Metal Pipes Research Articles

Method for measuring the mineralization of aqueous solutions in pipeline flows

A description of the hardware–software complex designed and manufactured for the operational assessment of the concentration of a dissolved substance in a water stream on the lower surface of metal pipes in various technological lines without sampling is presented. At the Trofimuk Institute of Petroleum Geology and Geophysics SB RAS the dependences of the electrical conductivity of aqueous solutions on temperature were studied under specific conditions – in an electrically conductive cell. Physical experiments were performed using solutions of different mineralization (from 0.5 to 300 g/L), in a measuring cell made of steel of small volume (8.14 cm3). Mathematical modeling of solution mineralization assessment has been performed.

Thermographic Investigation on Fluid Oscillations and Transverse Interactions in a Fully Metallic Flat-Plate Pulsating Heat Pipe

The present investigation deals with the quantification of fluid oscillation frequencies in a metallic pulsating heat pipe tested at varying heat loads and orientations. The aim is to design a robust technique for the study of the inner fluid dynamics without adopting typical experimental solutions, such as direct fluid visualizations through transparent inserts. The studied device is made of copper, and it is partially filled with a water–ethanol mixture (20 wt.% of ethanol). Heat fluxes locally exchanged between the working fluid and the device walls are first assessed through the inverse heat conduction problem resolution approach by processing outer wall temperature distributions acquired by thermography. The estimated local heat transfer quantities are therefore processed to quantify the fluid oscillatory behavior in every device branch during the intermittent flow and full activation regimes, thus providing a deeper insight into the heat transfer modes. After dealing with a further validation of the inverse approach in terms of oscillation frequency restoration capability, the wall-to-fluid heat fluxes referred to each channel are processed by means of the wavelet method. Scalograms and power spectra of the considered signals are presented for a time-based analysis of the working fluid oscillations, as well as for the identification of dominant oscillation frequencies. Fluid motion is then quantified in terms of the continuity of fluid oscillations and activity of channels by applying a scalogram denoising technique named K-means clustering method. Moreover, a statistical reduction of the channel-wise dominant oscillation frequencies is performed to provide useful references for the interpretation of the overall oscillatory behavior. The link between oscillations and transverse interactions is finally investigated. The vertical bottom-heated mode exhibits stronger fluid oscillations with respect to the horizontal mode, with fluid oscillation frequencies ranging from 0.78 up to 1 Hz. Nonetheless, the fluid motion is more stable in terms of oscillation frequency between channels when the device operates in the horizontal orientation probably due to negligible buoyancy effects. Moreover, thermal interactions between adjacent channels are found to be stronger when the oscillatory behavior presents similar features from channel to channel in horizontal orientation. The proposed method for fluid oscillation analyses in fully metallic flat-plate pulsating heat pipes can be effectively adopted to other flat-plate layouts without any need for transparent windows, thus reducing the overall complexity of experimental set-ups and providing, at the same time, a good insight into the inner fluid dynamics.

Using the Corner Reflection for Depth Evaluation of Surface Breaking Cracks in Concrete by Ultrasound

The corner echo is a well-known effect in ultrasonic testing, which allows detection of surface breaking cracks with predominantly perpendicular orientation to the surface as, for example, corrosion cracks in metal pipes or shafts. This echo is formed by two planes, the surface of the crack and the surface which the crack breaks. It can also be classified as a half-skip method, since a reflection of the pulse occurs on the backwall before the reflection at the defect takes place. In combination with the diffraction from the crack tip, the corner echo also allows crack sizing. As shown in this paper, the corner reflection can be used in civil engineering for nondestructive inspection of concrete. Commercially available low frequency ultrasonic arrays with dry point contact sources generate SH transversal waves with sufficient divergence of the sound field in order to detect corner reflections. Ultrasonic line-scans and area-scans were acquired with a linear array on flat concrete specimens, and the data were reconstructed by the Synthetic aperture focusing technique. If the angles and the area of reconstruction are chosen accordingly, the corner echo reflection can be distinguished from other ultrasonic information. The corner echo can thus be used as a method for deciding whether a crack is a partial-depth crack or a full-depth crack and thus for obtaining a statement about crack depth. This paper presents corresponding experimental results obtained on concrete specimens with artificial test defects and cracks induced under controlled conditions.

Design of a simple side-incident TE11 mode microwave probe for nondestructive pipe inspection

This study proposed a simple side-incident TE11 mode microwave probe for the rapid and long-range inspection of cracks in metallic pipes. The probe feeds the microwaves to a metallic pipe, which works as a waveguide; the reflection signal provoked by a defect is measured for detection and localization. The probe enables the detection of both circumferentially and axially oriented cracks, unlike those reported in earlier studies. To achieve better performance, numerical simulations were conducted to evaluate the conversion efficiency and optimize the insertion length of the coaxial cable and the exposed length of the cable core wire. The simulation results suggest that the optimized probe configuration is feasible for pipes with various diameters by proportionally changing the current probe configuration. Although injected microwaves propagated in two directions, the ratio of microwaves to one direction could be controlled by adjusting the inclination angle and the exposed length of the cable core wire. Subsequently, three TE11 probes fabricated according to the simulation results were used to detect circumferential and axial slits in a brass pipe. The results showed that circumferential slits in the vertical positions (parallel to the nontilted coaxial cable) and axial slits in the horizontal positions (perpendicular to the nontilted coaxial cable) caused large reflections, consistent with the electromagnetic field distribution of the TE11 mode microwaves in a circular waveguide. Further experiments verified the feasibility of the designed probe for pipes with different diameters and for directional pipe inspection.

A Low-Cost Through-Metal Communication System for Sensors in Metallic Pipes

Metallic pipes and other containers are widely used to store and transport toxic gases and liquids. Various sensors have been designed to monitor the environment inside metallic pipes and containers, such as pressure, liquid-level, and chemical sensors. Moreover, sensors are also used to inspect and detect pipe leakages. However, sensors are usually placed outside of the metallic pipes and containers and use ultrasound to monitor the internal unseen environment. This is mainly due to the fact that internal sensors cannot communicate with external data sinks without cables, but using cables can dramatically affect the metal-sealed structure. Wireless communication is desirable to communicate with internal sensors, but it experiences high attenuation losses since metal can block wireless signals due to its high conductivity. This article develops a low-cost through-metal communication system prototype using off-the-shelf electronic components. The system is fully reconfigurable, and arbitrary modulation and coding schemes can be implemented. We design a transmit module which includes a signal processing microcontroller, an amplifier, and a transmit coil and the receive module which includes a receive coil, an amplifier, and a microcontroller with demodulation algorithms and bit-error-rate (BER) calculations. The performance of the prototype is evaluated using various symbol rates, distances, and transmission power. The results show that the communication system can achieve a 500-b/s data rate with 0.01 BER and 3.4-cm communication range when penetrating an aluminum pipe with 7-mm thickness.

Development of a phased array flexible Rayleigh-wave electromagnetic acoustic transducer for pipe inspection

In this paper, a novel Phased Array fully Flexible Rayleigh-wave EMAT (PAFR-EMAT) suitable for inspection of curved surface based on flexible coil bias field magnet EMAT is proposed. The PAFR-EMAT consists of a flexible racetrack coil generating long pulsed bias magnetic field instead of the conventional permanent magnets, and flexible meander coils triggered in sequence to induce transient eddy current for exciting enhanced Rayleigh wave of MHz frequency. Based on the Lorentz force mechanism, pulsed electromagnetic fields and the generated ultrasonic waves of the proposed new EMAT are studied through numerical simulation at first. Experiments are conducted then to check the practical performance of the PAFR-EMAT for pipe inspection. Results show that the PAFR-EMAT has good performance in Rayleigh wave generation for inspection of the curved surface of metallic pipe and is capable to detect surface crack of small depth.

Evaluation of the applicability of microwave nondestructive testing to crack detection on a pipe inner surface

This study explores the applicability of microwave nondestructive testing to detect a metal pipe’s inner crack. Three-dimensional finite element simulations were conducted to study the inspectability of cracks using microwaves in different modes and the dependency of the reflection characteristics of microwaves on crack size. The simulation results showed that microwaves in the TM01 and TE01 modes can detect circumferential and axial cracks, respectively. The positive relationship between crack size and intensity corresponding to the reflected microwaves was obtained in simulations and then verified by experiments. In both simulations and experiments, the axial crack length showed a small influence on the results, especially for shallow crack detection. In the experiments, circumferential and axial cracks with a width of 0.3 mm were detected using microwaves. The experimental results revealed that signal amplitudes decreased when a slit penetrated a pipe wall, probably due to a microwave leakage.

Evaluation of the different inner and outer channel geometry combinations for optimum melting and solidification performance in double pipe energy storage with phase change material: A numerical study

Phase change materials (PCMs) have become preferable among latent heat storage methods due to their high energy storage densities and low energy losses. These properties of PCMs make it possible to use them in applications such as thermal storage of solar energy, cooling of electronic equipment, energy storage for buildings, and cooling of engines. Double-pipe energy storage (DPTES) with PCM can be used in cases where the production and consumption times of the thermal energy obtained from sources such as solar energy, geothermal water, and waste gas do not match. The fact that the thermal conductivity coefficients are quite low is one of the obstacles to the commercialization of PCMs and their use in more applications. Double-pipe energy storage (DPTES) with PCM can be used especially in cases where the production and consumption moments of the thermal energy obtained from solar energy do not match. In studies on DPTES with PCM, methods including different pipe geometries, extended surfaces, different PCM materials, microencapsulation of PCMs, eccentric inner pipe placement, nanoparticle usage, and metal foam addition have been investigated to increase thermal conductivity. The novelty of this study was to examine the effects of different inner and outer channel combinations on melting and solidification performance. In this direction, nine different inner and outer channel combinations of basic geometric shapes were modeled. Among these combinations, the combination with the highest melting rate and the shortest charging time was determined. Afterward, melting and solidification analyzes were made at the different positions of the inner and outer channels for the combination selected, and the most suitable energy storage design was created to make the most efficient use of the existing heat source. The results of the analysis revealed that the optimum design for melting, and solidification performance was the triangle-in-square configuration. With this configuration, it was increased the melting rate by 1.1 times and accelerated the charging time by 20 % for a 40-minute charging period compared to conventional DPTES (circle-in-circle). In addition, for the melting and solidification periods, the inverted and vertical placement of the triangle in the square revealed the best results. It was observed that the effect of the relative positions of the square and the triangle on the solidification rate was negligible. It is predicted that the results given in this study will be useful in designing the most compatible inner and outer channel geometries to increase energy storage efficiency in DPTES systems.

INVESTIGATION OF SCALE FORMATION ON GLASS PIPE COATINGS

The results of theoretical and experimental studies of the influence of scale deposits on heat exchange processes in vitrified pipes washed by seawater are presented. Experimental studies have shown that during long-term operation of heat exchangers, minor scale deposits with a layer thickness of up to 0.4 mm are observed on the surface of glass coatings of pipes, while a strong scale layer up to 2 mm thick is formed on the inner surfaces of metal pipes. The practical absence of deposits in vitrified pipes is explained by the increased cleanliness of the glass surface and its resistance to aggressiveness of substances dissolved in sea water. This eliminates the formation of large foci of scale on the glass surface and washing off the formed scale with a stream of seawater.

Optimization of Plating Process on Inner Wall of Metal Pipe and Research on Coating Performance.

An innovative brush plating process for preparing coatings on the inner wall of metal pipes is proposed, which aims to solve the limitations of current electroplating technology and improve the performance of the inner walls of metal pipes. While optimizing the process, the effect of working voltage on the microhardness, thickness, surface morphology, corrosion resistance, and elastoplasticity of the Ni coating on the inner wall of the tube was studied under the new process. The results indicate this technique can produce high-quality coatings on the inner wall of pipes in a simple and efficient manner. As the working voltage increases, the surface quality and comprehensive performance of the coating show an increasing trend followed by a decreasing trend. At 12 V, the coating exhibits the highest surface density and uniformity, the lowest surface roughness, the best corrosion resistance, and the maximum microhardness of 575.8 HV, with a corrosion current density of 1.040 × 10-5 A·cm-2, a corrosion rate of 0.122 mm·a-1, the maximum elastic recovery ratio he/hmax of 0.36, and the best deformation resistance. This study demonstrated the effectiveness of this method in improving the durability and functionality of metal pipes and its potential for various industrial applications.

Surface equilibrium and thermodynamics implications of the corrosion inhibition of mild steel in acid medium using quinine inhibitor

One problem faced by industries is the degradation of their metal pipes and machine parts which are exposed to chemically aggressive media. This has necessitated the search for cheap and non-toxic substances that can limit corrosion. The inhibition potential of quinine against the corroding of mild steel in 1M HCl medium was tested under varied concentration of quinine and temperature, using gravimetric method. The results showed that corrosion rate and weight loss decreased with increasing concentration of quinine and temperature up to 40 °C, while surface coverage, θ, and inhibition efficiency IE, increased as the concentration and temperature increased. Surface equilibrium studies showed that the inhibition action followed the Freundlich isotherm with value of adsorption intensity that suggests a cooperative adsorption mechanism in heterogeneous sites while thermodynamic analysis implied that the process of inhibition was endothermic having a positive value of ΔH (17.384 kJ mol-1), enthalpy-driven with a negative ΔS (-64.434 kJ mol-1K-1) and occurred by a physisorption mechanism. Positive ΔG obtained at the studied temperatures suggests that the corrosion process was rendered passive and unfeasible. These findings project quinine as a promising inhibitor for chemical degradation of mild steel in hydrochloric acid medium.

ASSESSMENT OF THE STATE OF STRESS AND DEFORMATION OF METAL CORRUGATED PIPE STRUCTURES TAKING INTO ACCOUNT ITS DIAMETER AND THICKNESSES OF THE CORRUGATED SHEET

The analysis of research works on the assessment of the stress-strain state of prefabricated metal corrugated structures of transport facilities was performed. It was established that the stresses and deformations of structures made of ZMGK depend on a complex of influencing factors: the amount of static and dynamic loads, the height of the backfill above the vault of the structure, the parameters of corrugation waves, etc. However, the interconnected effect of the pipe diameter and the thickness of the metal corrugated sheet on the stresses that occur in the metal pipe structures has not been established. The object of research is metal corrugated pipe constructions. To assess the stress state of the pipe, the influence on the stress of the cross-section of the pipe and the thickness of the metal corrugated sheet of the structure are taken into account. It was established that the geometric parameters of the cross-section of the pipe and the thickness of the metal corrugated sheet of the structure have a significant influence on the stress state of metal corrugated pipe structures. When the diameter of the pipe increases, the amount of stress that occurs in metal structures increases. However, with an increase in the thickness of the corrugated sheet, the amount of stress, with the same pipe diameter, decreases. Increasing the thickness of the sheet from 3.0 mm to 7.0 mm leads to a decrease in the stresses in the pipe metal by 50.39%. When the diameter of the pipe changes from 1.0 m to 6.0 m with a metal thickness of the corrugated sheet equal to 3.0 mm, the magnitude of the stresses increased by 7.38 times, with a sheet thickness of 4.0 mm ‒ by 7.8 times, with a thickness of 5.0 mm sheet – 8.08 times, 6.0 mm sheet thickness – 8.28 times, and 7.0 mm corrugated pipe sheet thickness – 8.43 times. It was established that the gradual increase in the thickness of the corrugated sheet of the structure leads to a decrease in the stress difference between the previous thickness of the sheet and the increased one. With a pipe diameter of 6.0 m, the stress difference that occurs when the thickness of the corrugated sheet is 3.0 mm and 4.0 mm is 21.35 MPa, with a thickness of 4.0 mm and 5.0 mm, the stress difference is 14.16 MPa, at 5.0 mm and 6.0 mm, the difference in stress values is 10.25 MPa, and with increased sheet thickness from 6.0 mm to 7.0 mm, the difference in stress values is 7.76 MPa. The obtained results of the stress state of prefab metal corrugated pipe structures can have practical application in the case of acceptance of the technical and economic justification, regarding the determination of the pipe diameter and the thickness of the metal corrugated sheet of the structure. One of the limitations of the application of these research results is the assessment of the stress state of the pipe made of prefabricated metal corrugated structures with the parameters of the corrugated waves of 150×50 mm. Other parameters of corrugation waves are not taken into account in this study.

Study on Corrosion of Buried Metal Pipeline by Stray Current Along Metro Line

This year, with the continuous improvement of China's subway system, serious corrosion problems of metal buried pipelines laid along the subway have attracted social attention. In order to discuss the corrosion mechanism, this paper briefly describes the corrosion status and characteristics of the subway stray current on the buried metal pipes, and introduces the characteristics of the subway stray current on the buried metal pipes, such as fast corrosion speed, large strength and wide influence range. The corresponding corrosion mechanism is summarized, and the detection and protection methods of stray current at home and abroad are introduced. Including pipe to ground potential test, soil potential gradient test, test piece method or polarization probe method test, current probe method test, intelligent stray current detector (SCM) test, corrosion inspection piece test, etc. The protection method of "giving priority to plugging, taking drainage as auxiliary, combining plugging with drainage, and strengthening monitoring" is proposed.

INTENSIFICATION OF HEAT TRANSFER IN HEAT EXCHANGE EQUIPMENT DURING CONDENSATION OF WATER VAPOR AFTER STEAM TURBINE INSTALLATIONS IN NUCLEAR POWER.

The determining parameter that characterizes the intensity of heat transfer in heat exchange equipment is the heat transfer coefficient, the value of which depends on the thermal resistances occurring in the corresponding equipment. Thus, in the heat exchanger-condenser of a steam turbine installation of a nuclear power station, this is the thermal resistance during heat transfer of cooling water in heat exchange tubes and during heat transfer of water vapor condensing in the intertube space. The value of the heat transfer coefficient also depends on the geometric and thermophysical characteristics of the heat heat exchange tubes, on the contamination of the cooling water, on the presence of air in the condensing vapors. According to the proposed scheme of the experimental setup of the "pipe in a pipe" type, calculations of the heat transfer coefficient were performed when using an external transparent glass pipe and an internal metal pipe, which was treated from the outside with a water-repellent coating that provides dropwise condensation of water vapor, as well as without treatment for film condensation. Contamination of the cooling water and the presence of air in the water vapor in both cases of condensation should be the same and as minimal as possible. The analysis of the results of the calculations allows us to draw the following conclusions: the change in the state of the outer surface of the heat exchange tubes increases the heat transfer coefficient during condensation of water vapor almost three times, which ensures an increase in the efficiency of heat transfer (more than 10%), and accordingly allows to reduce the working surface of the heat exchange equipment, which is especially relevant in modern conditions of operation of power equipment, when there is a need for emergency reconstruction of partially destroyed heat exchange equipment. Bibl. 11, Fig. 2.

A Novel Dual-Permanent-Magnet Mechanical Antenna for Pipeline Robot Localization and Communication

The demand for pipeline inspection has promoted the development of pipeline robots and associated localization and communication technologies. Among these technologies, ultra-low-frequency (30-300 Hz) electromagnetic waves have a significant advantage because of their strong penetration, which can penetrate metal pipe walls. Traditional low-frequency transmitting systems are limited by the size and power consumption of the antennas. In this work, a new type of mechanical antenna based on dual permanent magnets was designed to solve the above problems. An innovative amplitude modulation scheme that involves changing the magnetization angle of dual permanent magnets is proposed. The ultra-low-frequency electromagnetic wave emitted by the mechanical antenna inside the pipeline can be easily received by the antenna outside to localize and communicate with the robots inside. The experimental results showed that when two N38M-type Nd-Fe-B permanent magnets with a volume of 3.93 cm3 each were used, the magnetic flux density reached 2.35 nT at 10 m in the air and the amplitude modulation performance was satisfactory. Additionally, the electromagnetic wave was effectively received at 3 m from the 20# steel pipeline, which preliminarily verified the feasibility of using the dual-permanent-magnet mechanical antenna to achieve localization of and communication with pipeline robots.

Effect of domestic pipe materials on microbiological safety of drinking water: Different biofilm formation and chlorination resistance for diverse pipe materials

Microbial biofilms that develop in pipe walls can pollute domestic water systems. Understanding biofilm formation and its chlorine resistance in domestic pipe materials will help reduce the possibility of microbial pollution. This study investigates microbial biofilm formation and chlorine resistance in three representative domestic pipes: polypropylene random (PPR), stainless steel (SS), and copper. Biofilm formation determined using crystal violet staining, heterotrophic plate count, and adenosine triphosphate, and extracellular polymeric substance (EPS) content of several typical bacteria were determined before and after disinfection in the different pipe materials. Bacteria in PPR pipes develop significantly more biofilm biomass than in the two metal pipes. EPS content was highest in copper pipe, while lowest biofilm biomass and EPS contents was displayed in SS pipe. The bacteria with more biofilm biomass in three pipe materials appeared to be different. Bacterial chlorine resistance did not differ significantly between the three pipe materials. The chlorine resistance of the same single-species biofilm appeared to vary in the pipe materials, and it was influenced by physiological state of bacterial cells, such as EPS. The data reveal the significant effects of domestic pipe materials on biofilm properties, which mean the possibility of microbial pollution is different.

A thermodynamically consistent model for hydraulic transients in metallic pipes undergoing elasto-viscoplastic deformations

This work presents an extension of the fluid transient analysis to include the elasto-viscoplastic behavior of the pipe material. A previously developed quasi-2D flow model is employed as a basic framework, and the pipe’s elasto-viscoplastic behavior is added by considering constitutive equations formulated via an internal variables theory. The resulting governing equations form a non-linear hyperbolic system of partial differential equations whose approximated solutions are obtained by employing the method of characteristics followed by the Newton–Raphson method. The model is thermodynamically consistent, a feature that is consistently detailed in this work to uphold the application of energy-based theoretical analyses of the phenomenon. Taking as reference the transient responses obtained from an experimental installation that simulates an accident, the present approach is found to be fully consistent and valuable for simulating fast hydraulic transients in metallic materials experiencing plastic deformation. By comparing the pressure fluctuations of models with and without elasto-viscoplasticity, more attenuation and dispersion of the pressure responses are found when such behavior is considered. The elasto-viscoplasticity effect on the pressure responses is better understood when the connection between the viscoplastic mechanisms and energy dissipation is exposed. During the fluid transient, the pipe dissipates meaningful amounts of energy that cause a significant alteration in the whole fluid–pipe dynamics. Another numerical example, based on a hypothetical water hammer flow that causes plastic deformation in the pipeline, is also addressed. Such a case puts in evidence that not only the anelastic behavior of the pipe must be taken into account but also that an accurate description of the fluid friction may be significant to portray realistically fluid transient responses. At last, an assessment of the pipe integrity by means of a scalar damage variable theory is carried out to emphasize the application prospects of the present research.

Computational analysis of conductive fluid flow with tangential components of magnetic flux density and electric field in metallic and non-metallic circular pipe

This paper has focused on the study of flow characteristics of a steady conductive fluid through a circular pipe in the presence of an applied transverse uniform magnetic field. A numerical simulation of the fluid flow was performed using a multi-physics computational tool. The radial velocity distribution due to the effect of the tangential component of induced magnetic flux density and electric fields at various axial positions is examined in metallic and non-metallic surfaces of the circular pipe. This simulation study helps to analyse the effect of drag force on the variation in axial velocity close to the metallic and non-metallic walls. The induced electric potential is directed along the normal to the Laplacian tangential surface of the pipe. In addition to that, sigmoidal-shaped field profiles are observed when the fluid flow crosses from the upstream to downstream of the magnet edge and vice versa along the axial length of the circular pipe. Simultaneously, it is observed that the average velocity of the fluid flow decreases for a laminar and increases for turbulent Reynolds number. Streamline plots pertinent flow variable such as flow velocity are presented for non-conducting and conducting walls.

Preliminary assessment of the possibility to use large-diameter pipes of Х52 steel for transportation of pure gaseous hydrogen under pressure

To assess resistance to hydrogen embrittlement caused by the presence of hydrogen in the transported product, and, accordingly, suitability of pipes for hydrogen transport, the base metal of large-diameter pipes of X52 strength class manufactured by JSC “ChelPipe” (part of the PJSC “TMK” group of companies) was studied. The work included the study of pure gaseous hydrogen effect under pressure up to 10 MPa on change in mechanical characteristics of the base metal of large-diameter pipes (LDP) during preliminary hydrogen charging for various time periods in a stationary autoclave under pressure, and during simultaneous loading with a slow strain rate (SSRT) under expected operating conditions. Results of the X52 LDP metal study show that there is no significant impact on the effect of gaseous hydrogen under pressure for up to 144 hours on mechanical characteristics of the base metal determined by static uniaxial tension (decrease in ductile characteristics does not exceed 9 %). During SSRT at a rate of not more than 1·10–6 s–1 in pure gaseous hydrogen environment under a pressure of 10 MPa, the change in strength and ductile characteristics does not exceed 13 % in comparison with reference tests in nitrogen environment under the same pressure. The results obtained allow us to consider that the base metal of low-alloy pipe steel with ferrite-perlite microstructure of X52 strength class is sufficiently resistant to hydrogen embrittlement. Final confirmation of the possibility to use LDP made from steel under study will be the results of further qualification tests, including the study of the weld metal and heat-affected zone properties.

Fatigue analysis of metallic-plastic-metallic pipeline systems: A numerical study

Metallic (e.g., copper, steel and iron) and plastic (e.g., Polyethylene and Polyvinyl chloride) pipelines are often used in combination in water distribution networks (WDSs). The interface between a metallic pipe section and a plastic pipe section is typically associated with a significant change in hydraulic impedance (i.e., impedance mismatch). This impedance mismatch can result in significant pressure wave reflections during transient events, and multiple interfaces may induce repeated pressure waves bouncing in between. Limited studies have been conducted on the impact of these multiple wave reflections due to impedance mismatch, especially with respect to the risk of accelerated fatigue damage to the plastic pipe. The research presented in this paper investigates the pressure response of a metallic-plastic-metallic (M-P-M) pipeline system under repeated hydraulic transient events using analytical and numerical methods. The presence of additional cyclic hoop-stress loadings in the M-P-M configuration, both in frequency due to reflections and in loading magnitude due to superposition, has been demonstrated in comparison to a fully plastic pipe system under the same hydraulic transient event. The study investigates the impact of these additional loadings on the relative fatigue lifetime of the plastic section by adopting a fatigue analysis model based on the stress-life method. The results show that the plastic section in the M-P-M configuration can have a significant reduction in fatigue lifetime compared to the corresponding fully plastic configuration.