Leak Area Research Articles

Analysis of reactor water level measurements during the Fukushima unit 2 accident

The reactor water level measurement system in Fukushima was based on measuring the pressure difference between two water-filled pipes that were connected to the reactor at different elevations. A Japanese accident investigation committee has presented a hypothesis that a leak of superheated steam from the unit 2 reactor to the drywell caused evaporation of the water in the measurement system, causing the indicated water level to be much higher than the actual level. This article presents an analysis of the measurement system with the MELCOR code. The results support the hypothesis of a small leak, starting 78.5 h after the earthquake. The best agreement with the measurements was obtained with 8 cm2 leak area. The leak was probably located close to the water level measurement system, so that it caused localized heating in the drywell. The leak increased the fission product release to the environment because it bypassed the suppression pool. The calculated cesium release from unit 2 to the environment was 2.1% of the core inventory. Combined with the author’s earlier MELCOR calculations of units 1 and 3, the current estimate of the total Cs-137 release from all three accident units at Fukushima is 14.3 PBq.

Early Management of Esophageal Leak in Esophageal Atresia: Changing Paradigms.

Introduction: A leak at the esophageal anastomosis can occur in 10%-20% of cases of esophageal atresia (EA). Thoracoscopic repair is trans-pleural, with the potential development of an empyema. Standard treatment of an anastomotic leak in a stable patient is often nonoperative, which can lead to prolonged parenteral nutrition and hospitalization. Our objective is to show that early thoracoscopic redo anastomosis management is safe and feasible. Materials and Methods: Retrospective study of a case series of four infants, diagnosed with EA and treated with early thoracoscopic esophageal leak repair between 2013 and 2018. Variables analyzed included age, weight, type of EA, day of leak, surgical approach, time to start feeding, surgical complications, and follow-up. Results: Three patients were type III, and one was type I originally repaired with a thoracoscopic approach. Leaking of the anastomosis was found the second postoperative day in one patient, third day in two patients, and the fifth day in the last one. All were confirmed with an esophagogram. All patients were operated in the first 24 hours after diagnosis by the thoracoscopic approach. The site of leak was found and re-sutured. Patients started feeding between the third and fourth day through a transanastomotic tube, starting oral feeding at the seventh day after an esophagogram did not show a leak. No complications were found. Mean time to complete oral feeding was 10 days. Two patients needed esophageal dilations. Mean time of follow-up has been 33 months. Conclusion: Early thoracoscopic repair of an anastomotic leak can be considered an alternative to the standard nonsurgical management. The early re-suture of the area of leak is a change in paradigm, but it offers the benefits of preservation of the native esophagus, early resumption of enteral feedings, and a shorter length of parental nutrition and hospitalization. Level of Evidence: IV.

An analytical amplitude model for negative pressure waves in gaseous media

The negative pressure wave propagation method is an established Structural Health Monitoring (SHM) technique to locate leakages and defects in pipelines. The amplitude of negative pressure waves can be exploited to obtain information about the severity of the damage (e.g. leak flow rate and leak area) and are useful to determine the smallest detectable leakage flow rate of the negative pressure wave method. The current manuscript proposes an analytical amplitude model of negative pressure waves in gaseous media. The isentropic fluid equations that represent the leak phenomena are combined with acoustical equations expressing the generation of the negative pressure waves. The presented model has been experimentally validated over a broad range of pressurization cases, gaseous media, leak sizes and pipe diameter. The derivation of the model provides insight in the physics behind the occurring phenomenon while the model reveals all parameters affecting the negative pressure wave amplitude. It is derived that, depending on the pressurization type, a different formulation has to be used to predict the amplitude of the negative pressure waves. The amplitude model is, in view of its applications, both presented in function of the leakage flow rate as well as in function geometrical size of the leak.

Interdependence of flow and pipe characteristics in transient induced contamination intrusion: numerical analysis

Abstract Contaminant intrusion in pipelines during transients is a remarkable mechanism, which leads to a decline in the quality of the contained water. The negative pressure of water hammer pressure waves is the trigger for the suction of pollution from the surrounding leak area, and hence deteriorating water quality. The volume of contamination intruded into the pipeline is investigated using mathematical and numerical modeling of the phenomenon. To elucidate this phenomenon in real pipe systems, the intrusion amount is estimated for 72 different scenarios including: two lengths of pipeline (i.e. short and long), three different leak locations, three different fluid velocities in the pipe, two leak diameters and two pipeline materials (elastic and viscoelastic). The results showed that the amount of intrusion in viscoelastic pipes was clearly less than that in elastic pipes, especially in long pipelines. The critical zone of high intrusion risk is identified close to the downstream valve for small leak sizes, nevertheless, it is difficult to estimate this zone in the case of large leaks due to significant interactions between nodal components (valve, leak, reservoir).

Mechanisms of nasal high flow therapy in newborns.

In newborns, it is unclear how nasal high flow (NHF) generates positive airway pressure. In addition, the reported benefits of NHF such as reduction in work of breathing may be independent of airway pressure. The authors hypothesized that during NHF the area of leak and the flow determine airway pressure and that NHF can reduce the required minute ventilation to maintain gas exchange. In response to NHF, pressure was measured in the upper airways of 9 newborns and ventilation was measured in another group of 17 newborns. In a bench model, airway pressures were measured during NHF with different prong sizes, nare sizes, and flows. The airway pressures during 8 L/min NHF were greater when a larger cannula versus a smaller cannula was used (P < 0.05). NHF reduced minute ventilation in 16 of 17 neonates, with a mean decrease of 24% from a baseline of 0.66 L/min (SD 0.21) (P < 0.001), and was unrelated to changes in airway pressure; arterial oxygen saturation by pulse oximetry () and tissue CO2 were unchanged. In the bench model, the airway pressure remained <2 cmH2O when <50% of the “nare” was occluded by the prongs. As the leak area decreased, because of a smaller nare or a larger cannula, the airway pressure increased exponentially and was dependent on flow. In newborns NHF using room air substantially reduced minute ventilation without affecting gas exchange irrespective of a decrease or an increase of respiratory rate. NHF generates low positive airway pressure that exponentially increases with flow and occlusion of the nares.NEW & NOTEWORTHY In healthy newborns, nasal high flow (NHF) with room air reduced minute ventilation by one-fourth without affecting gas exchange but, in contrast to adults, produced variable response in respiratory rate during sleep. During NHF, pressure in the upper airways did not exceed 2 cmH2O at 8 L/min (3.4 L·min−1·kg−1) and was unaffected by opening of the mouth. NHF can generate higher pressure with larger prongs that decrease the leak around the cannula or by increasing the flow rate.

Traveling ability of pipeline inspection gauge (PIG) in elbow under different friction coefficients by 3D FEM

Pipeline inspection gauge (PIG) applied for dewatering and cleaning operation frequently suffers from blockage risk, especially in elbow section. Definitive solution to the blockage problems does not currently exist in literature. In this research, the concept of traveling ability is introduced to describe the performance of blockage avoidance, and it is defined by three influencing factors: sealing performance, which is expressed by the leak area ratio of the PIG cups; driving performance, which is evaluated by the necessary driving pressure, and collision possibility, which is described by the minimum distance between the PIG head or tail and the pipeline inner wall during pigging. The 3D finite element model (FEM) is adopted in this work and is verified by a custom–built experimental setup. Then, the FE model of the PIG running in elbow is established, and the effect of friction coefficients on the influencing factors is discussed. The results indicate that the traveling ability of the PIG will be obviously weakened under the condition with the higher friction coefficients. When the friction coefficient increases from 0.1 to 0.5, the sealing performance decreases by 27.7%; the driving performance decreases by 80% and the collision possibility increases by 94%. The researches of this work are beneficial for improving the PIG designment and avoiding the blockage risk.

499 Delayed distal migration of a balloon expandable valve-in-valve transcatheter aortic valve: a clinical case and review of the literature

Abstract Case Presentation A 70 year old man presented with recurrent dyspnea and new decrease in his left ventricular ejection fraction 5 months following valve-in-valve (ViV) TAVR (26 mm). A TEE revealed migration of his ViV TAVR towards the left ventricular outflow tract (LVOT) with resultant severe paravalvular leak (Figure 1A, 1B, 1C; yellow arrow showing the TAVR, red arrow showing the previously implanted bioprosthetic surgical aortic valve). A 29 mm balloon expandable TAVR was placed and deployed higher to ensure anchoring of the device and adequate sealing of the area of paravalvular leak (Figure 1D, 1E, 1F). This resulted in resolution of regurgitation with an intraoperative transvalvular gradient of 10 mmHg. At his 3-month follow-up visit, a TTE showed a well-seated TAVR with mild paravalvular leak and a mean gradient of 17 mmHg. He successfully completed cardiac rehab and his dyspnea improved to mild. Discussion As the population ages and younger patients receive surgical aortic bioprostheses (SAVR), the rates of deteriorated SAVR’s is only expected to grow in the future. The use of TAVR is now established as an alternative to redo surgery in patients with deteriorated SAVR"s, therefore, it is crucial to be able to recognize and treat device-related complications in a timely manner. The occurrence of distal migration of TAVR, i.e. displacement of the device towards the LVOT, is rare. The vast majority of cases are noted intra-procedurally; few delayed cases have also been reported, the latest being 3 years after placement. Device migration can lead to various complications, namely obstruction of the coronary ostia and myocardial infarction, severe paravalvular regurgitation and depending on the geometry of the LVOT and the mitral valve, the displaced device may impinge on the anterior leaflet of the mitral valve and cause severe mitral regurgitation. Treatment options include either open surgical removal of the migrated valve and placement of a SAVR or implantation of a ViV TAVR. The decision should be personalized after accounting for patient and device-related characteristics: the patient’s overall STS score, the presence and severity of LVOT calcification, uniformity and extent of aortic leaflet calcifications, height of the coronary ostia, optimal valve sizing and expansion and coaxial positioning of the TAVR. Prompt recognition and management of TAVR migration is critical to ensure optimal short and long-term outcomes in TAVR patients, especially as the indication of use keeps expanding and as TAVR recipients keep getting younger. Abstract 499 Figure. TAVR migration:pre and post-intervention

Coexistence of retinal angiomatous proliferation and pachychoroid phenotype.

Retinal angiomatous proliferation (RAP) is usually seen in the eye with thin choroid and drusen.[12] Pachychoroid is the morphological description of the thick choroid.[3] We herein report two cases of RAP noted in eyes with pachychoroid. Case 1 Fundus photograph of the right eye of a 48-years-old gentleman with 6/18, N8 vision showed RPE alterations [Fig. 1a and b]. Spectralis SDOCT line scan showed intraretinal edema, hyperreflective spot, subfoveal choroidal thickness (CT) of 436μ and dilated large choroidal vessels. Line scan through the area of thickening showed serous RPE detachment and edema [Fig. 1c and d]. Early phase fluorescein angiogram (FA) showed hyperfluorescence at fovea [Fig. 2a]. Indocyanine angiogram (ICGA) showed hot spot [Fig. 2b]. Late phase FA [Fig. 2c] showed a leak whereas ICGA [Fig. 2d] showed hypercyanescence at fovea amidst diffuse hypercyanescence due to choroidal hyperpermeability. A diagnosis of pachychoroid phenotype with RAP was made.Figure 1: (a) Color fundus photograph of the right eye shows retinal pigment epithelium (RPE) alterations (black arrow). (b) Confocal scanning laser ophthalmoscopy based multicolor image shows greenish hue (yellow arrow) owing to thickening. RPE atrophy is highlighted as reddish hue (black arrow). (c) Spectral domain optical coherence tomography (SDOCT) line scan through the fovea shows intraretinal thickening (yellow arrow) and hyperreflective spot (red arrow). Subfoveal choroidal thickness is 436 μ. Dilated Haller's layer vessels (yellow stars) are seen. (d) SDOCT line scan slightly above fovea shows serous RPE detachment (red arrow) and intraretinal edema (yellow arrow)Figure 2: (a) Early phase fluorescein angiography (FA) image of right eye shows hyperfluorescence at fovea. (b): Early phase indocyanine angiography (ICGA) shows hot spot at fovea. (c): Late phase FA image shows hyperfluorescence increasing in area and intensitiy suggestive of leak from retinal angiomatous proliferation (RAP). (d): Late phase ICGA image shows diffuse hypercyanescence at macula due to choroidal hyperpermeability in pachychoroid eyes. RAP is seen as focal increased hypercyanescence at foveaCase 2 Fundus photography of left eye of a 62 years old gentleman with 6/18, N10 vision revealed RPE alteration at fovea [Fig. 3a and b]. SDOCT scan through fovea showed hyperreflective spots, subretinal fluid, and CT of 336μ. Line scan above fovea showed prominent hyperreflective spot with dilated large choroidal vessel layer [Fig. 3c and d]. Early FA image showed hyperfluorescence corresponding to hyperreflective spot and leak in late phase [Fig. 4a and b] suggestive of RAP in an eye with pachychoroid phenotype.Figure 3: (a) Color fundus photograph of left eye shows RPE alterations (black arrow). (b) Multicolor image shows greenish hue nasal to fovea owing to thickening (yellow arrow). (c): SDOCT line scan through fovea shows hyperreflective spot (yellow arrow) at the level of outer plexiform layer. There is small subretinal fluid (red arrow). Subfoveal choroidal thickness is 336 μ. (d) SDOCT line scan superior to fovea shows well defined hyperreflective spot (yellow arrow) and shallow RPE detachment along with dilated Haller's layer vessels (yellow star)Figure 4: (a) Early FA image of left eye shows hyperfluorescence nasal to fovea. (b) Hyperfluorescence increased in size and intensity and corresponded to the hyperreflective spot seen on SDOCT, suggestive of RAPDiscussion Thickening of RPE and drusen in eyes with RAP hamper the diffusion of VEGF from RPE to choroid, which disturbs choroidal autoregulation leading to attenuation of choriocapillaris.[24] Thin choroid reduces the transport of metabolites back to retina, accentuating the retinal ischemia, and leading to RAP.[2] Attenuation of choriocapillaris is sine qua non of pachychoroid phenotype.[5] The pachychoroid neovasculopathy (PNV) in these eyes is a result of ischemic environment in sub-RPE space owing to attenuation of choriocapillaris.[3] Attenuation of choriocapillaris is common pathology between RAP and pachychoroid. It may be possible for eyes with pachychoroid to develop type 3 neovascularization or RAP in the manner in which they develop PNV. This plausible explanation for RAP in pachychoroid eyes needs to be substantiated in a larger case series. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Effects of Flow Hydraulics, Pipe Structure and Submerged Jet on Leak Behaviour

The aim of this paper is numerical and experimental study of the effects of flow hydraulics, pipe structure (particularly elastic behaviour) and submerged jet on leak behaviour. In this regard, experimental tests were performed on a high-pressure circulation set up. Experiments were performed on an old steel pipe and a High Density Polyethylene (HDPE) pipe discharged to the atmosphere in a wide range of pressures up to 50 m. To analyze the leak behaviour, the effect of the surrounding environment and the pressure on leak area, the experimental setup was modeled by ANSYS software. Then, the numerical model was validated using experimental results and used to analyze and generalize leakage results in other situations. The results indicated that: 1) Standard k-e turbulence model showed a better performance and relatively better results in modelling leakage in comparison with the other turbulence models, 2) Combining the Finite Volume and Finite Element methods for taking into account the impact of pressure allowed simultaneous examination of the pipe hydraulics and the structure of the leak area to obtain more reasonable results from hydraulic analysis of the flow and pipe structure, 3) Pressure fluctuations in the submerged jet affect the leakage discharge so that it is reduced compared to discharging to the atmosphere, 4) it was observed that the leakage exponent is close to the theoretical value of 0.5, considering the effect of pressure head on leak area behaviour. Furthermore, there is a linear relationship between pressure head and leak area for elastic pipes.

Spontaneous Intracranial Hypotension and the durability of Epidural Blood Patch

Abstract INTRODUCTION Spontaneous Intracranial Hypotension (SIH) remains a rare and difficult clinical entity to diagnose and treat. Epidural blood patch (EBP) is the mainstay definitive treatment for refractory cases and has mixed efficacy. We sought to evaluate recent efficacy and outcomes of EBP for SIH at our institution. We also sought to explore the viability of repeat blood patches for patients whose symptoms persisted or recurred. METHODS A total of 23 patients (14 women, 9 men, mean age 49) were seen and treated for SIH between Summer 2009 and Spring 2018. All patients underwent brain magnetic resonance imaging (MRI) with and without gadolinium contrast and T2-weighted spine MRI. Targeted EBPs were placed at 1-2 vertebral levels below identified or suspected areas of leak. Patients were seen within a week following initial EBP and repeat EBP was offered to patients with persistent symptoms. Patients were followed if symptoms persisted or for 6 mo following clinical relief of symptoms. RESULTS 22/23 (95.7%) patients presented with complaints of orthostatic headache, 3 (13%) patients presented with altered mental status (AMS) or focal neurologic deficit. Brain MRI demonstrated pachymeningial enhancement in 16/23 (69.6%) patients, and 5/23 (21.7%) patients had subdural hematoma (SDH) present. Dural leaks were successfully identified in 18/23 (78.3%) patients. 12/23 (52.2%) patients had symptomatic relief with initial EBP, 5/23 (21.7%) patients received repeat EBPs for persistent symptoms will all achieving relief after repeat EBP. About 5/12 (41.7%) patients had recurrent symptoms after initial relief with EBP, and 4/5 (80%) were successfully treated with a second EBP. The mean initial EBP volume and number of EBPs per patient was 21.7 mL. In total, 18/23 (78.2%) patients are currently asymptomatic with regards to their SIH. Mean follow-up in this cohort was 2.6 yr. CONCLUSION EBP is a viable option for the treatment of SIH caused by CSF leak. Repeat epidural blood patch is reasonable in cases of recurrent symptoms.

Vibration-based leak detection and monitoring of water pipes using output-only piezoelectric sensors

While access to potable water remain one of the grand challenges of the modern world, water distribution pipelines continue to degrade globally and pose a problem in overcoming this challenge. There is a need for data-driven decision-making in relation to identifying structurally degraded pipelines, typically used in water distribution, through monitoring and subsequent assessment in a smart manner. This explains the growing attention the area of leak and damage detection in water pipes. This paper presents the conception, development and experimental validation of a novel technology for leak detection in water pipes using sensors made from piezoelectric materials that converts strain from vibration into electrical energy. These monitors are self-powered and hence has the potential to be deployed more easily than those requiring external power to run. The paper details the fabrication and characterization of the sensors, the experimental design which details the design of a benchmark test rig developed and the test procedure to ensure repeatability. The paper subsequently demonstrates how harvested energy signatures are aligned to the location and extent of damage in the pipe by experimentally introducing leakage in the pipe. It presents the results from tests conducted to validate the idea. The conclusions and recommendations provide insights and directions into more extensive applications for these types of sensors for monitoring of our built infrastructure. It is expected that this paper will form an experimental benchmark for future work on this topic.

Spectral responses and identification of surface vegetation stressed by natural gas leakage

ABSTRACT The leakage of natural gas from underground storages can cause economic, safety, and ecological problems. However, when the leakage is slight, the gas concentration in surface atmosphere cannot reach the threshold for direct monitoring. Hyperspectral remote sensing can indirectly detect it through the spectral changes of vegetation in the leak area. A field experiment was performed, which took bean, corn and grass as test plants, to study the characteristics of canopy spectral changes under natural gas leakage stress. The results showed that the spectra of stressed vegetation changed significantly after three days of gas injection, which manifested an increase in the visible bands of 570–700 nm and a decrease in the near-infrared of 760–1000 nm. By performing ANOVA (Analysis of Variance) on the spectra of vegetation in the control and experimental plots, the bands with p< 0.05 and bigger F values were selected as the sensitive bands. And the natural gas stress index was constructed using the selected bands. A quantitative test by JM (Jeffries-Matusita) distance showed that the index could well identify (JM > 1.8) the stressed vegetation throughout the phenological plant cycle. This study can be applied to detect underground natural gas storage leakage spots by hyperspectral remote sensing.

The involvement of autotaxin in renal interstitial fibrosis through regulation of fibroblast functions and induction of vascular leakage

The accumulation of fibroblasts is a critical step in the development of fibrosis, and lysophosphatidic acid (LPA) promotes fibrosis by regulating multiple fibroblast functions. Autotaxin (ATX) is a key LPA-producing enzyme, and we hypothesized that ATX contributes to the development of renal interstitial fibrosis through LPA-mediated effects on fibroblast functions. In a mouse model of renal interstitial fibrosis induced by unilateral ureteral obstruction (UUO), the levels of renal ATX protein and activity increased with the progression of fibrosis in ligated kidneys, despite concurrent reductions in renal ATX mRNA. UUO enhanced vascular permeability in the renal interstitium, and ATX protein localized to areas of vascular leak, suggesting that vascular leak allowed ATX to enter the renal interstitium. In vitro studies showed that ATX induces the migration and proliferation of renal fibroblasts and enhances the vascular permeability of endothelial monolayers. Finally, pharmacological inhibition of ATX partially attenuated renal interstitial fibrosis. These results suggest that during the development of renal fibrosis, ATX accumulates in the renal interstitium and drives fibroblast accumulation and promotes renal interstitial vascular leak, thereby partially contributing to the pathogenesis of renal interstitial fibrosis. Taken together, ATX inhibition may have the potential to be a novel therapeutic strategy to combat renal interstitial fibrosis.

Experimental investigation on pressure–leakage relation for high-density polyethylene pipe

ABSTRACTLeakage control decision-making analysis needs a deep recognition of the pressure–leakage relationship. In this study, leakage behavior in High-Density Polyethylene (HDPE) pipes is investigated by a semi-industrial pilot-scale. Accordingly, some experiments were conducted on circular, longitudinal and circumferential slits for studying the effect of diameter, thickness, and material of pipes, forms, and dimensions of the leak opening, the surrounding environment, and temperature. New equations are presented to estimate the discharge coefficient for orifices and longitudinal slits in HDPE pipes. Leakage value from a longitudinal slit depends on elastic or plastic behavior of the leak area, to distinguish this, a new criterion has been introduced between elastic and plastic behaviours of the longitudinal slit. Results show that, for same leakagel area and pressure, the leakage rate of circumferential slits is generally more than orifices and less than longitudinal slits. Results of this study can be utilized for estimating the leakage rate.

Leakage location on water-cooling wall in power plant boiler based on acoustic array and a spherical interpolation algorithm

In a coal-fired power plant, locating the leak area during boiler hot-state operation has practical engineering value, has apart from its significance in proper shutdown procedures, repair-time reduction, and reduction of financial losses. In this study, we adopted a three-dimensional space location algorithm based on acoustic array to determine the location of water-cooling wall tube leaks in real time. We used a spherical interpolation algorithm to solve the location problem and adopted a time delay estimation based on SWITCH function to obtain the time of arrival. An acoustic location test platform was constructed for studying location accuracy in different location condition. Finally, a field study was performed to verify the spherical interpolation algorithm’s feasibility and practicability in a boiler. Results show that the proposed three-dimensional, eight-element array can locate the leak area during boiler hot-state operation.

Leakage Estimation in Water Distribution Network: Effect of the Shape and Size Cracks

The definition of the relationship between the leak outflow, the total head at the leak and other relevant parameters such as pipe stiffness, leak dimension and shape has been object of extensive studies. The attention to a correct estimation of leakages, leak law, is crucial for the management of water distribution systems. Water utilities, in fact, can reduce leakage levels through the leak detection or more usually by pressure management. In the last cases, the known of the relationship between leak discharge and pressure is fundamental. In recent decades, the use of the Torricelli equation has been questioned, because some experimental results showed that it can yield unsatisfactory results, and other formulations have been suggested to model water leakages in water distribution networks. To investigate the effectiveness of the formulations suggested by different authors, an experimental campaign was carried out at the Environmental Hydraulic Laboratory of the University of Enna (Italy) for leaks of different shape and size in polyethylene pipes. The results of the laboratory experiments contribute to clarify the applicability of the leak law for circular and rectangular leaks and suggest that Torricelli formulation is valid in absence of leak area deformation. Furthermore, the analysis contributes to the knowledge of the coefficients of the leak laws used to estimate the leakage outflow.

Experimental study of crack behavior in pressurized high-density polyethylene water pipes

Leakage of High-Density Polyethylene pipes are more sensitive to pressure. Longitudinal slits are the most failure in High-Density Polyethylene pipes that occur in water distribution networks. In the present study, longitudinal crack behavior in High-Density Polyethylene pipes is studied by a semi-industrial pilot-scale. Considering that longitudinal slits leakage behavior is a function of variations in leak area that can have elastic or plastic behavior, a new criteria has been introduced for the leak ares variation. The obtained results show that the slits can have plastic behavior even in normal pressures. Also, it is observed that the leakage exponent in the elastic phase is between 0.44 and 1.44 and it increases up to 2 in the plastic phase. Results of this study can be used to estimate the amount of leakage in High-Density Polyethylene pipes and to choose the appropriate leakage reduction strategies.•A new method is presented for evaluating the effective parameters on leakage in longitudinal slits in High-Density Polyethylene pipes including the water temperature.•A new method is presented for estimating discharge coefficient and leakage flow in longitudinal slits in High-Density Polyethylene pipes.•A new method has been introduced to distinguish the elastic or plastic behavior of the longitudinal slits.

ANALYSIS OF THE WIDTH OF PROTECTION ZONE NEAR A WATER SUPPLY NETWORK

Abstract A protection zone near the water supply network belongs to the proposals of limiting negative results of potential breakages of buried water pipes. Water leaking from a damaged pipe can create swallow holes or hollows, dangerous especially in the urban areas. The proposed zone is an area on the soil surface along a buried water network, where the outflow of water could be expected after a potential failure of the pipe. The infrastructure in this zone should be carefully planned to limit the social, economic and environmental costs in the case of leakage. The investigations included laboratory tests of a buried water pipe breakage for different cases of leak areas and values of hydraulic pressure head in a pipe as well as analysis of the obtained results and determination of a protection zone for the investigated cases on the basis of tolerance limits. The calculated values of the zone width (5 m if operating pressure is lower than 0.4 MPa, and 7 m otherwise) occurred high, mainly because of the high dispersion of the laboratory tests results. Moreover, we recommended the values of tolerance level to be assumed in calculations.

ANALYSIS OF DENICKELIFICATION PHENOMENON ON HEAT EXCHANGER TUBE

DeNickelification is common phenomenon which occurs for alloy metal containing sufficient amounts of Nickel when it is exposed at high temperature in long time periode. One of component which is made of alloy metal containing Nickel is heat exchangers tube. Heat exchanger is a part of processing unit that use for transfering heat from hot fluid to colder fluid through the combined mechanisms of conduction and convection. When the heat exchanger leaks, all of the processing system could be affected. In this research a leakage heat exchanger tube is investigated by failure analysis methods to find the root cause of failure. Several tests and examinations such as fractography, metallography examinations, SEM and EDS, hardnes as well as chemical compositions test are carried out to this tube to obtain detailed information for further analysis. Result of this reseach shows that some Cu residue, Ni, aggressive/corrosive ion such as Cl - and S 2- at the leak area of heat exchanger tube is found. These evidences indicated that denickelification was occurred on inner surface of heat exchanger tube caused by potential difference between Ni 2+ ion and Cu 2+ ion to form a galvanic cell. Furthermore, since the tube is flown by fluid material which contains aggressive / corrosive ions such as Cl - ion and S 2 - then pitting corrosion on inner surface of tube is formed. This mechanism had been taken place continuously during operation of heat exchanger and pitting corrosion keep growing until the tube leaks.

Pre-procedural fit-testing of TAVR valves using parametric modeling and 3D printing

BackgroundSuccessful transcatheter aortic valve replacement (TAVR) requires an understanding of how a prosthetic valve will interact with a patient's anatomy in advance of surgical deployment. To improve this understanding, we developed a benchtop workflow that allows for testing of physical interactions between prosthetic valves and patient-specific aortic root anatomy, including calcified leaflets, prior to actual prosthetic valve placement. MethodsThis was a retrospective study of 30 patients who underwent TAVR at a single high volume center. By design, the dataset contained 15 patients with a successful annular seal (defined by an absence of paravalvular leaks) and 15 patients with a sub-optimal seal (presence of paravalvular leaks) on post-procedure transthoracic echocardiogram (TTE). Patients received either a balloon-expandable (Edwards Sapien or Sapien XT, n = 15), or a self-expanding (Medtronic CoreValve or Core Evolut, n = 14, St. Jude Portico, n = 1) valve. Pre-procedural computed tomography (CT) angiograms, parametric geometry modeling, and multi-material 3D printing were utilized to create flexible aortic root physical models, including displaceable calcified valve leaflets. A 3D printed adjustable sizing device was then positioned in the aortic root models and sequentially opened to larger valve sizes, progressively flattening the calcified leaflets against the aortic wall. Optimal valve size and fit were determined by visual inspection and quantitative pressure mapping of interactions between the sizer and models. ResultsBenchtop-predicted “best fit” valve size showed a statistically significant correlation with gold standard CT measurements of the average annulus diameter (n = 30, p < 0.0001 Wilcoxon matched-pairs signed rank test). Adequateness of seal (presence or absence of paravalvular leak) was correctly predicted in 11/15 (73.3%) patients who received a balloon-expandable valve, and in 9/15 (60%) patients who received a self-expanding valve. Pressure testing provided a physical map of areas with an inadequate seal; these corresponded to areas of paravalvular leak documented by post-procedural transthoracic echocardiography. ConclusionWe present and demonstrate the potential of a workflow for determining optimal prosthetic valve size that accounts for aortic annular dimensions as well as the active displacement of calcified valve leaflets during prosthetic valve deployment. The workflow's open source framework offers a platform for providing predictive insights into the design and testing of future prosthetic valves.