Liquid Pipelines Research Articles

Use of Lower Harmonics of Pressure Oscillations for Blockage Detection in Liquid Pipelines

AbstractThe transfer matrix method was applied to detect partial blockages in liquid pipelines using the first four harmonics of the pressure oscillations produced by sinusoidal opening and closing...

An integrated detection and location model for leakages in liquid pipelines

Many liquids, such as water and oil, are transported by pipelines, where leakages can occur, causing energy wastage, environmental pollution, and risk to human health. This paper describes an integrated model implementing leak detection and location that can be used for background leakages, even micro-leakages in liquid pipelines. The model includes a dynamic monitoring module (DMM) and static testing module (STM). The DMM can detect larger leakages of background ones using the amplitude propagation and attenuation model of pressure waves. The STM, based on the pressure loss model, can detect micro-leakages, which is an effective compensation for the DMM. To verify the proposed model, experiments on the laboratory scale and in the field were carried out, and field applications were implemented. The results show that the integrated model can detect nearly all leakages. For the DMM, the smallest detected ratio of leakage orifice to pipe diameter (RLOPD) in the field is 1/41.4, with location errors on the order of 1%. For STM, the smallest detected leakage rate is just 0.0044%/h in the field. Thus, the model detects and locates leakages for liquid pipelines.

On the numerical simulation of sand transport in liquid and multiphase pipelines

Sand deposition in pipelines represents one of the problems that can arise in oil and natural gas production and transport. The main problems that sand can cause include the pipeline obstruction with the relative production loss, the increase of the lines erosion and corrosion and the compromising of the structural integrity. Moreover, there is a limit in the amount of sand that can be separated and removed. Therefore, methods and strategies to reduce the production of sand are key factors for safety and economic risks. In general sand deposition problems occur in different flow systems such as sand–multiphase mixtures of gas-oil-water or two-phase mixtures. In order to elaborate an effective method able to predict the amount of sand and to have a reliable prediction of sand transport velocity and entrainment processes, several factors requires to be considered, including sand characteristics, sand concentration, flow regimes, fluid properties and pipe properties.This paper presents the results of a detailed testing on the performance of a new sand transport model implemented in one-dimensional dynamic multiphase code, performed by comparing numerical results with experimental data. This study deals with both liquid-solid flow as well as gas-liquid-solid flow. The results demonstrate a good agreement between numerical and experimental data for the sand-liquid flow and sand transport in stratified gas-liquid flow, while show that for the sand transport in gas-liquid slug flow improvements are necessary.

Statistical analysis of environmental consequences of hazardous liquid pipeline accidents

Although pipelines are the safest method to transport fuels, they are associated with risks due to failures, leading to significant negative consequences. This paper investigates pipeline accident data provided by PHMSA (Pipeline and Hazardous Material Safety Administration) between 2010 and 2017, with a focus on environmental consequences of hazardous liquid pipeline accidents. The average amount of released product, the average time elapsed between the accident, the emergency response from the oil company, and the average costs of environmental remediation are estimated. The impact on soil, water, and wildlife is investigated for frequency and magnitude, where possible. It was found that, on average, 85% of product released after an accident remained unrecovered, 53% of accidents led to soil contamination, 41% of accidents impacted environmentally sensitive areas, and 92% of water crossing pipelines involved in accidents were uncased. From an annual average total cost of USD 326 million, annual average environmental damage and remediation costs were USD 140 million. This analysis assists in the diagnosis of challenges that might be addressed with improved maintenance and inspection programs, especially for pipelines at higher risk of negative environmental consequences. Finally, the performance of safety management systems should be improved to efficiently respond to emergencies.

A dynamic prediction method for probability of rupture accidents of a chloride process based on experimental corrosion data

A chloride process is especially prone to leakage incidents via vaporizer rupture and pipeline perforation, both of which are usually caused by corrosion. Rupture accidents may not occur frequently but nevertheless can results in explosions, poisoning and other severe consequences. The main factors affecting the corrosion process are the chloride ion concentration and the environmental temperature. In order to study the probability of rupture accidents, this paper first presents experimental research on the corrosion performance of liquid chlorine vaporizers and pipelines made with the steel Q345 and 20G, respectively. Different chloride ion concentrations (1–20 g/L) and environmental temperatures (30–90 °C) were considered in the corrosion experiment. The experiment lasted for 42 days, and the corrosion rate was calculated using weight loss technique. The experimental results show that 20G steel suffers more serious corrosion than Q345 steel and the degree of corrosion is determined by different factors working together. Among these experimental data, the corrosivity data related to 20G steel at the corrosion environment of low temperature with low concentration (30 °C, 1 g/L), as well as at high temperature with high concentration (80 °C, 20 g/L) were selected to establish the corrosion weight loss prediction model, based on which the accumulated wall thickness reduction was further calculated. Finally, a probability prediction model for the corrosive state was established based on Markov chains. Using the dynamic prediction method proposed in this work, it is capable to determine the corrosion situation of the chloride process through predicting the rupture probability before the coming into service of process equipment. Also, these prediction results can provide some guidance for the maintenance and help to reduce the risk of rupture accidents caused by corrosion in a chloride process.

Effect of rubber washers on leak location for assembled pressurized liquid pipeline based on negative pressure wave method

Abstract Leakage in pressurized pipelines is a serious problem in petrochemical plants because it might cause a fire or an explosion. The negative pressure wave (NPW) method is a practical method of locating leaks in a pipeline, and it has been used widely in the energy distribution industry. However, it is difficult to obtain the pressure wave velocity accurately and to localize leakage by using NPW method because of the complexity of real pipeline components, especially in assembled pipeline. Thus, in this study, the influence of assembly rubber washer on pressure wave velocity is analyzed; in addition, considering the effect of the rubber washer, a numerical method for calculating the velocity of pressure wave propagation in liquid pipelines is proposed. Then, the propagation velocity of NPWs is measured experimentally to verify the feasibility of the improved method on a self-made pipeline leak detection test platform. The results show that the presence of rubber washers in an assembled pipeline decreases the propagation velocity of NPWs and that the correction model established in this study can adequately modify the propagation velocity of NPWs. The improved method containing the modified formula can improve the accuracy of leak localization for assembled pressurized liquid pipelines.

Simark big EFOY Pro order from Canadian oil & gas services firm

Simark Controls Ltd – the Canadian subsidiary of German-based SFC Energy – has received a C$0.4 million (US$0.3 million) EFOY Pro fuel cell order from a major new customer in Canada. The unnamed oil & gas services provider will use the direct methanol fuel cells hybridised with solar modules in a weatherproof EFOY ProCabinet, to reliably power off-grid actuator valves on liquid pipelines.

Seismic Fragility of Steel Piping System Based on Pipe Size, Coupling Type, and Wall Thickness

In this study, a probabilistic framework of the damage assessment of pipelines subjected to extreme hazard scenario was developed to mitigate the risk and enhance design reliability. Nonlinear 3D finite element models of T-joint systems were developed based on experimental tests with respect to leakage detection of black iron piping systems, and a damage assessment analysis of the vulnerability of their components according to nominal pipe size, coupling type, and wall thickness under seismic wave propagations was performed. The analysis results showed the 2-inch schedule 40 threaded T-joint system to be more fragile than the others with respect to the nominal pipe sizes. As for the coupling types, the data indicated that the probability of failure of the threaded T-joint coupling was significantly higher than that of the grooved type. Finally, the seismic capacity of the schedule 40 wall thickness was weaker than that of schedule 10 in the 4-inch grooved coupling, due to the difference in the prohibition of energy dissipation. Therefore, this assessment can contribute to the damage detection and financial losses due to failure of the joint piping system in a liquid pipeline, prior to the decision-making.

An Integrated Prognostics Approach for Pipeline Fatigue Crack Growth Prediction Utilizing Inline Inspection Data

Fatigue cracking is a key type of defect for liquid pipelines, and managing fatigue cracks has been a top priority and a big challenge for liquid pipeline operators. The existing inline inspection (ILI) tools for pipeline defect evaluation have large fatigue crack measurement uncertainties. Furthermore, the current physics-based methods are mainly used for fatigue crack growth prediction, where the same or a small range of fixed model parameters is used for all pipes. They result in uncertainty that is managed through the use of conservative safety factors such as adding depth uncertainty to the measured depth in deciding integrity management and risk mitigation strategies. In this study, an integrated approach is proposed for pipeline fatigue crack growth prediction utilizing ILI data including consideration of crack depth measurement uncertainty. This approach is done by integrating the physical models, including the stress analysis models, the crack growth model governed by the Paris’ law, and the ILI data. With the proposed integrated approach, the finite element (FE) model of a cracked pipe is built and the stress analysis is performed. ILI data are utilized to update the uncertain physical parameters for the individual pipe being considered so that a more accurate fatigue crack growth prediction can be achieved. Time-varying loading conditions are considered in the proposed integrated method by using rainflow counting method. The proposed integrated prognostics approach is compared with the existing physics-based method using examples based on simulated data. Field data provided by a Canadian pipeline operator are also employed for the validation of the proposed method. The examples and case studies in this paper demonstrate the limitations of the existing physics-based method, and the promise of the proposed method for achieving accurate fatigue crack growth prediction as continuous improvement of ILI technologies further reduces ILI measurement uncertainty.

Development of vegetable intelligent farming device based on mobile APP

Poor realization of agronomic standards, low level of automation, time-consuming and labor-intensive farming are the main problems in traditional production process of vegetable. In order to improve vegetable cultivation intelligent and intensive level,reduce waste of production resources, an intelligent vegetable cultivation device was designed based on APP control, internet communications and image recognition technology, with the functions of remote control, precision sowing, quantitative dosing of liquid materials and weed recognition. The device mainly includes farming executing part, image processing part, STM32 microcontroller, and the APP which sends a command and control the device to work on the corresponding farming work. The precision seeding sowing worked through the gantry positioning and the cooperation of magnetic coupling tools and gas-suction sowing tools. By controlling the pump running time and monitoring flow volume with PVDF pressure sensor installed in the liquid pipeline interface, the liquid material was delivered quantitatively. Weed images were collected by CCD camera and recognition algorithm was developed based on BP neural network to obtain the weed location information. The test results show that the error rate of sowing was 2.75%, the passing rate of the plant spacing was up to 97.2%, no miss sowing occurs during the test; the error of the liquid delivery was within ± 5.8 g; true positive rate, true negative rate and accuracy of weed recognition were above 95%.

Improved PSO-based Method for Leak Detection and Localization in Liquid Pipelines

Based on inverse hydraulic–thermodynamic transient analyses and on an improved particle swarm optimization (PSO), a leak detection and localization method is proposed for liquid pipelines. The finite volume method is employed to numerically model the continuity, momentum, and energy equations. To determine the optimum-improved PSO algorithm and corresponding parameters, four types of algorithms were used for the analyses of a virtual pipeline. Accuracy, stability, robustness, and false alarm rate tests were conducted. The SIPSO algorithm has been shown to outperform the other algorithms. Two oil pipelines were utilized as example cases in conjunction with the use of the SIPSO algorithm. One of these pipelines was involved in a field opening experiment, while the other was involved in a real leak accident. The results demonstrated that smaller relative errors were achieved with the proposed method for the estimations of the location, coefficient, and starting time of the leak.

Canada’s federal database is inadequate for the assessment of environmental consequences of oil and gas pipeline failures

In Canada, the National Energy Board (NEB) regulates inter-provincial oil and gas pipelines and maintains historical records that contain data on oil and gas pipeline accidents; these data include information about operators, the accidents’ cause, and the resulting consequences. New inter-provincial pipelines are being built in Canada to transport fuels, but no comprehensive statistical analysis of the risk to environmental receptors exists. This study assesses the quality and quantity of NEB pipeline failure data available in Canada with a focus on environmental consequences and investigates differences between Canada and a more thoroughly studied jurisdiction, the United States, in tracking accident data. The discrepancies in agencies’ jurisdiction and regulated mileage are analyzed, along with reporting criteria and initial recording year. The level of detail provided by the two agencies is compared, identifying deficiencies in data collection. The Pipeline and Hazardous Materials Safety Administration (PHMSA) regulates 76% of pipelines in the United States, whereas the NEB only monitors 9% of pipelines in Canada. PHMSA provides four databases that include accidents from the 1980s for most pipelines and from 2011 for liquefied natural gas facilities; the NEB database includes accident data starting from 2008, which derive primarily from transmission pipelines. Information about environmental consequences is quite detailed in the US database, which reports 21 descriptive fields, whereas in Canada only two NEB database fields describe environmental outcomes. Moreover, dissimilarities in accident reporting criteria prevent the combination of data from the two agencies. Consequently, the NEB database does not allow for statistically robust and system wide analysis of the environmental consequences of pipeline failures in Canada. Furthermore, to calculate failure rates (annual number of accidents per kilometre of pipeline) for regulated pipelines, annual total mileage estimates are required. Mileage per year is provided by PHMSA for gas gathering, transmission, and distribution pipelines starting from 1984, and for hazardous liquid pipelines from 2004; the NEB provides annual mileage from 2010, a shorter period of record. The Canadian federal agencies are encouraged to improve accuracy and consistency in recording past accidents and in collecting pipeline data, with the goal of preventing and minimizing future pipeline failures.

Experimental and Numerical Analysis of Hydraulic Transients in the Presence of Air Valve

This paper focuses on the hydrodynamic behavior of liquid pipelines in the presence of air valves. The aim of installing such valves on pipeline systems is twofold: on one hand, they release the accumulated air content and on the other hand, they allow the outer air to entrain the system when the internal pressure falls beneath ambient pressure (i.e. vacuum formation). We study the hydraulic transients in the presence of such air valve by means of experimental and numerical methods. The experiments were performed using a special test section where the pipeline close to the air valve was built from plexiglas allowing visual access. Furthermore, pressure signals were recorded at several locations of the pipeline. Numerical analysis was also performed using the commercially available CFD software (ANSYS CFX). It was revealed that the entrained air separates well from the primary liquid and the mixture behaves as two distinct phases.

Modelling the pressurization induced by solar radiation on above ground installations of LPG pipeline systems

Pipelining Liquefied Petroleum Gas (LPG) is a mode of LPG transportation more environmentally-friendly than others due to the lower energy consumption and exhaust emissions. Worldwide, there are over 20000 kilometers of LPG pipelines. There are a number of codes that industry follows for the design, fabrication, construction and operation of liquid LPG pipelines. However, no standards exist to modelling particular critical phenomena which can occur on these lines due to external environmental conditions like the solar radiation pressurization. In fact, the solar radiation can expose above ground pipeline sections at pressure values above the maximum Design Pressure with resulting risks and problems. The present work presents an innovative practice suitable for the Oil & Gas industry to modelling the pressurization induced by the solar radiation on above ground LPG pipeline sections with the application to a real case.

Detecting Pipeline Leaks

This article explores technological advancements for detecting pipeline leaks. An ideal leak detection system should not only quickly detect both small and large leaks, but also do so reliably and not trigger false alarms. Operations in gas pipelines can differ quite a bit from those for liquids, so the experience gained in one type of line may not be entirely applicable when changing jobs. Fortunately, computer simulators are increasingly sophisticated, enabling operators to become comfortable handling a variety of situations. In December 2015, the American Petroleum Institute released a set of guidelines (RP 1175), written by a representative group of hazardous liquid pipeline operators, that established a framework for leak detection management. The focus of the guidelines is getting pipeline operators to use a risk-based approach in their leak detection program, with the goal of uncovering leaks quickly and with certainty. The best-case scenario is for leaks to not occur at all, and the industry is making great strides to keep them from happening. The combination of improved technology and risk-based management should enable operators to keep leaks small and contained, and reduce the impact on the environment as much as possible.

Corrosion Resistance of Transmission Pipeline Steel Coated with Five Types of Enamels

Corrosion is one of the main causes of incidents occurred in hazardous liquid and gas transmission pipelines in the USA, resulting in a loss of over $12 billion per year. In this study, the corrosion resistance of pipeline steel coated with five types of enamel was investigated in 3.5 wt% NaCl solution with linear polarization resistance and electrochemical impedance spectroscopy tests. Steel coupons were cut from API 5L X65 pipeline steel and coated with five types of enamels using the wet process. The microstructures of all enamel samples were examined by scanning electron microscopy. Experimental results indicate that all enamel coatings increase the corrosion resistance of pipeline steel, and pure enamel PE2, mixed enamels ME1 and ME2 have higher corrosion resistances than pure enamel PE1 and mixed enamel ME3.

Simplified risk assessment on fire hazard of LPG filling station

Layer of protection analysis (LOPA) was conducted on the fire hazard of LPG filling stations. Scenarios were developed for jet fire, pool fire, and boiling liquid expanding vapor explosion (BLEVE). For each scenario, independent protection layers (IPLs) of the LPG station were identified and their frequencies were estimated. Risk matrix to determine the risk category was constructed, combining consequence and frequency of each scenario. Three additional IPLs were considered, such as a firewall between the tank lorry parking area and LPG facility, water deluge system for tank lorry, and excess flow shutdown valve for liquid pipeline to stop unexpected excess flow. Adding such IPLs could markedly reduce the risk to the facility.

An Investigation of the Gathering System Options for a Hypothetical Field with Uniformly Distributed Production Wells

The gathering systems in the production wells are very crucial in the transportation of produced liquids from production wells to collection points such as the processing plant or central processing facilities. Liquid transmission pipelines are a part of the energy industry which involves the transportation of natural crude oil through pipelines. In this research the pipeline costs, material costs are proportional to pipeline diameter, whilst construction and design costs are approximately constant. The research shows that the bigger the length of the flow line, the bigger the total pressure drop, per unit length of the flow line for a given size and the type of pipe, the total pressure drop increases with length, whilst the pressure increases from 100 kpa to 250 kpa, and the length of the flow lines increases from 5.4 km to 12.5 km. The inlet pressure of 600 psig was used, as maximum inlet pressure with a design pressure of 1215 psig, with the assumption that protection against closed in tubing head pressure (CITHP) was protected. The investigation shows that a single flow line or trunk lines are not economical in transporting the fluids from the production wells, due to high -pressure drop in the flowline segments and it can affect pipeline diameters since pressure drop can lead to excess inlet pressure to push the liquid through the flow line and the operating costs can be excessive and result in insufficient pressure to pump or transport the fluids to the central processing facility. The modeling of the pressure drop in the flowline at different rates and for different sizes of nominal pipeline in the gathering systems was achieved.

Unified graph-based multi-fluid model for gas–liquid pipeline flows

We present a novel model of transient multiphase flow for gas–liquid mixtures in long pipelines. The study develops a general flexible formulation of a one-dimensional flow for complex multiphase mixtures in the presence of slip and mass exchange. Multi-fluid and drift–flux approaches are combined. The multi-fluid model governs the momentum balance for the fluids, and drift–flux correlations are used for modelling of the slip between individual components. A tree-like graph is introduced to describe the hierarchy of fluids and components within the mixture. The numerical implementation for an arbitrary number of components is based on the extension of the Semi-Implicit Method for Pressure-Linked Equations. Imbalances of equations are selected as criteria for iteration convergence. Specific corrections are discussed, including those proposed for the equilibrium gas-release model.

Simulation on effects of subcooler on cooling performance of multi-split variable refrigerant flow systems with different lengths of refrigerant pipeline

Multi-split variable refrigerant flow (VRF) systems have wide applications in offices and commercial buildings. In the multi-split VRF system, a subcooler is usually adopted to avoid flash vapor generation in the liquid pipeline. At present, the effects of the refrigerant pipeline length of the multi-split VRF system with a subcooler have not yet been investigated, nor the optimization of the subcooler. In this paper, the model of a multi-split VRF system with a subcooler has been developed and validated. In nine cases with different lengths of the main pipelines and the subcooling heat exchanger (SCHX), the cooling performance of a multi-split VRF system has been studied by simulation. The results indicate that the subcooler has little benefit in a system with a short pipeline, while it can help improve the coefficient of performance (COP) of a system with a long pipeline by controlling the bypass mass flow rate ratio in a proper range, and a higher maximum COP can be obtained by increasing the length of the SCHX in the subcooler. Furthermore, it is recommended to control the outlet superheated degree of the bypass stream in the SCHX in order to maximize the COP of a multi-split VRF system.