Pipe Test Research Articles

Environmental stress cracking of polyethylene pipe: Changes in physical structures leading to failure

The environmental stress cracking resistance (ESCR) was studied for pipe made of bimodal poly(ethylene-co-1-butene) copolymer. Ductile or brittle failures of the pipe were observed after pipe exposure to different temperatures and hydrostatic pressures. Changes in the phase composition, size of crystalline and amorphous domains and molecular mobility were studied in failed test pipes by DSC, SAXS, solid-state 13C NMR spectroscopy and time-domain 1H NMR T2 relaxometry. The ESCR test at 20 °C causes a decrease in crystallinity, which suggests lamellar fragmentation, whereas a slight crystallinity increase is observed at a test temperature of 70 °C. At both temperatures, molecular mobility in the amorphous phase decreases, suggesting stress-induced elongation of chain segments in the amorphous phase. ESCR tests at 95 and 110 °C led to crystallinity increases and lamellar thickening owing to partial melting and recrystallization during long-term pipe exposure to high temperatures. The test causes an increase in molecular mobility in the amorphous phase due to a change in partitioning of ethyl chain branches between the crystal-amorphous interface and the amorphous phase. The role of molecular mobility in the amorphous phase on the type of failure and on reorganization of semicrystalline morphology during the ESCR test is discussed.

Introducing a Precise System for Determining Volume Percentages Independent of Scale Thickness and Type of Flow Regime

When fluids flow into the pipes, the materials in them cause deposits to form inside the pipes over time, which is a threat to the efficiency of the equipment and their depreciation. In the present study, a method for detecting the volume percentage of two-phase flow by considering the presence of scale inside the test pipe is presented using artificial intelligence networks. The method is non-invasive and works in such a way that the detector located on one side of the pipe absorbs the photons that have passed through the other side of the pipe. These photons are emitted to the pipe by a dual source of the isotopes barium-133 and cesium-137. The Monte Carlo N Particle Code (MCNP) simulates the structure, and wavelet features are extracted from the data recorded by the detector. These features are considered Group methods of data handling (GMDH) inputs. A neural network is trained to determine the volume percentage with high accuracy independent of the thickness of the scale in the pipe. In this research, to implement a precise system for working in operating conditions, different conditions, including different flow regimes and different scale thickness values as well as different volume percentages, are simulated. The proposed system is able to determine the volume percentages with high accuracy, regardless of the type of flow regime and the amount of scale inside the pipe. The use of feature extraction techniques in the implementation of the proposed detection system not only reduces the number of detectors, reduces costs, and simplifies the system but also increases the accuracy to a good extent.

Experimental Evaluation of Water Supply Pipe Joints against Seismic Ground Deformation: A Four-point Bending Test

Due to permanent ground deformation (PGD) such as earthquakes and liquefaction, water supply pipes and connected joints may experience rotation and deflection through losing its function and complex water contamination. Since the specifications of joints are different in each country, evaluating joints are difficult to manage the functional maintenance of water network system. In this study, two metallic and three non-metallic pipe joints were selected through the joints commonly used in Korea. PGD simulation could be conducted through Four-point bending test which derives the result of deflection angle, moment, and strain value for damaged pipes. Each component showed above M-1 grade which resulted based on the grade of ISO 16134. To compare metallic pipe results, collar joint showed stronger binding force than the mechanical joint, but in deflection angle result mechanical showed higher value. In non-metallic pipe test, since its material contains large flexibility, strain value mainly affected its result. Based on this study, functional evaluation of water supply pipeline regarding the PGD was identified through comparing tendency of each joint characterization. Moreover, these data can be expected to be utilized as the basis of performance evaluation and critical component in piping design.

Centrifuge modelling of whole-life pipe–soil interaction in clay with different overconsolidation ratios

The touchdown zones of steel catenary risers and lazy wave risers are fatigue hotspots, where the risers interact continuously with the seabed due to hydrodynamic loading exerted on the host vessel. The whole-life interactions can range from small-amplitude daily motion cycles to motions that involve large-amplitude cyclic interaction with the seabed during storm events. A key design challenge that affects the fatigue life of these risers is the accurate modelling of the evolution of the riser–soil stiffness, throughout the whole life of the riser and for different soil conditions, including overconsolidated conditions, which may occur due to the geological history, ageing or biochemical processes of the sediments. This paper describes centrifuge model pipe tests simulating whole-life riser–soil interaction in normally consolidated and uniform overconsolidated clay samples, under successive sequences of cyclic motions. Results confirm that the whole-life soil stiffness evolution depends strongly on cyclic amplitudes, with reconsolidation-induced soil stiffness recovery after heavy remoulding, and is also influenced by the soil overconsolidation ratio, with a reduced tendency for soil hardening at higher soil overconsolidation ratios. This study provides insights into the relevant cyclic soil stiffness to consider when assessing the whole-life design of risers interacting with overconsolidated seabed sediments.

Evaluation of Cross-Sectional Deformation in Pipes Using Reflection of Fundamental Guided-Waves

Ultrasonic guided-wave technology has been successfully applied to detect multiple types of defects in pipes. However, cross-sectional deformation, which is a common defect, is less studied when compared with structural discontinuity defects in pipes. In this paper, the guided wave is employed to detect cross-sectional deformation. First, the effect of sectional deformation parameters on the reflection of guided waves is analyzed using a series of three-dimensional (3D) finite-element (FE) models, and the deformation parameters affecting the reflection are examined in light of the physics of the guided waves based on the FE results. The results show that the reflection occurs at the start of the cross-sectional deformation, while the subsequent gradual deformation region does not cause reflection. The reflection coefficient is dependent on the axial deformation severity, and the mode conversion ratio is dependent on the circumferential deformation extent. Second, an experimental study was conducted to evaluate guided-wave reflection characteristics due to pipe cross-sectional deformation in a realistic situation. Test pipes with local and overall deformations were manufactured, and the reflection from both types of deformation was investigated experimentally. The results show good agreement between the experimental measurement and the FE prediction. Two quantitative parameters, axial deformation rate δ and circumferential deformation rate β, are defined to represent the cross-sectional deformation, and are found to correlate well with the reflection coefficient and mode conversion ratio. The ratio of δ/β is suitable to be used to judge the deformation type.

Modeling of multiple crack initiation in polymer pipes under oxidative environment

In this study, a novel fundamental model for the multiple crack initiation behavior of polymer pipes transporting fluids with strong oxidizing agents was proposed. Because the oxidant diffuses into the polymer medium with consumption by oxidation, a volumetric sink of the diffused oxidant was considered. The degradation kinetics of the polymer pipes were modeled by diffusion using the reaction equations. To compare the released energy with the crack initiation, Green's function for the stress intensity factor of various crack numbers, sizes, and standard dimension ratios (SDRs) was developed. The number of crack initiations and durations were successfully simulated using potential energy analysis with cracking. At a relatively low internal pressure in an oxidative environment, multiple cracks were estimated with a proper scale of the crack length. Instead, it was predicted that one main crack would be initiated at a higher level of internal pressure. In addition, the knee points representing the slope change of the internal pressure-lifetime plot were shown between these different failure modes, in agreement with previous observations. The experimental results of sustained hydrostatic pressure tests of polymer pipes under chlorinated water can be accurately simulated by the proposed model.

THE EFFECT OF CORROSION DAMAGE ON THE OPERATION OF PIPELINES

Corrosion in trench-dipped pipelines occurs in areas of contact with soil and air, in areas of transition from one to another, and this can be a very serious cause. The purpose of this article is to study the effect of heterogeneous coatings applied to the surface of pipelines at the soil-air boundary on the rate of corrosion. Standard accepted methods can be used to study the electrochemical effects: the pH of the medium in which the pipe is laid and the difference between the electrode potentials on the metal surface of the pipe. During the testing of pipes, they should be covered with anticorrosive coatings.The purpose is to determine the extent to which anti-corrosion coatings during corrosion affect the corrosion of the pipe, which leads to a reduction in the rate of corrosion, while sharply reducing the depth of the wounds, which means a 20% reduction in metal loss. Keywords: main pipe, corrosion, differential aeration, protective coating.

Ring Hoop Tension Test for yield strength estimation: Numerical analysis for a novel correlation method and applicability for mechanical testing of tubes and pipes

The tubes and pipes manufacturing industry characterizes the mechanical properties of their products with a wide selection of standards, but most of them are qualitative testing methodologies. To estimate the mechanical properties from a quantitative point of view there are limited options in standards. In that sense, the standard tensile test is the preferred alternative by the manufacturers, but this option limits the mechanical estimation for the longitudinal direction of the tube–pipe product. Particular efforts have been made to design an alternative mechanical testing procedure to characterize the mechanical properties in the hoop direction of pipes and tubes. The Ring Hoop Tension Test (RHTT) was designed to fill this gap, but it shows limitations related to the required tooling and the influence of the frictional contact between the tooling and the ring specimen. In the nuclear industry, the Small Ring Test (SRT), a miniature test derivated from the RHTT, has been investigated in recent years. In this investigation, a novel RHTT was designed to overcome the limitations of SRT and RHTT, and a new procedure was implemented to estimate the yield strength of tubes and pipes. Numerical FEM simulations were performed to reach an optimum estimation method for the yield strength with the specific geometry of the SRT and a wide selection of pipe geometries with the RHTT. A set of hypothetical materials were designed to perform these analyses, taking into account the influence of Young’s modulus, proportional limit, hardening coefficient (based on the Ramberg–Osgood law), and presence of Lüders bands straining. To verify the results obtained from this numerical FEM analysis, experimental tests (standard tensile tests and RHTTs) and metallographic analysis were performed on aluminum Al 6063 T6 and copper C12200 R360 tubes, showing the capability of this optimized RHTT to estimate the yield strength in the hoop direction for anisotropic tubes and pipes.

Energy-based damage model incorporating failure cycle and load ratio effects for very low cycle fatigue crack growth simulation

An energy-based damage model for simulating very low cycle fatigue (VLCF) crack growth is proposed to improve the prediction accuracy of our previous model. Modifications are made to explicitly include the terms related to failure cycle and load ratio. The parameters related to these terms are determined from mean fatigue life model of the material. The proposed damage model is validated by comparing with through-wall cracked pipe test data for Type 316 stainless steel. Predicted failure cycles are very close to experimental data, improving the prediction accuracy of our previous model. Comparison of fracture surfaces also shows good agreement.

Objective and subjective evaluation of various aspects of hand performance considering protective glove’s constructional parameters

Hands are one of the most vital parts of the body, and many tasks are carried out by hands. Particularly in industrial environments, hands may be exposed to various dangers and consequently injuries; thus protection of them is of great prominence. In this study, the effects of wearing a group of industrial protective gloves on hand performance, were investigated. The mentioned gloves varied in terms of material, thickness, and also the amount of layers. This research evaluates the effect of gloves’ constituent materials, including tarpaulin, leather, and protective layers such as neoprene and spacer, and a cotton nonwoven layer for added hand comfort, on hand performance. Objective and subjective experiments were performed for the assessment of pain threshold force, hand strength (dynamometers and gripping/lifting pipe test), tactile sensitivity (“two-point” discrimination method), and manual dexterity (bolt closure, valve opening, and wrist motion range tests) and an acceptable linear correlation was obtained between the objective and subjective (Thurston’s pair-comparison judgments) outcomes. The results showed that wearing gloves and increasing the number of gloves’ layers, improved the protective performance concerning the increased pain threshold tolerance. On the other hand, wearing multi-layer protective gloves decreased the gloved hand tactile sensitivity, strength capability, and also the range of finger and wrist motion as a measure of manual dexterity.

Evaluation and comparison of different detection technologies on simulated voids near buried pipes

Erosion voids near buried pipes may reduce the service lives of buried infrastructure assets and present a concern to municipalities as they are difficult to detect accurately and effectively. Various technologies exist to detect erosion voids but limited testing has been performed to evaluate their effectiveness. In order to evaluate and compare different existing erosion void detection technologies, a blind experiment (i.e., without operators having prior information about void locations and geometries) was conducted. Two kinds of pipes were used for the evaluation: a corrugated steel pipe and a reinforced concrete pipe. A total of five artificial voids were made near the pipes. Four commercially available void detection technologies were evaluated: (i) conventional Backscatter Computed Tomography (BCT), (ii) handheld BCT, (iii) Ground Penetrating Radar (GPR) and (iv) Pipe Penetrating Radar (PPR). Additionally, Infrared Thermography (IRT) was also employed by the authors although this was not a blind study. Each technology and the data provided by that technology are presented. Based on the results, Handheld BCT and IRT were recommended for initial detection of the voids near corrugated steel pipes. To obtain higher accuracy and geometry detail, conventional BCT and PPR were suggested for the corrugated steel pipe and concrete pipe, respectively. GPR was able to detect a large void simulated between the two test pipes.

Three-dimensional nonlinear vibration model and fatigue failure mechanism of deepwater test pipe

In deepwater test condition, the riser–test pipe (tubing string) system (RTS) is subject to the vortex-induced effect on riser, flow-induced effect on test pipe and longitudinal/transverse coupling effect, which is prone to buckling deformation, fatigue fracture and friction perforation. To resolve this, the three-dimensional (3D) nonlinear vibration model of deepwater RTS is established using the micro-finite method, energy method and Hamilton variational principle. Based on the elastic–plastic contact collision theory, the nonlinear contact load calculation method between riser and test pipe is proposed. Compared with experimental measurement results, calculation results using the proposed vibration model in this study and the single tubing vibration model in our recent work, the correctness and effectiveness of the proposed vibration model of the deepwater RTS are verified. Meanwhile, the cumulative damage theory is used to establish the fatigue life prediction method of test pipe. Based on that, the influences of outflow velocity, internal flow velocity, significant wave height, as well as top tension coefficient on the fatigue life of test pipe are systematically analyzed. The results demonstrate that, first, with the increase in outflow velocity, the maximum alternating stress and the annual fatigue damage rate increased. The location where fatigue failure of the test pipe is easy to occur at the upper “one third” and the bottom of test pipe are easy to occur fatigue failure. Second, with the increase in internal flow velocity, the “one third damage effect” of the test pipe will decrease, and the “bottom damage effect” of the test pipe increased that needs the attention of field operators. Third, during field operation, it is necessary to properly configure the top tension coefficient so that there can be a certain relaxation between the riser and the test pipe, so as to cause transverse vibration and consume some axial energy and load. The study led to a theoretical method for safety evaluation and a practical approach for effectively improving the fatigue life of deepwater test pipe.

Foundations for a Fission Battery Digital Twin

As the nuclear industry moves toward construction of microreactors and next-generation reactors, these efforts pose new challenges. A digital-twin tool will reduce costs and risk through integration of the disparate systems used in the design, construction, and operation of these reactors. Recent investments at Idaho National Laboratory (INL) in open-source digital engineering and multiphysics framework development provide a foundation from which to create and evaluate a digital twin for nuclear reactors. This digital-twin tool will use the Single Primary Heat Pipe Extraction and Removal Emulator (SPHERE) and Microreactor AGile Non-nuclear Experimental Testbed (MAGNET) as case studies to develop a digital twin with both single and 37 heat pipe test articles. The digital twin will provide the capabilities of remote monitoring and unattended operation (autonomous control) of these systems. A digital twin is a digital replica of an operating asset that can display data received from live sensors, update a physics model for the asset with the received data, compute predictive results of operational status with artificial intelligence (AI) to aid in optimizing asset use, and apply asset control accordingly. This twin will be developed through integration of the open-source technologies Deep Lynx (a data-warehouse technology) and the Multiphysics Object-Oriented Simulation Environment (MOOSE), physical-asset sensors, and physical-asset controls. Specifically, the general AI will successfully predict the events described as MAGNET heat pipe article test cases (such as heat pipe failure) using integrated data from the MAGNET sensors and physics-based models, including developed meta models. The integration of open-source INL software and AI assets with sensor data from a test bed will lead to a repeatable framework and guide for the creation of future digital twins. The team will also perform AI model training and experimentation to determine what models and features are most important to enable intelligent, autonomous control as well as to evaluate and determine best practices for digital-twin cybersecurity.

Study of the Hydraulic Performances of Two Inducers in Water—CO2 Mixture—Toward Performance Improvement With Suppression of Prerotation

Abstract The inducers increase the pressure available at the inlet of the impellers of centrifugal pumps. This technological solution may induce instabilities, such as prerotating flow at partial flow rates. The scientific literature offers studies on the cavitation in the inducers, as well as on the associated instabilities. However, studies describing devices that improve the behavior in these unstable regimes are rare. This is particularly true for fluids like aviation fuels or liquids with dissolved gases. In this work we expose, an experimental study for two axial inducers carried out at low flow rates in cavitating and noncavitating regimes in a closed-loop equipped with a transparent test pipe. The working liquid is water with and without dissolved CO2. We employ a camera and a high-speed camera to take the photographs of the dynamics of the cavitation structures. The experimental campaign provided results of head breakdown comparison. The added dissolved CO2 gas at a concentration of 300 mg L–1 does not change the overall inducers' performance in noncavitating regime. The paper presents also the impact of some of inducers' geometrical parameters on their cavitating performance. The authors observed prerotating flow instability, which they tried to decrease by incorporating a grooved ring into the inlet side of the inducers. It is found that prerotating structures are much less developed in the upstream when a grooved ring is employed.

Applying Data Mining and Artificial Intelligence Techniques for High Precision Measuring of the Two-Phase Flow’s Characteristics Independent of the Pipe’s Scale Layer

Scale formation inside oil and gas pipelines is always one of the main threats to the efficiency of equipment and their depreciation. In this study, an artificial intelligence method method is presented to provide the flow regime and volume percentage of a two-phase flow while considering the presence of scale inside the test pipe. In this non-invasive method, a dual-energy source of barium-133 and cesium-137 isotopes is irradiated, and the photons are absorbed by a detector as they pass through the test pipe on the other side of the pipe. The Monte Carlo N Particle Code (MCNP) simulates the structure and frequency features, such as the amplitudes of the first, second, third, and fourth dominant frequencies, which are extracted from the data recorded by the detector. These features use radial basis function neural network (RBFNN) inputs, where two neural networks are also trained to accurately determine the volume percentage and correctly classify all flow patterns, independent of scale thickness in the pipe. The advantage of the proposed system in this study compared to the conventional systems is that it has a better measuring precision as well as a simpler structure (using one detector instead of two).

Investigation on three-dimensional vibration model and response characteristics of deep-water riser-test pipe system

Under deep-water test conditions, a riser-test pipe system (RTS) is subject to the vortex-induced effect on the riser, flow-induced effect on the test pipe, and longitudinal–transverse coupling effect. Further, the system is prone to buckling deformation, fatigue fracture, and friction perforation. A three-dimensional (3D) nonlinear vibration model of deep-water RTS was established using the micro-finite method, energy method, and Hamilton variational principle. Based on the elastic–plastic contact collision theory, a nonlinear contact load calculation method between the riser and test pipe was proposed. According to field parameters in the South China Sea and the similarity principle, a vibration test bench for the RTS was designed. The experimental measurement results and the calculation results obtained from the proposed vibration model and the single tubing vibration model developed in our recent study were compared. Based on this comparison, the correctness and effectiveness of the proposed vibration model of the deep-water RTS were verified. Then, the vibration characteristics of the RTS for the BY5-2-1 well in the South China Sea were analysed. The results demonstrate that, first, in the vibration fatigue analysis of the test pipe, the influence of its own local high-frequency vibration cannot be neglected. Second, long-term collisions will cause friction and wear failure in the RTS. In the safety analysis of the RTS, the wear problem of the RTS caused by the collision between the riser and test pipe cannot be neglected. Third, the position where the test pipe is prone to strength failure is mainly located in the upper and lower parts. The field designer should focus on the safety of the pipe at these locations.

Micromachined Thermocouple for Rapid Detection of Ultrahigh Heat Flux at High Temperature

This article presents a novel high temperature heat flux (HTHF) sensor based on micromachined thermocouple (MTC) to meet the needs of transient high heat flux detection in ultrahigh temperature environments, such as fire research, high-power pulsed lasers testing, and aerospace engineering. The targeted design, fabrication, and package of an MTC-based HTHF sensor with excellent heat dissipation capacity are proposed, and relevant experiments were conducted in two aspects. First, powerful laser tube-based tests at ambient temperature show that such a sensor can detect a heat flux high to 10.8 MW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with an extremely fast response; its response time, in this case, is 1.9 ms. And then, turbine engine test pipe based tests at high temperature reveal that the sensor with water cooling could survive at 1200 °C for at least 100 s. Compared to conventional heat flux sensors, it is more sensitive to transient heat flux changes and has a faster response speed. Such satisfactory performance makes the sensor extremely competitive in ultrahigh heat flux detection in extremely harsh environments.

Application of the ESI Virtual Performance Solution 16.0 software package for simulation of technological tests of pipes

The results of simulation of technological tests of pipes of 73&times;5.5 mm gauge made of steel 20 are considered. Two types of tests (for flattening and expansion) are performed using the ESI Virtual Performance Solution software and the Visual-Crash PAM 16.0 module. The possibilities of using this software package for solving tasks of plastic forming, as well as for predicting the technological properties of pipes of various assortments in order to save metal for samples and reduce the complexity of assessing the pipes quality, are demonstrated. The results of solving tasks in the form of the distribution of stress-strain state indicators over the volume of samples are presented, the critical degrees of deformation at the moment of failure are determined, and the obtained data are compared with known experimental ones. Formulas for calculating normalized quality indicators based on the results of technological tests of pipes for flattening and expansion are proposed, examples of calculations for pipes of the considered assortment are given.

Statistical analysis of the results of mechanical tests of metal and pipes of trunk pipelines

Modern approaches to processing large bulk of data accumulated as a result of mechanical testing, based on statistical analysis and machine learning methodology are discussed. The factors affecting the strength and durability of pipe products are considered. The stages of the initial data preparation are analyzed and the main steps of basic statistical processing, correlation and variance analyses, approaches to grouping and ranking of test data are discussed. The results of the developed approaches are demonstrated by the example of constructing a classification by steel grades and technical conditions of the pipe production according to the actual mechanical characteristics of the pipe metal. The real effect is shown on the example of the estimating the number of pipe defects that require priority to repair. The presented algorithms can be used as the elements of the formed information base and data banks in the field of pipeline transportation of oil and oil products. The developed approaches require a comprehensive testing and further development towards taking into account the actual loading of the pipe and assessing the failure probability.

The Effect of Heavy-Duty Vehicle Crossings on the State of Stress of Buried Pipelines

The aim of this article is to quantify the loads exerted by heavy-duty vehicles when crossing over buried pipeline. This problem arises in connection to the question pertaining to the use of protective sleeves (casings) applied to gas pipelines in regions with increased demands on pipeline operation safety. An experiment was conducted on a test pipe section made from L360NE pipeline steel equipped with strain gauges along the pipe perimeter, measuring strains in the axial and circumferential directions. Strain measurements were taken after back-filling the pipe trench, then during vehicle crossings over the empty pipe, and again after pressurizing the test pipe with air. Strain-based hoop stresses at the surface of the empty test pipe were found to exceed 30 MPa after back-filling the trench and increased to more than 40 MPa during the vehicle crossings. Similarly, axial stresses reached extremes of around 17 MPa in compression and 12 MPa in tension. Applying internal air pressure to the test pipe resulted in a reduced net effect on both the hoop and axial stresses.