Pipeline Pressure Research Articles

Variation of Hydraulic Resistance in Pressure Pipelines of an Open-Type Hydraulic System

Pressure distributive pipelines with path distribution of fluid are part of various technical systems. Pressure losses at abrupt and smooth pipe reductions are components of total pressure losses in these pipelines. After all, the equalization of fluid distribution along the length of distributive pipelines is achieved, in particular, by reducing their diameter in the direction of flow. Depending on the configuration of the pipe reductions, pressure losses at this pipeline element can vary. For an open-type hydraulic system, a regulatory characteristics of pressure in the pipeline has been obtained with a constant fluid flow in a general form. The influence of measures necessary to change energy losses in the pipeline on the hydraulic resistance of the unregulated section of the pipeline has been taken into account. Options for these measures have been proposed for a pressure pipeline with pipe reduction.

Analysis of dependences for hydraulic calculation of pipes made of polymer materials

Assess the influence of the equivalent roughness coefficient and roughness parameters on the value of the calculated pressure losses in pipelines made of polymer materials. Consider normalized calculation dependencies for the hydraulic calculation of pressure pipes made of polymer materials. Assess the difference in the pipeline hydraulic characteristics constructed using various formulas. Give recommendations on the choice of calculation dependence for determining the coefficient of hydraulic resistance, determining the specific pressure loss along the length for pipelines made of polymer materials. The dependence of the calculated specific pressure loss along the length on the equivalent roughness coefficient has been constructed. Hydraulic calculations were carried out using various calculation dependencies to determine the coefficient of hydraulic resistance of a pipeline with a diameter of 400 mm, made of PVCO 500, on a 1 km long section. The hydraulic characteristics of the pipeline are obtained and comparative results of calculating the values of specific pressure losses along the length when calculated using different calculation dependencies are presented. The magnitude of the change in pressure loss along the length is determined depending on the change in the value of the equivalent roughness coefficient. A calculation formula is recommended for determining the coefficient of hydraulic resistance for pipes made of polymer materials, taking into account the values of the height and step roughness parameters. Key words: polymer pipeline, pressure pipeline, roughness parameters, hydraulic calculation, pressure losses.

Assessment of methane emissions from pressure regulation stations in China

Pressure regulation stations are responsible for transporting natural gas downstream and are an indispensable part of the gas supply chain. In recent years, countries and enterprises have attached increasing importance to methane emission accounting. However, methane emissions from pressure regulation stations are still not comprehensively understood and accounted for. In this study, methane emissions from 21 pressure regulation stations under normal conditions were quantified using the Environmental Protection Agency's (EPA's) “Other Test Method 33 A” (OTM 33 A) in three regions of China: the eastern, northern, and central regions of China. The results showed that the emission rate from pressure regulation stations generally lied in the order of 10−1-10−3 kg/h, whereas the measured methane emission rate (MMER) with 95% confidence interval (95%CI) was 0.671 (0.066, 3.040) (kg/h), which was determined from the bootstrapping measurements from all pressure regulation stations. The MMER (95%CI) values were 0.051 (0.026, 0.102) for East China, 2.263 (0.095, 8.317) for North China, and 0.004 (0.003, 0.005) (kg/h) for Central China, showing a relatively obvious skewed distribution. Overall, MMER had a diminutive correlation with gas throughput and pipeline pressure. In contrast, the degree of correlation of pipeline pressure was higher than that of gas throughput.

Determination of Pipe Diameter Using Optimization Method

During the design phase of engineering networks, a critical issue remains the selection of pipe diameters that minimize capital investments for transporting the heat carrier from the heat source to the consumers. Object of study: a pressurized pipeline of circular cross-section with a moving heat carrier. Subject of study: total monetary costs for transporting the heat carrier as a function of the chosen pipeline diameter. Objective of study: to determine the pipe diameter that achieves maximum cost savings for transporting the heat carrier under given design conditions. Research methods: theory of hydraulic calculation for circular cross-section pipelines and theory of heat transfer through a single-layer cylindrical wall under steady-state conditions. Research results: using an example from a centralized heating system pipeline section, it was established that for a mass flow rate of the heat carrier equal to 32.9 t/h, the optimal pipe size would be 76×3 mm (nominal diameter 70 mm). Under current tariffs for thermal energy (24.82 USD/Gcal) and electrical energy (6.65 USD/(MW⋅h)), the total monetary costs for transporting the heat carrier over a heating season would be 56.28 USD per 1 running meter of pipeline. In comparison, with a nominal diameter of 50 mm, the total costs amounted to 90.37 USD; with a diameter of 80 mm, the costs were 63.29 USD. The developed method for hydraulic design calculations is universal and can be applied in the design of engineering networks where the working medium is a moving heat carrier (steam or hot water).

Analysis of sensitivity to hydrate blockage risk in natural gas gathering pipeline

During the operational process of natural gas gathering and transmission pipelines, the formation of hydrates is highly probable, leading to uncontrolled movement and aggregation of hydrates. The continuous migration and accumulation of hydrates further contribute to the obstruction of natural gas pipelines, resulting in production reduction, shutdowns, and pressure build-ups. Consequently, a cascade of risks is prone to occur. To address this issue, this study focuses on the operational process of natural gas gathering and transmission pipelines, where a comprehensive framework is established. This framework includes theoretical models for pipeline temperature distribution, pipeline pressure distribution, multiphase flow within the pipeline, hydrate blockage, and numerical solution methods. By analyzing the influence of inlet temperature, inlet pressure, and terminal pressure on hydrate formation within the pipeline, the sensitivity patterns of hydrate blockage risks are derived. The research indicates that reducing inlet pressure and terminal pressure could lead to a decreased maximum hydrate formation rate, potentially mitigating pipeline blockage during natural gas transportation. Furthermore, an increase in inlet temperature and terminal pressure, and a decrease in inlet pressure, results in a displacement of the most probable location for hydrate blockage towards the terminal station. However, it is crucial to note that operating under low-pressure conditions significantly elevates energy consumption within the gathering system, contradicting the operational goal of energy efficiency and reduction of energy consumption. Consequently, for high-pressure gathering pipelines, measures such as raising the inlet temperature or employing inhibitors, electrical heat tracing, and thermal insulation should be adopted to prevent hydrate formation during natural gas transportation. Moreover, considering abnormal conditions such as gas well production and pipeline network shutdowns, which could potentially trigger hydrate formation, the installation of methanol injection connectors remains necessary to ensure production safety.

Research on the vibration mechanism of compressor complex exhaust pipeline based on transient flow

The periodic exhaust of the compressor often induces gas flow fluctuations within the pipeline, leading to vibrations. Excessive vibration can lead to fatigue, cracks, loosening of components, and resulting in local leakage, which may easily lead to fire, explosion, and secondary hazards. Therefore, in this paper, a computational model for the transient flow field of the compressor exhaust pipeline was established, using the pulse excitation method and Fluent software, the natural frequencies of the gas column in the pipeline were calculated, and the patterns of oscillation decay of the gas column wave propagating back and forth within three exhaust pipes were researched. The mechanism behind the pipeline pressure pulsation and the influence of pipeline structural parameters on the natural frequencies of the gas column were explored. The calculation results show that the first-order natural frequency of the gas column is very close to the double frequency of the compressor excitation frequency at 3.33Hz, and the second-order natural frequency of the gas column is very close to the quadruple frequency of the compressor excitation frequency at 3.33Hz, which may cause significant pipeline vibrations. Altering the pipeline structure, especially when influenced by airflow branching after a tee junction, results in complex changes in the natural frequencies of the gas column. Furthermore, the structural natural frequencies of the pipeline were obtained through the finite element. It has been observed that resonance phenomena exist among the structural natural frequencies and their harmonics of the pipeline and the natural frequencies of the gas column and their harmonics, as well as multiples of the excitation frequency. These results lay the foundation for understanding the vibration mechanism of the pipeline and finding ways to reduce vibration.

Molecular insights into the wettability of antifreeze protein-adsorbed hydrate surface: Application to hydrate anti-agglomeration

Adding kinetic inhibitors (KIs) to prevent hydrate formation or anti-agglomerate agents (AAs) adsorbed on hydrate crystals to suppress particle aggregation are both effective means to eliminate hydrate blockage in pressurized pipelines. Antifreeze proteins (AFPs) are representative KIs that hinder hydrate growth via the interfacial adsorption mechanism. This implies the possibility of interfacial modification and simultaneous anti-aggregation effects, which yet have not been explored. Here molecular dynamics (MD) simulations were employed to determine the possible anti-aggregation performance of AFP. Specifically, we identified larger contact angles, that is, the enhanced hydrophobicity, of AFP-adsorbed CH4 hydrate under the dodecane oil phase. This indicates the possible dual inhibition effects of AFP to ensure oil transportation. However, no significant effects of AFP on wettability were observed in the systems with the CO2 hydrate substrate or gas environment. This contrasting behavior was explained by the differences in the hydrogen-bonding formation and interaction strength between substrates and water droplets, which are strongly influenced by the charged residues of AFP. Additionally, we compared AFP with traditional surfactants and emphasized that the anti-aggregation abilities of additives are intricately linked to their functional group arrangements and inherent structures. Our work provides molecular-level guidance for designing effective hydrate inhibitors with dual performance to ensure flow assurance.

Study on transient characteristics of pipeline under centrifugal pump shaft stuck condition

In the pump system, the water hammer effect generated by the shaft stuck accident will cause great harm to the pump and piping system. In order to reveal the transient characteristics of the pipeline during the transition process of vane-pump shaft stuck, three shaft stuck time of Δt = 0.5 s, Δt = 1 s and Δt = 1.5 s is tested by building a closed test bench of centrifugal pump. And establish a 1:1 closed system three-dimensional model to study the external characteristics and internal flow field changes of the pump and piping system during the transition process of the shaft stuck. The study shows that: The rotational speed curves are non-linearly decreasing; the patterns of change in flow rate show a roughly exponential function trending downward; the heads during the shaft stuck will fall rapidly and reach the reverse extreme value. For the pump inlet piping system, the pressure of each place in the speed down to 0 rpm before the peak, the pressure of the outlet pipeline is always down to the reference pressure. Under the same shaft stuck condition, the pressure change in each place of the inlet piping system is basically the same, and the pressure reaches the peak at the same time. The maximum pressure of the inlet and outlet piping is at the rear 3/4 of the elbow. The closer to the face of the inlet and outlet of the elbow, the greater the load force applied; with the elbow as the demarcation, the pressure gradually increases along the flow direction. By revealing the transient mechanism of system piping during centrifugal pump shaft stuck transient process, it provides a reference basis for the design and accident safety assessment of vane-type pumping system.

ИНСТРУМЕНТЫ ЦИФРОВИЗАЦИИ В ПРАКТИКЕ ПРОЕКТИРОВАНИЯ ПРИ РЕКОНСТРУКЦИИ ПОДЗЕМНЫХ ТРУБОПРОВОДОВ БЕСТРАНШЕЙНЫМИ МЕТОДАМИ

The article focuses on the possibilities of multi-optional design of repair and rehabilitation works on dilapidated pressure pipeline networks with the use of automated complexes in order to achieve minimum energy costs in water transportation with regard to the temperature factor. Two automated programs based on hydraulic and energy calculation operations are presented as digital tools. As a basic variant of reconstruction of dilapidated pipelines, the trenchless Swagelining technology was accepted. It is realized by pulling pre-compressed polymer pipes into old pipelines with their subsequent straightening. The paper presents information on regulatory and technical documentation and the application of advanced technology, installation and operation conditions, as well as comparative assessment of energy consumption after reconstruction of dilapidated sections of pipelines with polymer pipes with the possibility of minimizing energy consumption during water transportation under non-isothermal conditions of pipeline operation.

Estimating the line packing time for pipelines transporting carbon dioxide

During the operation of pressurised pipelines transporting compressible fluids, line packing is employed as an effective method that uses the pipeline itself as a buffer storage, compensating for fluctuations in the fluid supply or demand. While in large-capacity natural gas transmission systems, reaching maximum operating pressures during line packing is usually not of practical concern, in small capacity pipelines transporting low-compressibility fluids, such as liquid or dense-phase CO2, line packing can occur quickly, and therefore, estimating the line packing times becomes important to ensure avoiding exceeding the pipeline maximum allowable operating pressure. In this study, a correlation for estimating the line packing time is derived from the transient mass balance in the pipeline. The proposed correlation accounts for the pipeline overall dimensions, operating pressure and temperature, and the fluid properties, namely density and the expansion coefficient. The correlation is also adopted for the calculation of pipeline unpacking times caused by unbalanced discharge from a pipeline. A verification study on line packing in a dense-phase CO2 pipeline shows that within the ranges tested, the proposed correlation estimates conservatively the line packing times with ca. 15 % deviation from the results of simulations obtained using a rigorous transient pipeline flow model. The proposed correlation is also verified against predictions obtained using a parabolic flow model and is recommended for estimating line packing times for both dense-phase and gas-phase CO2 at pressures and temperatures in the ranges 2 - 12 MPa and 280 – 330 K, respectively. The limitations of the proposed line packing time correlation are discussed.

Simulation of distributed network elements in CAS MAXIMA and server online calculations in the educational process

Pressure pipelines are an important part of the water management infrastructure. Water supply networks pump the liquid to the consumer with the help of pumps (or supply it from a water tower) to specified points. The functioning of the entire urban infrastructure depends on the correct calculation and reliable operation of these areas. This paper shows the implementation of a computer calculation of one of the branched network options using numerical methods in the CAS MAXIMA computer algebra system, its graphic subsystem of symbolic mathematics, and the use of the author's online calculation program with a client-server implementation - https://www.k123.org.ua/jgIHjob1.html .
 The implementation of elements of computer calculations in the educational process allows the generation of an unlimited number of individual variants of initial data. The implementation of computer calculation requires the availability of automatic online generation of answers for each stage of iterative calculations. The task of generating online answers is the basis of the program development.
 An educational online platform is offered for researching the optimality of numerical, graphic and audio formats for setting the problem. The formats of the web form for entering output data have been studied. Online calculations reduce the time spent on typical monotonous operations. Additional possibilities of instant online calculations and visual graphic visualization of calculation results expand the possibilities of modeling individual elements of a branched network.
 The online program allows you to use computer calculations, expand the culture of using applied mathematical methods for engineering calculations, introduce algorithms and data structures, and solve the main task of training future engineers - to ensure a modern level of education and readiness to solve new problems.

Structural optimization model of confined polyhedral composite subsea pipelines under pressure and thermal fields

This paper investigates the structural optimization of a polyhedral composite subsea pipeline (cylinder) under pressure and thermal fields. The pipeline is confined tightly and deforms inward when it is subjected to external loadings. The interface is frictionless between the pipeline and its surrounding medium. Based on the above assumptions, thin-walled shell principles, and an admissible displacement function, the potential energy of a pipeline per unit length is obtained explicitly by simplifying the radius and bending rigidity. After taking the first derivative of the potential energy, two equilibrium equations are obtained. By combining these two equations, the critical buckling pressure of the polyhedral pipeline is expressed analytically with the inclusion of the temperature effects. Then, the present analytical study is compared with other numerical and experimental results, and excellent agreements are reached. A configuration factor is defined as the buckling pressure between the polyhedral and circular pipeline. Finally, parametric studies show the configuration factor decreases with the increase of thickness-to-radius ratio, the increase of the number of sides, and the increase of the temperature variation, respectively. Therefore, a polyhedral pipeline with a low thickness-to-radius ratio is recommended in engineering practices since it may reduce the material cost.

Application of pipeline leakage detection based on distributed optical fiber acoustic sensor system and convolutional neural network

Underwater pipelines are exposed to harsh environments, including high salinity, multi-modal vortex corrosion, and severe wave interference. Their safety is essential for the development and transportation of marine energy. Therefore, real-time safety monitoring of long-distance energy pipelines is of great strategic importance for ensuring the safety of life and property and energy security. With the rapid development of energy development, the corrosion and leakage mechanisms of natural gas pipelines, as well as their identification and early warning, have become the focus of attention. Optical fiber sensing technology has been applied to various energy safety monitoring fields. However, the mechanism of sound source fluctuations in pipeline leakage and the mutual coupling mechanism between distributed optical fiber sensing technology and leakage sound waves are not yet clear. This paper establishes a model based on sound wave propagation and leakage noise response, derives a quadratic fitting relationship between pipeline pressure fluctuations and leakage orifices and a relationship between leakage noise source standard deviation and orifices, and proposes a complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) permutation entropy underwater natural gas pipeline leakage signal recognition method based on distributed optical fiber acoustic sensing technology. The results of theoretical analysis are verified by experiments. It shows that the signal processing method of CEEMDAN permutation entropy is superior to traditional noise reduction methods, which can better preserve the features of the original signal; the radial basis function (RBF) neural network model can accurately identify four different leakage features with an accuracy of 88.15%, and its recognition stability and generalization ability are superior to convolutional neural network, backpropagation, and random forest. Therefore, the research results of this paper provide a new method for safety monitoring in the application of energy pipeline transportation engineering, and expand the potential application scenarios of distributed acoustic sensing sensor systems and RBF neural networks.

Experimental study on acoustic signal characteristic analysis and time delay estimation of pipeline leakage in boilers

Acoustic signal detection technology has significant advantages in detecting the leakage and bursting of heat exchange pipes in boilers. To address the current lack of sound signal data for steam medium leakages and the problem of large errors in the complex sound field environment of power plants, we performed an innovative experimental comparative analysis of leakage acoustic signals under a dual medium of compressed air and steam to provide a reference for detecting leakage acoustic signals. During the experiment, the time and frequency domains were analyzed by changing the pressure of the leakage pipeline and aperture of the leakage hole, and the spectrogram and power spectrum of the leakage acoustic signal were obtained using fast Fourier transform and autocorrelation analysis. The results showed that the signal value of the leakage medium increased with increasing pipeline pressure and leakage aperture and that the energy of the steam leakage acoustic signal was greater than that of compressed air under the same pressure and aperture because of its larger specific heat capacity. In addition, the complete empirical mode decomposition of adaptive noise (CEEMDAN) algorithm was introduced into the denoising decomposition of the leakage sound signal in the furnace, and the average error of the time delay value of the leakage acoustic signal calculated using the CEEMDAN algorithm was observed to be within 5%.

Research on Material Selection Method and Brittle Fracture Mechanism of High-Pressure Pipeline

Aiming at the problem of the brittle fracture of pressure pipeline, the elastic constraint structure is described by using members and engineering building structures, and the concept of elastic constraint is proposed. Through the stress field analysis of the pressure pipeline under internal pressure, it is found that the pressure pipeline under internal pressure is an elastic constraint structure. The elastic constraint effect is applied to the pressure pipeline to explore the influence of elastic constraint effect on the brittle fracture of pressure pipeline. The critical wall thickness and limit load of different materials are calculated by the limit bearing formula. Through simulation analysis of materials with different yield ratios and pipelines with different wall thicknesses of the same material (yield ratio is the ratio of yield strength to tensile strength), it was found that pressure pipelines made of the same material have an increased load-bearing capacity as the wall thickness increases, but their own elastic constraint effects are becoming more obvious, and the probability of the brittle fracture of the pipeline is higher. When the wall thickness of pressure pipelines made of materials with different yield ratios is certain, the lower the yield ratio is, the more likely the pipeline is to generate plastic deformation and the larger the deformation capacity is; the higher the yield ratio, the poorer the plastic deformation capacity of the pipeline and the smaller the deformation capacity. Pipelines with large yield ratio are more sensitive to the brittle fracture than those with small yield ratio.

Residual Swin transformer-based weld crack leakage monitoring of pressure pipeline

Residual Swin transformer-based weld crack leakage monitoring of pressure pipeline

Analysis of the Influence of Condensation on the Mechanical Properties of Corrugated Compensators in Pressure Pipelines

The reliability design of pressure pipelines under special conditions such as high temperature, high pressure, and even state transformation, includes an essential section on the performance analysis of the corrugated compensator. Based on powder mechanics, a model for the accumulation of condensate in the corrugated compensator was established, and the flow-solid coupling issue was resolved by simulating the condensation process through adjustments to the wall pressure. As a consequence of simulations, the characteristic curve of the condensation process of shortening and subsequently elongation was discovered. The study implies that condensation can produce additional stress that is up to four times greater than the normal state. This additional stress increases with condensate density and the condensate’s proximity to fluid characteristics. This research provides guidance for designing pressure pipeline operating conditions, predicting and monitoring medium condensation, and corrugated compensator failure analysis.

Experimental Investigation of Column Separation Using Rapid Closure of an Upstream Valve

In this study, the phenomenon of column separation that occurs in the downstream pipeline of a rapid closure valve is experimentally investigated. Special attention is paid to the dynamic behavior of the formation, growth, and collapse processes of cavities, which are observed using a high-speed camera. Synchronized images of cavity patterns and measured pressure histories are analyzed to elucidate the process of water column separation, the mechanism of column separation events, and the influence of parameters on the transient flow. Experimental results indicate that during the collapse process of vapor cavities, a superposition phenomenon involving a positive pressure wave and collapse wave occurs, resulting in a nearly three times rise of Joukowsky pressure. In all test cases, the maximum pressure of the pipeline exceeded 150 times the reservoir static pressure. A new classification for a water hammer combined with cavitation (four types of pressure oscillation patterns) is proposed based on whether the duration of column separation decreases sequentially and the maximum pipeline pressure follows the first collapse of cavities at the valve. As the initial flow velocity increases, there is generally an increase in maximum pressure; however, this trend may be scattered under certain operation conditions.

Experimental Study on Gas-Solid Two-Phase Flow Characteristics of a Vertical Cyclone Combustor System.

According to the design and operational parameters of the cyclone liquid slag-discharging boiler, an experimental platform for the cyclone burner was designed and constructed in a cold state based on the principle of similarity. The experimental study investigated the effects of parameters, such as swirl-vane angles, coal concentration, operating parameters, and particle size, on the flow distribution and vertical riser resistance characteristics of the vertical cyclone burner. The results showed that there were differences in flow distribution among the cyclone burners, and the most uniform flow distribution was achieved when the swirl-vane angle of the primary air was 30°. The concentration of pulverized coal significantly influenced the pressure drop in the vertical ascending section, which increased with higher concentrations of pulverized coal. When the concentration of pulverized coal remains constant, the pipeline pressure drop is minimized at a primary air velocity of 7.5 m/s. As the secondary wind speed increased, the pressure drop consistently rose; when the secondary wind speed is 22 m/s, the pressure drop of the pipeline is the maximum; however, excessively high secondary wind speeds were found to be detrimental to the formation of an optimal aerodynamic field in the burner. Furthermore, when the pulverized coal concentration was held constant, materials with larger particle sizes exhibited the highest pressure drop. When the particle size increases from 50 to 150 μm, the pressure drop of the vertical riser segment also increases. Finally, based on the Barth additional pressure drop theory, the pressure drop formula of the vertical riser is fitted by a dimensional analysis method, and the correlation formula of the pressure drop test of gas-solid two-phase flow in the vertical riser is obtained.

Influences of Sediment Particles on Air Vessel Water Hammer Protection Effect in the Long-Distance Water Supply Systems

Abstract Long-distance water supply systems are important measures to improve the water resources distribution, and the water hammer protection devices such as air vessels are usually added in the project to ensure the safety and stable operation. However, the sediment particles are always ignored in the design. Hence, a numerical model and program were established for sediment laden water hammer based on the method of characteristics (MOC). Using the proposed model, the water hammer protection influences of sediment particles parameters are simulated for the same pipeline system of a water supply project. The result shows that the resistance loss of sediment-laden water in pipelines is larger than that of water, and the initial head of pump needed to be increased to ensure the water levels of downstream reservoirs are consistent. After power failure and pump stopping, the negative pressure wave of sediment-laden water is 2.97 m higher than that of water, and the theoretical minimum internal pressure along pipelines is 7.8 m lower. With the same air vessel protection, the lowest minimum internal pressure heads along pipelines decrease with the increase of quantities of sediment, while the results show no obvious influence by changes of median particle diameters. The lowest absolute pressure of pipeline could reach −0.69 m under the condition of 50 kg/m3 quantity of sediment and 0.05 mm median particle diameter. The relevant research results are of great significance sediment-laden water hammer numerical simulation and water hammer protection design.