Pipeline transportation is an economical and safe way to transport oil and gas. However, if not properly maintained, pipelines can experience leaks. This is why leak detection systems (LDS) are so important. They help to identify and localize leaks, as well as enhance system reliability and reduce downtime. This article provides an overview of pipeline leak detection and location systems, along with a comparison of the various technologies available.
External and Internal Leak Detection Systems
The two main types of pipeline leak detection systems are external and internal. External systems detect leaking product outside the pipeline, while internal systems use instrumentation to monitor internal pipeline parameters. These parameters are then used to infer a leak. The method of leak detection chosen for a pipeline is dependent on a variety of factors, including pipeline characteristics, product characteristics, instrumentation and communications capabilities, and economics.
External Leak Detection Systems
External leak detection systems are used to detect and localize leaks outside of the pipeline. These systems typically use acoustic or seismic sensors to detect the sound of a leak, infrared or ultraviolet cameras to detect plumes of leaking gas, ground penetrating radar (GPR) to detect changes in soil density or composition, or fiber optic cables to detect changes in optical properties.
Internal Leak Detection Systems
Internal leak detection systems use instrumentation to monitor internal pipeline parameters, such as flow, pressure, and fluid temperature. These systems are typically used to detect small leaks that are not visible from the outside. Examples of internal leak detection systems include Computational Pipeline Monitoring (CPM), which uses mathematical models to detect changes in the pipeline parameters, and pressure wave analysis, which uses pressure measurements to detect changes in the pipeline.
Performance Criteria
When selecting a leak detection system, it is important to consider the performance criteria of the system. These criteria include sensitivity, reliability, accuracy, and robustness. The system should be able to detect small leaks quickly and accurately, and should be reliable enough to detect even the smallest leaks.
TABLE1- LEAK DETECTION AND LOCATION SYSTEMS
Leak Detection and Localization in Pipelines using Continuous External Systems
Leak detection and localization in pipelines is a crucial task to ensure the safety and integrity of the pipeline. There are several methods available for this purpose, including fiber optic cable, acoustic systems, sensor hoses, and video monitoring. Each of these methods has its own advantages and limitations. This article provides an overview of each of these methods.
Fiber Optic Cable
Fiber optic cable is a reliable and effective way of detecting and localizing leaks in pipelines. It is installed alongside the pipeline and takes temperature measurements along the entire length of the pipeline. If a leak occurs, the cable detects changes in temperature due to the substance being transported through the pipeline, such as a local warming or cooling. This method offers high accuracy in detection and localization, but the limitation is the limited length of cable.
Acoustic Systems
Acoustic systems use the principle that escaping liquid creates an acoustic signal (sound) as it passes through a perforation in the pipe. When a leak occurs, the resulting frequency acoustic signal is detected and analyzed by system processors. The sound is detected by rods inserted along the pipeline, and the sound pressure level is measured on a logarithmic scale. This method has the advantage of high detection and localization accuracy, but it requires a large number of sensors for longer pipelines.
The pressure amplitudes of sound waves are commonly
measured on a logarithmic scale (dB), called Sound Pressure
Level (SPL).
where po is the pressure amplitude of a reference sound.
Sound Pressure Level is proportional to the power generated by
the gas upon expansion, expressed as (2)
where M is the mass flow rate of the jetting gas, T is gas
temperature at the orifice, M is the molecular weight, and R is
the gas constant.
Sensor Hoses
Sensor hoses are used to detect mediums in pipelines. They are laid along the pipeline, and a material is disposed at least in the vicinity of the sensor hose. The material reacts when in contact with the medium to be detected to produce a substance being capable of diffusion and being detectable. This method is useful for short pipelines, but the position of the cable must be selected according to the medium.
Video Monitoring
Video monitoring is used to visually inspect the interiors of pipelines. It is commonly used to determine the condition of small diameter sewer lines and household connection pipes. With CCTV, location of leaks, points of infiltrations, paved-over manholes, pipeline breaks, and lost articles such as rings or other valuables can be accomplished without the disadvantages accompanying the digging up of the pipeline.
Leak detection and localization in pipelines is a critical task that requires reliable and effective methods to ensure the safety and integrity of the pipeline. There are several methods available for this purpose, including fiber optic cable, acoustic systems, sensor hoses, and video monitoring. Each of these methods has its own advantages and limitations, and it is important to consider these factors when choosing the right method for a particular application.
Leak Detection in Pipelines: Comprehensive Overview of Continuous Internal Systems
Pipelines are an essential part of our daily lives, delivering essential resources like natural gas and oil. But these pipelines can be subject to leaking, which can have far-reaching impacts on the environment, businesses, and people. That’s why it’s essential to have reliable systems in place to detect and prevent pipeline leaks.
In this article, we’ll explore the different continuous internal systems used for leak detection in pipelines. We’ll also look at the pros and cons of each system, as well as their cost and complexity.
Pressure Point Analysis
Pressure point analysis is a leak detection method based on the statistical properties of a series of pressure or velocity pipeline measurements taken at one point. A leak changes the hydraulics of the pipeline, which affects the pressure or flow readings. The pressure wave source spreads out from the leak point to the leak upstream and downstream ends. This allows the leak point to be determined based on the pressure difference detected by sensors on both sides of the pipe, its length, and the negative pressure wave velocity.
The advantage of pressure point analysis is its ability to detect small leaks which may not be detected by other methods. However, it’s difficult for this method to localize leak points.
Mass Balance Method
The mass or volume balance method is based on the principle of conservation of mass. This states that a fluid that enters the pipe section either remains in the pipe section or leaves the pipe section. For a normal cylindrical pipeline, the flow entering and leaving the pipe can be metered. The mass of fluid in the pipe section can be estimated from the pipe dimensions and measurements of state variables such as pressure and temperature. A leak is identified when less fluid leaves the pipe than is expected from the measurements of input flow and estimates of the pipe contents.
The mass balance method is sensitive to arbitrary disturbances and dynamics of the pipeline, which may lead to false detection issues.
Statistical Systems
Statistical leak detection systems use methods and processes from decision theory to optimize the leak decision. The hypothesis-test for leak detection based on the uncompensated mass balance uses either a single measurement, or multiple measurements made at different times.
To assign a single
measurements (∆m) to H0 and H1 hypothesis, an alarm limit γ is
defined [14]. The test defined as (3)
Real-Time Transient Model (RTTM)
RTTM stands for Real-Time Transient Model, and it uses mathematical models based on physical laws such as conservation of mass, conservation of momentum and conservation of energy. RTTM methods can be seen as an enhancement of balancing methods, as they additionally use the conservation principles of momentum and energy.
The modern RTTM based systems calculate the flow in the pipeline from the pressure and temperature at the inlet and outlet. This calculated flow is then compared to the measured flow (from a flow meter at inlet and outlet). The difference between calculated and measured values for the inlet (or for the outlet) is around zero.
The advantages of RTTM are its ability to model steady-state and transient flow in a pipeline, as well as its ability to detect leaks during both steady-state and transient conditions. However, the cost and complexity of RTTM systems are significant.
Other Pipeline Leak Detection Methods
In addition to the continuous internal systems described previously, there are a few other methods used for pipeline leak detection and location. These include acoustic leak detection, infrared detection, and vapor sensing. Each of these methods has its own unique advantages, and they should be evaluated to determine which is most suitable for the particular pipeline being monitored.
Fig. 4 exhibits an Extended-Real Time Transient Model (ERTTM) have unique leak signature analysis feature which
differentiate from RTTM.
Conclusion
Leak detection in pipelines is essential for the safety of businesses, people, and the environment. While there are a variety of continuous internal systems that can be used for leak detection and location, each system has its own unique advantages and disadvantages. It’s important to evaluate these systems carefully to determine which one is the best fit for the particular pipeline being monitored.
Ground Penetrating Radar: An Effective Tool for Pipeline Leak Detection
With the increasing demand for natural gas and other mineral resources, the need to keep oil and gas pipelines secure has become more critical than ever. This is why various methods of leak detection have been developed, one of which is Ground Penetration Radar (GPR). GPR is an effective tool for detecting leaks in pipelines, as it can detect leaks from a long distance and is able to penetrate through difficult soil conditions.
What is Ground Penetrating Radar?
Ground Penetrating Radar (GPR) is a non-destructive method of sensing that uses electromagnetic waves to detect and identify features underneath the surface of the earth. GPR works by sending electromagnetic pulses into the ground and analyzing the reflected signals that bounce back. The reflected signals indicate the presence of subsurface objects and their characteristics.
GPR is often used to detect the location and size of underground pipes, as well as the presence of leaks in them. GPR is also used to detect underground utilities, such as cables, pipes, and other objects, as well as for archaeological purposes.
How Does GPR Work for Pipeline Leak Detection?
GPR is most effective for detecting and locating leaks in pipelines. It works by sending electromagnetic pulses into the ground and analyzing the reflected signals that bounce back. The reflected signals indicate the presence of subsurface objects and their characteristics.
Through GPR, the location and size of underground pipes can be detected, as well as the presence of leaks in them. By analyzing the reflected signals from the subsurface, GPR is able to detect the presence of water in pipes, which indicates a potential leak.
GPR is able to penetrate through difficult soil conditions, making it an effective tool for detecting leaks in pipelines located in areas with difficult soil conditions. It is also able to detect leaks from a long distance, making it an ideal tool for detecting leaks in long pipelines.
Advantages and Disadvantages of GPR for Pipeline Leak Detection
GPR has many advantages for pipeline leak detection, including the ability to detect leaks from a long distance and the ability to penetrate through difficult soil conditions. GPR is also non-destructive and can detect leaks with high accuracy and resolution.
However, there are some drawbacks to using GPR for pipeline leak detection. GPR is not suitable for long pipelines, as it can be difficult to detect leaks in long pipelines due to the large amount of data that needs to be analyzed. Additionally, GPR can be difficult to use in clay soils, as iron pipe corrosion products can hide cast iron pipes from the GPR, resulting in decreased reflection and increased radio frequency (RF) signal attenuation.
Leak Detection and Location Systems: An Overview of Performance Evaluation
Leak detection and location (LDL) systems are used to detect and locate leaks in pipeline networks. These systems are important for the efficient operation of pipeline networks and for the safety of workers and the surrounding environment. This article provides an overview of the performance evaluation of leak detection and location systems.
Types of Leak Detection and Location Systems
Leak detection and location systems can be classified into two main types: internal and external systems. Internal systems monitor the pressure and flow of the pipeline network in order to detect leaks. These systems are sensitive to small leaks and can detect them quickly. External systems use acoustic, infrared, or other types of sensors to detect and locate leaks. These systems can detect small leaks, but they are slower at detecting them compared to internal systems.
System Performance Comparison
The performance levels of leak detection and location systems can be measured using various criteria. These criteria include accuracy, speed, sensitivity, cost, and reliability. According to studies, there is no system that is rated good for all of these criteria. The performance of each system varies depending on the pipeline operating conditions and the quality of the hardware or instrumentation system used.
Environmental Assessment
Before installing a LDL system, an environmental assessment must be conducted to determine whether the environmental conditions, such as air, land, water, and energy, could affect the functionality of the system.