High Density Polyethylene Pipe Research Articles

An efficient numerical approach for simulating soil-pipe interaction behaviour under cyclic loading

Understanding soil-pipe interaction during cyclic axial displacement is essential for the design and evaluation of buried pipeline systems. This study introduces an efficient and practical numerical approach using beam-spring-interface elements to simulate soil-pipe interaction behaviour. Numerical predictions of the evolution of shear and normal stress distributions around the pipe are validated against full-scale experimental results for steel and high-density polyethylene pipes buried in sandy soils. Three different backfill cover depths and soil densities ranging between loose and dense were considered to allow a rigorous comparison between the numerical predictions and the experimental results. The results show that the proposed approach provides a high-fidelity representation of the complex soil-pipe interaction behaviour at the interface zones, including stress cyclic degradation, hardening and softening, cyclic accumulative contraction and stabilization. This numerical framework provides accurate predictions for a fraction of the computational cost of a full three-dimensional finite element analysis.

Simulation of heat transfer in a landfill with layered new and old municipal solid waste

Due to rapid degradation of the newly filled municipal solid waste (MSW), the local temperature of the waste layer increases greatly. The mechanical parameters related to waste degradation and the deformation of high-density polyethylene (HDPE) pipes in the waste body will be affected by the elevated temperature. To predict the temperature distribution in the anaerobic landfill, a one-dimensional heat transfer model is established in this study. This model considers the stratification of the saturated and unsaturated zones, and the layering of new and old waste. Furthermore, a single peak model for heat production is applied as the source term of heat production. The stratification of the unsaturated and saturated zones is considered by distinguishing the difference in heat conductivity and specific heat capacity. The layering of the new and old waste layers is considered by distinguishing the difference in the length of time that waste has been degraded to produce heat. Based on the numerical calculation method, the temperature distribution in a landfill with layered new and old MSW is well simulated. The position where the maximum temperature occurs and the variation in the temperature at the edge of new and old waste are elucidated. The sensitivity analysis shows that the influence of the density on the temperature distribution is more significant. Besides, the stratification of saturated–unsaturated waste should also be considered in landfills.

The effect of annealing time on morphology, mechanical properties, and thermal conductivity of HDPE pipes produced by rotational shear

The high-density polyethylene (HDPE) pipes containing a large amount of shish-kebab structures were produced by a self-developed rotational shear system (RSS). The effect of different annealing time on morphology, mechanical properties, and thermal conductivity of HDPE pipes with shish-kebab structures was studied. The results showed that there were two models for the change of shish-kebab structures after annealing at 125 ℃: partial melting and annealing recrystallization under short-term annealing conditions (< 120 min), and new elongated kebabs formation under long-term annealing conditions (≥ 120 min). Under short-term annealing conditions, the hoop tensile strength increased by 2.21% and thermal conductivities in both directions also increased slightly. However, under long-term annealing conditions, the hoop tensile strength increased by 19.12% (from 73.56 MPa to 87.63 MPa), and the thermal conductivity of out-of-plane increased by 7.77% due to the higher interlocking degree of shish-kebab.

Comparing Short-Term Performance of Corrugated HDPE Pipe Made with or without Recycled Resins for Transportation Infrastructure Applications

AbstractIn recent years, corrugated high-density polyethylene (HDPE) pipes manufactured from recycled resins have been on the rise for infrastructure sectors as a result of their numerous advantage...

Investigation of the Properties of High-Density Polyethylene Pipes used in Kurdistan for Piping System of Potable Water

&#x0D; &#x0D; &#x0D; &#x0D; High-density polyethylene (HDPE) pipes are recently used in the water distribution network in Kurdistan to replace the old pipes. In this investigation, two types of HDPE pipes (namely A and B) available in the local market have been studied and their properties were compared. Mechanical properties through tensile tests have been investigated and valuable data were collected that could provide a guideline reference for the designers and end-users utilizing these pipes for water supply networks. Furthermore, the HDPE samples were analyzed by differential scanning calorimetry (DSC). Results showed that the ultimate tensile strength recorded for pipe B was greater than pipe A by 8%. Besides, both the elongation at break and strain at break for pipe A was outperformed by almost 6%. On the other hand, the tests showed that the transition from elasticity behavior to ductility behavior for pipe B occurs earlier in comparison to pipe A. It was noted from the gathered information that the two tested pipes were within the standards with variations in their characteristics.&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D;

Experimental study on gasketed bell-and-spigot joint behaviour of lined-corrugated HDPE pipe subjected to normal fault

Although the structural response of pipelines has been studied in relation to different geohazards, few studies have focused on the behaviour of flexible pipeline joints. In this paper, the response of a bell-and-spigot joint in a 600 mm dia. lined-corrugated high-density polyethylene (HDPE) pipe was investigated under differential ground movements imposed using a facility that simulates a normal fault. Two experiments were undertaken in this facility. In the first experiment, the kinematic responses of the pipe joint (i.e. axial, shear displacements and rotational angles) were measured using particle image velocimetry and string potentiometers. Strains were also monitored using optical fibres. In the second experiment, the pipe was sealed and leakage of the joint was captured through monitoring the internal vacuum pressure of the pipe. The results show that axial shortening, rotational angle and shear displacement of the pipe joint increased with increasing fault offsets. The joint began to leak when axial shortening, rotational angle and shear displacement of the pipe joint were 0·65 mm, 0·44° and 3·40 mm, respectively, and the joint clearly lost its functionality when those values reached 0·85 mm, 0·58° and 4·32 mm.

Liquid temperature effect on the hydraulic shock wave velocity in polyethylene pipes

Introduction. Providing people with high quality drinking water has always come first. However, its transportation through pipeline systems was often associated with some problems, such as the temperature of the water and the environment, as well as the possibility of water hammer on certain pipe sections. This was especially true for systems that use polyethylene pipes. Temperature is a key factor affecting the flexibility properties of polyethylene pipes, and it affects not only the design, but also the investment in the development of water supply networks. The purpose of these studies was to study the effect of water and ambient temperature on the density, properties of the pipe material and the speed of propagation of a hydraulic shock wave in polyethylene pipes.Materials and Methods. In the experiments performed, the method of field research was used, when tests are carried out on specialized equipment on samples specially made for the pursued purposes. Here, samples of high-density polyethylene pipes were used, which were subjected to tensile tests on a tensile testing machine, and each experiment was carried out three times.In the course of the experiments, the samples were exposed to certain temperature regimes (both external and internal), while the influence of the hydrodynamic pressure of the liquid in the pipe was also investigated, as a result of the change in time of the liquid velocity in its sections. To do this, the samples were supplied with liquid under a certain pressure in order to find out the influence on the pipes of an effect known as water hammer.Results. In the course of the research, it was found that the value of the elastic modulus of high-density polyethylene PE100 decreases with increasing water temperature, and the decrease at a temperature of 60° C reaches 60.21% compared to its value at a water temperature of +4° C. Based on the results of experiments to determine the effect of the elastic modulus of polyethylene with increasing temperature, an exponential equation was derived to calculate the value of the polyethylene coefficient as a function of time E = 1.312e-0,01t with the correlation coefficient R2 = 0.988 ; and based on the results of the studies carried out to calculate the value of the propagation velocity of a hydraulic shock wave, an exponential equation was derived as a function of time C = 275.9e-0,01t with the coefficient correlation R2 = 0.987 .Discussion and Conclusions. In the course of the research, it was found that such a phenomenon as water hammer has a harmful effect on the pipe walls, which, if possible, should be avoided even at the design stage of the water supply network. During the experiments, it was found that with an increase in temperature, the values of the elastic modulus of polyethylene decreased with a simultaneous decrease in the values of the propagation velocity of the hydraulic shock wave.

Time reversal of waves in hydraulics: experimental and theoretical proof with applications

Time reversal of waves is an intriguing wave property that underpins a breadth of applications in physics and engineering. Waves contain information about their sources and the media through which they propagate. Thus, time reversal of measured wave signals has the potential of localizing and characterizing wave sources and of inferring the properties of the medium. Herein, we experimentally demonstrate the time reversibility of acoustic waves propagating in water-filled viscoelastic high-density polyethylene (HDPE) pipes. Evidently, the two mechanisms that restrict time reversal are the stability of wave paths to perturbations and damping. Perturbations, however, are found to grow slowly in time (∼t 1/2) and are not critical for the time reversal of waves. To evaluate the effect of damping, we perform an order of magnitude analysis on the non-reversible terms of the coupled waveguide momentum equations and derive a dimensionless time reversal parameter TR showing that damping develops linearly with time (i.e. TR ∼ t). Subsequently, we apply the TR parameter to our experiments and relevant experimental proofs from the literature to find that the time reversal of waves only holds for TR ∼ 1 or less; hence providing a criterion to estimate the range over which time reversal-based wave techniques and methodologies are valid. Finally, we discuss the various existing applications of time reversal in hydro-environmental research and engineering and anticipate that the presented work will stimulate further development.

Investigation on Physical and Mechanical Properties of High Density Polyethylene (PE100) Using Novel Catalyst

Novel catalyst called super active catalyst for the production of high density polyethylene (HDPE) pipes grade 100 was prepared and localized for the first time in Iran. The purpose of this paper is to evaluate the performance of the new catalyst and compare it with Finix-112 catalyst which is a commercial catalyst for the production of HEPE grade 100. Extensive experiments were performed on the physical and mechanical properties of the product using both catalysts including melt flow index, particle size distribution, volatility, density, bulk density, scanning electron microscope-energy dispersive x-ray analysis, charpy impact strength. Comparison of the results showed that the hydrogen responsibility performance of the product with super active catalyst is 19%, charpy impact is 16.7% and pressure condition in first reactor about 28% was better than product with Finix-112 catalyst. Home-made super active catalyst can be a good alternative to imported finix-112 catalyst and save a considerable amount of foreign currency.

Experimental and numerical study of shallow‐buried high‐density polyethylene pipeline under collapse touchdown impact

AbstractThe debris from structures produced during the blasting demolition of engineered buildings (structures) may fall near buried pipelines, which threaten the integrity of the buried gas pipeline. In this paper, the dynamic response of nearby shallow‐buried high‐density polyethylene (HDPE) gas pipelines under collapse impact loads was investigated. The stress‐strain curve and material parameters of the HDPE pipe were obtained through uniaxial tensile tests. The strain distribution of buried pipelines under collapse loading was obtained. Subsequently, a 3D nonlinear finite element (FE) model of a buried HDPE pipeline impacted by a collapsed body was established. Finally, the effects of the impact velocity, touchdown angle, touchdown mode, offset distance, and pavement structure on the mechanical behavior of buried HDPE pipelines were analyzed in detail. The results show that, as the touchdown velocity and angle of the collapsed body increase, the von Mises stress of the pipeline is significantly affected. The pipe section close to the center of the impact zone tends to be damaged due to the von Mises stress reaching the maximum tensile strength. The maximum von Mises stress of the pipeline that is impacted by the edge of the collapsed body is the smallest, but the buried pipeline undergoes the largest displacement. The rigidity of the overlying pavement structure has a significant impact on the reliability of the buried HDPE gas pipeline. The stress concentration areas of buried pipelines mainly appear on the top, bottom, and the arches of the pipeline.

Rig Load Prediction Model in Horizontal Directional Drilling within Water-Rich Unstable Strata

In horizontal directional drilling (HDD) construction, the rig pulling load is the load directly applied to the rig, which is an important basis for selecting power and checking capability of drilling equipment. Existing models cannot directly calculate the rig pulling load during the pull-back process. In this study, a model that takes into account the influence of the drill string and the soil pressure was developed to predict rig pulling load. The accuracy of the model is verified by comparison with existing models and field tests. The results show that pullback capability of rig should be determined by the maximum rig load instead of the maximum pull head load. For lighter high-density polyethylene (HDPE) pipes, using the mud with good lubrication function is the most effective to reduce the maximum rig load, however, for heavier steel pipes, the most effective way to reduce the maximum rig load is choosing pipe delivery method with less resistance. The field test proves that the model can predict the rig load accurately when installing pipes in water-rich unstable strata.

Experimental and numerical investigations on damage assessment of high-density polyethylene pipe subjected to blast loads

Buried high-density polyethylene (HDPE) pipelines have been extremely vulnerable to terrorist attacks and third-party damage in recent years, so it is important to study the vibration response and safety criterion of buried HDPE pipelines under the action of surface blast loads. In this paper, based on the full-scale field tests, the damage characteristics of HDPE pipes under the action of surface blast loads are studied. Next, a 3D numerical calculation model was established to analyze the response characteristics of the buried pipes subjected to surface blast loads and its reliability was verified using the field monitoring data. Then, the safety of the pipes under different blast load conditions was studied in combination with numerical simulation software, and different damage models of the pipe were established based on damage theory. The results show that the peak particle velocity (PPV) of both the pipe and the surface increases as the distance from the explosive decreases, and the vibration velocity of all measurement points is dominated by the vertical direction (Y). Meanwhile, as the surface explosive is triggered, the pipe is prone to overall bending deformation in the axial direction, resulting in the destruction of the pipe. Finally, based on the comprehensive numerical calculations, numerical simulation results were obtained for different damage levels of the pipes under surface blast loading. What’s more, the damage prediction model of the pipes is also proposed, and the critical curves corresponding to different damage levels are derived.

Measurement of Structural Performance of Fusion Weld with Change of Welding Parameters in High-Density Polyethylene

Abstract In the last few decades, the use of high-density polyethylene (HDPE) is continuously increasing such as HDPE pipes. These pipes are frequently used in the construction of long-buried infrastructures including water mains, sewers, and gas pipelines. These pipes are available in standards lengths and can be customized as per desired lengths using the fusion welding technique. In this article, the effect of changing the welding parameters such as temperature, heat, and soaking time on the performance of the fusion welding joint in HDPE is presented. The structural performance is measured by comparing the tensile strength of the unwelded and welded structure. Furthermore, the structural performance of extruded HDPE pipes and injection-molded HDPE fittings, such as elbows, tee-joints, and close end cap connections, are also discussed. The findings of this research are very useful in understanding and improving the structural performance of HDPE fusion welds with the help of comparative studies based on tensile strength on the welded joint in HDPE.

Experimental investigations of the critical values of J-integral and crack tip opening displacement (CTOD) of high-density poly-ethylene PE100 elbow

The present study aims to characterize the cracking behaviour of high-density poly-ethylene (HDPE) pipe elbow. Experimental studies were performed to determine the mechanical behaviour of HDPE and study the anisotropy of the material. Tension tests were performed on compact tension (CT) specimens to identify the toughness value, expressed by the critical value of the J-integral JIc. These tests were carried out on specimens cut from a PE100 plate with a different orientation angle with respect to the extrusion direction. The testing results have shown that HDPE can be considered as an isotropic material. The methods used to calculate the JIc value resulted in different value. Due to these uncertainties, a study of a failure criteria using crack tip opening displacement (CTOD) was proposed and conducted. The combination of the J-integral and “CTOD” method gave the possibility to determine for the critical value of the J-integral as a value of the fracture toughness of the HDPE. The obtained results suggest that the value of 8.4 kJ/m2 can be considered as the JIc fracture toughness required to initiate the crack for the HDPE.

Impact of operational temperature changes and freeze\u2013thaw cycles on the hydraulic conductivity of borehole heat exchangers

A large share of the primary energy is consumed to provide space heating. Geothermal energy offers a regenerative alternative. For reasons of efficiency and environmental protection, it is important to ensure the system integrity of a borehole heat exchanger (BHE). Previous investigations have focused on the individual components of the BHE or on the grout and pipe systems’ integrity. This study focused on the analysis of the hydraulic system integrity of the complete subsoil–grout–pipe system as well as possible thermally induced changes. For this purpose, a pilot-scale experiment was built to test a 1-m section of a typical BHE under in situ pressure, hydraulic and temperature conditions. During the tests the hydraulic system permeability of the soil and the BHE was measured continuously and separately from each other. In addition, the temperature monitoring array was installed in a 50-cm cross-sectional area. Significant temperature-related fluctuations in the sealing performance could be observed. Hydraulic conductivity limits required by VDI 4640-2 (Thermal use of the underground—ground source heat pump systems, 2019) were exceeded without frost action. The succeeding application of freeze–thaw cycles further enhances the system permeability. The study shows that the thermally induced effects on the system integrity of the BHE are larger and more significant than the subsequent frost-induced effects. The hydrophobic character of the high-density polyethylene (PE-HD) pipes as well as its high coefficient of thermal expansion seem to be the main points of weakness in the system. Optimization research should focus on the interface connection between grout and pipe, whereby hydrophilic pipe materials such as stainless steel or aluminum should also be considered as well as manipulation of the pipe surface properties of PE-HD.

Degradation of sunlight exposure on the high-density polyethylene (HDPE) pipes for transportation of natural gases

High-density polyethylene pipes are prevailing in transportation of combustible natural gases, so their reliability deserves special attention. Amongst the diverse ageing effects that are usually taken into account, including internal pressure, chemicals, temperature and vibration etc., the effect of sunlight exposure has been seldom concerned because the natural weathering test takes a really long time. Though the Xenon arc lamp is always used to simulate the ultraviolet environment, the natural weathering test is still the optimum to evaluate the performances degradation of materials to simulate the actual service conditions. In this paper, such a natural weathering test with sunlight exposure time up to 24 months was performed on the PE100 class high-density polyethylene pipes. The mechanical and the chemical properties before and after the test were measured to evaluate the extent and trend of degradation, and particularly the Fourier transform infrared microscope was utilized to quantitatively investigate the oxidation degradation mechanism in the microscopic level.

Simulation Analysis of Limit Operating Specifications for Onshore Spoolable Reinforced Thermoplastic Pipes.

Spoolable reinforced plastic line pipes (RTPs), exhibiting a series of advantages such as good flexibility, few joints, long single length, light weight, easy installation, etc., have been widely used in the onshore oil and gas industry such as oil and gas gathering and transportation, high pressure alcohol injection, water injection, sewage treatment, and other fields. However, due to the lack of clear standard specificationof the limit operating properties for RTPs, three typical failure modes, i.e., tensile, flexure, and torsion, frequently occur in terrain changes, construction operation, and subsequent application, which seriously affects the promotion and use of RTPs. In this paper, the stress distribution of a non-bonded polyester fiber reinforced high-density polyethylene (HDPE) pipe (DN 150, PN 2.5 MPa) was systematically studied by the finite element method (FEM), and then the limit operating values under the axial tensile, coiled bending, and torsion load were determined. The corresponding experiments were conducted to validate the reliability and accuracy of the FEM model. The FEM results showed that the critical strain for axial tensile was 3%, the minimum respooling bend radius was 1016.286 mm, and the limit torsion angle of this RTP was 58.77°, which are very close to the experimental results. These limit values will be useful to establish normative guidelines for field construction and failure prevention of onshore RTP.

Scale precipitation on HDPE pipe by degassing of CO2 dissolved in water

Abstract In Algeria, high-density polyethylene (HDPE) is widely used in drinking water pipes. This study is focused on the precipitation of calcium carbonate, a major constituent of scale, from calcocarbonically pure (CCP) water in HDPE pipe. Studying scaling in natural conditions is very difficult because it occurs over many years. For this, accelerated scaling is caused by the degassing CO2 dissolved in water. The kinetic study has shown that the germination time and the critical pH decrease with the hardness (30, 40 and 50 °f) and temperature (30, 40 and 50 °C) of water. On the other hand, scaling process efficiency (η) and the supersaturation coefficient (Ωcal) of CaCO3 increase with these parameters. The CaCO3 precipitation occurs both in solution and on walls of HDPE. By the weighing method, it is shown that the deposit mass increases with hardness and temperature. Calcium carbonate precipitates much more in homogeneous phase than in heterogeneous one. The study also showed that heterogeneous nucleation on HDPE is much less important than on PA, PVC, chrome and Inox. These measurements are supported by the characterization of X-ray diffraction deposits and by scanning electron microscopy, which recognizes that the precipitate obtained consists mainly of calcite.

An Accurate and Efficient Fitness-For-Service Assessment Method of Pipes with Defects under Surface Load

With continued urbanization in China, the construction of urban gas pipelines is increasing, and the safety of gas pipelines are also increasingly affected by urban development and the increased scope of buildings and roads. Pipes with defects are more likely to fail under the surface loads. In this study, uniaxial tensile tests of high-density polyethylene (HDPE) pipes were carried out to obtain the real material parameters of pipe. A pipeline-soil interaction finite element model of HDPE pipeline with defects under surface load was established. The failure mechanism of the urban gas pipeline was studied and the influence of parameters such as internal pressure, defect position, defect depth on the mechanical behavior, and failure of pipelines were analyzed. A failure criterion for HDPE pipes with defects under surface load was proposed based on the limit-state curves obtained under different working conditions. Furthermore, an accurate and efficient fitness-for-service assessment procedure of pipes with defects under surface load was proposed. The results showed that maximum Mises stress of the pipeline gradually increased with increasing surface load and the position of maximum stress changed from the top and bottom of the pipe to the defect position and both sides of the pipe. Finally, when Mises stress of the HDPE pipe exceeds the yield limit, failure will occur. Internal pressure, defect location, and defect depth were found to influence the failure process and critical surface load of the pipeline. Safety evaluation curves of the gas pipeline with defects under surface load were obtained by calculating the critical failure load of the pipeline under various working conditions. Finally, a nonlinear fitting method was used to derive a formula for calculating the critical surface load under different defect parameters. The proposed method provides a useful reference for urban gas pipeline safety management.

Pressure Effects on the Lifetime of Gas High Density Polyethylene Pipes

Abstract The purpose of this study was to propose low gas pressure effects on lifetime of natural gas high-density polyethylene (HDPE) pipes by thermal-oxidative aging. The new method to assess the lifetime of HDPE natural gas pipes is based on gas pressure testing. An approach to monitor oxidative induction time (OIT) has been used to predict lifetime. Natural gas HDPE pipes were used to evaluate the effects of low gas pressures on oxidative induction time. In order to emphasize the pressure effects, relatively low temperatures at 45, 55, 65, and 75 °C were utilized for the exposure. The low-pressure conditions were created using air at levels of 0, 0.1, 0.2, 0.3, and 0.4 MPa. The property of high density polyethylene pipes was effectively monitored using the low pressure OIT test. The results show that the aging reaction rate of high density polyethylene pipes increased exponentially with temperature and gas pressure according to the Arrhenius equation. Analytical models were developed to predict the aging reaction rate and lifetime of natural gas HDPE pipes.