Electrofusion Research Articles

The failure mechanism of field polyethylene gas pipeline with gas leakage at electrofusion joint

PurposeA section of in-service PE gas pipeline in Guocun, Beijing, was found to appear gas leaking at the electrofusion (EF) joint. This study is dedicated to reveal the material cause of EF joint failure to help with a more accurate prediction of service life of PE gas pipe and further normalize the construction of PE gas pipeline.Design/methodology/approachDefect detection was carried out on the leaking EF joint using ultrasonic phased array. The mechanical degradation and structural aging behavior was studied by tension test, FTIR technology, TG test and DSC test. The organic components in the soil surrounding the PE gas pipe failure area were qualitatively identified.FindingsThe results showed that the organic surfactants in the soil environment could accelerate the aging behavior of PE material, leading to a deterioration of mechanical properties and a serious reduction in the ability of the PE pipe and EF joint, especially at the welding defect, to resist external force.Originality/valueA novel study was conducted to investigate the failure cause of the EF joint of in-service PE gas pipe, incorporating the analysis of environmental factors and structural deterioration.

Convolutional Neural Network Based Defect Recognition Model for Phased Array Ultrasonic Testing Images of Electrofusion Joints

AbstractThis technical brief proposes a defect recognition model to recognize four typical defects of phased array ultrasonic testing (PA-UT) images for electrofusion (EF) joints. PA-UT has been proved to be the most feasible way to inspect defects in EF joints of polyethylene pipes. The recognition of defects in PA-UT images relies on the experience of operators, resulting in inconsistent defective detection rate and low recognition speed. The proposed recognition model was composed of an anomaly detection model and a defect detection model. The anomaly detection model recognized anomalies in PA-UT images, meeting the requirement of real-time recognition for practical inspection. The defect detection model classified and located defects in abnormal PA-UT images, achieving high accuracy of defects recognition. By comparing detection models, optimizing parameters and augmenting dataset, the anomaly detection model and defect detection model reached a good combination of accuracy and speed.

Experimentation and optimization of HDPE pipe electro fusion and butt fusion welding processes

Recently, pipe welding has been widely applied in the pipe fitting operations. There are many types of pipe welding facilities available. In this research work, experimental investigations related to Electro fusion and Butt fusion welding of HDPE pipe and optimization of different welding process parameters are performed. In electro-fusion welding a fitting device is used for joining of two pipes namely called ‘fusion coupler’. Fusion coupler has a copper coil which is wounded in inner surface of coupler. Two pipes are fitted in the coupler and the current is applied in the coil with the help of kitrik pin which has provided in the coupler to generate heat and finally to create the weld. In butt-fusion welding for joining of two pipes, the welded joint is produced with the help of heated plate. After performing the welding, the joints are tested for tensile strength using universal testing machine. Two performance parameters viz. temperature and tensile strength and three process parameters viz. Starting Welding voltage, Specific fusion time and Cooling time for Electro fusion welding and Heating plate temperature, Drag pressure, Welding pressure for Butt fusion welding of HDPE pipes (82 mm inner diameter and 8 mm wall thickness) are optimized using Grey relational analysis optimization technique. The optimized parameters for electro fusion welding of these pipes are welding voltage, specific fusion time, cooling time and optimized parameters for Butt welding are heating plate temperature, drag pressure, welding pressure.

Reinforcement bars tying types in reinforced concrete

In huge reinforced concrete structures, it is often difficult to distribute the reinforcing bars, especially at the connection regions, to keep the spacing between bars within the minimum acceptable limits as recommended in the global specifications standard, by using the common methods such as, overlapping or welding, therefore, a new method for bonding was introduced, using mechanical joints and electro fusion bonding method, and comparing these methods with the maximum strength of reinforcing bars without joints and the failure location within maximum strength limits outside the joints.

Synthesis of galaxite by plasma fusion & its application in refractory for cement rotary kiln

In India, chromite is used for making magnesia chrome bricks due to its low modulus of elasticity. But the use of magnesia chrome bricks in the sintering zone of cement rotary kilns causes environmental pollution due to the formation of Cr+6 compounds. In order to meet the above challenges and to satisfy the operational demands due to use of alternative fuels, now-a-days, galaxite spinel is being used in place of chromite as a chrome free material. Galaxite is not available in nature and electro fusion is the main process by virtue of which it is industrially manufactured. However, the main drawback of electro-fusion process is both time and energy consumption. In such a backdrop, the present work has been carried out which describes the synthesis of galaxite by plasma fusion process and also the characterization of its refractory properties for application in cement rotary kilns. This alternative process is absolutely new, faster in approach and also economically viable. The developed magnesia galaxite brick shows higher performance rate and is also economically cost effective as compared to the conventional magnesia chrome and magnesia galaxite bricks, presently available in the market.

Effects of Processing Parameters on Tensile Shear Strength of Woven CF/PPS Laminates joined by Electro Fusion Welding

Effects of Processing Parameters on Tensile Shear Strength of Woven CF/PPS Laminates joined by Electro Fusion Welding

Ultrasonic Inspection of Electrofusion Joints of Large Polyethylene Pipes in Nuclear Power Plants

High-density polyethylene (HDPE) pipe has many advantages such as good flexibility, corrosion resistance, and long service life. It has been introduced into nuclear power plants for transportation of cooling water in U.S. and Europe. Recently, four HDPE pipelines (PE4710) were used in essential cooling water system with operating pressure of 0.6 MPa and operating temperature of no more than 60 °C in a newly established AP1000 nuclear power plant in Zhejiang, China. The outside diameter and thickness are 30 in. and 3.3 in., respectively, which are much larger and thicker than traditional HDPE pipe for natural gas. This brought forward a challenge for nondestructive testing (NDT) and safety assessment of such pipes. In this paper, a solution for inspecting electrofusion (EF) joints of thick-walled HDPE pipes is presented, and the results of an on-site inspection of the nuclear power plant are revealed. To expand the thickness up-limit of previously developed ultrasonic-phased array instrument, an optimization method was proposed by calculating weighing effects of different testing parameters and introducing the concept of overall performance according to practical requirement, by comprehensively considering sensitivity, penetration, signal-to-noise ratio (SNR), resolution, and accuracy. Typical defects were found in field inspection. The result shows that the presented technique is capable of inspecting EF joints for connecting large-size HDPE pipes used in nuclear power plants.

Semiautomatic High Frequency Ultrasonic Testing System for Welded Plastic Pipes

The present paper proves the feasibility of a semi-automatic control system of high frequency ultrasound for welded plastic pipes, by ultrasonic methods. The paper presents the main existing types of plastic materials, the technological joining possibilities, the problems that may occur in welding and control and the reasoning of the chosen examination method. The theoretical size of the reference ultrasonic parameters for the propagation of ultrasounds through the flawless juncture. The samples were welded using electro fusion (EF) under different working conditions. The samples were assessed circumferentially, every 10 degrees, on different working frequencies. A semi-automatic control system was designed and developed. For the optimal working frequency, a set of 10 measurements was done, in similar working conditions, on the automatic control stand, in order to test the systems’ capability and the results’ repeatability. The measured values were compared with the limits considered to be admissible using Shewhart statistic control charts.

熱可塑性CFRP積層板の電気式融着接合に及ぼす炭素繊維抵抗発熱体の影響

熱可塑性CFRP積層板の電気式融着接合に及ぼす炭素繊維抵抗発熱体の影響

위상배열초음파를 이용한 손상된 열가소성 플라스틱배관 전기융착부 비파괴검사

열가소성 플라스틱배관의 전기융착부에 대한 비파괴검사방법은 융착부의 안전성을 확보하고 장기적인 신뢰성을 확보하기 위한 방법이다. 정상적인 방법에 의하여 융착된 접합부에서도 배관의 진원도와 전기융착 소켓과의 진원도 차이 또는 기공 등에 의해 융착부에 결함이 발생할 수 있다. 본 연구에서는 위상배열초음파를 이용하여 손상된 폴리에틸렌 전기융착부의 검사를 수행하였다. 검사 대상인 250mm 직경의 폴리에틸렌 배관 전기융착부는 1994년 12월에 융착되었으며 실제 작동 압력은 2.45kPa이다. 2004년 2월 소켓 이음부 근처에서 가스가 누설되어 수거되었다. 손상된 전기융착부에 대하여 첫 번째로 육안검사를 실시하고 다음에 위상배열초음파를 이용한 비파괴검사를 실시하였다. 그리고 절단 검사를 실시하여 각각의 검사 결과와 비교하였으며 위상배열 초음파를 이용한 검사결과와 절단 검사 결과가 동일함을 확인하였다. Non destructive testing(NDT) methods of electrofusion(EF) joints of thermoplastics pipes are required for fusion joint safety and for the long term reliability of a pipe system. Electrofusion joints, which are joined at the proper fusion process and procedures, may encounter defects due to the difference of ovality between pipes and coupling, improper fusion process or porosity result from electrofusion joining. These defects can cause the failure of pipeline and by extension, they can be caused the limit to expand the use of plastics pipes. This paper studies inspection results using ultrasonic imaging method for damaged polyethylene electrofusion joints. Gas was leaking from 250mm diameter polyethylene electrofusion joints at February 2004 which was electrofused at December 1994 and operation pressure was 2.45kPa. First, surface inspection was conducted and then in order to find the types of defects examination using ultrasonic imaging method was performed. Lack of fusion and inappropriate inserting for polyethylene pipes into electrofusion coupling were found and causes of the gas leak were judged that misalignment and insert defect. Cutting inspection was performed and each inspection results were compared to. Results of ultrasonic imaging method and cutting inspection were the same.

Safety Assessment of Cold Welding Defect in Electro-Fusion Joint of Polyethylene Pipe

Cold welding defect is the most common defect in electro-fusion (EF) joint for connecting polyethylene (PE) pipe. In our previous study [1], the cold welding defect is successfully inspected by an eigen-line method based on phased array ultrasonic testing technology. However, limited research has been reported on the acceptance criterion of cold welding defect in EF joint. In this paper, the bonding strength of EF joint is measured using a peeling test. The bonding energy of welding interface is calculated both by phenomenological model and deformation energy analysis method. EF joints with different degrees of cold welding are made and used for peeling tests. The results show that the bonding energy of fused interface rises rapidly after bonding and then goes through a plateau region. The starting point of the plateau region in the bonding energy versus welding time curve is regarded as the minimum required welding time of EF joint. Based on bilinear fitting, the acceptance criterion of cold welding defect is proposed.

The impact of pulsed electric fields on cells and biomolecules: Comment on “Lightning-triggered electroporation and electrofusion as possible contributors to natural horizontal gene transfer” by Tadej Kotnik

The discovery of a horizontal gene transfer (HGT) revolutionized the evolutionary biology. Suddenly, a long developed concept of a phylogenetic tree, where all organisms share a common ancestor, could not describe the outcome of gene transfer between perceived unrelated organisms [1]. Consequently, a new concept – net of life – is emerging [1]. In the “net of life”, each organisms is a combination of shared ancestry and HGT [2]. T. Kotnik reviews the history of biological classification in the human history and positions the role of HGT in the transformation of “phylogenetic tree” to the “net of life” [3]. Although the most frequent mechanisms for HGT are biological: bacterial conjugation, bacterial competence for DNA uptake and viral transduction, T. Kotnik emphasized in this work the role of a physical phenomena – lightning – as a potential trigger of HGT. To answer the question, if HGT could happen before biological mechanisms had evolved, T. Kotnik analyzes the potential of lightening induced electroporation on HGT. Electroporation is the increase of biological cell membrane permeabilization by externally applied pulsed electric fields (PEF) [4], probably by the formation of aqueous pores in the cell membrane [5–7]. As described by T. Kotnik, the formation of pores leads to reversible electroporation (REP), electrofusion (EF), and irreversible electroporation (IEP). I would like to point out to two important properties of PEF: 1) heterogeneity of microbial population response to PEF and 2) the effects of PEF on biomolecules. In the natural marine and fresh water environments, more than two million bacteria species exist [8]. Research on food disinfection by PEF showed the tremendous variation in the different species resistance to PEF. Bacterial properties that affect the electroporation threshold are cell size and shape [9], membrane structure [10], membrane charge [11], cells concentration [12] and growth stage [13]. Given the large number of species of bacteria in marine environment it is likely that IEP, REP and EF happen simultaneously at the same depth. It appears that in nature, the number of species plays a significant role in the PEF induced effects in the population: increasing the number of species increases the probability of each of the IEP, REP and EF events. This is different from classical laboratory electroporation studies where PEF are applied on a single species to induce the desired single effect.

Development of Nondestructive Test and Safety Assessment of Electrofusion Joints for Connecting Polyethylene Pipes

Polyethylene (PE) pipes are widely used in transporting natural gas since 1960s. However, there are few published literatures on method for safety assessment of PE pipes. This paper introduces recent work in developing ultrasonic nondestructive testing (NDT) equipment and research on safety assessment of electrofusion (EF) joints of PE pipes. According to the geometrical characteristics and ultrasonic response, defects in EF joints can be divided into four categories, i.e., poor fusion interface, voids, structural deformity, and over welding. The defect of the poor fusion interface includes three typical forms, i.e., cold welding, unscraped oxide skin, and contamination of the fusion interface. Cold welding, which is the most common and dangerous defect, has been successfully detected by using ultrasonic NDT equipment and assessed with a patented cold welding Eigen-line method.

Impact analysis of clearance occurring between polymeric pipe and connector in the process of electrofusion (EF) weldment of pipes

In this investigation, all parameters having impact on quality of electrofusions (EF) welding of polyethylene pipes were reviewed. Among those outstanding points recognized, one has been carefully and selectively studied. Impact of clearance between fittings and pipes and its effect on the strength of EF weldment at such a location has been chosen for analysis. Obtained results from modeling of finite element of EF fitting in ANSYS have been compared with the actual experiments conducted in the welding process. Convergences of the findings on comparison basis are satisfactory. Quality of welding has been measured mechanically through tension testing of the welded pieces. Two points in particular have been scrutinized while conducting the test: first, tensile strength of the weld and then elongation of the weld surface at rupture point.

Application of Neuro-Wavelet Algorithm in Ultrasonic-Phased Array Nondestructive Testing of Polyethylene Pipelines

Polyethylene (PE) pipelines with electrofusion (EF) joining is an essential method of transportation of gas energy. EF joints are weak points for leakage and therefore, Nondestructive testing (NDT) methods including ultrasonic array technology are necessary. This paper presents a practical NDT method of fusion joints of polyethylene piping using intelligent ultrasonic image processing techniques. In the proposed method, to detect the defects of electrofusion joints, the NDT is applied based on an ANN-Wavelet method as a digital image processing technique. The proposed approach includes four steps. First an ultrasonic-phased array technique is used to provide real time images of high resolution. In the second step, the images are preprocessed by digital image processing techniques for noise reduction and detection of ROI (Region of Interest). Furthermore, to make more improvement on the images, mathematical morphology techniques such as dilation and erosion are applied. In the 3rd step, a wavelet transform is used to develop a feature vector containing 3-dimensional information on various types of defects. In the final step, all the feature vectors are classified through a backpropagation-based ANN algorithm. The obtained results show that the proposed algorithms are highly reliable and also precise for NDT monitoring.

Defects classification and failure modes of electrofusion joint for connecting polyethylene pipes

AbstractAs electrofusion (EF) technology is widely used in connecting polyethylene (PE) pipes and other plastic pipes or composite pipes, research in safety assessment of EF joints has been of major concern. EF joints with defects are very common in practical applications. These defects may greatly reduce the mechanical performance of the EF joints and threat safety running of the pipeline system. To evaluate hazard of these defects and provide a basic understanding for the failure mechanism of EF joints, a comprehensive study on defects and failure modes is conducted in this work. The defects in EF joints are classified into four categories: poor fusion interface, over welding, voids, and structural deformity. The forming reasons of these defects are analyzed in detail. The mechanical properties of EF joint containing these defects are investigated by conducting peeling tests and sustained hydraulic pressure tests. Test results show that there are three main failure mode of EF joint under inner pressure, that is, cracking through the fusion interface, cracking through the fitting, and cracking through copper wire interface. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

A Model for Predicting Temperature of Electrofusion Joints for Polyethylene Pipes

With the increasing application of electrofusion (EF) welding in connecting polyethylene (PE) pipes for gas distribution, more effort has been invested to ensure the safety of the pipeline systems. The objective of this paper is to investigate and understand the temperature distribution during EF welding. A one-dimensional transient heat-transfer model was proposed, taking the variation in the rate of power input, the phase transition of PE, and the thermal contact conductance between heating wire and PE into consideration. Then, experiments were designed to verify the power input and the temperature. The measured values of the power input were shown to be in good agreement with the analytical results. Based on ultrasonic test (UT), a new “Eigen-line” method was presented, which overcomes the difficulties found in the thermocouples’ temperature measurements. The results demonstrate good agreements between prediction and experiment. Finally, based on the presented model, a detailed parametric study was carried out to investigate the influences of the variation in the power input, the physical properties of PE, and the thermal contact conductance between heating wire and surrounding PE.

Cloned blastocysts produced by nuclear transfer from somatic cells in cynomolgus monkeys (Macaca fascicularis)

In nonhuman primates (NHPs), there have so far been few reports about nuclear transfer (NT), especially using adult somatic cells. The objective of this study was to determine the developmental competence of NT embryos derived from various somatic cells embryonic stem (ES), amniotic epithelial, cumulus, or fetal fibroblast cells] and the nuclear transfer method, such as electro fusion or piezo microinjection, activation with chemical reagent [ionomycine/6-dimethylaminopurine (DMAP), calcium ionophore A23187/DMAP, or cycloheximide (CHX)] and reprogramming time (1, 2, or 4 h; in this study, the duration from injection or fusion to activation was defined as the reprogramming time). Our results showed that a 1-h reprogramming and activation with ionomycin/DMAP are suitable for NT in monkeys. Developing cleaved embryos up to the six-cell stage was similar among all experiments. However, beyond the eight-cell stage, developmental rates were higher in NT embryos reconstructed with fetal fibroblast cells and amniotic epithelial cells, and we were able to produce NT blastocysts from these cells. Interestingly, electro fusion is sufficient for amniotic epithelial cells and piezo microinjection is better suited for fetal fibroblast cells to produce NT blastocysts, thus suggesting that the best method for somatic cell NT may be different between cell types.

Exposure to the electrofusion process can increase the immunogenicity of human cells.

The cellular products obtained following electrofusion (EF) of dendritic cells (DC) and tumour cells have shown promise as cancer vaccines. The immunogenicity of these preparations has been attributed to the presence of small numbers of DC-tumour hybrids and the contribution of the non-hybrid tumour cells present has received little attention. In this report, we investigated the effect of the EF process on the immunogenicity of allogeneic human cells, in particular the colorectal cell line, SW620. EF conditions were optimised to yield the maximum number of DC-SW620 hybrids co-expressing tumour associated antigen (TAA) and DC associated antigens. Exposure of SW620 to EF induced significant increases (P < 0.05) in apoptosis and necrosis. Pre-exposure of SW620 to the EF buffer alone [0.3 M glucose, 0.1 mM Ca(CH3COO)2 and 0.5 mM Mg(CH3COO)(2)] resulted in significant increases in TAA uptake by DC during co-culture (P < 0.05). DC phenotype was, however, not altered by exposure to EF treated tumour cells. In co-cultures of PBMC responders with SW620, the levels of IFNgamma release and cytotoxic activity were significantly increased (P < 0.05) by pre-exposure of the SW620 to EF. Pre-exposure of allogeneic non-T cells, the colorectal cell line Lovo and a breast cancer cell line (MCF7) to EF also significantly (P < 0.05) increased the levels of IFNgamma release by responding PBMC. These results demonstrate that the EF process itself can increase the immunogenicity of at least some human cell types independently of hybrid formation. These findings suggest that EF protocols should be evaluated with regard to the possibility that DC-tumour hybrids may not contribute all, or even most, of the immunostimulatory capacity present in preparations of EF treated cells.

Investigation of appropriate cooling times for electrofusion jointing of PE pipes for gas distribution

AbstractThis study evaluates three types of fusion zones between electrofusion (EF) joints and pipes that were laid underground after three different cooling times following fusion. The study establishes the relationship between the cooling time and the fusion performance. The object was to determine an appropriate cooling time for EF jointing. Only a slight difference was observed in the molecular structure, e.g., the degree of crystallinity, while distinct differences were observed in deformation, morphology, and tensile creep strength. Based on these results, the effect of a temperature profile during the cooling process on the fusion zone was simulated. The simulation showed that the state of the fusion zone (melting, semi‐solid, or solid) when the pipe was laid underground was the main factor affecting the tensile creep strength, i.e. long‐term performance. These analyses provided criteria for choosing an appropriate cooling time.