A method for simulating the entire leaking process and calculating the liquid leakage volume of a damaged pressurized pipeline

Highly efficient molecular film for inhibiting volatilization of hazardous nitric acid

Nitric acid, an important basic chemical raw material, plays an important role in promoting the development of national economy. However, such liquid hazardous chemicals are easy to cause accidental leakage during production, transportation, storage and use. The high concentration and corrosive toxic gas generated from decomposition shows tremendous harm to the surrounding environment and human life safety. Therefore, how to inhibit the volatilization of nitric acid and effectively control and block the generation of the toxic gas in the first time are the key to deal with the nitric acid leakage accident. Herein, a new method of molecular film obstruction is proposed to inhibit the nitric acid volatilization. The molecular film inhibitor spontaneously spread and form an insoluble molecular film on the gas-liquid interface, changing the state of nitric acid liquid surface and inhibiting the volatilization on the molecular scale. The inhibition rate up to 96% can be achieved below 45 °C within 400 min. Cluster structure simulation and energy barrier calculation is performed to elucidate the inhibition mechanism. Theoretical analysis of energy barrier shows that the specific resistance of the inhibitor significantly increased to 460 s·cm-1 at 45 °C, and the generated energy barrier is about 17,000 kJ·mol-1, which is much higher than the maximum energy required for nitric acid volatilization of 107.97 kJ·mol-1. The molecular film obstruction strategy can effectively inhibit the volatilization of nitric acid. This strategy paves the way for preventing the volatilization of liquid hazardous chemicals in accidental leakage treatment.

Mathematical modelling and simulation of leak detection system in crude oil pipeline

A first-order differential leak detection model that accurately detects leaks in a crude oil pipeline is presented. This model incorporates a leak factor K_L in the axial direction, which is simulated by applying the finite element method of numerical solution using COMSOL multi-physics software. Additionally, the model includes the transport equation for turbulent kinetic energy and the rate of kinetic energy model. Eigenvalues for velocities and pressures were determined and plotted against time for various pipe segments. The system is stable when the Eigenvalue is zero, but a leak is declared when the Eigenvalue for pressure or velocity is less than one. The study shows that pressure measurements are more sensitive parameters for detecting leaks than velocity measurements, and the sinusoidal waveform characterizes leak behaviours for velocity.

Experimental and Numerical Study of Natural Gas Leakage and Explosion Characteristics

Frequent occurrence of indoor natural gas explosion accidents seriously threatens the safety of people and property. To determine the law of indoor natural gas leakage and explosion hazards, based on experiment and simulation, the nature of natural gas explosion, the distribution law of natural gas volume fraction, flame propagation, temperature, and shock wave overpressure were studied. The results show that the flame structure can be divided into three zones, i.e., preheat zone, reaction zone, and product zone. OH + CO ⇔ H + CO₂ is the main exothermic reaction in the combustion process. The overall distribution law of natural gas volume fraction shows that the higher the position, the greater the volume fraction, and the closer the distance to the leak source at the same height, the greater the volume fraction, and the natural gas volume fraction of the hose falling off is the largest under different leakage conditions. The difference in the wrapping structure of the kitchen package has a significant impact on the diffusion distribution of natural gas. The flame development goes through five stages of ignition, slow burning, detonation, slow burning, and extinguishing. The indoor temperature reaches about 1400 °C. Although the simulated value of shock wave overpressure is larger than the experimental value, the relationship between overpressure and distance is expressed by Y = A + B * ln(X + C). This study can provide certain technical support for natural gas accident rescue. The research can provide certain technical support for natural gas accident rescue and can also be used for accident investigation to form the determination procedure and method of leakage location and leakage amount.

Visual Leakage Inspection in Chemical Process Plants Using Thermographic Videos and Motion Pattern Detection

Liquid leakage from pipelines is a critical issue in large-scale chemical process plants since it can affect the normal operation of the plant and pose unsafe and hazardous situations. Therefore, leakage detection in the early stages can prevent serious damage. Developing a vision-based inspection system by means of IR imaging can be a promising approach for accurate leakage detection. IR cameras can capture the effect of leaking drops if they have higher (or lower) temperature than their surroundings. Since the leaking drops can be observed in an IR video as a repetitive phenomenon with specific patterns, motion pattern detection methods can be utilized for leakage detection. In this paper, an approach based on the Kalman filter is proposed to track the motion of leaking drops and differentiate them from noise. The motion patterns are learned from the training data and applied to the test data to evaluate the accuracy of the method. For this purpose, a laboratory demonstrator plant is assembled to simulate the leakages from pipelines, and to generate training and test videos. The results show that the proposed method can detect the leaking drops by tracking them based on obtained motion patterns. Furthermore, the possibilities and conditions for applying the proposed method in a real industrial chemical plant are discussed at the end.

Pressure Signal Enhancement of Slowly Increasing Leaks Using Digital Compensator Based on Acoustic Sensor

Pipeline leak detection technologies are critical for the safety protection of pipeline transportation. However, they are insensitive to slowly increasing leaks. Therefore, this study proposes an enhancement method for slowly increasing leak signals. By analyzing the characteristics of pressure signals of slowly increasing leaks, a digital compensator is developed to overcome the disadvantages of pressure signals and enhance the pressure signals. According to the frequency response analysis of the digital compensator, the enhancement principle is the parameter adjustment of the digital compensator. Therefore, this paper further proposes an adaptive adjustment method of the parameter to enhance different degrees of leak signals online in real-time, and the proposed method is evaluated using two field pipelines. The experimental results demonstrate that this method is suitable not only for enhancing slowly increasing leaks but also for enhancing abrupt leaks.

Simulation of the Transient Characteristics of Water Pipeline Leakage with Different Bending Angles

Rapid global development has resulted in the widespread use of water pipelines in industrial and agricultural production and life. During water transportation and deployment, water pipes with different angles need to be positioned according to different geographical and topographical problems. Flowmaster simulation software was used to simulate the leakage process of pipelines with different angles. The transient characteristics of fluids in the pipeline were studied in detail. The influences of parameters, such as the bending coefficient R/D (R is the turning radius of pipe, D is the inner diameter of pipe), leakage position, and leakage aperture on the transient flow law of pipelines with and without leakage, were analyzed. The results show that the periodic decay of the upstream flow and pressure curve at the valve with and without leakage has an insignificant relationship with the bending coefficient R/D; however, the amplitude of the sudden position change is positively correlated with the magnitude of R/D. The leakage aperture is positively correlated with the leakage flow and negatively correlated with the pressure value at the leak location node. The farther the leak position is from the valve, the greater the amplitude of the valve end pressure and the upstream flow curve, and symmetric fluctuations occur.

Pipeline Leak Detection and Location Based on Model-Free Isolation of Abnormal Acoustic Signals

Pipeline leaks will lead to energy waste, environmental pollution and a threat to human safety. This paper proposes a pipeline leak detection and location method based on the model-free isolation of abnormal (leak and operation) signals. An acoustic signal is first decomposed into “sub-signals” according to its zero-crossing points. Then, based on the definition of signal-to-noise ratio (SNR), the function between the SNR of sub-signal and the number of abnormal sub-signals is established, following which the position of each abnormal sub-signal in the acoustic signal is obtained by tracing its index. Based on this and the cross-correlation analysis, the operation sub-signals can be filtered, which is helpful for the precise leak location. The experimental results demonstrate the computational efficiency and lower false/missing alarm rate of the proposed method that provides an innovative solution for pipeline leak detection.

Recent Advances in Pipeline Monitoring and Oil Leakage Detection Technologies: Principles and Approaches

Pipelines are widely used for the transportation of hydrocarbon fluids over millions of miles all over the world. The structures of the pipelines are designed to withstand several environmental loading conditions to ensure safe and reliable distribution from point of production to the shore or distribution depot. However, leaks in pipeline networks are one of the major causes of innumerable losses in pipeline operators and nature. Incidents of pipeline failure can result in serious ecological disasters, human casualties and financial loss. In order to avoid such menace and maintain safe and reliable pipeline infrastructure, substantial research efforts have been devoted to implementing pipeline leak detection and localisation using different approaches. This paper discusses pipeline leakage detection technologies and summarises the state-of-the-art achievements. Different leakage detection and localisation in pipeline systems are reviewed and their strengths and weaknesses are highlighted. Comparative performance analysis is performed to provide a guide in determining which leak detection method is appropriate for particular operating settings. In addition, research gaps and open issues for development of reliable pipeline leakage detection systems are discussed.

A quantitative risk-assessment system (QR-AS) evaluating operation safety of Organic Rankine Cycle using flammable mixture working fluid

Mixture of hydrocarbon and carbon dioxide shows excellent cycle performance in Organic Rankine Cycle (ORC) used for engine waste heat recovery, but the unavoidable leakage in practical application is a threat for safety due to its flammability. In this work, a quantitative risk assessment system (QR-AS) is established aiming at providing a general method of risk assessment for flammable working fluid leakage. The QR-AS covers three main aspects: analysis of concentration distribution based on CFD simulations, explosive risk assessment based on the TNT equivalent method and risk mitigation based on evaluation results. A typical case of propane/carbon dioxide mixture leaking from ORC is investigated to illustrate the application of QR-AS. According to the assessment results, proper ventilation speed, safe mixture ratio and location of gas-detecting devices have been proposed to guarantee the security in case of leakage. The results revealed that this presented QR-AS was reliable for the practical application and the evaluation results could provide valuable guidance for the design of mitigation measures to improve the safe performance of ORC system.