Polyethylene Gas Research Articles

An integrated risk assessment methodology based on fuzzy TOPSIS and cloud inference for urban polyethylene gas pipelines

Due to the superior performance of polyethylene (PE) gas pipes, an increasing number of PE pipelines are being used in urban areas. However, PE gas pipelines are basically located in densely populated areas with high consequences. Once a leak occurs, combustion and explosion accidents can easily happen causing a major threat to human life and property. Furthermore, the assessment results of the common risk assessment methods often have great uncertainty and deviation. It is difficult to accurately identify the main indicators that need priority management. To address these problems, this paper proposes a novel methodology by integrating a fuzzy TOPSIS model and cloud inference for conducting risk assessments of urban PE gas pipelines. The developed methodology is composed of two branches. In the first branch, a rapid risk assessment model for PE pipelines is established to determine whether there are some special emergency situations, which can be directly identified as high risk. In the second branch, a detailed risk assessment process is adopted to obtain the final result, which mainly includes risk factor analysis, risk status assessment and risk classification. Among them, risk factor analysis is used to establish a risk index system and develop a risk index management strategy by means of mathematical statistics and the fuzzy TOPSIS analysis method. The risk status assessment is used to determine the final risk value based on the virtual cloud and fault tree analysis, which is mainly realized by the triangular fuzzy number, structural entropy weight method and backward cloud transformation algorithm. Finally, the risk assessment results of PE gas pipelines are clearly presented in the form of cloud inference, and the final risk classification is determined. The case study shows that the pipeline in this section is at the medium risk level, and the management of time-related indicators and third-party damage is given priority. The result is consistent with the actual situation, which verifies the effectiveness and practicability of the methodology.

A Method for Grading the Hidden Dangers of Urban Gas Polyethylene Pipelines Based on Improved PLC Methods

The classification of hidden dangers in urban gas pipelines plays a vital role in the smooth operation of urban gas pipelines and in solving the problem of hidden safety dangers in urban gas pipelines. In recent years, the number and proportion of polyethylene (PE) pipelines in urban gas pipelines are increasing day by day, but the current classification of hidden dangers in urban gas pipelines is still based on steel pipelines, and the classification method is highly subjective. Therefore, this paper proposes an improved PLC method that integrates the use of a risk matrix and compensation coefficient to solve the problem of grading the hidden dangers of PE pipelines of urban gas. The improved PLC method is based on the failure database of urban gas PE pipelines to obtain the vulnerability and severity of consequences when determining the initial level of hidden dangers, and the compensation coefficient is modified according to regional vulnerability, ease of rectification, condition around the pipeline, positioning technology, leak detection technology, and emergency ability, which can effectively reduce the subjectivity of hidden danger classification. Using the improved PLC method to classify urban gas pipelines for hidden dangers can provide pipeline operating companies with a basis for decision making in the process of hidden danger disposal and effectively reduce pipeline safety risks.

Finite Element Analysis of Buried Polyethylene Gas Pipeline under Traffic Load

Finite Element Analysis of Buried Polyethylene Gas Pipeline under Traffic Load

Fuel gas production through waste polyethylene gasification using bauxite residue as the oxygen carrier

In this study, waste polyethylene (PE) was gasified to produce alternative gas fuel using bauxite residue (BR) as an oxygen carrier in a two-stage reactor. PE was pyrolyzed in the first stage, and the volatiles were subsequently gasified with BR. The influences of temperature and mass ratio on the fuel gas composition were determined. The experimental results indicated that a higher temperature benefits gas production. The gas yield was 0.714 Nm3/kg at 850 °C, and the CH4 yield was 0.231 Nm3/kg. Increasing the BR mass ratio (Fe2O3 to fuel) could lead to over-oxidization (combustible gas production values were 0.531 Nm3/kg and 0.503 Nm3/kg at ratios of 1:2 and 1:4, respectively). Compared with the traditional oxygen carrier Fe2O3, BR showed a stronger oxygen release capability. The oxygen efficiency of BR was over 100% higher than that of Fe2O3. Moreover, the three-stage reactor improved the quality of gas (gas yield was 0.771 Nm3/kg and the production of H2, CH4, and CO accounted for 33.425%, 31.349%, and 19.186%, respectively) compared to the two-stage reactor. Furthermore, the Fe contained in the BR was reduced to Fe3O4, which might have contributed to the magnetic separation. Therefore, the results offer a promising method for the efficient utilization of waste plastic and BR.

Corrigendum to “Assessments of key features and Taguchi analysis on hydrogen rich syngas production via gasification of polyethylene, polypropylene, polycarbonate and polyethylene terephthalate wastes” [Int J Hydrogen Energy 46(58) (2021) 29846-29857

Corrigendum to “Assessments of key features and Taguchi analysis on hydrogen rich syngas production via gasification of polyethylene, polypropylene, polycarbonate and polyethylene terephthalate wastes” [Int J Hydrogen Energy 46(58) (2021) 29846-29857

Time-dependent analysis of buried high-density polyethylene (PE100) pipelines with a scratch defect subjected to touchdown impact loading of blasting collapsed body

The collapsed body generated by the blasting demolition of buildings or structures is likely to impact the buried high-density polyethylene (PE) gas pipelines, which would severely affect the pipeline safety and integrity. In this work, the dynamic response of buried PE100 gas pipelines containing a scratch defect under the touchdown impact was investigated. The tensile tests of scratched PE100 specimens were conducted. A strict 3D finite element (FE) model was then established to simulate the impact process on the scratched PE pipeline. The verified model was employed to investigate the time-dependent response and ultimate bearing capacity of the pipeline under the touchdown load. Parameter effects including the scratch dimensions, defect location, internal pressure and touchdown velocity were examined. The results show that a critical scratch depth equal to 20% of the wall thickness existed, above which the scratch significantly reduces the yield strength and ductility of PE100 material. At the moment when the collapsed body impacts the soil, the maximum von Mises stress, cross-sectional change rate and vibration velocity of the scratched pipeline increases rapidly to the peak value. The maximum von Mises stress and displacement of the pipeline are highly dependent on the scratch depth, defect location, internal pressure and touchdown velocity. A critical internal pressure of 0.6 MPa was determined, exceeding which the ultimate bearing capacity of the scratched PE pipeline is significantly reduced. The significance order of the parameters is: touchdown velocity > scratch depth > internal pressure > scratch width > scratch length.

РОЗРАХУНОК КОЕФІЦІЄНТА ГІДРАВЛІЧНОГО ОПОРУ В ГАЗОВИХ МЕРЕЖАХ НАСЕЛЕНИХ ПУНКТІВ

The consequences of applying Hofer's formula for the coefficient of hydraulic resistance instead of the formulas provided by the current normative document DBN B.2.5-20-2018 in gas-dynamic calculations of gas networks of settlements have been established by mathematical modeling. The influence of this change in the mathematical model on the results of calculating the coefficient of hydraulic resistance in steel and polyethylene gas networks of low, medium and high pressure depending on the mode of gas movement is revealed.

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.

On the issue of technical diagnostics of polyethylene gas pipelines

The article presents the comparative characteristics of polyethylene pipes after a 50-year period of operation, lists the factors affecting the physical and mechanical properties of pipes and requiring consideration when conducting research. Practical possibilities of assessing the technical condition of long-term operating polyethylene gas pipelines and approaches to extending their service life are considered.

Experiment on a distributed fiber optic interferometric sensing system to monitor and locate urban high-density polyethylene gas pipe leakage

A distributed fiber optical interferometric sensing system was built to monitor and detect urban high-density polyethylene gas pipe leakage. To eliminate the phase drift, the digital phase generated carrier scheme was designed to demodulate the phase difference of interferometers induced by high-density polyethylene gas pipe leakage. Then the empirical mode decomposition and approximate entropy were combined to process fiber optic interferometric signals. Finally, leakage points were located by the null-frequency spectrum after empirical mode decomposition filter denoising. The lab-scale test validated the distributed fiber optical interferometric sensing system leakage location performance and demonstrated a reduced leakage accident missed alarm rate.

Assessments of key features and Taguchi analysis on hydrogen rich syngas production via gasification of polyethylene, polypropylene, polycarbonate and polyethylene terephthalate wastes

Plastics have a considerable contribution on volumetric portion of the worldwide municipal solid waste. Gasification of plastic waste is an efficient thermo-chemical approach with a bright outlook. In the present study, the steam gasification of polyethylene, polypropylene, polycarbonate and polyethylene terephthalate waste was modeled. The effects of key features including steam to plastic waste ratio, temperature, moisture content, and pressure were assessed on hydrogen-rich syngas compositions and exergy destruction rate. Taguchi approach was utilized to investigate and optimize the process. The findings revealed that the gasification of polypropylene waste led to the highest hydrogen production at all processing conditions. However, the lowest exergy destruction rates belonged to polyethylene waste gasification. The results of analysis of variance showed that steam to plastic waste ratio had the highest contributions on hydrogen production and exergy destruction rate with 53.13% and 59.53%, respectively. Signal to noise ratio analysis was hired to multi-objective optimize the plastic waste gasification. Polyethylene waste, 1.75 of steam to plastic waste ratio, 1300 K of temperature, 10% of moisture, and 400 kPa of pressure were the optimum conditions. Hydrogen production was 66.71% and exergy destruction rate was 54.86 kW at the optimum conditions.

Using machine learning to automate ultrasound-based classification of butt-fused joints in medium-density polyethylene gas pipes.

Polyethylene (PE) pipes are widely used in gas distribution. Their joints are prone to various flaws and are the most problematic part of the pipeline, so the infrastructure industry requires an effective inspection technique. Butt-fusion (BF) is the most common method of joining PE pipes. In this research, we investigated the applicability of machine learning (ML) to automate the ultrasonic inspection of PE pipe BF joints. Flawless and defective joints were fabricated. A-scan signals were collected from each group of samples using a customized chord transducer, with the aim of developing and assessing the viability of ML approaches to the problem of joint classification. We compared several ML approaches to the problem and found that convolutional neural networks were most performant, classifying signals with an F1 score of 0.874 in a four-class problem (identifying defect presence and type) and of 0.912 in binary classification (defect presence/absence only). Our results show that an ultrasonic chord-type transducer approach can effectively resolve flawless samples versus those with coarse contaminants or cold fusions and that an ML approach can be used to effectively assess these ultrasonic signals. Our findings can be used to develop a portable, efficient, user-friendly, and inexpensive device for in-field joint inspections.

Modification of the standardized pressure test method for use in leakage testing of gas pipelines made of PA-12 polyamide

Before being put into operation, gas pipelines are subjected to leakage and strength pressure testing. In the case of plastic gas pipelines, a combined leakage and strength test is performed at a pressure of 1.5 ´ MOP. In Poland, in accordance with the applicable regulations, the plastic material from which gas pipelines can now be built is polyethylene. In other countries gas pipelines are also built of another material, which is PA12 polyamide. Piping systems made of this material are used to transmit gas at a pressure of 1.6 MPa. Both polyethylene and polyamide gas pipelines, after loading them with internal pressure, will undergo deformation with time, which is called the material creep phenomenon. As a result, in pressure leakage tests of gas pipelines made of thermoplastics, such as polyethylene and polyamide, it is necessary to take this phenomenon into account. Due to the different properties of polyethylene and polyamide, the amount of deformation per unit time will be different, and therefore the test procedures that are used for polyethylene gas pipelines cannot be directly used for testing polyamide gas pipelines. An example of such a procedure is the one described in point A.27 of PN-EN 805: 2002. It is mainly used for leakage testing of polyethylene water pipelines and its application for leakage testing of PA12 polyamide gas pipelines with a MOP of 1.6 MPa requires changes in the test conditions. The article presents the concept of modifying the parameters of the hydrostatic method, taking into account the different properties of PA12 pipes compared to polyethylene pipes. Particular attention was paid to the higher value of Young's modulus and the related ring stiffness of PA12 polyamide pipes compared to polyethylene pipes. In order to obtain the appropriate deformation of the pipe resulting from the material creep, the time of holding the sample under pressure was experimentally extended before starting the actual test. After establishing the required test conditions for the sealed system, tests with simulated leaks were carried out. The obtained results of tests on airtight samples and with simulated leakage confirmed the possibility of using the modified method to test the tightness of PA 12 polyamide gas pipelines with a MOP of 1.6 MPa.

Axial Pullout Behavior of Buried Medium-Density Polyethylene Gas Distribution Pipes

Abstract This paper presents an experimental investigation into the axial pullout behavior of buried medium-density polyethylene (MDPE) pipes under various pulling rates. Tests were conducted in a ...

Detection algorithm of defects on polyethylene gas pipe using image recognition

Aiming at the defects in the polyethylene (PE) gas pipeline, a defect detection algorithm based on image recognition is proposed. Firstly, the collected image is preliminarily screened to obtain the image with defects. Gamma correction algorithm is used to enhance the image, and then dual filtering is used to eliminate the interference of noise on image recognition. Then the defect edge is extracted by the improved traditional Sobel edge detection algorithm. Image defects are segmented by adaptive threshold method, and defect contours are effectively extracted through an open operation. Finally, the defect feature parameters are extracted and inputted into an optimized support vector machine for defect recognition. The experimental results show that the detection algorithm in this paper can effectively improve the observability of the image. Through the trained support vector machine, it can effectively identify the open joint, crack, and deformation defects. The recognition rate of pipeline image defects reached 96.3%.

Development of Protective Gas Pipes Sleeves for Operation in Permafrost Soils

Experimental studies were carried out and causes of emergencies with gas pipes in protective sleeves used in construction of gas pipelines were identified. Protective sleeve design has been developed that excludes deformation or destruction of gas pipeline during groundwater freezing in the annulus. Model tests of polyethylene gas pipeline in steel casing, using polyethylene foam as an element that compensates expansion of water during freezing, showed complete exclusion of deformation of gas pipes during freezing. Test results of developed designs of protective casings showed the possibility of widespread use to improve reliability and safety of gas supply.

Natural gas-supported gasification of polyethylene and wood mixtures in a porous medium reactor

Valorisation of plastic waste or forest-agroindustrial residues poses an opportunity to reduce landfilling and to obtain value-added products simultaneously. Through thermal partial oxidation, hydrocarbon fuels can be gasified and converted into syngas. Particularly, hybrid porous media reactors allow gasifying low-grade fuels in an efficient eco-friendly way. In this work, the natural gas-supported gasification of polyethylene and wood mixtures in a porous bed reactor is studied. The reactor is designed and built to operate in semi-continuous mode. The temperature evolution, the reaction wave propagation rate, and the resulting concentration of the main gas species (H2, CO, CH4, CO2, NOx, and UHC) were measured for different polyethylene and wood mixtures, keeping an optimum natural gas-to-air ratio of 0.8. The influence of the gasification conditions on the reaction pathways and the process development is analysed by sampling the system in two representative moments. The maximum syngas production was 23.86 vol%, which was obtained when loading only 100% polyethylene, while the maximum energy return on investment of 49% was registered for the highest biomass fraction in mixture. The semi-continuous operation design was validated based on the thermal behaviour and the combustion wave displacement. This experimental work shows promising results in the search for solutions to gasify solid wastes in continuous mode.

Experimental Study on Aging Performance of Polyethylene Gas Pipelines

Currently, there is a lack of adequate standards for evaluating the integrity inspection cycle of polyethylene (PE) gas pipelines. In this study, a series of photo-oxidation accelerated-aging experimental tests for PE80 gas pipe samples were performed. The attenuation laws of several critical performance parameters, such as micro-morphology, tensile strength, and thermal stability tests, were established. These parameters were determined at different aging times. A novel comprehensive performance evaluation method for pipeline integrity was developed using the analytic hierarchy process, and a reasonable inspection period for pipeline integrity was identified. The results showed that the samples experienced two stages of aging: rapid aging stage and aging platform stage. During the rapid aging stage, the comprehensive evaluation index for the aging performance decreased rapidly. However, the comprehensive evaluation index for the aging performance remained almost unchanged during the aging platform stage.

Fracture behavior of pre-cracked polyethylene gas pipe under foundation settlement by extended finite element method

Polyethylene (PE) pipes are often used for transporting gas and water, which play an important role in lifeline engineering. Such pipes, especially with notches, scratches or cracks, can be subject to actions inflicted by nature or man-made factors. To ensure that the pipes can continue to operate, even after being subjected to foundation settlement, it is necessary to study the fracture behavior of the pipes. In this work, a model was developed based on extended finite element method (XFEM) to study the fracture behavior of pre-cracked PE pipe under foundation settlement. Key parameters' effects on ultimate bearing capacity, including initial crack sizes, internal pressures and transition section length, were determined. Tensile results demonstrate that the stress-strain relationship of the pre-cracked PE pipe specimen involves two-stage, i.e., the elastic stage and the failure stage. There was obvious crack propagation in the macro fracture profile when the tensile test was performed on pre-cracked PE specimens. Simulation results demonstrate that the initial crack depth exerts a more significant influence on the ultimate bearing capacity for the pipe than the initial crack length. The internal pressure will enhance the bending resistance of the pipe, which inhibits crack propagation. In addition, the length of the transition section exerts a significant influence on crack propagation.

Linear low-density polyethylene gasification over highly active Ni/CeO2-ZrO2 catalyst for enhanced hydrogen generation

Steam-gasification of linear low-density polyethylene (LLDPE) waste to hydrogen-rich gas has been studied systematically over nickel (10wt.%) loaded on a variety of supports (Al2O3, CeO2, and CeO2-ZrO2) synthesized using a novel solvent deficient method (SDM). The hydrogen selectivity order of the catalysts was reported as Ni/CeO2-ZrO2>Ni/CeO2>Ni/Al2O3. The highest catalytic H2 selectivity of the Ni/CeO2-ZrO2 catalyst was reported to be ∼76vol.%, and was attributed to the smaller nickel crystals that were finely dispersed on the support, and to formation of Ce1-xZrxO2-δ solid solutions. The Ce1-xZrxO2-δ solid solution in the Ni/CeO2-ZrO2 catalyst was observed to be bi-functional, thus reflecting the acceleration of the water gas shift and the oxidation of carbon to CO and CO2. The better resistance of the Ni/CeO2-ZrO2 catalyst towards coke deposition also indicated its potential for commercial-scale applications for the steam gasification of plastics. Therefore, this research provides an advanced route to recycle LLDPE plastic waste into hydrogen fuel, which presents both economical and environmental benefits.