Leak Detection Process Research Articles

GIS-BASED REAL-TIME GAS LEAK DETECTION SYSTEM AT BASKENT NATURAL GAS DISTRIBUTION COMPANY

Abstract. Natural gas has been used for heating and production purposes in Turkey since 1987, and every passing year, the natural gas pipeline network continues to expand with investments. The distribution of natural gas within urban areas is achieved through a complex network structure formed by the joining of Polyethylene (PE) and Steel (ST) pipes using various connection elements. This complex structure is susceptible to deformation over time due to various reasons such as corrosion in steel lines, manufacturing errors in connection elements in PE lines, and other factors. As a result, natural gas leaks occasionally occur in these pipelines. The leakage control process in natural gas pipelines is carried out using specially designed equipment and vehicles equipped for this purpose. However, while these systems may be sufficient for collecting the necessary data for leak detection, the complex structure of the distribution network and the necessary data for leak detection, the complex structure of the distribution network and the necessity of performing this process with multiple teams bring about many challenges in terms of tracking, management, and reliability of the operation. At this point, the advancement of GIS (Geographic Information System), mobile, and communication technologies has made it possible to overcome these challenges. In this study, a real-time GIS-supported leak detection system developed using these technologies for Başkent Natural Gas Distrubition Inc. (Başkentgaz), which provides natural gas distribution services in Ankara, has been described. The study discusses the benefits brought by this system to the natural gas leak detection process.

Detection of Water Leakage in Drip Irrigation Systems Using Infrared Technique in Smart Agricultural Robots.

In the future, the world is likely to face water and therefore food shortages due to reasons such as global warming, population growth, the melting of glaciers, the destruction of agricultural lands over time or their use for different purposes, and environmental pollution. Although technological developments are important for people to live a more comfortable and safer life, it is also possible to reduce and even repair the damage to nature and protect nature itself thanks to new technologies. There is a requirement to detect abnormal water usage in agriculture to avert water scarcity, and an electronic system can help achieve this objective. In this research, an experimental study was carried out to detect water leaks in the field in order to prevent water losses that can occur in agriculture, where water consumption is the highest. Therefore, in this study, low-cost embedded electronic hardware was developed to detect over-watering by means of normal and thermal camera sensors and to collect the required data, which can be installed on a mobile agricultural robot. For image processing and the diagnosis of abnormal conditions, the collected data were transferred to a personal computer server. Then, software was developed for both the low-cost embedded system and the personal computer to provide a faster detection and decision-making process. The physical and software system developed in this study was designed to provide a water leak detection process that has a minimum response time. For this purpose, mathematical and image processing algorithms were applied to obtain efficient water detection for the conversion of the thermal sensor data into an image, the image size enhancement using interpolation, the combination of normal and thermal images, and the calculation of the image area where water leakage occurs. The field experiments for this developed system were performed manually to observe the good functioning of the system.

The leak detection process modeling

The paper describes formalized description concept of the expiration gas process through product manufacturing defects in the control of tightness: Model Internal description based on the use of parameters of circuit theory and mathematical model of the external description made by means of functional expansions obtained on the basis of mathematical models experimental research of the implemented software package external description. A dynamic model of the outflow of gases through product defects is presented by the Wiener-Voltaire equations. The proposed method for studying the outflow of gases through product defects consists a simulation object whose input is subjected to an external action with constant other variable parameters and registration of the output signal. The experimental data are compared with the results of theoretical calculations based on the molecular model of the outflow process.

Study on Leak Detection Model and Influencing Factors of Vehicle Fuel Evaporation System

Abstract The evaporative emission and leak of vehicle fuel cause serious pollution to the environment. In order to find out the main influencing factors of the leak detection process of vehicle fuel evaporation system, the leak process and main influencing factors of vehicle fuel evaporation system were studied by means of simulation calculation and experimental research. The leak detection model of fuel evaporation system was established. The pressure decay process was simulated and calculated by matlab/simulink, and the calculated value was compared with the experimental value. The maximum relative error does not exceed 9.52%, indicating that the established mathematical model of pressure change is in good agreement with the test results, and the established mathematical model has high accuracy. Based on the positive pressure decay method, an experimental bench for leak detection of the fuel evaporation system was built, and the influence of different initial pressures and fuel volumes on the leak detection process of the fuel evaporation system under two leak hole diameters of 1 mm and 0.5 mm was studied. The results show that different initial pressures correspond to different decay rates. The greater the initial pressure is, the higher the pressure decay rate becomes. The higher the pressure decay rate is, the clearer the signal is, which is more conducive to leak detection. The fuel volume has a great influence on the pressure decay process, especially when the fuel volume is 80%, the difference in fuel volume is also 30%, and the pressure difference between 50% and 80% fuel volume is much larger than that between 20% and 50% fuel volume. Therefore, it is more important to select the appropriate range of fuel volume when conducting leak detection of the fuel evaporation system.

Development of backward transient analysis in visco-elastic pressurized pipes

This paper aims to develop a backward analysis version of the inverse transient leak detection method for plastic pipes. To carry out the analysis, the structure of the Kelvin–Voigt model is modified to match the numerical structure of the backward model. Brunone unsteady friction is also discretized to make it correspond to the numerical structure. In order to investigate the performance of the improved backward transient model for pipes with visco-elastic properties, the results of this model are compared to the results of the inverse transient model applied to two cases of considering and neglecting the unsteady friction effects. The results show that in the case with a larger leak size, both models performed well. In the case with a smaller leak size, the advantage of eliminating uncertainties in the backward transient analysis (BTA) model led to the success of the model in two of three runs of leak detection; while the inverse transient analysis (ITA) in this case encountered a significant error. The unsteady friction has a negligible effect on the quality of the leak detection process in both cases. Due to the effects that the use of laboratory data with known and simple structure can have on the quality of the results, more real-life data are required to better evaluate the BTA's performance against the ITA.

An Automated Approach of Detection of Memory Leaks for Remote Server Controllers

Memory leaks are a major concern to the long running applications like servers which make the working set to grow with the program. This eventually leads to system crashing. This paper discusses a staged approach to detect leaks in firmware of remote server controller. Remote server controller monitors the server remotely with many processes running in the background. Any memory leak in the long running applications pose a threat to the performance of the system. The approach adopted here filters the processes running in the system with leaks based on time threshold in the first stage. These processes with leaks are passed to the next stage where precise memory leak detection is done using the open source dynamic instrumentation tool Valgrind. The system leverages an automated leak detection approach that invokes the leak detection process on encountering any severity in the system and generates a consolidated leak report. The proposed approach has less impact on the performance of the system and is faster compared to many available systems as there is no need to modify or re-compile the program. In addition, the automated approach offers an effective technique for detecting possible leakages in early software development phases.

An underground pipeline leakage monitoring and precise positioning method based on multi-point signal compensation

Underground pipelines are an important infrastructure for cities and an important basis for ensuring the normal operation of urban production and life. As the earliest types of pipelines built in the urban underground pipe network, the water supply network and the heat pipe network of many cities have already experienced aging phenomena. Pipeline leakage and pipe burst accidents frequently occur, resulting in serious waste of water resources and greatly increasing operating costs [1]. At the same time, there are major security risks. Pipeline leak detection is an important task. There are many kinds of pipeline leakage detection methods [2], and the best one is the water leakage detection correlator, which can locate the location of the leakage point. However, the correlation instrument can not eliminate the environmental noise interference well during the leak detection process, and the positioning result sometimes has a large deviation. In order to solve this problem, an underground pipeline leakage monitoring and precise positioning method based on multi-point signal compensation is proposed. The method increases the third acquisition point of the noise signal, and compensates for the positioning deviation caused by the environmental noise through the signal of the third point, achieving accurate positioning of leak points.

Leak Detection Using Flow-Induced Vibrations in Pressurized Wall-Mounted Water Pipelines

Wireless sensor networks (WSN) provide a powerful solution to the task of monitoring the operational conditions of buried and non-buried pipes of different lengths and materials. Due to the limited energy stored in the sensor nodes, the use of low-power vibration sensors becomes the preferred choice. However, the monitoring of vibrations for leak detection in wall-mounted pipelines, and the associated complexities are not adequately dealt with in the literature. This article offers to fill this gap by presenting a feasibility study of leak detection in wall-mounted water pipelines through vibrations measurements using low-power accelerometers. The work is divided into two steps: Firstly, a careful analysis is performed to understand the effect of various fittings such as clamps, bends, and leaks of various sizes, on the vibrations produced. Then this knowledge is used to find the best locations for placement of nodes in order to efficiently detect leaks of various sizes. This analysis revealed two important facts: (a) difficulty in detecting medium-size leaks as their vibrations and those from the no-leak condition are very indistinguishable, (b) vibrations measured away from the leak are of a small benefit to the leak detection process. Consequently, 3 different learning models are applied, all fed with information from multiple nodes, in order to reliably detect leaks and classify their size. Comparing the performances of these models shows that the Support Vector Machine (SVM)-based model gives the best results, in that for the worst case of medium-size leaks and with the use of one sensor, the worst accuracies for leak detection and leak size classification have remarkably been improved from being respectively 51% and 36% with one sensor, to being 88% and 93%, respectively, with only a moderate increase in the number of sensors to four.

Big data on the shop-floor: sensor-based decision-support for manual processes

Analytics applications are becoming indispensable in today’s business landscape. Greater data availability from self-monitoring production equipment allows firms to empower individual workers on the shop-floor with powerful decision support solutions. To explore the potential of such solutions, we replicate an important manual leak detection process from high-tech composite manufacturing and augment the system with highly sensitive sensors. Based on this setup we illustrate the main steps and major challenges in developing and instantiating a predictive decision support system. By establishing a scalable and generic feature generation approach as well as leveraging techniques from statistical learning, we are able to improve the forecasts of the leak position by almost 90%. Recognizing that mere forecast information cannot be evaluated with respect to business value, we subsequently embed the problem in an analysis of the underlying searcher path problem. We compare predictive and prescriptive search policies against simple benchmark rules. The data-supported policies dramatically reduce the median as well as the variability of the search time. Based on these findings we posit that prescriptive analytics can and should play a greater role in assisting manual labor in manufacturing environments.

Ozone Generation during High-Voltage Leak Detection: Fiction or Reality?

In order to further clarify if and how much ozone is generated during high-voltage leak detection and to identify measures to reduce the impact of ozone generation on product quality, a highly sensitive analytical system was employed to investigate the generation of ozone at different operational conditions of high-voltage leak detection integrity testing. The analytical system is based on oxidation of Iodide ions in solution and identification of the Iodine formed by N, N-Diethyl-p-phenylendiamine (DPD) according to DIN 38403. Sensitivity of the system was found suitable to detect ozone levels as low as 0.025 ppm (mg/L). High-voltage leak detection process parameters-inspection speed, high voltage, filling level of the ampoule, and exposure time to the ampoule to high voltage-were varied between maximum and minimum values applicable in integrity testing of different ampoule sizes. For variation of exposure time, ampoules were repetitively tested by the leak testing machine to achieve a maximum exposure time of the ampoule up to 24 s (exposure time during production ≤2.4 s). No ozone was detected during the study under all inspection conditions. Even repeated exposure of the ampoules to high-voltage leak detection did not result in generation of measurable ozone levels. It has to be concluded that high voltage leak detection is not prone to causing oxidation of the drug products.LAY ABSTRACT: For drug products in ampoules, 100% integrity testing is requested both by European and US regulations. Detection of integrity defects like small holes or cracks in the ampoule can be performed by numerous methods. Due to automation requirements, only three methods have been used during routine production-vacuum decay, head space infrared spectroscopy, and high-voltage leak detection. High-voltage leak detection is the most common method used in the pharmaceutical industry for 100% integrity testing of ampoules, but resent publications showed considerable oxidation of an air-sensitive active pharmaceutical ingredient during the integrity testing process. It was assumed that ozone generated in the inside of the vial due to exposure of the product to the high voltage during the testing process may be responsible for this result. As ozone is a very aggressive and non-selective oxidant, this result posed a serious thread not only to this product but also to the quality of many other products subjected to integrity testing by high-voltage leak detection.

Role of Outgassing of ITER Vacuum Vessel In-Wall Shielding Materials in Leak Detection of ITER Vacuum Vessel

ITER Vacuum Vessel is a torus-shaped, double wall structure. The space between the double walls of the VV is filled with In-Wall Shielding Blocks (IWS) and Water. The main purpose of IWS is to provide neutron shielding during ITER plasma operation and to reduce ripple of Toroidal Magnetic Field (TF). Although In-Wall Shield Blocks (IWS) will be submerged in water in between the walls of the ITER Vacuum Vessel (VV), Outgassing Rate (OGR) of IWS materials plays a significant role in leak detection of Vacuum Vessel of ITER. Thermal Outgassing Rate of a material critically depends on the Surface Roughness of material. During leak detection process using RGA equipped Leak detector and tracer gas Helium, there will be a spill over of mass 3 and mass 2 to mass 4 which creates a background reading. Helium background will have contribution of Hydrogen too. So it is necessary to ensure the low OGR of Hydrogen. To achieve an effective leak test it is required to obtain a background below 1 × 10-8 mbar 1 s-1 and hence the maximum Outgassing rate of IWS Materials should comply with the maximum Outgassing rate required for hydrogen i.e. 1 x 10-10 mbar 1 s-1 cm-2 at room temperature. As IWS Materials are special materials developed for ITER project, it is necessary to ensure the compliance of Outgassing rate with the requirement. There is a possibility of diffusing the gasses in material at the time of production. So, to validate the production process of materials as well as manufacturing of final product from this material, three coupons of each IWS material have been manufactured with the same technique which is being used in manufacturing of IWS blocks. Manufacturing records of these coupons have been approved by ITER-IO (International Organization). Outgassing rates of these coupons have been measured at room temperature and found in acceptable limit to obtain the required Helium Background. On the basis of these measurements, test reports have been generated and got approved by IO. This paper will describe the preparation, characteristics and cleaning procedure of samples, description of the system, Outgassing rate Measurement of these samples to ensure the accurate leak detection.

Analytical study of the performance of a geomembrane leak detection system.

The electrical detection of leaks in geomembranes is a method that allows identifying leakage of contaminants in lined facilities (e.g. sanitary landfills, pollutant ponds, etc.). The procedure in the field involves placing electrodes above and below the geomembrane, to generate an electrical current, which in turn engenders an electric potential distribution in the protective layer (generally a clayey soil). The electric potential will be greater in areas with higher current density, i.e. near leaks. In this study, we combined models from the literature to carry out a parametric analysis to identify the variables that most influence the amplitude of the electrical signals produced by leaks. The basic hypothesis is that the electrical conduction phenomena in a liner system could be depicted by a direct current circuit. After determining the value of the current at the leak, we calculated the electric potential distribution according to the model of Darilek and Laine. This enabled analysing the sensitivity of the parameters, which can be useful in the design of landfills and facilitate the location of leaks. This study showed that geomembranes with low electrical resistance (owing to low thickness, low resistivity, or extensive area) can hinder the leak detection process. In contrast, low thickness and high resistivity of the protection layer magnify the leak signal.

Model falsification diagnosis and sensor placement for leak detection in pressurized pipe networks

Pressurized pipe networks used for fresh-water distribution can take advantage of recent advances in sensing technologies and data-interpretation to evaluate their performance. In this paper, a leak-detection and a sensor placement methodology are proposed based on leak-scenario falsification. The approach includes modeling and measurement uncertainties during the leak detection process. The performance of the methodology proposed is tested on a full-scale water distribution network using simulated data. Findings indicate that when monitoring the flow velocity for 14 pipes over the entire network (295 pipes) leaks are circumscribed within a few potential locations. The case-study shows that a good detectability is expected for leaks of 50L/min or more. A study of measurement configurations shows that smaller leak levels could also be detected if additional pipes are instrumented.

Leak detection with tracer gases; sensitivity and relevant limiting factors

After briefly dealing with some basic questions concerning vacuum leak detection based on tracer gases, the factors which determine the smallest detectable leak rate are discussed. It is shown that this frequently overrated specification not only depends on the lowest measurable partial tracer gas pressure, but also on the lowest detectable tracer gas concentration, the effective volume flow rate at the inlet of the tracer gas detector and above all other factors on the total gas flow from the test object to the pump. It is demonstrated that high sensitivity leak testing can only commence provided the gas flow which is mainly due to outgassing, is sufficiently low after a suitable pumpdown period. The task of the LN 2-trap of conventional leak detectors is that of pumping out condensible gases to increase the helium concentration, thus reducing the time required for the commencement of the actual leak detection process. In the counterflow-type helium leak detector the same task is performed by a high vacuum pump, whereby it relies on the much lower compression of diffusion and turbomolecular pumps for lighter gases as compared to heavier gases. Finally a helium leak detector is described which is equipped with a double-entry vacuum pump. The test object is connected to the inlet with a high volume flow rate and a mass spectrometer is connected to the second inlet. The forevacuum connection lies between the two pumps which are arranged on-axis.

A high vacuum chamber with a dynamic seal for varying ion attitude and velocity relative to the entrance of a mass spectrometer: Anon,Dept Electronics and Instrumentation, Rep NASA-CR-77447, July 1966 ( Arkansas Univ, Little Rock)

After briefly dealing with some basic questions concerning vacuum leak detection based on tracer gases, the factors which determine the smallest detectable leak rate are discussed. It is shown that this frequently overrated specification not only depends on the lowest measurable partial tracer gas pressure, but also on the lowest detectable tracer gas concentration, the effective volume flow rate at the inlet of the tracer gas detector and above all other factors on the total gas flow from the test object to the pump. It is demonstrated that high sensitivity leak testing can only commence provided the gas flow which is mainly due to outgassing, is sufficiently low after a suitable pumpdown period. The task of the LN2-trap of conventional leak detectors is that of pumping out condensible gases to increase the helium concentration, thus reducing the time required for the commencement of the actual leak detection process. In the counterflow-type helium leak detector the same task is performed by a high vacuum pump, whereby it relies on the much lower compression of diffusion and turbomolecular pumps for lighter gases as compared to heavier gases. Finally a helium leak detector is described which is equipped with a double-entry vacuum pump. The test object is connected to the inlet with a high volume flow rate and a mass spectrometer is connected to the second inlet. The forevacuum connection lies between the two pumps which are arranged on-axis.