Integrity Of Pipes Research Articles

Experimental evaluation of a heat pipe cooled structured reactor as part of a two-stage catalytic methanation process in power-to-gas applications

Establishing the power-to-gas process as a suitable energy storage in future energy systems requires process simplification in order to make it competitive. An intensified methanation reactor concept could contribute to this overall goal. The present work suggests a new catalytic methanation reactor with heat pipe integration into a structured reactor. This approach benefits from the highly industrial maturity of the methanation process and simultaneously addresses the requirements of new applications in power-to-gas processes. The concept comprises a metallic body, which is perforated by channels for internal gas preheating, reaction channels and spaces for the incorporation of heat pipes. Calculation of the radial temperature profiles provided the limits for the channel geometry. Three layers of internal manifolds at different heights distribute, collect and divert the gas. Heating cartridges integrated at the bottom of the reactor enable rapid start up from cold conditions. The metallic block structure facilitates the sealing of the pressurized reaction space and the scaling. First experiments with a 5 kW prototype prove that the maximum temperature is kept more than 100 K below calculated adiabatic synthesis temperatures. Furthermore, the integration in a lab-scale two-stage test rig with intermediate water removal demonstrates the Substitute Natural Gas (SNG) production with grid-injectable quality.

Monitoring pipe wall integrity using fiber Bragg grating-based sensing of low-frequency guided ultrasonic waves

Recent literature shows that low-frequency ultrasonic guided waves experience mode confinement and loss of axi-symmetry in pipes with axially uniform features such as eccentricity. Considering extended wall loss as a case of uniform eccentricity, this paper proposes to monitor pipe integrity by measuring changes to the modal structure of low-frequency axisymmetric L(0,2) longitudinal guided waves. Fiber Bragg gratings are shown to be effective in detecting changes to L(0,2) modal characteristics, providing a novel route to health monitoring of pipe assets.

A Capsule-Type Electromagnetic Acoustic Transducer for Fast Screening of External Corrosion in Nonmagnetic Pipes.

For fuel transmission and structural strengthening, small-diameter pipes of nonmagnetic materials are extensively adopted in engineering fields including aerospace, energy, transportation, etc. However, the hostile and corrosive environment leaves them vulnerable to external corrosion which poses a severe threat to structural integrity of pipes. Therefore, it is imperative to nondestructively detect and evaluate the external corrosion in nonmagnetic pipes. In light of this, a capsule-type Electromagnetic Acoustic Transducer (EMAT) for in-situ nondestructive evaluation of nonmagnetic pipes and fast screening of external corrosion is proposed in this paper. A 3D hybrid model for efficient prediction of responses from the proposed transducer to external corrosion is established. Closed-form expressions of field quantities of electromagnetics and EMAT signals are formulated. Simulations based on the hybrid model indicate feasibility of the proposed transducer in detection and evaluation of external corrosion in nonmagnetic pipes. In parallel, experiments with the fabricated transducer have been carried out. Experimental results are supportive of the conclusion drawn from simulations. The investigation via simulations and experiments implies that the proposed capsule-type EMAT is capable of fast screening of external corrosion, which is beneficial to the in-situ nondestructive evaluation of small-diameter nonmagnetic pipes.

Bearing capacity of stabilized soil with expansive component confined by polyvinyl chloride pipe

Confined stabilized soil (CSS) was the composite system that used polyvinyl chloride pipe to confine stabilized soil with the binder consisting of expansive and cementing components, aimed at treating foundation in corrosive environments. Bearing capacities of CSS cylinders were studied considering variations of mass ratio of expansive component and cementing component (E = 0–1.00) and confinement stiffness (K = 0.16–0.52 GPa). Initial lateral strain, stress-strain curve, and failure mode were recorded. Confinement mechanism was analyzed, energy absorption capacity (EAC) was calculated, and confinement model was discussed by comparing experimental values with predictions using 10 widely used models for confined concrete. The application of CSS was also evaluated considering influence of interfacial bonding strength under different loading conditions and integrity of confinement pipe. Results show that CSS offers high compressive strength and ductility, ultimate strength (fcc′) and corresponding axial strain, and EAC are 1.75–4.81, 6.45–25.09, and 65.31–154.64 times the unconfined ones, respectively. High content of expansive component is permitted, which can not only enhance ultimate strength of unconfined stabilized soil (fco′) but make confinement pipe participate in the confinement to the core stabilized soil as soon as the application of axial load, retarding the cracking of core stabilized soil. Effect of E on SER (strength enhancement ratio) of fcc′ is dominated by affecting fco′, while SER of fcc′ increases with approximately exponential growth with K increasing. Axial stress–strain cures are significantly bilinear, but accurate confinement model should be developed incorporating influence of expansive component. Sufficient interfacial bonding strength can be built in CSS, which further enhances the bearing capacity, while fcc′ and EAC are slightly affected by integrity of confinement pipe.

Assessing the integrity of in service polyethylene pipes

The service life of Polyethylene (PE) pipes is influenced by many factors including type of PE resin used, time in service as well as service location. Assessing the integrity of PE pipes which have been in service using standard test methods is complicated by the requirement that samples should be sectioned directly from the used pipe wall. In this current study, a new fatigue test method, termed the Cyclic PENT (CPENT), is described that allows direct testing of unaltered material sectioned from the pipe wall. The CPENT was combined with oxidation induction time measurements to provide information on the relative ranking of pipes which have been in service for a time period of 20–40 years from 3 different service locations. It was found that both service location and in-service time are important factors when assessing the remaining life of PE pipes.

Seam pipes for process industry-fracture analysis by using ring-shaped specimens

Pipelines are commonly used in process industry for transport of fluids, as well as granular solids, due to their numerous advantages in comparison to other transportation means. Pipe integrity is essential for a reliable work of the entire plant, as well as for safety assurance. Also, serious ecological consequences may follow the pipeline failure in some cases, i.e. due to the leak of toxic, flammable or otherwise dangerous fluids in a chemical or some other plant. Therefore, it is very important to examine the fracture behaviour of pipelines, which is done here by testing the recently proposed ring-shaped specimens exposed to bending. The specimens were fabricated from a seam pipe for pressure applications (allowed for usage on temperatures up to 300?C). Initial defects, very narrow notches, were machined either in the base metal and weld metal (seam) or in the base metal only. Regardless of the defect position, ductile fracture mechanism is observed in all specimens. The results show that the ring-shaped specimen can be successfully used for fracture characterisation of pipeline material, especially for thin-walled pipes which are not suitable for production of standard fracture mechanics specimens due to the insufficient wall thickness.

An axial crack growth prediction procedure initiated at butt welded joint (Growth prediction for surface crack deeper than semi-circular and that retarded at weld fusion line)

Structural integrity of cracked pipes is assessed by predicting crack growth. In the fitness-for-service code of the Japan Society of Mechanical Engineers (JSME), the crack growth is predicted using stress intensity factor at the deepest and surface points. A semi-elliptical crack is assumed not to become deeper than a semi-circular crack. However, in reality, the stress corrosion cracking initiated at nickel alloy welds stops growing at the fusion line and becomes deeper than a semi-circular crack. Furthermore, crack shape is close to a rectangular shape rather than a semi-elliptical shape. In this study, validity of the JSME code procedure was discussed for predicting the growth of stress corrosion cracking at nickel alloy welds. Crack growth was simulated by finite element analysis together with an auto meshing technique. Various residual stress distributions and retardation of the crack growth at the fusion line were considered in the simulation. It was demonstrated that the growth prediction procedure prescribed in the JSME code brought about a conservative prediction even if the crack became deeper than the depth of a semi-circular shape crack. It was revealed that, when the growth to the surface direction was retarded at the fusion line, the change in crack size in the depth direction could be predicted conservatively by the current JSME procedure. It was suggested that, when the retardation at the fusion line is assumed in the growth prediction, the crack shape should be modelled by a rectangular shape.

Validation of BS 7910; assessing the integrity of pipes containing axial flaws

The results of hundreds of large scale fracture tests have been collected from various sources and analyzed in accordance with the latest version of the BS 7910 fitness for service (FFS) standard and, in selected cases, with R6 and/or the API 579-1/ASME FFS-1 fitness for service standard. This analysis aims to provide further validation of BS 7910 and identify where modification is needed. The tests cover a wide variety of materials, flaw geometries (surface, embedded, through thickness) and loadings (pressure, bending, residual stress), thus validating the standard over a wide spectrum of applications. All the tests are analyzed with the use of the basic assessment option (Option 1), which requires only the basic tensile properties and fracture toughness of the component, and selected tests are re-analyzed using more advanced methods.During the analysis, close attention was paid to the results of 173 tests on pipes with axial flaws, where an apparently arbitrary safety factor on reference stress is included in BS 7910, but not in other standards, leading to apparently lower defect-tolerance when BS 7910 is used. The history of this part of the standard, along with approaches used in other standards, was investigated. A modified equation, without this safety factor, was used in the analysis of the tests, where applicable, and compared with results from other standards. The comparison between the approaches shows the BS 7910 safety factor to be unnecessary, with all test results falling outside the failure assessment diagram (FAD), but with less conservatism, as they lie closer to it.

Validation of fracture toughness characteristics of nuclear plant piping and safety margin analysis by using CP specimen

Generally, due to the limited sizes of the pressure piping in a nuclear power plant, it is difficult to obtain valid data from fracture resistance tests examining on the real pipe. Thus, the leak-before-break (LBB) concept which is widely used for design and estimation of pressure piping system is determined based on the fracture resistance (J-R) curves of fracture resistance tests on various types of specimens. However, the fracture resistance tests show that the specimen geometry and loading configuration have a strong effect on the J-R measurement. Thus, a fracture test using a pipe specimen of real scale needs to be carried out to obtain accurate fracture behavior for the exact integrity evaluation of a piping system. Therefore, to estimate the integrity of real pipes based on elastic-plastic fracture mechanics, we have to first establish the new test method for fracture resistance evaluation of nuclear piping using the real pipe.In this paper, we present the current state of a fracture resistance evaluation using a compact pipe (CP) specimen and the validity of the test method was reviewed by comparing the fracture resistance test results from the CP specimens and real pipes. In addition, the safety margin of the piping was evaluated by using a crack driving force diagram and the results were analyzed.

Spatial-temporal reliability analysis of corroding cast iron water pipes

Destructive effects of pipeline structural failure on the worldwide social, environmental and financial aspects reveal the importance of accurate reliability assessment of these infrastructures. In this research, the structural integrity of water cast iron pipes is assessed by a spatial-temporal reliability analysis. Random field representation is used for taking the spatial variability of corrosion depth into account. A probabilistic model for correlation length of corroded cast iron surfaces is developed using the data collected from in-service pipe samples in the West of Melbourne, Australia. To this aim, the randomness associated with involved parameters in the deterioration process is acknowledged by Monte Carlo simulation, and limit states criteria are checked for individual failure mode and also for combination of them in order to execute a multi-failure mode reliability assessment for finding the likelihood of the time of pipeline failure.

Analysis of pipeline installation in unplanned flooding condition

During installation of subsea pipelines contingencies may occur, compromising their structural integrity. Therefore, it is important to predict the consequences to the pipe integrity during unplanned flooding scenario, which may result from pipeline fracture from overbend if the laying vessel loses position or if valves are accidentally installed open or leak. This paper evaluates the global static configuration and the capability of a subsea pipeline to resist to combined loading consisting of hydrostatic pressure, bending moment, and tension, using two catenary equations, considering one cable segment heavier than the other one to represent the flooded part. In addition, in order to evaluate the viability of laying a pipeline in unplanned flooding condition, DNV limit equations are employed. The developed methodology might be used as a conceptual design guidance given its simplicity and reasonable accuracy.

Towards optimised and reconstructable sampling inspection of pipe integrity for improved efficiency of non-destructive testing

Abstract This work proposes a sampling inspection framework for point measurement non-destructive testing of pipelines to improve its time and cost efficiencies. Remaining pipe wall thickness data from limited dense inspection are modelled with spatial statistics approaches. The spatial dependence in the available data and some subjective requirements provide a reference for selecting a most efficient sampling inspection scheme. With the learned model and the selected sampling scheme, the effort of inspecting the residual part of the same pipeline or cohort will be significantly reduced from dense inspection to sampling inspection, and the full information can be reconstructed from samples while maintaining a reasonable accuracy. The recovered thickness map can be used as an equivalent measure to the dense inspection for subsequent structural analysis for failure risk estimation or remaining life assessment.

Comparison of Parent and Butt-Fusion Material Properties of Unimodal High-Density Polyethylene

The U.S. nuclear power industry is seeking U.S. Nuclear Regulatory Commission (USNRC) approval to use high-density polyethylene (HDPE) in safety-related applications. The USNRC had granted approval for the use of HDPE for safety-related service water applications, with limitations, to Catawba (Duke Energy Corp., Catawba, SC) and Callaway (Union Electric Co., Callaway, MO) based on separate relief requests submitted by the licensees. The nuclear industry continues to show increasing interest in utilizing HDPE in safety-related piping systems. In order to evaluate and maintain the structural integrity of HDPE pipes, the material properties and the fracture resistance behavior must be fully characterized. Although there has been extensive work on material property development of HDPE, most of the investigations have been focused on the parent (base) material. Hence, the material property and fracture resistance behavior of the butt-fusion region have not been comprehensively investigated. In this paper, tensile, dynamic mechanical analysis (DMA), and slow crack growth (SCG) tests were performed for unimodal PE 4710 HDPE material. Specimens were machined from both parent piping material and butt-fusion regions. The test results indicate that the tensile and DMA properties show no significant differences between parent and butt-fusion joint materials. However, in terms of SCG resistance, the time to failure for butt-fusion joint material was an order of magnitude lower than that of the parent material.

Risk Assessment of Oil Pipeline Accidents in Special Climatic Conditions

The present study identifies the main accidents’ factors and causes for oil pipeline located in Siberia and operated in special climatic conditions. Various types of pipeline accident scenarios were modeled. It is showed that the most dangerous scenarios are oil spills fire and oil vapor explosion due to the loss of piping integrity (rupture) of the pipeline’s section, laying on marshlands and oil spill on the water surface due to the loss of piping integrity (puncture). The most probable scenario is oil spills fire due to the loss of piping integrity (puncture) of the pipeline’s section, laying on dry lands and marshlands. To estimate the scenarios «event tree analysis» is used. Also such risk indexes as individual, societal, public and potential risks were determined.

Ductile fracture of pipe-ring notched bend specimens – Micromechanical analysis

Integrity of pipes is typically assessed by testing fracture mechanics specimens, such as compact tensile (CT) or single-edge notched bending (SENB). However, for some pipe dimensions it is not easy or possible to fabricate a specimen conforming to the requirements of standard procedures. A new type of specimen is proposed recently, which can be advantageous for relatively small pipe diameters and axial defects - the pipe ring notch bend specimen - PRNB.In this work, criteria for failure by ductile fracture of PRNB specimens are determined experimentally and by application of micromechanical analysis. The influence of size of the specimen, as well as size and shape of the stress concentrator, is analysed. The results of this study, along with previous authors’ results, lead to the conclusion that the pipe ring specimens can be applied in integrity assessment of pipes with defects. Also, the benefits of their application include much simpler fabrication and the same material history as the pipe itself.

Engineering Approach Based on Reference Stress Concept for Calculating J and Crack Opening Displacement of Complex-Cracked Pipes

In this study, an engineering approach for estimations of fracture mechanics parameters, i.e., J-integral and crack opening displacement (COD), for complex-cracked pipes was suggested based on reference stress concept, where stress-strain data of the material was used to assess structural integrity of complex-cracked pipes. In the present study, new reference loads that can reduce the dependency on strain hardening of the material have been suggested for complex-cracked pipes under each loading mode. By using the proposed optimized reference load for complex-cracked pipes, J-integral and COD estimation procedures have been proposed based on the reference stress concept together with the elastic solutions for complex-cracked pipes. The predicted J-integrals and CODs based on the proposed method have been validated against published experimental data and FE results using actual stress–strain data. Moreover, the predictions using the proposed methods are also compared with those using the existing solutions for simple through-wall cracks (TWCs) based on reduced thickness analogy concept.

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In this work, we performed a finite element analysis (FEA) to characterize the mechanical behavior of the composite pipe Fiberspar in order to investigate the structural integrity of composite pipes for crude oil transport in Colombia.Tests according to ASTM D2290 standard were performed in the laboratory to determine the tensile ultimate strength and compare the results with the numerical model.Failure criteria Tsai-Wu and Tsai-Hill were considered for the pipes working at different pressures, including operational pressure and, thus, the failure values and critical layers were identified.

Modal and Vibration Analysis of Filter System in Petrochemical Plant

Filter systems are widely used in petrochemical plants for removing solid impurities from hydrocarbon oils. The backwash is the cleaning process used to remove the impurities on the sieves of the filters without a need to interrupt the operation of the entire system. This paper presents a case study based on the actual project of a filter system in a petrochemical plant, to demonstrate the significant effect of vibration on the structural integrity of piping. The induced vibration had led to the structural fatigue failure of the pipes connecting the filter system. A preliminary assessment suggested that the vibrations are caused by the operation of backwashing of the filter system. A process for solving the vibration problem based on the modal analysis of the filter system using the commercial finite element software for simulation is therefore proposed. The computed natural frequencies of the system and the vibration data measured on site are assessed based on the resonance effect of the complete system including the piping connected to the filters. Several approaches are proposed to adjust the natural frequencies of the system in such a way that an optimal and a reasonable solution for solving the vibration problem is obtained.

Plastic Limit Analysis of Piping with Local Wall-Thinning under Elevated Temperature

In order to evaluate the safety and integrity of piping with local wall-thinning at elevated temperature, a numerical method for plastic limit load of modified 9Cr-1Mo steel piping is proposed in the present paper. The limit load of piping at high temperature is defined as the load-carrying capacity after the structure has served for a certain time period. The power law creep behavior with Liu-Murakami damage model is implemented into the commercial software ABAQUS via CREEP for simulation, and the Ramberg-Osgood model is modified to consider the material deterioration effect of modified 9Cr-1Mo steel by introducing the creep damage factor into the elasto-plastic constitutive equation. For covering the wide ranges of defect ratios and service time periods, various 3-D numerical examples for the piping with local wall-thinning defects, and creep time are calculated and analyzed. The limit loads of the defected structures under high temperature are obtained through classic zero curvature criterion with the modified Ramberg-Osgood model, and the typical failure modes of these piping are also discussed. The results show that the plastic limit load of piping containing defect at elevated temperature depends not only on the size of defect, but also on the creep time, which is different from the traditional plastic limit analysis at room temperature without material deterioration.

LNG 연료 선박용 FGSS의 고압 기화기와 출입구 배관에 대한 구조 건전성 평가

LNG 연료 선박용 FGSS의 고압 기화기와 출입구 배관에 대한 구조 건전성 평가