage at multiple positions with good accuracy and distinguish them effectively.

A novel method of risk assessment based on cloud inference for natural gas pipelines

The safety of natural gas pipelines not only is very important to the economy but also significantly affects social security, considering the flammable property of natural gas. This study proposes a risk assessment method based on cloud inference, with multiple factors such as third-party damage, corrosion damage, misuse of factors, design flaws, biological erosion, aging factors, and so on. First, an assessment index system is established, considering the risk factors that may lead to an accident by using a fault tree analysis (FTA). Second, the index weights and index scores are established via the analytic hierarchy process (AHP) and expert scoring method, respectively. Third, the marking results of experts are transformed into the numerical characteristics of a cloud model by using the backward cloud generator. Finally, the whole assessment cloud droplet distribution of a natural gas pipeline is acquired by using the normal cloud generator and virtual cloud. The risk assessment result of natural gas pipelines using the cloud inference method indicates that the whole risk evaluation level can be clearly shown. Moreover, the cloud inference method can solve the fuzziness and randomness of the quantitative description and qualitative concept transformation in the risk assessment process for natural gas pipelines.

Safety First, Environment Last: Improving Regulation of Gas Pipeline Leaks

Domestic natural gas production has increased significantly in recent years, with technological advances enabling the development of vast shale gas reserves previously considered inaccessible. Increased shale gas development has had many benefits, enhancing energy security, reducing consumer costs, and stimulating economic growth. However, it has also presented new challenges, particularly for environmental management. Natural gas is often touted as a “clean” fossil fuel. Supporters emphasize that, compared to coal and oil, the combustion of natural gas produces fewer emissions of mercury and other air toxins that threaten public health. Moreover, natural gas combustion also results in fewer climate-damaging greenhouse gas emissions than coal or oil. These savings at the point of combustion may, however, be offset by greenhouse gas emissions further up the supply chain. Methane – a short-lived but potent greenhouse gas – is released throughout the natural gas production process. Significant releases occur during the transportation of natural gas, including as a result of leaks from aging pipelines. Much of the pipeline system was installed over forty years ago and has degraded over time. Corrosion and graphitization have led to cracking of pipelines, resulting in gas leakage. Recognizing this, the Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA) has called on pipeline operators to accelerate the replacement of aging pipeline systems. While some progress has been made, it is likely to be several years before operators complete all replacement work. In the interim, significant amounts of natural gas may be lost as a result of leaks from aging pipelines. Moreover, even after those pipelines are replaced, leakage may continue due to cracks and/or other defects in newer systems. Pipeline leaks present a major risk to public safety and cause significant environmental damage. Seeking to minimize these adverse impacts, the PHMSA has adopted regulations governing leak detection and repair under the Natural Gas Pipeline Safety Act of 1968 (49 U.S.C. § 1671 et seq.). The Act requires adoption of regulations that are “designed to meet the need for gas pipeline safety . . . and protecting the environment.” The current regulations do not, however, achieve these dual purposes. Rather, the regulations focus primarily on minimizing risks to public safety and do little to advance environmental outcomes. The PHMSA now has an opportunity to enhance regulation of gas leaks so as to provide for greater environmental protection in accordance with the Natural Gas Pipeline Safety Act (49 U.S.C. § 1671 et seq.). In January 2015, as part of its efforts to curb methane emissions from natural gas production, the Obama Administration announced plans to update the regulations. To inform the update process, this White Paper analyzes the current regulations with respect to leak detection, repair, and reporting. It recommends changes to those regulations designed to encourage improved leak management. These include: Pipelines should be regularly inspected for leaks. Federal regulations currently require pipeline operators to conduct system inspections to detect leaks. Frequent inspections must be conducted, one or more times per year, in business districts and other populated areas. In more remote locations, however, several years may elapse between inspections. Consequently, in those locations, leaks may go undetected for extended periods. To ensure prompt leak detection, all pipelines should be inspected for leaks at least annually. More frequent inspections may be required for pipelines at high risk of gas leakage. Leaks detected on the pipeline system should be repaired promptly. Pipeline operators classify leaks based on the risk they pose to public safety. The most serious leaks, classified as hazardous to the public, must be repaired promptly. Leaks classified as non-hazardous can, however, generally be left unrepaired. The classification of a leak is based largely on its proximity to buildings, rather than its size. Thus, leaks in isolated areas may be classified as non-hazardous and left unrepaired, even if they release substantial amounts of natural gas. Going forward, pipeline operators should be required to repair all large leaks (regardless of location) immediately and smaller leaks within one year of detection. It is likely to be simplest to include this requirement in the federal regulations; however, the requirement could also be incorporated into state pipeline safety rules. Gas losses due to pipeline leaks should be measured and reported. Pipeline operators are required to report, to the PHMSA, the number of leaks repaired each year. Notably however, operators generally do not report the number of unrepaired leaks. Moreover, operators do not quantify the volume of gas lost through such leaks. This makes it difficult for regulators and others to assess the extent of gas leakage. To facilitate such assessment, operators should be required to accurately measure the volume of gas lost through leaks. The results of these measurements should be reported to the PHMSA. The PHMSA should make the reported measurements available to other interested parties.

Discussion on Leakage Detecting Techniques for Natural Gas Pipeline

Natural gas pipeline leakage will directly threaten the safety of pipeline facilities as well as people's life and property, thus causing larger malignant accident or indirect losses. Therefore, timely and accurately found natural gas pipeline leakage, leakage position and leakage measuring tool have great significances. This paper summarizes all kinds of technical methods of natural gas pipeline leakage detection and safety warning, discusses the basic principle, scope, technical maturity, the advantages and disadvantages.

Safety distance between underground natural gas and water pipeline facilities

A leaking water pipe bursting high pressure water jet in the soil will create slurry erosion which will eventually erode the adjacent natural gas pipe, thus causing its failure. The standard 300mm safety distance used to place natural gas pipe away from water pipeline facilities needs to be reviewed to consider accidental damage and provide safety cushion to the natural gas pipe. This paper presents a study on underground natural gas pipeline safety distance via experimental and numerical approaches. The pressure–distance characteristic curve obtained from this experimental study showed that the pressure was inversely proportional to the square of the separation distance. Experimental testing using water-to-water pipeline system environment was used to represent the worst case environment, and could be used as a guide to estimate appropriate safety distance. Dynamic pressures obtained from the experimental measurement and simulation prediction mutually agreed along the high-pressure water jetting path. From the experimental and simulation exercises, zero effect distance for water-to-water medium was obtained at an estimated horizontal distance at a minimum of 1500mm, while for the water-to-sand medium, the distance was estimated at a minimum of 1200mm.

Natural Gas Pipeline Design and B31.8 Code

Since 1935 the safety incorporated in natural gas distribution and transmission pipeline design has been promulgated and developed through the Code for Pressure Piping prepared and updated by the B31.8 Committee of ASME. This was a voluntary code until it was used by the U.S. Department of Transportation to develop mandatory design standards brought about by the Natural Gas Pipeline Safety Act of 1968 and its subsequent amendments. The DOT used the B31.8 Code to prepare the Federal Safety Standards for design which then produced code language which was mandatory rather than voluntary. The current ASME Guide for Gas Transmission and Distribution Piping Systems links the ANSI B31.8 Code to the Federal Safety Standards and provides one basis for compliance with natural gas safety design methods for engineers and gas operators engaged in this field. A correlation is drawn to express the relationship of the B31.8 Code to present day Federal Standards.

Responsibility of Gas Utilities for Pipeline Safety

Described herein is the history of Natural Gas Pipeline Safety legislation from 1951 to 1970 and the origin of the B31.8 ANSI Code at the request of the Federal Power Commission. The writer served on the B31.8 Committee both as the representative of FPC and has continued to serve since 1962 as an industry representative and therefore has presented an insider's view of the progress of the safety regulations from both sides. The legislation adopted by Congress in 1970 and the utilization of the B31.8 Code as the keystone on which the Department of Transportation established its minimum standards are presented, many verbatim and others with language changed to set their standards in performance language. The basic theme is, however, the fact that cooperation of government and industry has proven itself and contributed to the public both in safety and service but more so in maintaining just and reasonable costs.

The State's Role in Gas Safety Program

In order to comply with the requirements of the Natural Gas Pipeline Safety Act of 1968, and federal standards for gas safety, state regulatory agencies must perform the following functions with respect to intrastate gas transmission pipelines; investigate and determine the cause of pipeline accidents; cause the filing of inspection and maintenance plans by the pipeline operators; verify the operator's compliance with the plans; enforce minimum federal safety standards; require record keeping by pipeline operators to inform operators of degree of safety of the pipelines; and report state agency's saftey activities to the Office of Pipeline Safety, Department of Transportation. Accidents occurring on intrastate facilities may also be reviewed by the National Transportation Safety Board, Department of Transportation; the Federal Power Commission assumes limited jurisdiction with respect to loss of service. State agencies have a responsibilty to develop new safety standards which are reasonable and proper under correct current circumstances.