Lifetime Of Pipes Research Articles

Non-collinear wave mixing to determine physical ageing in PVC pipelines

The ultrasonic signal amplitudes obtained from non-collinear wave mixing has previously shown significant changes for physically aged Poly-Vinyl Chloride (PVC) pipes, demonstrating the method's effectiveness in assessing the ageing condition of PVC. However, the exact relationship between the measured amplitudes and the extent of physical ageing in PVC has yet to be established. Additionally, it has not yet been validated against established methods or applied to determine the service lifetime of PVC pipes. This study outlines a three-step process to validate the effectiveness of the non-collinear wave mixing technique for assessing the physical ageing of PVC pipelines. Firstly, the non-collinear wave mixing results are compared with the established laboratory method of differential scanning calorimetry, to validate the scattered wave amplitude measurements. Secondly, employing the Arrhenius relation, service lifetime estimates derived from non-collinear wave mixing results align within the expected magnitudes, emphasizing the technique's potential for in-situ pipeline inspections. Finally, a material model is utilized to estimate the Third Order Elastic Coefficient (TOEC) m based on the measured amplitudes, demonstrating a linear correlation with annealing time. A 50% change in TOEC m signifies a brittle state, indicating a high risk of failure. A combination of experimental and analytical analyses highlighted TOEC m variations as the primary factor influencing non-collinear wave mixing amplitude changes during physical ageing. This comprehensive approach also highlights the importance of incorporating diverse factors to precisely forecast and oversee the performance of PVC pipes in real-world environments.

The Effectiveness of Na<sub>2</sub>CrO<sub>4</sub> to Inhibit Corrosion Rate of a A106 Grade Pipe in the Furnace Circulating Cooling Water with the Weight Loss Method on Pipe Lifetime Determining

Pipes from industrial process flow diagrams have a predictable risk of failure or damage, so that periodic inspections are carried out. Corrosion that occurs in the pipe can cause a risk of leakage or blockage of the pipe flow which can be fatal to the fluid distribution process. This damage can be anticipated by inhibitors adding and predicting the corrosion rate. This research was conducted to determine the effective concentration of Na2CrO4 inhibitor to inhibit the corrosion rate and predict the lifetime of the furnace cooling water circulation pipe using the weight loss method. Na2CrO4 inhibitor is a type of anodic inhibitor that works by passively the anode by inhibiting corrosion on a whole metal surface. The study begins with the preparation stage, cutting the pipe into specimens of a certain size, smoothing the surface and weighing the initial weight. The testing phase was carried out by immersing the specimens at various times of 120 h, 240 h and 360 h with Na2CrO4 inhibitor variations concentration was 0%; 0,3%; 0,6%; and 0,9%. The corrosion rate was calculated by re-weighing the specimen after the immersion process. The results showed that the most effective inhibitor concentration was 0.6% with a corrosion rate of 0.3021 mmpy and the Remaining Service Lifetime (RSL) was 9.399 years.

Damages in vitrified clay sewers in service for 130–142 years

The aim of the study was to analyze the damage occurring in vitrified clay sewers operated for a period of 130–142 years based on the results of their CCTV testing. In view of the fact that there are very large differences in the assessment of the forecast lifetime of sewer pipes, as reported by the different institutions, and significant differences in the survival functions developed for these pipes, particular attention has been paid to identification of the causes of this situation. One of the most important results of the research and analyses conducted is demonstration that models predicting the durability of vitrified clay pipes and the survival functions created for them should be developed separately for sewers laid in dry soils and water-saturated soils. The research has also shown that various so-called primary damages were observed in sewers, which occurred during transport, storage, and installation of pipes. Failure to take into account the possibility of these damages in the durability models being developed and in the related survival functions makes it impossible to predict the actual durability of these pipes. An analysis of the results also confirmed the thesis formulated on the basis of studies of vitrified clay pipes in Canada that the deterioration of vitrified clay pipes is not age-dependent when the pipes are properly designed and installed, with no damage during installation.

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.

Numerical investigation of the effect of moisture and impurity on long-term creep behavior of polymer composite pipes

Nowadays, composite pipes, due to their unique properties such as high stiffness to weight ratio and excellent corrosion resistance, play a significant role in the industry. Composite pipes are usually loaded by internal hydrostatic pressure for a long time. Therefore, their long-term creep behavior has been considered as a severe issue. Although the experimental method is a reliable and standard studying method, it is costly and time-consuming, especially in creep studies. Therefore, researchers have been looking for alternative methods. In this regard, the primary purpose of this study is to model the long-term creep behavior of composite pipes considering moisture and impurities, such as short fibers and sand layers (which are commonly used in composite pipes). In this research, a comprehensive approach is provided, relying on available short-term creep experimental data on the pure resin, to predict the long-term behavior of each type of composite, particularly composite pipes. By employing Python script, the high-level algorithm is developed to model the creep behavior of lamina by using the micromechanics model considering the impurity. The effect of stress on the viscoelastic behavior of lamina is modeled. Then creep behavior of a lamina is developed to composite laminates by employing a finite element model. Finally, the failure in the laminated composite is examined. The results predicted by the present study have a good agreement with available experimental data. Results reveal that moisture reduces the lifetime of composite pipes. Furthermore, results are extended for 50 years, and the failure pressure is estimated, which the percent error is 2.6% approximately compared to available experimental data.

Incorporating use phase chemical leaching and water quality testing for life cycle toxicity assessment of cross-linked polyethylene (PEX) piping

Life cycle assessment (LCA) is increasingly being considered in material selection decisions for residential drinking water piping, but chemical leaching during the use phase has typically been excluded, even though the delivery of safe water is the core function of water distribution infrastructure. We have quantified the contribution of leached organics to life cycle human toxicity of piping materials through the integration of empirical leaching data within LCA. Eight cross-linked polyethylene (PEX) pipe brands were examined. Upstream emissions from PEX pipe production were combined with empirical total organic carbon (TOC) data from leaching tests for new pipes. The total mass of organic contaminants ingested over the pipe's lifetime was estimated by fitting leaching data with kinetic models and integrating leaching concentrations and daily water use over time, rather than using an initial concentration that does not accurately depict actual lifetime exposures. Potential human toxicity from use phase ingestion was evaluated using a range of human effect factors from the consensus USEtox model to create plausible bounds of toxicity through different exposure and effect scenarios. New non-carcinogenic human toxicological effect factors were derived for approximately half of the 62 leached organic compounds identified. Results indicate that potential human toxicity from upstream pipe production generally exceeds use phase toxicity, but that leached contaminants can be a substantial contributor to overall life cycle toxicity, depending on the PEX brand, particularly for carcinogenic effects. Deleterious effects can be reduced both by thorough system flushing after initial installation and periods of stagnation, but also through improvements in manufacturing processes that reduce upstream emissions. The bounding approach demonstrates a viable method for considering water quality in LCA when comprehensive characterization and concentration data are not available.

Long-term testing methods for HDPE pipe - advantages and disadvantages: A review

High-density polyethylene (HDPE) has become a material of interest for culverts and drainage pipelines as a result of its numerous advantages. The issue of service-life expectancy of HDPE pipes made with recycled versus virgin resins has been the focus of research studies over the past several years. A number of recent studies have confirmed that HDPE is durable with an extended service-life performance of over 100 years. Nevertheless, exposure criteria, such as environment and service conditions, could affect pipe service life. Consequently, giving specific figures on the durability of HDPE pipes needs to be clearly addressed. Such concerns were raised by Quebec’s Ministry of Transportation (MTQ) to assess the durability of HDPE pipes made with recycled or virgin resins taking into consideration exposure conditions in northern climates. This paper provides an overview of the research on the main factors and mechanisms that affect HDPE pipe lifetime. Methods for predicting the lifetime durability of HDPE pipes—including the creep rupture strength, stress crack resistance, and oxidation—are introduced, emphasizing the advantages and disadvantages of each technique. Studies conducted on the fatigue performance of the pipes are highlighted. Moreover, an overview of studies on the use of HDPE pipes manufactured with recycled resins for transportation infrastructure applications is also presented.

Lifetime estimation of heat pipes in space applications using particle filtering, Arrhenius and FIDES methods

As one of the thermal management elements, heat pipes are frequently used in cooling or heat recovery systems. They are devices that can quickly transfer large amounts of heat with a slight temperature difference between hot and cold sources. The present study aims to evaluate and measure the lifetime of heat pipes in space applications such as spacecraft and satellites. In order to investigate the lifetime of heat pipes in different operating temperatures, three prediction methods of particle filtering, Arrhenius, and FIDES are applied. Innovative approaches are adopted to combine the Arrhenius and FIDES methods besides adjusting the FIDES method for mechanical devices. The failure times at the accelerated temperatures are estimated through the particle filtering method as well as linear and exponential regressions, and failure times at the operating temperatures are estimated by the Arrhenius model. The FIDES method adds more aspects of reliability to the prediction procedure, such as the quality of the used materials, technical conditions of the manufacturing process and the stress cycles applied to the heat pipes. A sensitivity analysis is also performed on the failure criteria. The results show that the failure time for the heat pipes is between 12 and 60 years, which entirely fits the related standards.

Severity of emergency natural gas distribution pipeline incidents: Application of an integrated spatio-temporal approach fused with text mining

The transportation of natural gas often relies on pipelines which require constant monitoring and regular maintenance to prevent spills or leaks. Pipeline incidents could pose a huge adverse impact on people, the environment, and society. Numerous efforts have been invested to identify contributing factors to pipeline incidents so that countermeasures could be developed to proactively prevent some incidents and reduce incident severities or impacts. However, the countermeasures may need to vary for different incidents due to the potential heterogeneity between incidents, and such heterogeneity is likely related to the geology, weather, and built environment which vary across space and time domain. The objective of this study is to revisit the correlates of pipeline incidents, focusing on the spatial and temporal patterns of the correlations between natural gas pipeline incident severity and contributing factors. This study leveraged an integrated spatio-temporal modeling approach, namely the Geographically and Temporally Weighted Ordered Logistic Regression (GTWOLR) to model the natural gas pipeline incident report data (2010–2019) from the U.S. Pipeline and Hazardous Material Safety Administration. Text mining was performed to extract additional information from the narratives in reports. Results show several factors have significant spatiotemporally varying correlations with the pipeline incident severity, and these factors include excavation damage, gas explosion, iron pipes, longer incident response time, and longer pipe lifetime. Findings from this study are valuable for pipeline operators, end-users, responders to jointly develop localized strategies to maintain the natural gas distribution system. More implications are discussed in the paper.

Monitoring of mechanisms of formation of corrosive aggressiveness of soils and grounds of underground gas pipeline routes and on its basis assessment of service life of gas pipes in various soil-climatic zones

The experience of studying the problem of corrosive aggressiveness of soils and grounds in terms of improving the reliability of Gazprom’s pipeline systems operation is summarized and presented. Soil factors causing surface corrosion of gas pipelines in soil conditions are studied. Based on the obtained results, it was suggested to evaluate not only the corrosive aggressiveness of soils and the gas pipe lifetime, but also the corrosive resistance of pipe metal in corrosive environments. Special attention is paid to the stress corrosion cracking formation mechanism.

Soil Load on Plastic Pipe and its Influence on Lifetime

Abstract Lifetime of plastic pipes can be estimated by integration of a power law describing the crack kinetics. However, this procedure requires an FEM (finite element method) calculation of the possible crack propagation in the pipe to obtain stress intensity factor dependency on the crack length. It is very important for the simulation to consider every possible load that is acting on the pipe. This contribution deals with FEM modelling of a pipe that is loaded by internal pressure, residual stresses and soil loads. Comparison of the factors and pipe lifetime estimation is carried out.

Probabilistic failure investigation of small diameter cast iron pipelines for water distribution

At present, a significant proportion of Australia’s ageing water infrastructure is composed of cast-iron pipes. The corrosion of cast-iron pipes is the main triggering factor for Australia’s water industry. It has been found that the failure mode of small diameter water mains (<300 mm external diameters) from Yarra Valley Water is mainly the longitudinal failure (hoop-stressed) instead of broken back failure, which is unexpected. Therefore, the purpose of this paper is to examine the failure mechanism of longitudinal failure of small diameter cast-iron pipes. The observational failure database provided by Yarra Valley Water show limited data availability. This has stimulated the focus of this paper: to examine the corrosion mechanism by utilising probabilistic inverse analysis for unknown physical parameters. Focusing on the likelihood of failure, this paper investigates the performance of small diameter cast-iron pipes by using statistical analysis based on the observational failure lifetime data within pipe cohorts. Background studies on the deterioration of cast-iron pipes due to corrosion are made to help set up the probabilistic physical modelling (PPM). Using the updated corrosion parameters, the lifetime probabilities of failure and the hazard rate of the cast iron model are derived from PPM. Last, it is found that the modelling results agree reasonably well with prediction curves of statistical data, indicating that the proposed method for pipe lifetime prediction is promising.

Predicting remaining lifetime of drill pipes basing upon the fatigue crack kinetics within a pre-critical period

he research results are obtained without any support in the form of grants or projects. The authors express their gratitude to the Academician of the National Academy of Sciences of Ukraine, Professor Ye.I. Kryzhanivskyi for his specialized consultations and discussions of the research result.

Critical lifetime of HDPE pipes through damage and reliability models

Damage models are not directly applicable on high-density polyethylene (HDPE) pipes. In this paper, static and strain-unified theory damage models are adapted to fit the HDPE case by substituting the dynamic tests’ endurance limits by preloading simulation through notch and stiffness evaluation. Then, tensile and burst tests are following up to evaluate the specimens’ residual life. Compared to virgin specimens, the rupture limit of old HDPE pipes’ specimens had dropped significantly and their elongation decreased from 275 mm to about 26 mm. The degradation of the seven categories of specimens are different. Indeed, the degradation is too noticeable, disappearance of the plastic phase, for the categories 6 and 7, which are in the bottom of the pipe. Then, a reduced plastic phase on the lateral categories 4 and 5 showing an important impact of degradations. Finally, a larger plastic phase for the categories 1 and 2 taken from the top of the pipe, showing a medium impact of degradation. Thus, the use of the stiffness factor, reflecting the variability of degradation of the different categories of specimens, and the thickness reduction as life fractions for both aged and neat HDPE specimens was possible. The developed strains damage model compared to static burst pressures’ one confirmed the damage stages and the critical life fraction of HDPE pipes. By comparing these models, the drastic change of HDPE pipes’ behavior, from a ductile to a brittle one, have been proved. These findings allowed us to find out the critical life fraction of neat and old HDPE pipes, which has been confirmed by comparing the burst pressure curves of a notched and an old pipe. The presented approach is cost effective allowing a deep analysis of HDPE pipes failure and damage quantification through simply made models based on static tensile and burst test instead of tedious and very costly dynamic ones.

Accelerated testing method to estimate the long‐term hydrostatic strength of semi‐crystalline plastic pipes

The ability to quickly develop predictions of the service lifetime of plastic pipes at different load levels allows designers to choose the best plastic material and design pipe for a specific application. Additionally, it helps material producers to rapidly design, manufacture, test, screen, and modify the base polymeric material. The aim of this study is to introduce a combined experimental and analytical framework to develop accelerated lifetime estimates for semi‐crystalline plastic pipes which is sensitive to the structure, orientation, and morphology changes introduced by changing processing conditions. To accomplish this task, high density polyethylene (HDPE) is chosen as the exemplary base material and custom fixtures are developed to admit tensile and hoop burst tests on the as‐manufactured HDPE pipes. A pressure‐modified Eyring flow equation is employed to predict the rupture lifetime of HDPE pipes using the measured mechanical properties under uniaxial tensile and compression loading in different temperatures and strain rates. The method allows the prediction of pipe service lifetimes in excess of 50 years using experiments conducted over approximately 10 days instead of the traditional 13 months. POLYM. ENG. SCI., 60:879–888, 2020. © 2019 Society of Plastics Engineers

Lifetime prediction of natural gas polyethylene pipes with internal pressures

Abstract The purpose of this study was to propose a lifetime prediction model of aging natural gas polyethylene (PE) pipeline with various internal pressures by thermal-oxidative aging (TOA) test and oxidative induction time (OIT) test. By using a pressured natural gas PE80 pipe under the condition similar to actual urban natural gas working condition, an improved TOA experimental set-up was built, and had been used for accelerated TOA test of pressured PE pipes at different test temperatures. By using dynamic curve linearization method and based on Arrhenius fit of the data, an empirical lifetime prediction model of thermal oxidative aging law for PE pipes was developed to extrapolate lifetime of PE80 pipes with internal pressures. The results show that under the test internal pressure of 0.1 MPa, 0.2 MPa, 0.3 MPa, and 0.4 MPa, the lifetimes of aging PE gas pipes with internal pressure are 14%, 24.5%, 36.1%, and 41.6% shorter than those without internal pressure.

Creep Lifetime Assessment of Pressure-Tight Pe100 Pipes Based on a Slow Fatigue Crack Growth

Polyethylene pipes are widely used in water supply, gas, and sewage systems due to their excellent mechanical properties. A slow crack growth is the primary fracture mechanism for the pipes under long-term internal pressures. If the creep loading is treated as a special case of fatigue loading, the slow crack growth kinetics of polyethylene is defined in fatigue fracture tests at different stress ratios and extrapolated to creep crack kinetics. Linear elastic fracture mechanics concepts became the basis for predicting the creep lifetime of pressure-tight pipes subjected to various hoop stresses from extrapolated (synthetic) creep crack growth curves, and the prediction is in good agreement with the standard extrapolation in accordance with ISO 9080.

Optimal conditions for accelerated thermal ageing of district heating pipes

Technical lifetime prediction of polymeric materials is often based on accelerated ageing tests at elevated temperatures. Samples are exposed to relatively high temperatures to accelerate the natural degradation processes. For district heating pipes, accelerated thermal ageing is the ordinary method used to determine the lifetime of pipes. According to the Standard EN 253:2009 + A1:2013, the district heating pipes shall be subjected to an accelerated thermal ageing for a long period of time at 160 ˚C or 170 ˚C. The lifetime is determined by extrapolation using the Arrhenius relationship. However, papers published recently have questioned this method, especially the high temperatures used for ageing of the pipes and the use of Arrhenius equation to describe the complicated degradation mechanisms, which can result in the erroneous estimation of the technical lifetime.Our investigation has shown the complexity of the pipe’s degradation mechanisms. The behaviour of mechanical shear strength at elevated temperatures (T > 130 °C), suggests an alteration rather than an acceleration of the degradation mechanisms. Accelerated ageing tests should reproduce the proper natural ageing mechanisms. The analyses of PUR’s thermal conductivity and its chemical structure by FTIR confirmed the degradation patterns.

Polyolefins Made with Dual Metallocene Catalysts: How Microstructure Affects Polymer Properties

AbstractSlow crack growth resistance correlates with the lifetime of polyethylene pipes. Since this measurement may take considerable time, alternative ways to estimate it help expedite the development of new polyethylene resins. The primary structural parameter (PSP2), calculated from the distribution of molecular weight and short chain branching of polyethylenes, can predict the stress crack growth resistance of polyethylene resins without needing to measure it over long periods of time. In this investigation, a model is developed to calculate PSP2 of ethylene homopolymers and ethylene/1‐hexene copolymers made with two metallocene catalysts. For each metallocene, the effect of the following parameters on PSP2 is investigated: (1) polymer mass fraction, (2) polymer average molecular weight, and (3) average comonomer fraction. The simulation trends agree with previously published experimental results. The generated 3D surface response plots are useful guides for the design of polyethylenes having optimized slow crack growth resistance.

ANALISIS REMOVAL SCALING SILIKA PADA JALUR RE-INJEKSI BRINE PEMBANGKIT LISTRIK ENERGI PANAS BUMI DENGAN MENGGUNAKAN ASAM FLUORIDA

Silica scale formation on the brine re-injection lines of geothermal power plants can lead to serious problems because it increased pressure drop and failure of the safety devices. One of the most effective methods to solve the problem is acidification of silica scaling using hydroflouric acid (HF). HF has a unique characteristic that is highly reactive with SiO2, easily obtained in the market and cheap. The use of HF can increase the rate of material corrosion in re-injection lines material. The use of HF should be adjusted to the appropriate concentration so it can dissolve silica scale optimally without shortening its life service. The concentration of HF used in the experiment were 5, 10, and 15% wt. The results showed that the optimum concentration of HF in dissolving silica at 15%. This is due to its ability to dissolve the crust mostly greatest than most other concentration that is equal to 21% of the total dissolved silica. The rate of corrosion on the material re-injection line with a concentration of 15% is equal to 0.647 mm/y and provide about 4.63 years life time of pipe.