Polymer Pipes Research Articles

Using Dune Sand in Controlled Low-Strength Material for Backfilling: Field Installation and Numerical Simulation

The deflection of buried pipes depends on the exerted load and the embedment material. The portion of the exerted load transferred by the embedment material depends on the stiffness of the embedment material relative to that of the pipe. In the current study, four glass-reinforced polymer (GRP) pipes were buried in two different locations at the same depth under different geotechnical and installation conditions. For each of the test locations, two installation methods, namely controlled low-strength material (CLSM) and crushed rock, were used. The CLSM mixes were designed based on available native soil to satisfy the flow and strength criteria. Pipe deflection was meticulously measured at different stages of installation. In both cases, the behavior of the pipe showed the superior performance of CLSM as the backfill material. The behavior of the pipe was also evaluated by numerical modeling. The results of the numerical simulation were then compared with field test results, which showed a reasonable agreement. The pipe deflection was also predicted by a semiempirical equation and a numerical solution for the hardened CLSM. The effect of trench width on the vertical deformation was also evaluated through a parametric study.

Mid Infrared Tomography of Polymer Pipes

Mid-infrared signals in the 2–5 μm wavelength range have been transmitted through samples of polymer pipes, as commonly used in the water supply industry. It is shown that simple through-transmission images can be obtained using a broad spectrum source and a suitable camera. This leads to the possibility of tomography, where images are obtained as the measurement system is rotated with respect to the axis of the pipe. The unusual 3D geometry created by a source of finite size and the imaging plane of a camera, plus the fact that refraction at the pipe wall would cause significant ray bending, meant that the reconstruction of tomographic images had to be considered with some care. A result is shown for a thinning defect on the inner wall of a polymer water pipe, demonstrating that such changes can be reconstructed successfully.

Analyzing the long-term creep behavior of composite pipes: Developing an alternative scenario of short-term multi-stage loading test

Glass Fiber Reinforced Polymer pipes (GFRP) are used in a variety of industries such as water, oil and gas, aerospace and chemical industries. In the present paper, the creep response of GFRP pipes undergoing compressive transverse loading is analyzed through experimental observations and numerical modeling. Firstly, the long-term creep response of a GFRP pipe is investigated under single-stage loading till more than 400 days. Then, the creep response of another sample from the same pipe is evaluated under multi-stage loading with four 720-h steps (totally 2880 h). Theoretical modeling is performed using a two-level model based on short-term viscoelastic behavior of resin. A procedure is proposed to replace a long-term creep test under a single stage loading with short-term creep tests with multi-stage loading. The proposed procedure is validated through experimental study. The proposed multi-stage creep test scenario is very valuable to reduce the duration of experimental creep test. Utilizing the proposed method during the design process of a GFRP pipe, the creep response of the pipe can be estimated and its long-term properties can be ensured by performing equivalent short-term tests. The proposed procedure is validated through experimental study.

Biological resistance of polymeric pipeline materials

Currently, the problems of biodeterioration are becoming crucial in assessing the durability of buildings and structures for various purposes. Metal, reinforced concrete, polymer, and other products and structures, including the pipelines for water and gas supply, water disposal, etc., are subject to biodeterioration. Biodeterioration processes in construction are considered in many scientists and specialists’ works. From their works it follows that changes in the properties of pipeline materials as a result of microbiological corrosion can lead to a shutdown of facilities, accidents. Materials are exposed to biological and mechanical influences in natural conditions, therefore, the need to study various factors: the chemical composition of the materials used, density, temperature range, and the field of these materials’ use of relevant.The article presents the studies’ results of soil corrosion of samples from polymer pipes. The descriptions of pipeline materials from different manufacturers are given., The samples were selected for the research from thermoplastic polymers based on polyethylene and polypropylene, including those reinforced with fiberglass. The samples were aged in various layers of soils belonging to the groups of chernozems and loams. Methods for assessing the materials’ accreting degree by microorganisms are given. In the course of the research, the species composition of microorganisms accreting on the samples during the tests was established; the data on changes in the samples’ mass content are revealed. The results can be used to assess the biological resistance of pipeline materials.

On the mechanical behaviour of industrial PVC pipes under pressure loading: experimental and numerical studies

The purpose of this work is to assess the circumferential mechanical characteristics and the mechanical strength of industrial PVC pipes, especially under pressure loading. The investigation and the prediction of the resistance to deformation or failure of PVC pipes under internal pressure are essential to develop their potential application. To this end, two approaches are retained in this paper. The first one consists of developing an experimental apparatus devoted to study the mechanical properties of PVC pipes at laboratory scale. A split disk tensile (SDT) apparatus was developed according to the tensile test machine available in our laboratory. Such developed apparatus permits to characterize successfully more than one pipe diameter. The second approach consists of building a successful finite element (FE) model which will be able to predict the mechanical response of the pipes when submitted to pressure loading in radial direction. The obtained experimental and numerical results were firstly evaluated and then, their correlation was discussed. The robustness and efficiency of the FE model is assessed on the basis of the experimental/numerical correlation analysis. From the main results, the established model is shown to well predict the mechanical properties of polymeric pipes when will be exposed to mechanical loadings and other factors.

An analytical solution for nonlinear vibration and post-buckling of functionally graded pipes conveying fluid considering the rotary inertia and shear deformation effects

In this paper, a nonlinear Timoshenko beam model is considered to analytically investigate post-buckling and nonlinear vibration of flexible fluid-conveying pipes made of functionally graded materials. Closed-form expressions are presented to study the effects of shear deformation and rotary inertia on the post-buckling behavior and nonlinear vibration of fluid-conveying functionally graded pipes for the first time. It is assumed that the material property of the functionally graded material pipe is changed continuously along the direction of the pipe wall thickness based on a simple power law. Considering the Von-Karman nonlinear strain components and using the Hamilton's principle, the nonlinear governing equations for vibration and buckling of the functionally graded pipe conveying fluid are derived. These nonlinear governing equations are discretized by applying the Galerkin's procedure. The homotopy analysis method is employed to determine the closed-form expressions for the nonlinear frequency and the time history of vibration of the functionally graded pipe. The influences of rotary inertia and shear deformation on the buckling behavior, critical fluid velocity, nonlinear frequency and non-dimensional amplitude of the system are investigated and discussed in detail. The effects of physical parameters of the pipe conveying fluid on the divergence fluid velocity are studied by considering polypropylene random and functionally graded polymer pipes. The numerical results attest to the importance of considering rotary inertia and shear deformation in analyzing of short functionally graded material pipes especially for stiffer materials with higher initial amplitudes.

Composite helical micro pile’s bearing capacity

It is proposed to use two options of piles’ bearing capacity calculation based on existing Russian codes. Calculation of pipe’s section for an axial load is proposed either. Results of these calculations are compared to the site tests made earlier. Comparison of test results with calculations makes clear that existing methods for helical piles calculation are too conservative. Calculated soil’s bearing strength is 6 times lower than test results. Calculation method of pipes’ FRP sections is proposed. Existing fiberglass section bears almost double of the soil’s capacity. Optimization is proposed. Research provides results of bearing strength installed to weak clay helical fiberglass micro pile. Pile was designed, produced and provided by Composite Group LLC. Pile is made with pultruded fiber reinforced polymer pipe and screw produced with cast iron. Screw is glued to the FRP pipe by epoxy. In addition rivets strengthen connection detail. This structure is stable for corrosion, ground electricity. FRP screw pile has small weight and high strength. All the benefits and disadvantages of the composite piles are described below.

Effect of integrating polymeric pipes on the pressure evolution and failure assessment in cast iron branched networks

Pressure response and structural integrity assessment of cast iron and HDPE pipes were investigated in this study. The failure analysis of pipes in a branched network was considered taking into consideration the maximum stress generated by hydraulic transient events and the presence of an initial external semi-elliptical defect. The numerical study was conducted based on a developed non-conventional transient solver that incorporates the viscoelasticity of polymeric pipes. Considering the replacement of pipes located in sensitive zones with high-density polyethylene (HDPE) pipes, the pressure evolution of the network was evaluated for different network states at different locations. The integration of polymeric pipes in the originally cast-iron network provided remarkable pressure wave damping and dispersing in some locations. Since the failure of pipes with a corrosion crater is likely to occur when the admissible stress is reached, a structural integrity analysis was conducted. Failure Assessment Diagram (FAD) using the SINTAP code was considered to calculate the safety factors for cast iron pipes with different metallic-plastic combinations, whereas a semi-empirical model that calculates the J-integral is used for HDPE pipes. The results of this study conclude that high attention should be paid when a longitudinal crack is located in the pipelines. It may be possible for integrated polymeric pipes to alleviate the risk of failure in the network. However, under large crack geometries, additional measures should be taken.

Polyethylene/Clay/Graphite Nanocomposites as Potential Materials for Preparation of Reinforced Conductive Natural Gas Transfer Pipes

A series of high-density polyethylene/Cloisite 20A/graphite nanocomposites were prepared via melt blending for the production of polymeric pipes for natural gas transfer. The microstructural, mechanical, thermal, electrical and barrier properties of prepared nanocomposites were investigated. An intercalated morphology was observed for prepared nanocomposites. Improved mechanical properties e.g. over 148 % increase in Young’s modulus were observed by incorporating the nanoparticles into the polyethylene matrix. The thermal analysis showed that the melting point of polyethylene was slightly increased by incorporating both fillers, i.e. Cloisite 20A and graphite in it, and the crystallinity was depended on the type of filler. The results showed that the MFI values decreased by incorporating the fillers into the polyethylene matrix and further decreases were observed by increasing the contents of the filler. It was also found that a considerable amount of electrical conductivity is created in graphite loaded nanocomposites. The natural gas permeability investigations revealed of more than 51 % decrease in the permeability by incorporating 5 wt.% of Cloisite 20A to the polyethylene. It was concluded that the prepared nanocomposites due to their enhanced mechanical, thermal and barrier properties along with the conductive nature are excellent materials to be used in the production of polymeric pipes in natural gas distribution and transportation networks.

Issue of annular space filling requirement in engineering networks renovation justification

The main research aim was to determine the feasibility of filling the annular space with cement or other mortar during the renovation of dilapidated drainage networks with one of the common trenchless methods, i.e. by pulling pipes of smaller diameter through them (stalks from a roll). If polymer pipes are used for pulling, justification for the use of filling is necessary, due to their specific properties, which can affect the pipeline system strength and hydraulic performance. The article discusses the need for the pipelines annular space cementation during trenchless repairs.

Effect of End-to-End Connectors in Elastic GFRP Gridshell

The presence of end-to-end connectors for lengthening the glass fiber reinforced polymer (GFRP) pipes in elastic gridshell causes imperfections in the structure. Such geometrical imperfections alter the structural properties of members and affect the overall performance of the structure. Hence, for a comprehensive analysis of such structures, the aforementioned imperfections need to be acknowledged. In this study, an equivalent rigid part (ERP) for the connector was proposed for taking into account the effect of connectors in the structural analysis. The applicability of ERP for predicting the deformation of structural members was first verified by bending beam models. A typical GFRP elastic gridshell was further utilized for investigating the effects of connectors (with two different arrangement) in the shape and stress of the structure. Results show that proposed ERP is practicable for simplifying the end-to-end connectors in the structural analysis model. Significant differences in results were found between the analysis with and without the consideration of end-to-end connectors, and therefore the effect of connectors should be considered during structural analysis of elastic gridshell.

Leaching of organic material in polymeric pipes distributing desalinated water

Polymeric pipes have now become a favourite choice for water distribution networks. However, the role of polymeric pipes with respect to quality of water distributed has not been extensively studied. These studies are critical for desalinated water distribution as the water can be aggressive to its surroundings. The objective of this study was to identify the leaching of organic carbon from three different polymeric pipes; polyvinyl chloride (PVC), polypropylene (PPR) and polyethylene (PE). The study investigated the role of pH and residual chlorine concentrations on the leaching of organic carbon. Laboratory-based pipe loop systems using desalinated water was used to investigate the leaching of organic matter (OM). The results revealed that the migration of organic material was in the order of PE > PPR > PVC. Results indicated the lowest level of potential precursors of disinfection by-products (DBP) was present in PVC pipes, compared to PPR and PE pipes.

Measurement of ozone produced by 10 MeV electron accelerator Yazd in various currents

In this study, the concentration of ozone gas in various currents which arises by 10 MeV electron beam of RHODOTRON TT200 electron accelerator (Belgium) in the Radiation Application Research School (Yazd, Iran) was measured and studied continuously. All experiments were measured at the normal temperature (25̂C) and normal pressure (1 ATM) under normal working conditions of the electron accelerator, while accelerator's ozone fans were operating. For the accurate measurement, ozone gas is transmitted through a gas pump and polymer pipes. While so far, online measurement of ozone gas has not been measured in various currents of the electron accelerator (RHODOTRON TT200). The purpose of this study is the continuous measurement of ozone gas in various currents from 0.5 mA to 3 mA of RHODOTRON TT200, via three methods (Iodometry, UV-Visible, Portable Monitor-Series 500) and then the results of the measurements in different methods are evaluated with each other.

Calculation of the parameters of the hydraulic transport of enrichment waste in polyethylene pipes

In the article, a new method is presented for calculating hydraulic slope and critical speed of cleaning reject hydrotransportation through the polyethylene pipelines, which is based on the Methodology for Calculating Hydrotransport Plants for Tailings Transporting and Inwashing at the Iron Ore Mining and Processing Enterprises. This methodology was approved by the State Construction Committee of the Ukrainian SSR in its Temporary Instructions on Technology of the Tailing Dump Arrangement and was used in the design of all of the waste storage facilities in the Krivyy Rih ore-dressing and processing enterprises. For the conditions of the experiments, it was shown that experimental multiplier in the formula for calculating critical speed of hydrotransportation was depended on the pipeline diameter, free fall acceleration, kinematic coefficient of water viscosity and absolute roughness of the pipe inner surface. The acknowledgement of these factors made an empirical constant in the considered formula dimensionless and close to average value of the constants in the formulas obtained by other similar methods. With the considered method, it is proved that experimental constant in the formula for calculating critical speed of hydrotransportation is inversely proportional to the cubic root of the roughness of the pipeline inner surface, while coefficient of proportionality is a universal constant, which does not depend on the properties of the pipeline material and is equal to 10.1. Therefore, for determining critical speed of hydrotransportation through the polymer pipes by using this method, it is necessary to multiply critical speed for steel pipe with a similar diameter by the cubic root of ratio of roughness of the inner surfaces of the steel and polymer pipelines. It is further shown that value of hydraulic slope significantly depends on the operating coefficient, which shows by how many times coefficient of friction hydraulic resistance in the polyethylene pipe operating in supercritical flow regime exceeds the same value in case of critical flow regime for the same pipe. The research results allowed finding formulas for calculating hydraulic slope and critical speed of the iron-ore cleaning reject hydrotransportation through the polyethylene pipelines, which are based on the dependencies obtained for the steel pipes and value of absolute roughness of the pipeline inner surface.

Time-domain Analysis of Laboratory Experiments on the Transient Pressure Damping in a Leaky Polymeric Pipe

The pressure damping occurring in pressurized pipes with a leak during transients has been examined as a diagnostic tool – the so-called transient damping method (TDM) – mainly from the theoretical and numerical point of view. On the contrary, the experimental data are limited to few cases. As a consequence, there is a need of an extensive experimental analysis of the role played on the pressure damping by leak parameters (size, location and initial pressure). On the basis of the laboratory tests executed on a polymeric pipe, it is shown that, while the magnitude of the injected pressure wave does not affect the damping, the initial pressure, the leak size and location influence it plainly. Moreover, an experimental evidence is provided of the ambiguity in the time-domain of the transient pressure damping pointed out by numerical experiments. Precisely, it is demonstrated that different combinations of the leak parameters can lead to the same pressure damping. The obtained results indicate that the TDM can give a reliable assessment of the pipe status only if it is integrated with other diagnostic tools, such as the interpretation of the pressure signal during the first characteristic time of the pipe.

EXPERIMENTAL CHARACTERIZATION OF COMPRESSION PERFORMANCE OF CARBON-BASALT HYBRID FILAMENT WOUND PIPES BEFORE AND AFTER IMPACT

This paper describes the effects of different stacking sequences and fiber content ratios on the compression and the compression-after-impact (CAI) behavior of hybrid carbon�basalt (C�B) fiber-reinforced polymer pipes. Hybrid composite pipes composed of eight layers of ± 55°/90°2/± 55°/90°2 were manufactured utilizing the filament winding technique. A series of axial compression tests were carried out on the composite pipes based on ASTM D3410 standard for the nonimpacted and impacted specimens at 100-J impact energy. Residual compressive strength, damage tolerance and failure modes were examined and analyzed for different composite pipe configurations before and after an impact. The results showed that the specimens with fiber content ratio 50:50 C�B fibers exhibited better impact resistance as compared with specimens of fiber content ratio 75:25 C�B fibers, under the same conditions of impact energy. Furthermore, despite carbon fiber sustaining highest compressive force among nonimpacted samples, it exhibited the highest percentage reduction in residual compressive force after impact, at 62%, as such having the worst impact damage tolerance for a given energy level. Specimens with basalt fiber on the outer surface (i.e., Nos. 3 and 6) and alternative fiber specimens (i.e., Nos. 5 and 8), which showed a good response to the impact, sustain high values of the compressive loads for both content ratios. © 2020 by Begell House, Inc.

ON APPLICATION OF PIPES FROM POLYMER MATERIALS FOR FIELD PIPELINES

According to the Federal State Budgetary Institution «Central Dispatch Office of the Fuel and Energy Complex» for 2018, in Russia 92 % of incidents and accidents with oil spills occurred due to corrosion. At the same time, about 45 % of pipelines are operated in aggressive soils, 30 % - in slightly aggressive environments, and only 10 % do not need active anti-corrosion protection. According to Rostechnadzor, the total length of the field pipelines reaches 300 thousand km. At the same time, the deterioration of the main stock of production pipes reaches 70 %. Since the most used material for the construction of pipelines is steel, the main problem in the transportation of hydrocarbons is external and internal corrosion of pipelines. In this regard, one of the key points is the replacement of metal pipelines with reinforced polymer pipes that combine corrosion resistance, low moisture absorption, and high dielectric performance. The aim of this work is to analyze the use of pipes made of polymeric materials for field pipelines used to transport hydrocarbons in Russia and abroad. Tasks: - analysis of the operating experience of reinforced polyethylene pipes used for the transportation of hydrocarbons in Russia and abroad; - consideration of the main problems arising during the operation of composite pipelines; - comparison of the characteristics of pipes used in different countries. In the course of the study, the regulatory documents on foreign and domestic polymer pipelines were studied and a generalized analysis of these pipes was carried out. The problems faced by the oil and gas industry in the transportation of hydrocarbons are identified. The history of Western and domestic use of polymer pipelines is considered, on the basis of which the relevance of the use of composite pipelines based on polyethylene is substantiated.

Modeling of heat and mass transfer processes in cooling towers and structure optimizing of polymer filler

The closed water recycling systems with the main element being the evaporative water cooling devices or cooling towers are used to cool the main equipment of industrial enterprises. During these processes the recycled water is being polluted and lost, therefore it is necessary periodically provide this water volume from natural sources. Improving the efficiency of cooling towers can reduce the negative factors of such systems’ operation. This article presents the researchof the aerodynamic characteristics of heat-and-mass exchange packs of cooling towers made of vertical polymer pipes. The design of the optimized cooling tower filler unit is described and recommendations for improving the efficiency of evaporative cooling process of the circulating water are given.

Hydro-mechanical response in polymeric pipes assuming interaction of fluid

In this article, the instable velocity of fluid in the pipes with internal fluid is studied. The force induced by the fluid is assumed in radial direction and is obtained by Navier-Stokes equation considering viscosity of fluid. The displacements of the structure are assumed by thick shell element. The final equations are calculated by Hamilton's principle. Numerical procedure of differential quadrature (DQ) is utilised for presenting the instable velocity of fluid. The influences of length, radius and thickness of pipe as well as boundary conditions are shown on the instable velocity of fluid. The outcomes are compared with other published articles where shows good accuracy. Numerical results indicate that with enhancing the thickness of pipe, the instable velocity of fluid is increased. In addition, the instable velocity of fluid of clamped-clamped (CC) pipe is higher than other SS pipe.

Hydro-mechanical response in polymeric pipes assuming interaction of fluid

Hydro-mechanical response in polymeric pipes assuming interaction of fluid