A survey on gas leak detection and localization techniques

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Abstract

Gas leaks can cause major incidents resulting in both human injuries and financial losses. To avoid such situations, a considerable amount of effort has been devoted to the development of reliable techniques for detecting gas leakage. As knowing about the existence of a leak is not always enough to launch a corrective action, some of the leak detection techniques were designed to allow the possibility of locating the leak. The main purpose of this paper is to identify the state-of-the-art in leak detection and localization methods. Additionally we evaluate the capabilities of these techniques in order to identify the advantages and disadvantages of using each leak detection solution.

Highlights

► State-of-the-art in leak detection techniques is presented. ► Leak detection methods that have leak localization capabilities are pointed out. ► Advantages and disadvantages of each technique are presented.

Introduction

The worldwide natural gas transport and distribution network is a complex and continuously expanding one. According to the study presented in (TRB, 2004), pipelines, as a means of transport, are the safest but this does not mean they are risk-free. Therefore, assuring the reliability of the gas pipeline infrastructure has become a critical need for the energy sector. The main threat considered, when looking for means of providing the reliability of the pipeline network, is the occurrence of leaks.

Regardless of their size, pipeline leaks are a major concern due to the considerable effects that they might have. These effects extend beyond the costs involved by downtime and repair expenses, and can include human injuries as well as environmental disasters. The main causes of gas pipeline accidents are (EGIG, 2008): external interference, corrosion, construction defects, material failure and ground movement.

To counteract the disastrous effects of gas leaks, considerable effort has been invested, during the last decades, in designing gas leak detection techniques. However, revealing the presence of a gas leak is not sufficient in order to define an efficient counteracting measure. Before deciding on a set of corrective actions, other information has to be known such as: the location of the leak, its size, etc. These subjects were also in the focus of research done in the field of pipeline reliability assurance.

The occurrence of gas leak-related incidents was studied by several organizations which published statistics on the reported incidents. One of these studies, made on the sub-sea pipeline systems (SLR, 2009), states that, between 1996 and 2006, a number of 80 pipeline rupture incidents were reported in the Gulf of Mexico and Pacific areas. Based on data gathered in this report, the calculated probability of a catastrophic incident, for the specified area, is 0.43 incidents per year. Another survey (Konersmann, Kühl, & Jörg, 2009), which focuses on the risks of pipeline transportation, covers incidents that occurred in Europe and on the American continent presenting the main causes of pipeline failure. According to this report, in the province of Alberta/Canada alone, there have been 1326 reported gas leaks in the 2001–2005 period. A different report shows that large pipelines (i.e. with a length of 800 miles or more) can expect at least one reportable leak-related incident per year (ADEC, 1999). This evidence indicates that the risk of incidents caused by gas leaks is substantial despite the great variety of leak detection methods available and serves as motivation of our work.

The main purpose of this paper is to identify the state-of-the-art in gas leak detection techniques and to present localizing capabilities, as well as other important features, for each of the studied methods. We achieve this by performing an extensive survey of the literature in the field, covering results from academia as well as industry reports.

A number of reviews on the subject of gas leak detection techniques were done in the past either as part of research papers/technical reports on a certain leak detection method and other gas related subjects (Batzias, Siontorou, & Spanidis, 2011; Folga, 2007; Liu, Yao, Gallaher, Coburn, & Fernandez, 2008; Matos, Powell, Davies, Zhang, & Moore, 2006; Zhang, 1997) or as a result of research dedicated to this specific purpose (ADEC, 1999; El-Shiekh, 2010; Geiger, Werner, & Matko, 2003; Jolly, Morrow, O'Brien, & Service U.S.M.M, 1992; Loth, Morris, & Palmer, 2003; Scott & Barrufet, 2003; Sivathanu, 2003; Stafford & Williams, 1996; Turkowski, Bratek, & Słowikowski, 2007; USDT, 2007; Wang, Lambert, Simpson, & Vitkovsky, 2001). Although they provide a good overview on existent leak detection techniques, these surveys are either succinct, omitting several leak detection methods or, in some cases, not of a recent date.

In order to decide which leak detection technique is more suitable for a given setting, a comparative performance analysis is necessary. For this we compare the studied methods by a set of common features using performance reports from literature. As a conclusion, and apparently future trend, a hybrid approach combining different detection methods to achieve the required system performance would be the best choice.

This paper is organized as follows. The analyzed methods are first classified, in Section 2, by a number of different criteria ranging from the measured physical quantity to the amount of human intervention required. Each of the identified methods are then described in Sections 3 Non-technical methods, 4 Hardware based methods, 5 Software based methods followed by a compared performance analysis in Section 6. Finally, the conclusion of this work is presented in Section 7.

Section snippets

Classifying leak detection technologies

For the purpose of this survey we first look at classifying the available leak detection techniques. Several criteria are considered for classification, some of which are: the amount of human intervention needed, the physical quantity measured and the technical nature of the methods.

If the degree of intervention needed from a human by each detection method is chosen to classify these methods, we distinguish three categories:

  • automated detection - complete monitoring systems that, can report the

Non-technical methods

As stated, these methods involve personnel patrolling along the pipelines looking for visual effects of a gas leak, smelling substances that might be released through a leak or listening to specific sounds that can be made by gas as it leaks out. Sometimes trained dogs are used as they are more sensitive to the smell of certain gases (Kennedy, 2005; Quaife & Acker, 1993). The sensitivity of dogs, depending on the target compound, has been found to be in the 10 parts-per-billion (ppb) - 500

Acoustic methods

Escaping gas generates an acoustic signal as it flows through a breach in the pipe. Thus, this signal could be used to determine that a leak has occurred. To record the internal pipeline noise, acoustic sensors have to be used. They can be integrated in handheld detection devices employed by personnel patrolling the pipeline or in intelligent pigs that travel through the pipeline inspecting it (Furness & van Reet, 2009). Continuous monitoring is also done by installing acoustic sensors outside

Mass/volume balance

The mass or volume balance leak detection technique is based on the principle of mass conservation. An imbalance between the input and output gas mass or volume can reveal the existence of a leak (Liou, 1996; Parry, Mactaggart, & Toerper, 1992). The volume of gas exiting a section of the pipeline is subtracted from the volume of gas entering this section and if the difference is above a certain threshold, a leak alarm is given. The mass or volume can be computed using the readings of some

Compared performance analysis

The performance level of a leak detection system can be established by a series of factors. Some of the criteria that are usually used to evaluate the performance of leak detection systems are (Stafford & Williams, 1996): the ability to determine the location of the leak, the detection speed and the ability to estimate the size of the leak. In Table 1 we summarized the most important features offered by each studied detection technique including also these criteria. The following abbreviations

Conclusions

A wide variety of leak detecting techniques is available for gas pipelines. Some techniques have been improved since their first proposal and some new ones were designed as a result of advances in sensor manufacturing and computing power. However, each detection method comes with its advantages and disadvantages.

Leak detection techniques in each category share some advantages and disadvantages. For example, all external techniques which involve detection done from outside the pipeline by visual

Acknowledgments

This work was supported by the CNCSIS-UEFISCDI project number PN II-IDEI 940/2008.

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