High Density Polyethylene Pipe Research Articles

Optimizing the Design of a Vertical Ground Heat Exchanger: Measurement of the Thermal Properties of Bentonite-Based Grout and Numerical Analysis

We prepared bentonite-based grouts for use in the construction of vertical ground heat exchangers (GHEs) using various proportions of silica sand as an additive, and measured the thermal conductivity (TC) and specific heat capacity (SHC) of the grouts under saturated conditions. Furthermore, we performed numerical simulations using the measured thermal properties to investigate the effects of grout-SHCs, the length of the high-density polyethylene (HDPE) pipe, the velocity of the working fluid, and the operation time and off-time during intermittent operation on performance. Experimentally, the grout TCs and SHCs were in the ranges 0.728–1.127 W/(mK) and 2519–3743 J/(kgK), respectively. As the proportions of bentonite and silica sand increased, the TC rose and the SHC fell. Simulation showed that, during intermittent operation, not only a high grout TC but also a high SHC improved GHE performance. Also, during both continuous and intermittent operation, GHE performance improved as the working fluid velocity increased, and there was a critical working fluid velocity that greatly affected the performance of the vertical GHE, regardless of operation mode, high-density polyethylene (HDPE) pipe length, or grout thermal properties; this value was 0.3 m/s. Finally, during intermittent operation, depending on the operation time and off-time, critical periods were evident when the ground temperature had been almost completely restored and any beneficial effect of intermittent operation had almost disappeared.

Heat exchange mechanisms in energy tunnel systems

Ground Source Heat Pump (GSHP) systems are known for their efficiency in space heating and cooling, using the ground as a source of energy. The ground energy can be accessed by the implementation of GSHP systems into subsurface structures such as transport tunnels. This technology comprises the embedment of High-Density Polyethylene (HDPE) pipes into the tunnel lining, converting it into tunnel ground heat exchangers (tunnel GHEs). There are studies available on the thermal interaction between the ground and the tunnel GHEs in the current literature. However, to properly evaluate the thermal performance of tunnel GHEs, the two-way thermal interaction between the tunnel GHEs and both the ground and the tunnel air must be considered. This requires the consideration of the ground conditions and the tunnel air temperature variations. In this work, the tunnel GHEs, the air inside the tunnel and the surrounding ground are modelled using finite element techniques. The models account for groundwater flow in the ground and induced airflow in the tunnel area. Numerical results highlight the significant effect of groundwater flow velocity on the temperature distribution pattern in the ground, the air temperature variations within the tunnel area and the average fluid temperature within the tunnel GHEs. To accurately capture the temperature variations in the tunnel air, it is crucial to account for both conduction and (induced) convection inside the tunnel as numerical results show significantly different temperature distribution inside the tunnel area in comparison to when only pure conduction is considered. In practice, the very common under/over-estimation of GSHP systems performance (including tunnel GHEs) is related – to a certain extent – to the lack of understanding regarding the operational environment of these systems (i.e., groundwater flow and tunnel air interactions with the activated lining). It may also lead to an inadequate air ventilation system design.

Laboratory evaluation of buried high-density polyethylene pipes subjected to localized ground subsidence

The serviceability loss of buried high-density polyethylene (HDPE) double-wall corrugated pipes caused by localized ground subsidence has been reported all over the world. Beam-on-nonlinear spring model is widely used to analyze the structural responses of buried pipes to the localized ground subsidence underneath the pipe. However, the pipe–soil separation is not considered by the beam-on-nonlinear spring model which assumes bonded interaction between the pipe and soil. This is because the spring stiffness could not be assigned as zero. The bonded interaction between pipe and soil is not able to capture the pipe behavior and characteristics of load distribution around the pipe when pipe–soil separation occurs. This study presents a series of large-scale model tests aiming to investigate the performance of buried HDPE double-wall corrugated pipes subjected to the localized ground subsidence. Movable plates installed at the bottom of the model test box are lowered down to simulate the localized ground subsidence. Earth pressures, pipe vertical displacements, and settlements at the backfill surface are monitored. For comparison purpose, free field condition (i.e., without pipe) is also tested. The test results demonstrate that soil settlement troughs above buried pipes are shallower and wider than those at the same elevation in the free field condition. Earth pressures at the top of the pipe are found to increase due to the negative soil arching, i.e., earth pressure is greater than the overburden pressure. It is suggested that three-dimensional soil arching, i.e., soil arching effects in both the transverse and longitudinal directions of the tested pipe, should be considered in calculating the earth pressures at the pipe top. The pipe–soil separation is substantiated by the observation that earth pressure measured at the bottom of the pipe is zero. Finally, empirical equations are proposed to correlate the volume of pipe displacement profile with the volume of settlement trough at the backfill surface to facilitate evaluation of the performance of the pipes subjected to the localized land subsidence.

Numerical methods for hydraulic transients in visco-elastic pipes

In technical applications involving transient fluid flows in pipes, the convective terms of the corresponding governing equations are generally negligible. Typically, under this condition, these governing equations are efficiently discretized by the Method of Characteristics. Only in the last years the availability of very efficient and robust numerical schemes for the complete system of equations, such as recent Finite Volume Methods, has encouraged the simulation of transient fluid flows with numerical schemes different from the Method of Characteristics, allowing a better representation of the physics of the phenomena.In this work, a wide and critical comparison of the capability of Method of Characteristics, Explicit Path-Conservative (DOT solver) Finite Volume Method and Semi-Implicit Staggered Finite Volume Method is presented and discussed, in terms of accuracy and efficiency. To perform the analysis in a framework that properly represents real-world engineering applications, the visco-elastic behaviour of the pipe wall, the effects of the unsteadiness of the flow on the friction losses, cavitation and cross-sectional changes are taken into account. Analyses are performed comparing numerical solutions obtained using the three models against experimental data and analytical solutions. In particular, water hammer studies in high density polyethylene pipes, for which laboratory data have been provided, are used as test cases. Considering the visco-elastic mechanical behaviour of plastic materials, 3-parameter and multi-parameter linear visco-elastic rheological models are adopted and implemented in each numerical scheme. Original extensions of existing techniques for the numerical treatment of such visco-elastic models are introduced in this work for the first time. After a focused calibration of the visco-elastic parameters, the different performance of the numerical models is investigated. A comparison of the results is presented taking into account the unsteady wall-shear stress, with a new approach proposed for turbulent flows, or simply considering a quasi-steady friction model. A predominance of the damping effect due to visco-elasticity with respect to the damping effect related to the unsteady friction is confirmed in these contexts. Moreover, all the numerical methods show a good agreement with the experimental data and a high efficiency of the Method of Characteristics in standard configuration is observed. Finally, three Riemann Problems are chosen and run to stress the numerical methods, taking into account cross-sectional changes, more flexible materials and cavitation cases. In these demanding scenarios, the weak spots of the Method of Characteristics are depicted.

Properties of Nanocomposites Based on High-Density Polyethylene

High-density polyethylene (HDPE) is one of the principal thermoplasts for manufacturing various types of pipes. Existing grades of HDPE pipes have poor physicochemical properties so that new thermoplastic construction materials with multifunctional properties must be used. These problems could be solved effectively by developing composites that allow the use of nanotechnologies to strengthen the polymer matrix and improve the initial property set.

Effect of short chain branches distribution on fracture behavior of polyethylene pipe resins

In this paper, a series of unimodal and bimodal high density polyethylene (HDPE) pipe resins with the similar molecular weight distribution and low short chain branches (SCB) contents were investigated to discover the relationship between short chain branches distribution (SCBD) and fracture behaviors. Three characterization methods, namely temperature rising elution fractionation (TREF), high temperature gel permeation chromatography (HT-GPC) and self-annealing fraction (SSA), have been effectively combined to qualitatively analyze investigate the SCBD of HDPE pipe resins. The results showed the preference of incorporation of SCB into long chains caused the enhancement of yielding stress and strain hardening (SH) modulus, and thus the extension of rupture time. On one hand, this kind of SCB distribution is conductive to induce the nucleation of long chains and form more void volume in the neighborhood of long chains indicating faster migration speed of polymer chains. On the other hand, short chains with less SCBs are easy to rapidly occupy nearby sites on the crystal growth front of long chains to co-crystallize. Whereas, these HDPE resins with the more SCBs incorporated into short chains spent much longer time occupying the growth front, so that parts of these types of short chains form very thinner lamella differentiated from the main crystallizing region. During the initiation and propagation of craze, these parts were firstly broken and their resistance to slow crack growth was based on the incorporating degree of SCBs into short chains. Therefore, besides molecular weight distribution, SCBD is another main cause for long-term properties of HDPE pipe resins.

Investigation on the hot melting temperature field simulation of HDPE water supply pipeline in gymnasium pool

Abstract In view of the special needs of the water supply and drainage system of swimming pool in gymnasium, the correlation of high density polyethylene (HDPE) pipe and the temperature field distribution during welding was investigated. It showed that the temperature field distribution has significant influence on the quality of welding. Moreover, the mechanical properties of the welded joint were analyzed by the bending test of the weld joint, and the micro-structure of the welded joint was evaluated by scanning electron microscope (SEM). The one-dimensional unsteady heat transfer model of polyethylene pipe welding joints was established by MARC. The temperature field distribution during welding process was simulated, and the temperature field changes during welding were also detected and compared by the thermo-couple temperature automatic acquisition system. Results indicated that the temperature of the end surface of the pipe does not reach the maximum value, when it is at the end of welding heating. Instead, it reaches the maximum value at 300 sand latent heat occurs during the welding process. It concludes that the weld quality is the highest when the welding pressure is 0.2 MPa, and the heating temperature of HDPE heat fusion welding is in the range of 210 °C–230 °C.

A method for mechanical property assessment across butt fusion welded polyethylene pipes

The use of high-density polyethylene pipes in gas and water distribution networks is steadily growing worldwide. If the resistance of plain pipes is at present time well established using appropriately designed standards, welding issues continue to be globally approached equally in terms of structure and mechanical properties. Consequently, further practical investigations should be aimed at studying mechanical properties in the weld region which includes the melt zone and its heat-affected zones. This work presents a method based on removing layers in order to assess localized variances in mechanical properties throughout the weld seam in both radial and circumferential directions. An experimental plan based on specific machining operations allowed testing 39 standard specimens representing the weld volume matter in three concentric layers for given pipe dimensions and their counterpart standard unwelded ones. The typical stress–strain behavior of semi-crystalline materials is preserved in welded and unwelded specimens but with different characteristic limits. At the weld inner layers, properties such as elastic modulus, yield, and failure stresses displayed lower values, whereas in welded outer layers, the tendency is inversed. The cold drawing extend remained approximately steady for unwelded and welded cases across the pipe wall. This property is less affected by the presence of the weld as it described a constant material flow which is mostly a function of available material quantity for yielding. The approach developed in this study gives consistent indications on welding quality around the pipe weld and across the thickness. Accordingly, outermost and innermost welded layers may exhibit lower or even bad-quality welds as imperfections can concentrate stresses at the joint interface because of cold weld problems. Such method enabled detecting 23% of failures at the weld seam from outer and inner layers while the middle layer did not reveal any failure at the weld. The causes of this behavior are approached using crystallinity evolution in welded and unwelded pipes.

Study of reliability index for high-density polyethylene based on pipe standard dimension ratio and fracture toughness limits

The reliability of high-density polyethylene (HDPE) pipes remains a central issue for gas transportation and distribution networks. The objective of this study is to investigate the estimation of reliability index (β) for a plastic pipe using the critical stress intensity factor (KIC) as the maximum limit for safe operating conditions. Simulations are performed as a function of operating pressure, crack length, and standard dimension ratio (SDR) for three fracture toughness levels (low, moderate, and high). In addition, the study compares results from three hoop stress calculations methods (thin, thick, and ISO plastic pipe equation). Based on design recommendation for reliability index, it is found that both operating pressure and crack length show comparable behaviors. However, the thick wall pipe results overestimate (β) for every KIC level. In all cases, it is found that the higher the critical stress intensity factor, the better the reliability index. Results obtained with the standard ISO pipe formula are more realistic, as they are usually around the design recommendation, i.e., SDR basis indicates that it is a true conservative design approach incorporating both upper and lower thickness limits. The importance of all variables (thickness, diameter, crack length, pressure, and fracture toughness) is also discussed.

The Extent of Damage Identification Method Using Extrusion Machine Overall Equipment Effectiveness (OEE) in PT. XYZ

PT. XYZ was a company that has been producing many different type of a pipe, the PVC (Poly Vinyl Chlorida) pipe, the HDPE (High Density Polyethylene) pipe and the gutters pipe that used for clean water irrigation, the pipe installation of housing complex, the industrial waste disposal, for reservoirs and telecommunication. The process of making a pipe is often hampered on an extrusive engine because it used during 24 hours a day and the maintenance schedule of the machine has not been applied regularly. We need to do identification about the damages of exstrusive machine with a Total Productive Maintenance using the Overall Equipments Effectiveness (OEE) method. From the research, it can be seen that the set up time to an extrusive machine still took a long time and the production volume of the machine was still low. The effectiveness of the performance from extrusive machine also have not been able to achieve the OEE's standard that was 88 % .

Fault Identification in Pipeline System Using Normalized Hilbert Huang Transform and Automatic Selection of Intrinsic Mode Function

Pressure transient analysis has been widely used to monitor the condition of pipelines and its assessment in water distribution systems. This is a low-cost nonintrusive technique with the ability to locate uncertainties (leak, pipe fitting, blockage) at a greater distance from the measurement point. In this research, Normalised Hilbert Huang Transform (NHHT) is used as the method to analyse the pressure transient signal. However, this method has difficulty in selecting the suitable intrinsic mode function (IMF) for the advance data analysing. As an alternative, Integrated Kurtosis-based Algorithm for z-filter Technique (Ikaz), which allows automatic selection of intrinsic mode function (IMF) been used to substitute the NHHT limitation in this study. The analysis is conducted on a 67.9-meter Medium High-Density PolyEthylene (MDPE) pipe installed with single artificial leak simulator at a water pressure in the range of 1-4 bar.

Procurement Assessment of High-Density Polyethylene Pipe in Department of Water Supply and Sewerage, Nepal

Procurement Assessment of High-Density Polyethylene Pipe in Department of Water Supply and Sewerage, Nepal

Thermo-physical and mechanical characteristics of sand-based lightweight composite mortars with recycled high-density polyethylene (HDPE)

Today, a large number of research projects are concerned with the recycling of plastic waste to be reused in the field of construction. This work, which is part of a research programme, focuses on the valorization of plastic waste from high density polyethylene (HDPE) pipes, to be used as aggregates. The HDPE aggregates were used as partial replacements of natural sand at 0, 15, 30, 45 and 60%, for the same volume. Only one particle size of the HDPE aggregates was used in each composition of the lightweight composite mortars (LWCM). Prismatic specimens 4 × 4 × 16 cm3 were prepared with a ratio W/C = 0.5. The density of the composite mortars was measured in the fresh and cured states. The compressive and flexural strengths, the thermo-physical characteristics as well as the ultrasonic pulse velocity (UPV) and the dynamic modulus of elasticity (Ed) were also investigated. In addition, composite mortars were analysed using a Scanning Electronic Microscope (SEM). Laboratory tests revealed encouraging results. Compared to the normal composite mortar (NMC), outcomes showed that composite mortar with 60% HDPE aggregates (LWCM60) increased ductility and reduced by 73% the dynamic modulus of elasticity. Analyses using SEM indicated that HDPE aggregates exhibited low adhesion to the cementitious matrix and mortars with higher HDPE rates improved the energy performance of composite mortars (LWCM).

Protection of Buried Pipe under Repeated Loading by Geocell Reinforcement

With increase in cities’ population and development of urbane life, passing buried pipelines near ground’s surface is inevitable in urban areas, roads, subways and highways. This paper presents the results of three-dimensional full scale model tests on high-density polyethylene (HDPE) pipe with diameter of 250 mm in geocell reinforced soil, subjected to repeated loading to simulate the vehicle loads. The effect of geocell’s pocket size (55*55 mm and 110*110 mm) and embedment depth of buried pipe (1.5 and 2 times pipe diameter) in improving the behaviour of buried pipes was investigated. The geocell’s height of 100 mm was used in all tests. The repeated load of 800 kPa was applied on circular loading plate with diameter of 250 mm. The results show that the pipe displacement, soil surface settlement and transferred pressure on the pipe’s crown has been influenced significantly upon the use of geocells. For example, the vertical diametric strain (VDS) and soil surface settlement (SSS), in a way that using a geocell with pocket size of 110*110 mm reduces by 27% and 43%, respectively, compared with the unreinforced one. Meanwhile, by increasing buried depth of pipe from 1.5D to 2D, the use of geocell of 110*110 mm delivers about 50% reduction in SSS and VDS, compared with the unreinforced soil.

Identifying mechanically induced chemical changes to vintage grade high density polyethylene pipes during squeeze-off

Squeeze-off is widely used within the gas industry for temporary interruptions to supply, both when extending and repairing the polyethylene (PE) pipe network. Over the years a number of pipe failures, have been attributed to damage caused at the squeeze-off location, often linked to non-standard squeeze-off practices. The purpose of this paper is to examine PE pipes that have been squeezed in the laboratory under ASTM and non-ASTM standard conditions to determine if any changes to the PE structure can be measured. Changes in the PE due to squeeze-off was measured by FTIR at the squeeze-off ear. The carbonyl index (CI), a measure of polymer degradation, was calculated for the various squeeze-off conditions and it was found that over-compression of the PE pipe caused the greatest amount of damage to the pipe and that is directly linked to the integrity of the pipe prior to being squeezed-off.

Comparison of viscoelastic models with a different number of parameters for transient simulations

AbstractThe numerical and analytical models used for transient simulations, and hence for the pressurized pipe system diagnosis, require the definition of a rheological component related to the pipe material. The introduction and the following widespread use of polymeric material pipes, characterized by a viscoelastic behavior, increased the complexity and the number of parameters involved in this component with respect to metallic materials. Furthermore, since tests on specimens are not reliable, a calibration procedure based on transient test is required to estimate the viscoelastic parameters. In this paper, the trade-off between viscoelastic component accuracy and simplicity is explored, based on the Akaike criterion. Several aspects of the calibration procedure are also examined, such as the use of a frequency domain numerical model and of different standard optimization algorithms. The procedure is tested on synthetic data and then it is applied to experimental data, acquired during transients on a high density polyethylene pipe. The results show that the best model among those used for the considered system implements the series of a spring with three Kelvin–Voigt elements.

Pipe leak diagnostic using high frequency piezoelectric pressure sensor and automatic selection of intrinsic mode function

In a recent study, the analysis of pressure transient signals could be seen as an accurate and low-cost method for leak and feature detection in water distribution systems. Transient phenomena occurs due to sudden changes in the fluid’s propagation in pipelines system caused by rapid pressure and flow fluctuation due to events such as closing and opening valves rapidly or through pump failure. In this paper, the feasibility of the Hilbert-Huang transform (HHT) method/technique in analysing the pressure transient signals in presented and discussed. HHT is a way to decompose a signal into intrinsic mode functions (IMF). However, the advantage of HHT is its difficulty in selecting the suitable IMF for the next data postprocessing method which is Hilbert Transform (HT). This paper reveals that utilizing the application of an integrated kurtosis-based algorithm for a z-filter technique (I-Kaz) to kurtosis ratio (I-Kaz-Kurtosis) allows/contributes to/leads to automatic selection of the IMF that should be used. This technique is demonstrated on a 57.90-meter medium high-density polyethylene (MDPE) pipe installed with a single artificial leak. The analysis results using the I-Kaz-kurtosis ratio revealed/confirmed that the method can be used as an automatic selection of the IMF although the noise level ratio of the signal is low. Therefore, the I-Kaz-kurtosis ratio method is recommended as a means to implement an automatic selection technique of the IMF for HHT analysis.

Combined Use of Jute Geotextile-EPS Geofoam to Protect Flexible Buried Pipes: Experimental and Numerical Studies

This paper addresses the results of the experimental and numerical studies conducted on 4.2 mm thickness and 110 mm diameter high-density polyethylene (HDPE) pipes buried in fly ash material overlying stone dust beds. The model tests were performed using single and double layers of expanded polystyrene (EPS) geofoam as compressible inclusions. In addition to that, jute geotextile was used as a reinforcement for the infill fly ash along with EPS geofoam inclusion to obtain induced trench condition. The test beds were subjected to loading on the fly ash surface with the help of a rigid steel plate to simulate as a strip footing in different embedment depths of the pipe (1–3 times pipe diameter). The test results revealed that the pressure and strain values in the pipe reduced significantly in the presence of EPS geofoam and jute geotextile related to the location of the pipe. In the case of double layers of EPS geofoam could induce reduction of the pressure up to 87.2% and strain about 63.5% respectively depending on the density and width of EPS geofoam. Whereas, at the same burial depth, in the presence of jute geotextile together with EPS geofoam can be reduced up to 93.8 and 73.4% for pressure and strain respectively depending on EPS geofoam density and number of reinforcement. Moreover, the jute geotextile-EPS geofoam combination of model test results were validated with finite element program. A good agreement was observed on pressure-settlement response and pipe strain between experimental and numerical investigations. The numerical studies show that the jute geotextile distributes stresses in the lateral direction and then the stresses on the pipe significantly reduced.

Using developed creep constitutive model for optimum design of HDPE pipes

Unlike metal pipes, high density polyethylene (HDPE) pipes are not susceptible to erosion and corrosion. However, the most important mechanical feature of the HDPE pipes is that this material creeps even at room temperature. Therefore, it is essential to study the creep behavior of this material in order to develop a model. In this paper, creep behavior of HDPE at different temperature and stress levels has been experimentally studied to obtain the creep constitutive parameters of the material. These parameters are used to predict the creep behavior of different structures such as HDPE pipes. For this purpose, a number of specimens have been machined from industrial manufactured pipe walls. Uniaxial creep tests have been carried out and creep strain curves with time for each test were recorded. Then, a constitutive model is proposed for HDPE based on the experimental data and optimization methods. The results of this model have been compared with the test data and good agreement is observed. The developed constitutive model and reference stress method (RSM) were used to produce graphs which provide optimum creep lifetime and design conditions for HDPE pipes that are subjected to combined internal pressure and rotation. These graphs can facilitate the design process of HDPE pipes.

Numerical Modeling of Installation of Steel-Reinforced High-Density Polyethylene Pipes in Soil

AbstractSteel-reinforced high-density polyethylene (SRHDPE) pipe uses steel ribs to carry loads and plastic cover to prevent the steel ribs from corrosion so that it overcomes the disadvantages of ...