The use of a proper leak detection system in pipelines is of crucial importance in water transmission systems. In these methods, we should consider the time and accuracy of leak detecting procedure for preventing energy loss and reducing environmental impacts. In these days, seawater transmission lines are used for cooling systems, and for injecting water into the oil wells to improve oil recovery. Due to the more environmental impacts of saltwater, the leak detection system must have appropriate accuracy and speed in leak detection. The purpose of this paper is to choose a leak detection system for a saltwater transmission line. First of all, the specifications of different leak detection systems are provided. Finally, according to the mentioned project conditions, the most suitable method-fiber optic system-is recommended for these conditions. The most important advantages of this system are high accuracy, rapid leak detecting, and the ability of online monitoring of other parameters, such as temperature distribution or detecting intrusion into the buried line areas. These abilities result in improving safety and optimizing operating costs.

leakage in water transmission systems and distribution networks in addition to waste of water and energy, can cause a declined water quality due to exposure to contaminants at low pressure conditions as well as damages to roads, buildings, and infrastructures. Therefore and due to its negative impacts on economics, environmental, and social safety, determination and control of leakage is one of the most important and complex topics in water supply systems engineering. The current research investigated transientbased techniques for leak detection in Polyethylene water pipe systems. For this purpose, firstly an inverse transient analysis (ITA) tool was developed, and then for testing and validating this model, extensive experiments were carried out at Hydraulic Laboratory of Shahid Chamran University of Ahvaz to collect the necessary data. A selected set of data corresponding to two leak locations with different sizes was used to assess the ITA method. Results indicated that the leak location can be accurately pinpointed using a sample size equal to one period (T=4L/a) of the collected pressure in ITA. The error for estimation of the location for a significant leak was between 0. 17% and 2. 17% of the pipe length. Also, using two periods (2T) of the pressure signal, the uncertainties in leak quantity estimation were satisfactory, as less than 23% of the real leak quantity. Additionally, the comparison between the observed data and the numerical results in different conditions indicated that the hydraulic model estimated the transient pressure accurately by just incorporating the pipe wall viscoelasticity into the model.

There are two destructive and nondestructive inspection methods to ensure the operation of pipelines, pressure vessels and defects in industrial sheets. One of the important issues in oil and gas transmission lines and pressure vessels is leakage issue. The leak test is one of the nondestructive testing methods that relates to the entry or exit of a fluid from a high pressure environment to a low pressure environment. Acoustic emission is one of the nondestructive methods which is used for leakage locating. The jet produced due to leakage causes the pipe to vibrate and so acoustic waves will propagate through the pipe. Due to different source-sensor distances, acoustic sensors will capture the signals with time delay. In this study the first arriving time and so time delay between sensors can be estimated using Akaike Information Criteria method. Acoustic signals will capture using two R15a sensors located on two sides of leakage. In this study, first leakage tests were carried out on a pressurized pipe. The results showed that using AIC technique leakage location can be done with a mean error of 1. 4%. In the next step, experiments were carried out to locate the acoustic source on a steel sheet. The results showed that using AIC method, an acoustic source location can be estimated with an average error of 3. 92%.

Today, pipe systems are the most common facilities to convey various fluids from one place to another. In such facilities faults like leaks lead to advert consequences such as economic losses and social health threats. The fact that early detection of leaks can play a prominent role in reducing the amount of these undesired impacts has absorbed noticeable attention from researchers to this field of study. This paper presents a literature review on major aspects of hydraulic transient-based leak detection in pipe systems over the past three decades. The value of the present study is that an extensive database of peer-reviewed publications is brought together under a meticulous survey. It describes the trends, status and pinpoints the areas with a need for further investigation in the future. Uniquely, it contains information for over 95 publications in a tabular form, presenting domain type, analysis approach, optimization technique, topographic complexity of the case study, leak unknowns and validation approach.

In the upcoming study, the 175 kilometers oil products pipeline is simulated by Pipeline Studio software, the equipment needed to remove fluid from the pipe has been installed at different points of the pipeline, and a number of ten removal tests have been performed. In each test, the operational data related to the pipeline and other data are recorded and the results of each stage of the tests are compared with the outputs of the software model. In the following, two methods to identify the location of the leak in the pipeline including negative pressure waves and the intersection of the hydraulic gradient have been introduced and they have been used to calculate the location of the leak in the tests. The calculation results showed that both methods had acceptable accuracy in finding the leak location, but the comparison of the two methods showed that negative pressure waves had a better performance (11% error vs. 18%) in estimating the leak location. The high correspondence between the diagrams extracted from the software and the real conditions ensures that the Pipeline Studio software can be used not only in the pipeline design phase but also in the analysis of operational changes and its results could be help in a better understanding of pipeline.Keywords: leak detection in pipeline, negative pressure waves, hydraulic gradient line, oil transmission pipeline, pipeline simulate with Pipeline Studio.

Passive acoustics has been recognized as an important strategy for long-term detection and monitoring of underwater gas leaks in natural sites or in underwater gas pipelines. The ability of an acoustic system to detect underwater gas leaks is primarily controlled by the signal-to-noise ratio (SNR) of bubble sounds. In the current research, it is tried to provide the possibility of detecting the leakage signal with low flow rate and in the presence of strong noise by using the CFAR method. In this regard, "Bellhop" software was used to model the underwater acoustic channel. According to previous researches, the minimum detectable leakage flow rate for the threshold-based detection method is equal to 2 liters per minute (at a maximum distance of 0.5 meters from the leakage location) and the SNR required by this method for detection is also equal to 6 dB. . Considering the lower power of the signal with low flow rate and as a result lower SNR compared to the high rate of leakage current, it is shown in the simulated scenario that by using the CFAR method, the acoustic signal of leakage with low flux can be detected. also identified On the other hand, the performance of the OS-CFAR method is much better than other methods, and it provides the possibility of detecting the leakage signal with low flux even at very low SNR values (up to SNR = -10 dB).

Pipes burst and leakage rates in water distribution networks are growing with increasing of pipes age. Therefore, pipe rehabilitation and replacement programs would be necessary during the pipes life time. This is a complicated problem in which budget restriction has an important impact. This paper introduces a simple model to determine the best time for leak detection and pipe replacement programs using pipes break records. Assuming a linear relationship between pipes break rate with time, the operation cost for three different steps of: pipe repair, leak detection and pipe replacement are evaluated and the best time for commencing of each scenario is calculated. To highlight advantages of the proposed methodology, it is applied to a pipe network in one of the Iranian cities. At first pipes break records are gathered for a period of six months using a standard format. Then the best time for leak detection and replacement programs are determined and sensitivity of the results to different parameters is evaluated. It can be concluded that the proposed methodology produces a powerful tool to be used in water distribution networks and help decision makers to choose the best option considering budget restrictions.