Tube Failure Research Articles

Studies on glass/epoxy and basalt/epoxy thin-walled pressure vessels subjected to internal pressure using ultrasonic ‘C’ scan technique

Fiber reinforced nanocomposite tubes are playing a vital role in the transportation of fluids in petrochemical industries, where these composite tubes store fluid under pressure. Therefore, it is important to estimate the amount of pressure that can be handled by the tubes and investigate the damage mechanisms of composite tubes using non-destructive testing techniques. In this work, mechanical properties and the pressure withstanding capability of different weight percentages (0, 0.5, 1 and 1.5 wt%) of silica nanoparticles added in glass/epoxy and basalt/epoxy composite tubes are investigated. Before performing these tests, the transmission electron microscopy (TEM) analysis was performed to ensure the uniform distribution of silica nanoparticles in the epoxy. Further, mechanical tests were carried out. The fractured surface of composites was analyzed using scanning electron microscopy (SEM). The Weibull modeling was used to predict the theoretical tensile, flexural and impact strength values. Further, hydrostatic pressure tests were performed, and then full-field damage assessments were performed using the ultrasonic ‘C’ scan. It was found that basalt/epoxy/silica nanocomposite tubes exhibited better mechanical and pressure withstanding capability, owing to the presence of higher amounts of iron and aluminum oxides, than their counterparts of glass/epoxy/silica nanocomposite tubes. Numerical analysis was also performed to confirm the allowable pressure limits of the composites under hydrostatic load. The failure of tubes has not occurred below allowable pressure values, which indicate good correlations with experimental results. The results of the study will help to design and manufacture composite tubes with better pressure withstanding capability at a reasonable cost.

Numerical Assessment of the Structural Damage of a Composite Lining Water Conveyance Tunnel Subjected to Reverse Fault Conditions

In this paper, the structural responses and failure characteristics of a new type of water conveyance tunnel lining structure subjected to reverse fault conditions were numerically investigated by considering multiple loads and interaction separation modes between different structural layers. This study proposes a new evaluation standard for the safety level of the damage state of the composite lining water conveyance tunnel. It also discusses the influences of fault dislocation displacement (Δf), dip angle (β), and the mechanical properties of the surrounding rock in the fault fracture zone on the water conveyance tunnel response and damage. The results indicate that the buckling failure of the steel tube under axial compression is the dominant failure mode of the composite lining structure. With increasing fault dislocation displacement, the axial compressive strain and circumferential shear strain of the composite lining are most severely damaged on the sliding plane. With decreasing fault dip angle, the axial compressive strain of the composite lining weakens, while the bending and shear strains increase. The increase in rock stiffness in the fault fracture zone reduces the damage scope but increases the composite lining structural damage severity. Overall, the numerical results of this study provide a better understanding of the failure mode and damage process of composite lining water conveyance tunnels under reverse fault conditions; therefore, this study can serve as a reference for composite lining structure disaster assessments.

Long Tunneled External Ventricular Drains with Shunt Valves: A Technical Note

External ventricular drain (EVD) is a basic operation in neurosurgery. Due to the limitation of its safe duration, some patients need to receive multiple drainage operations. We describe the long tunneled EVD (LTEVD) with shunt valves that effectively avoid multiple operations as a technical note. The difference is that the middle part of the drainage tube is connected by an externalized shunt valve. The drainage tube is buried under the skin and the outlet is in the abdomen. The technique and more details are described. The connection between the LTEVD and the shunt valve is simple and the required materials are easily accessible. Externalized valves allow the cerebrospinal fluid to be visualized and more controllable, making it easier for physicians to manage the cerebrospinal fluid. No drainage tube failure or secondary infection was observed. The indwelling time of the drainage tube was greatly extended. LTEVD is effective and simple. It allows visual control of drainage flow, prolonging catheter indwelling time and eliminating the need for multiple surgeries.

Flexural Performance of Prestressed Composite Recycled Aggregate Slabs with Steel Tube Trusses

A new type of prestressed composite recycled aggregate floor slab was developed and its flexural performance was studied. The composite floor comprises a top cast-in-place slab made of recycled coarse aggregate concrete and a bottom precast concrete slab with grouted steel tube trusses. The cracking load, ultimate load, deflection, steel tube strain, concrete strain and failure process are studied for different contents of recycled coarse aggregates. Results show that the mechanical performance of the prestressed composite recycled aggregate slab has two distinctive stages. And the load bearing capacity decreases with the increase in the amount of recycled coarse aggregates. When the composite slab fails, the prestressed steel wires in the tension zone yield and concrete in the compression zone is crushed. This failure characteristic reflects that the reinforcement ratio of the component is appropriate. The cracking moment and ultimate moment calculation formulas of the composite slab are established and could predict the cracking and failure points. In the formulas, the influence of the amount of recycled coarse aggregates on the flexural capacity is considered. By controlling the content of recycled aggregates, the composite slabs with steel tube trusses can be sued in practical applications.

Corrosion failure analysis of the heat exchanger in a hot water heating boiler

The corrosion failure of the heat-exchanger made of 20G steel in a hot water heating boiler was investigated. The morphology and phase compositions of the corrosion products were analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM) with energy disperse spectroscopy (EDS). The results showed that the boiler feed water did not meet the water quality standard, which contained excessive ion concentrations of Ca and Mg and dissolved oxygen content. At the surface of failed tubes, loose corrosive products containing numerous cracks provided micro-channels for Cl- diffusion into the matrix of 20G steel, thus leading to the local electrochemical reaction. This continuous and Cl-induced electrochemical erosion at some positions led to a vicious cycle which caused more severe damage to the tube, finally resulting in a perforation failure of the tube. To avoid this kind of accident happening, some suggestions are given in this paper.

Mechanical performance of marine concrete filled CFRP-aluminum alloy tube columns under axial compression: Experiment and finite element analysis

This study presents the mechanical performance of marine concrete filled carbon fiber reinforced polymer (CFRP)-Aluminum alloy tube columns (CFRP-CFAT) through axial compression experiment and finite element analysis. 18 specimens were tested including 3 marine concrete filled aluminum alloy tubes (CFAT) and 15 CFRP-CFATs. The effects of the CFRP pasting position (outer and inner CFRP) and the number of CFRP layers were investigated. The typical failure pattern of specimens without inner CFRP was waist drum failure of aluminum alloy tube and concrete crushed, aluminum tube and concrete of specimens with inner CFRP were shear failure, the CFRP of all specimens was fractured. CFRP and aluminum alloy tube have fine deformation coordination performance. With the confinement of CFRP, the ultimate bearing capacity and energy absorption capacity of CFRP-CFATs were increased by up to 60.0% and 37.3%, respectively, also effectively inhibited the damage development of specimens. Moreover, a finite element model was developed, a parametric study was carried and a model for calculating the ultimate bearing capacity of CFRP-CFAT was proposed. The simulated results and calculated results were consistent with experimental results.

Investigation on vibration parameters in aluminum finned tube arrays subjected to water cross flow

PurposePredicting the critical velocity is crucial at the instability threshold for shell and tube heat exchangers in order to prevent tube failure due to vibrations. In this study, the vibration response of an aluminum tube bundle subjected to water cross flow was analyzed experimentally. Aluminum tubes are preferred over steel tubes because of aluminum tubes' excellent corrosion resistance, ease of manufacture, and high thermal efficiency.Design/methodology/approachThe fluid elastic instability and vortex shedding mechanisms in a finned tube array of aluminum tubes with a base tube diameter of 19.05 mm and pitch of 34 mm were investigated. The current study considers parallel triangular finned tube arrays with fin heights of 3 mm and 6 mm with a uniform fin thickness and fin pitch. The plain tube array was tested to compare the finned tube array results. The tube vibration response was measured using an accelerometer mounted on the middle tube of the third row. In order to define the fluid elastic instability behavior of various tube arrays, the critical velocity at the instability threshold is measured. By finding the Strouhal number at the small peaks before instability, the vortex shedding behavior of the tube arrays is examined.FindingsThe results reveal that the critical velocity at instability for coarse finned tube arrays increases as the fin height increases. The effect of the tube material is evaluated by comparing the results with those previously reported for parallel triangular tube arrays made of steel. Finally, the occurrence of vortex shedding in a tube array is confirmed based on the Reynolds number and Strouhal number relationship. The instability constant K for the plain tube array of steel and aluminum material are 4.97 and 4.87, respectively.Originality/valueThis paper provides the research findings on the effect of fin height on coarse density finned tube array. This will add substantial knowledge to the literature in the field of fluid elastic instability and vortex shedding, which is needed for the safe functioning of shell and tube heat exchangers.

Coupled CFD-FEA simulation of bulging tube failure in hot temperature zone

Bulging tube failure is common when tubes are exposed to high temperatures. The most prevalent reasons of bulging tube failure are more heating and creep deformation. This research article simulates the most typical causes of tube bulging failure. Coal-fired power station boiler tubes from diverse processing industries display identical bulging tube failures when loaded with pressured fluid and placed inside a higher temperature zone.The differential in temperature between the outside and inner tube walls and compressed fluid inside the tube demonstrates efficient thermal expansion on the metal tube wall in the form of creep ductile deformation. By merging traditional CFD (Computational Fluid Dynamics) and FEA (Finite Element Analysis) models, this research provides a technique based on fluid structures. The thermal-structural behavior of tube deformation can be predicted using a combined CFD-FEA simulation of tube bulging failure. The CFD modeling solves the increment in fluid pressure inside the metal tube and the increment in temperature inside and outside the metal tube. FEA modeling aims to solve the thermal and structural behavior due to radial deformation and thermal expansion caused by thermal loads. Coupled CFD-FEA Simulation swelling tube failure in a hotter zone shown a clear idea of the high pressure and enhanced temperature, creep ductile deformation of tube wall in which the possibilities of tube failure are greater.

Numerical Study on the Effect of Deposit Layer on the Minimum Wall Thickness of Boiler Water Tube under Different Operating Conditions

Water wall tube temperature is a major parameter in the steam generator design which has a significant role in keeping the steam generator available. Thus, knowing the tube average temperature in different operating conditions is very important to avoid the causes of tube failures. High temperatures are a major cause of various types of failures, such as overheating, hydrogen damage, thermal stress, etc. Furthermore, deposits on the inner tube wall contribute to such failure by changing the thermal resistance of the tube wall, which causes a significant increase in the tube wall’s average temperature, consequently lowering the allowable stress. Therefore, the model was created by using ANSYS FLUENT (Canonsburg, PA, USA) to determine the wall average water tube wall temperature considering the deposit layer thickness (magnetite). Furthermore, this model was verified. It was found that increasing tube thickness can increase the average tube temperature but combining it with increasing deposit thickness leads to higher temperatures. In other words, the effect of the deposit on the tube with higher thickness is higher than on the tube with lower thickness. By discussing the minimum thickness of the water wall tube, the suitable selection of the tube thickness and courses of action concerning the operating conditions that minimize the potential overheating of water tubes in the furnace section of the boiler can be determined.

HEART Hybrid Methods for Assessing Human Reliability in Coal-Fired Thermal Power Plant Process

The assessment of human reliability is crucial in serious processes and operations, such as planned maintenance, unplanned maintenance, and troubleshooting in a coal-fired thermal power plant, as the nature of these processes poses significant threats. When the literature is examined, the evaluation of human reliability in any type of power plant, especially coal-fired thermal power plants, is limited. In order to fill this gap, we systematically assessed human reliability in an accident that occurred during a repair of a tube failure in a boiler in a coal-fired thermal power plant. The HEART (human error assessment and reduction technique) method was used in a hybrid way alongside the fuzzy AHP and SWARA (step weight assessment ratio analysis) methods. Although the HEART method is a practical, understandable, and easy-to-implement human reliability assessment method, the APOE (assessment of the proportion effect) value depends on the decision of a single decision maker. This study aimed to eliminate this deficiency and compare human error possibilities using HEART–fuzzy AHP and HEART–SWARA methods. This hybrid method can be used in the operation of all coal-fired thermal power plants and provides practical contributions to minimize human error.

Endoscopic transcanal surgery of pars tensa cholesteatoma: Preliminary results

Introduction and objectivesThe aim of the present study is the assessment of exclusive endoscopic ear surgery for the management of primarily acquired pars tensa cholesteatoma, which is commonly linked to the failure of the Eustachian tube leading to the formation of retraction pockets. Materials and methodsPatients suffering from primarily acquired pars tensa cholesteatoma, who underwent primary surgery in our clinic, between 2014 and 2018 were included in this retrospective study. The disease was classified according to the EAONO/JOS system. Exclusive endoscopic ear surgery was performed for patients without mastoid involvement, while a microscopic–endoscopic tympanoplasty was carried out in case of mastoid extension. We assessed the recidivism rate during the follow-up. ResultsCholesteatomas belonged to stage I in 28% of cases, to stage II in 68% and only one patient was stage III. Only a portion of the pars tensa was involved in 13 instances, the whole pars tensa in 3 and both the tensa and the flaccida in 9. 17 out of 25 patients underwent exclusive endoscopic ear surgery and 8 needed a combined approach. We discovered 1 recurrence and 6 residual diseases. ConclusionsWith only one case of recurrence in our series, we showed how pars tensa cholesteatoma cannot be exclusively explained through Eustachian tube dysfunction, but also through a ventilation blockage between the Eustachian tube and other mesotympanic areas due to the formation of intratympanic folds. Endoscopic ear surgery proved highly effective in the control of recurrences and it should be considered the treatment of choice.

Hydrogen Embrittlement of a Boiler Water Wall Tube in a District Heating System

A district heating system is an eco-friendly power generation facility with high energy efficiency. The boiler water wall tube used in the district heating system is exposed to extremely harsh conditions, and unexpected fractures often occur during operation. In this study, a corrosion failure analysis of the boiler water wall tube was performed to elucidate the failure mechanisms. The study revealed that overheating by flames was the cause of the failure of the boiler water wall tube. With an increase in temperature in a localized region the microstructure not only changed from ferrite/pearlite to martensite/bainite, which made it more susceptible to brittleness, but it also developed tensile residual stresses in the water-facing side by generating cavities or microcracks along the grain boundaries inside the tube. High-temperature hydrogen embrittlement combined with stress corrosion cracking initiated many microcracks inside the tube and created an intergranular fracture.

Bearing behavior of high-performance concrete-filled high-strength steel tube composite columns subjected to eccentrical load

In order to study the bearing capacity of high-performance concrete-filled high-strength steel tube (HCHST) composite stub columns subjected to eccentrical load, 22 HCHST composite stub columns, 4 concrete-filled steel tube (CFST) composite stub columns and 8 high-performance concrete-filled steel tube (HCST) composite stub columns were designed with the cubic compressive strength of concrete (fcu), the yield strength of steel tube (fy), the thickness of tube wall (t), the eccentricity (e) and slenderness ratio (λ) as the main parameters. Considering the nonlinear constitutive model of concrete and simplified constitutive model of steel, the finite element (FE) model of HCHST composite stub columns was established by ABAQUS software. By comparison with the existing test results, the rationality of the constitutive model and boundary conditions was verified. The variation of ultimate bearing capacity and the typical failure modes of HCHST composite stub columns under different parameters was analyzed. The results show that the specimens exhibit obvious bulge outward at the end of the steel tube and shear failure at the end of concrete. High-performance concrete (HPC) can significantly improve the ultimate eccentrical compression bearing capacity of composite columns, and high-strength steel tubes have better restraint effect on HPC. With the increasing of t, the ultimate eccentrical compression bearing capacity and the load-holding capacity of HCHST columns increases gradually, while the ultimate eccentrical compression bearing capacity decreases gradually with the increasing of λ and e. By introducing the reduction coefficient of eccentricity (φ1) and the reduction coefficient of slenderness ratio (φ2), the calculation formula of the eccentric bearing capacity of HCHST columns is proposed by statistical regression, which can lay a foundation for the application of HCHST columns in practical engineering.

No tube left behind: feeding tube failure and endoscopic retrieval

The patient was a 55-year-old woman with a deficiency of adenosine deaminase 2 characterized by transfusion-dependent red cell aplasia and immune thrombocytopenia, who underwent reduced-intensity matched unrelated donor hematopoietic stem cell transplantation. Because of a complex clinical course including a systemic inflammatory response and protein-calorie malnutrition, she received placement of a nasogastric tube (Kangaroo Entriflex, Cardinal Health, McGaw Park, Ill, USA) during her prolonged hospitalization.

Engineering Poster E12: A holistic approach to reducing small-bore fitting and tubing failures in oil and gas facilities

Poster E12 Small-bore piping and instrument tubing vibration failures are not just a hidden risk to production, reliability, and safety, but also a frequent source of emissions through leaks and plant flaring when issues arise. Vibration-induced failure risks are often overlooked and detected too late, despite making up a significant portion of leaks and lost production incidents. Conventional approaches to managing these hidden risks have resulted in recurring failures and unplanned downtime at process plants. Large inventories of Small-Bore Fittings (SBFs) and tubing generally require management as most are integral parts of the plant and can be classed as safety and/or production critical. Small-bore tubing assemblies are at risk of fatigue failure due to a general lack of awareness of the best-practice design for reducing vibration response and how to manage this risk. A holistic approach to manage and pro-actively reduce small-bore piping and tubing vibration anomalies in the field is presented in this paper. This involves a risk-based assessment approach combined with the use of digital tools to register, manage, and visualise the status of the risk to the plant and the improvement in risk with the implementation of remedial actions. Best-practice and a short case study is discussed to demonstrate how the approach can be implemented to effectively reduce and manage vibration-induced small-bore piping and tubing failure incidents. To access the poster click the link on the right. To read the full paper click here

Study on the mechanical behavior of L‐shaped concrete‐filled steel tubular columns under axial compression

AbstractIn this paper, a total of six different ribbed and two nonribbed L‐shaped concrete‐filled steel tubular (CFST) short columns are designed; finite element modeling and calculations are carried out and verified with measured results. The optimal ribbing method among the ribbing methods applied is proposed. The mechanisms of the longitudinal stress of the concrete, longitudinal stress of the outer steel tube, and lateral compressive stress of the concrete for the L‐shaped CFST short column without ribs and with the optimal ribbing method are compared and analyzed. The results show that the optimal ribbing method involves setting half‐width longitudinal stiffening ribs in the middle of the two wide sides of the L‐shaped steel tube. The stiffening ribs can delay the occurrence of local buckling failure of the steel tube, thus strengthening the restraining effect of the steel tube on the concrete and improving the uniformity of the longitudinal stress of the core concrete. In addition, based on an analysis of a large number of parameters, four methods for calculating the bearing capacity of nonribbed L‐shaped CFST short columns are compared. A design formula for the bearing capacity of ribbed L‐shaped CFST columns is proposed by considering the improvement in the concrete performance. The calculation results agree well with the finite element and experimental results, and the error is <5%.

Case Report of Speech and Ambulation Ability After Five Years Therapy in a Six-Year-Old Boy with Habilitation Sixth Lumbar Spina Bifida with Meningocele Post Resection and Hydrocephalus Post VP Shunt

ABSTRACT
 Introduction: Spina bifida, a congenital spinal cord injury, is a complex disability that results from a failure of the caudal neural tube to fuse early in embryonic development. Spina bifida affects about 300.000 newborns each year worldwide. Hydrocephalus is common in children with spina bifida, developing in 80% to 90% of children with myelomeningocele. Anatomical abnormalities in which the myelomeningocele sac occurs is associated with neurological, motor and sensory deficits. They showimpaired speech and ambulation.Case presentation: We report a six-year-old boy was taken to the hospital by his parents because he could not stand and walk since he was born. At birth there was a lump on the lower back, and the patient also had hydrocephalus, then surgery had been performed. The patient was diagnosed with sixth lumbar spina bifida and hydrocephalus with meningocele. He had some delay in gross motor, fine motor and language development. The patient had history of seizures. He received trunk control exercise, pelvic stabilityexercise, positioning and handling, coordination exercises and fine motor skills to increase independence in activities of daily life. The patient obtained 4 years exercises of speaking, comprehension, vocabulary and articulation. The child also received attention and concentration enhancement exercises.Conclusion: A patient with spina bifida requires a lifelong commitment by the patient, family, and the health care personnel involved in the treatment. The medical goal is to maintain stable neurological functioning throughout the patient’s lifetime. The wide range of extensive speech and ambulation impairments and long-term disabilities in patients with spina bifida present a considerable challenge to the management of these patients.Keywords: ambulation, hydrocephalus, meningocele, speech, spina bifida

Abstract No. 572 Outcomes of balloon percutaneous gastrostomy tube placements

Gastrostomy tube failures contribute to increased patient burden and are associated with hospital readmission and increased utilization of healthcare resources. The purpose of this study is to compare the outcomes of the novel balloon gastrostomy technique with the standard serial dilation.

Data Driven Technique for Palm Oil Mills Boiler Water Quality Monitoring in State of Perak Malaysia

Steam boilers are widely used in oil palm mills industries which physically converting the water into steam. Heating water in the boiler allows solid waste such as potassium, calcium, magnesium, silica and ions to stay in the boiler and creates a solid waste layer that coats the tubes and boilers. This strong coating would increase the heating surface of the boiler and decrease the efficiency of heat transfer. This situation will also increase the consumption of fuel, causing the boiler to overheat, which in turn leads to tube failure. The impact of this issue will cause losses to the oil palm plantation due to the shutdown of unplanned plants. Therefore, for this study, Statistical Process Control (SPC) has been utilized to monitor the quality of the 6 parameters of the boiler and boiler feedwater for palm oil mill in Perak State Malaysia to overcome the problem stated above. Boxplot has been utilized to monitor continuously the parameter based on the probability distribution of the data according to ASME guidelines. The findings from this analysis show that some of the palm oil mills is able to maintain their boiler quality accordingly, however, on controlling the silica, hardness and total iron, its need further improvement.

A holistic approach to reducing small-bore fitting and tubing failures in oil and gas facilities

Small-bore piping and instrument tubing vibration failures are not just a hidden risk to production, reliability, and safety, but also a frequent source of emissions through leaks and plant flaring when issues arise. Vibration-induced failure risks are often overlooked and detected too late, despite making up a significant portion of leaks and lost production incidents. Conventional approaches to managing these hidden risks have resulted in recurring failures and unplanned downtime at process plants. Large inventories of Small-Bore Fittings (SBFs) and tubing generally require management as most are integral parts of the plant and can be classed as safety and/or production critical. Small-bore tubing assemblies are at risk of fatigue failure due to a general lack of awareness of the best-practice design for reducing vibration response and how to manage this risk. A holistic approach to manage and pro-actively reduce small-bore piping and tubing vibration anomalies in the field is presented in this paper. This involves a risk-based assessment approach combined with the use of digital tools to register, manage, and visualise the status of the risk to the plant and the improvement in risk with the implementation of remedial actions. Best-practice and a short case study is discussed to demonstrate how the approach can be implemented to effectively reduce and manage vibration-induced small-bore piping and tubing failure incidents.