Tube Leakage Research Articles

ANALISA KEGAGALAN PLATEN TUBE SUPERHEATER PLTU TELUK SIRIH

Superheater is a main part of boiler that serves as one of steam temperature riser after water evaporated by heat inside a boiler. The steam comes out from boiler drum, by utilizing hot air flowinside boiler. Superheater tube is a very important part of process inside the plant, with a high operating temperature of 540°C (in PLTU Teluk Sirih). Because of this, the tube will be maintained by inspection on each scheduled shutdown. Leakages often occur in platen tube of superheater, exactly at its bend or elbow tube. To know causes of the leakages of the part, we conducted observation analysis i.e., visual observation (metallographic testing), spectrometry and hardness test. From the metallographic test analysis, pearlite and ferrite phases present. At the leakage part, it could be observed the tube has lost much of pearlite phase caused by heating. Pearlite micro structure indicates hardness of a material. In spectrometry test of the leaked tube sample using ASTM SA213 T22 standard, value of carbon rises very high by 0.148 from normal value, 0.15 at maximum. We also obtained from it average hardness of 178 HB (ASTM standard). From analysis of the superheater platen tube, damage caused by abrasion of bad materials hit the tube and decreasing pearlite phase caused by temperature changes. Tiny parts of the tube that hit by steam fell eroded and over time the tube broken. Another thing we can conclude is burst of fire in boiler may cause thinning and tube leakage.

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.

Leak Compensation During Volume Guarantee With the Dräger Babylog VN500 Neonatal Ventilator.

To investigate how compensating for endotracheal tube leaks by targeting the leak-compensated tidal volume affects measured physiologic and ventilator variables during neonatal mechanical ventilation. Retrospective observational study. A level III Neonatal ICU. We enrolled 30 neonates who were ventilated using synchronized intermittent positive pressure mode with volume guarantee and had at least 12 hours of continuous detailed recording of ventilation variables. Infants were treated using the Dräger VN500 ventilator (Dräger, Lübeck, Germany), which uses a proprietary algorithm to measure and compensate for endotracheal tube leaks. Eleven were ventilated without leak compensation and 19 with leak compensation. Detailed ventilation data were collected and analyzed at 1 Hz, with intermittent blood gas values. The percentage of leak was less than 20% in 73% of leak-compensated inflations, and the volume of the leak compensation was less than 1 mL/kg in 97.3% of inflations. Between the two groups, ventilation variables were comparable, except the percentage of leak that was significantly (p = 0.005) higher in the recordings with leak compensation. Without leak compensation, the mean expired tidal volume was maintained very close to the set level up to 50% leak, but with leaks greater than 50%, it declined progressively. With leak compensation, the mean leak-compensated expired tidal volume was well maintained even with leak greater than 90% although with large variability. Without leak compensation, the difference between the maximum allowed inflating pressure and the peak inflating pressure decreased progressively as the leak increased. This did not occur with leak compensation. The median PCO2 was slightly higher with leak compensation. During volume guarantee ventilation with a Dräger VN500 ventilator, without leak compensation the expired tidal volume declined after 50% leak. With leak compensation, the tidal volume was maintained even with a large leak. With leak compensation, there was a more stable peak inflating pressure, although the PCO2 was slightly higher.

Corrosion Inhibition by a Caesalpinia Sappan L Modified Imidazoline for Carbon Steel API 5L Grade X60 in HCl 1M Environment

Acidizing is one of the stimulation technologies in the oil and gas industry by removing scale, rust, debris or other acid-soluble particulates on the pipe tubing internal surface. The most common acid used is HCl. To avoid problems such as pipe or casing tubing leak due to acidic corrosion, during the acidizing normally applied with inhibition treatment by inorganic corrosion inhibitor with various compositions including quaternary ammonium salts, solvent and often some surfactant to strip oil from acid reactive surfaces. However, most of these compounds are not only expensive but also toxic to the marine environment. It is an obvious remark to point out the importance of low cost, green corrosion inhibitors which is safe to the environment. The wood extract has become important as an environmentally acceptable, readily available and renewable resource for wide range of inhibitors. A Caesalpinia Sappan L modified imidazoline has been synthesized and used as a corrosion inhibitor for carbon steel in API 5L X60 in HCl 1M environment.The aim of the investigation is to find low dosage-high efficiency green corrosion inhibitor.The testing techniques include wheel test weight loss measurement, Tafel polarization and Electrochemical Impedance Spectroscopy (EIS), Fourier Transform Infra-red Spectroscopy (FTIR). The results of weight loss studies correlated well with those of polarization and Impedance Spectroscopy. Inhibition performance for both Caesalpinia Sappan L modified imidazoline ( CS IMI) and Imidazoline (IMI) increases with increasing inhibitor concentration. The formulated Caesalpinia Sappan L modified imidazoline ( CS IMI), and Imidazoline (IMI) inhibitors give a greater than 90% inhibition efficiency with dosage 25 ppm at a temperature of 90-140°F. Caesalpinia Sappan L modified imidazoline (CS IMI), and Imidazoline (IMI) show comparable inhibition performance. However, at temperature 140oF, Imidazoline (IMI) seems to have a slightly better performance, indicating better thermal stability. Caesalpinia sappan bioactive agents are brazilein and chalcone, and its inhibition mechanism by physisorption obey Langmuir Isotherm, this mode will control charge transfer at surface metal and electrolyte.This result confirms that Caesalpinia sappan modified imidazoline is very promising for the development of green corrosion inhibitors for oil and gas application

Endotracheal tube size to leakage ventilation and tracheal dilatation.

This study analyzed the clinical factors with the aim to determine the relationship between endotracheal tube (ETT) size and leakage ventilation (LV) and tracheal dilatation. All patients with ETT intubation and ventilator support for more than 6months were retrospectively evaluated. The inner tracheal diameter (TD) was measured over image at the starting and 6months after ventilator initiated. We compared the clinical factors, outcomes and complications between patients with and without LV, as well as with and without a TD enlarging more than 25% after 6months (TDn). Logistic regression analyses of factors related to the LV and TDn were performed. The cut-off points of the ratio of outer diameter of ETT (OD) to TD were set and evaluated for their accuracy of predicting LV and TDn. 689 patients were enrolled initially and eventually 199 patients were included, of which 52 and 66 patients were identified to have LV and TDn, respectively. Patients with LV had a higher peak inspiratory pressure (PIP), smaller initial ETT OD/TD and higher incidence of pneumonia. Patients with TDn had a higher PIP, larger initial OD/TD and higher incidence of pneumonia. A higher PIP and smaller initial OD/TD were significantly related to LV and a higher PIP and larger initial OD/TD were significantly related to TDn. The incidence of LV and TDn was higher in patients with an initial OD/TD less than 0.51 and more than 0.54, respectively. The initial ETT OD/TD ratio is a predictor for LV and TDn.

Steam generator leakage in lead cooled fast reactors: Modeling of void transport to the core

Steam generator tube leakage and/or rupture (SGTL/R) is one of the safety issues for pool type liquid metal cooled fast reactors. During SGTL/R, water is injected from high-pressure secondary side to low-pressure primary side. The possible consequences of such an event include void transport to the core that has adverse effects on the reactor performance including heat transfer deterioration and reactivity insertion.This paper addresses the potential transport of steam bubbles to the core and subsequent void accumulation in the primary system in ELSY conceptual reactor. A CFD model of the primary coolant system for nominal operation is developed and verified. Bubble motion is simulated using Lagrangian tracking of steam bubbles in Eulerian flow field. The effects of uncertainties in the bubble size distribution and bubble drag are addressed. A probabilistic methodology to estimate the core and primary system voiding rates is proposed and demonstrated.A family of drag correlations by Tomiyama et al. (1998) provide the best agreement with the available experimental data. Primary system and core voiding analysis demonstrate that the smallest (sub-millimeter) bubbles have the highest probability to be entrained and remain in the coolant flow. It is found that leaks at the bottom region of the SG result in larger rates of void accumulation.

Copper tubing failure due to ant-nest corrosion

Ant-nest corrosion is a type of premature and localized failure, which is observed in Cu tubes used mainly in air-conditioning and heat exchanger units, induced by the presence of organic matter. Leakage takes place within a short period of time after unit installation and frequently causes pipeline and equipment damage accompanied with loss of refrigerant liquid. In the present paper, case histories concerning such type of insidious corrosion phenomena are presented. Metallographic examination on cross-sections revealed that a particular pitting corrosion mechanism is activated, driving to a tunnelling-type “tortuous” pit propagation, causing rapid metal tube perforation and leakage.

The Effects of Mouth Opening and Throat Pack Placement on Uncuffed Nasal Endotracheal Tube Leakage and Delivered Tidal Volumes in Mechanically Ventilated Pediatric Patients Undergoing Dental Procedures.

Intubation for pediatric patients is frequently performed with an uncuffed endotracheal tube (ETT), which may result in an incomplete tracheal seal, resulting in gas leakage (leak). The purpose of this study was to assess the effect of (1) mouth opening and (2) throat pack placement in sealing and/or minimizing this leak to an acceptable level while providing adequate tidal volumes in mechanically ventilated patients. This prospective study of 2- to 6-year-olds undergoing general anesthesia with nasal intubation for dental procedures in the New York University-Lutheran Medical Center operating room was conducted between March 2015 and October 2015. Three sequential tidal volume (VT) measurements were recorded: postintubation with the neck extended, with mouth opened, and after throat pack placement. Twenty-five subjects were included in the analyses. For subjects in whom no leak was detected, only throat pack placement statistically improved VT. This is in marked contrast to numerically large, statistically significant effects, relative to baseline, for mouth opening (±23.2 mL, p < .009, 21% increase from baseline) and throat pack placement (±46 mL, p < .009, 41% increase from baseline) when a leak was detected. In children 2-6 years of age, nasal intubation with uncuffed ETTs that have incomplete tracheal seal have improved VT with mouth opening and throat pack placement. This finding suggests that the intubation procedure is a process that extends through positioning, mouth opening, and throat pack placement.

Application of Digital Drainage System in Postoperative Refractory Prolonged Air Leaks after Pulmonary Surgery

背景与目的术后持续性肺漏气是肺部手术后最常见的并发症之一。数字化胸腔引流系统（digital drainage system, DDS）被认为具有准确、客观、舒适、患者耐受性好、经济等优点。本研究旨在总结DDS用于肺部手术后难治性持续性大量漏气的临床疗效。方法术后5天和7天分别是胸腔镜和开胸术后持续性肺漏气（prolonged air leak, PAL）的界限；本研究将难治性持续性大量漏气定义为达到PAL时间2倍及以上且漏气持续达2度以上，可伴有明显皮下气肿或纵隔气肿等相关并发症。2016年1月-2016年12月间，应用数字化胸腔引流系统结合胸膜固定术治疗符合上述标准的病例共8例，收集相关临床资料并总结分析。结果本组病例中肺叶切除术6例，肺段切除2例。平均术后持续漏气（17.3±5.1）d，DDS平均使用时间（5.6±3.7）d。平均术后引流量（3, 550.6±1, 881.1）mL。应用DDS前后的平均引流量为（2, 615.6±1, 741.2）mL和（935.0±242.7）mL。平均住院时间（18.1±5.0）d。结论数字化胸腔引流系统用于肺部手术后难治性持续性大量漏气安全可行，可提供更大的负压吸引值，从而促使患肺复张为后继的胸膜固定术创造条件，并缩短引流天数和住院时间。

CFD analysis of temperature imbalance in superheater/reheater region of tangentially coal-fired boiler

This paper presents a CFD analysis of the flow, velocity and temperature distribution in a 700 MW tangentially coal-fired boiler operating in Malaysia. The main objective of the analysis is to gain insights on the occurrences in the boiler so as to understand the inherent steam temperature imbalance problem. The results show that the root cause of the problem comes from the residual swirl in the horizontal pass. The deflection of the residual swirl due to the sudden reduction and expansion of the flow cross-sectional area causes velocity deviation between the left and right side of the boiler. This consequently results in flue gas temperature imbalance which has often caused tube leaks in the superheater/reheater region. Therefore, eliminating the residual swirl or restraining it from being diverted might help to alleviate the problem.

Pressure Gastric Ulcer From an Over-Inflated Gastrostomy Tube Balloon: An Unusual Cause of Upper Gastrointestinal Bleeding

Percutaneous endoscopic gastrostomy (PEG) is one of the most commonly performed endoscopic procedures used for the establishment of enteral feedings in patients with dysphagia and in the elderly population with poor oral intake. Approximately 160,000-200,000 endoscopic PEG tube placement are performed each year in the United States. Despite its high success rate (>95%), major complications have been reported in 1% to 3% of cases. Endoscopically placed PEG tubes are more durable and longer lasting because an internal bumper of the tube holds the gastric wall firmly against anterior abdominal wall. This prevents easy dislodgement of the tube and minor leakage around the stoma. Dislodged endoscopic PEG tubes with a mature gastro cutaneous fistula can be replaced at the bedside with a PEG tube with a balloon. This avoids the need for a repeat endoscopy. Though cost effective the clinician should be properly trained about proper technique to avoid adverse outcomes. One such outcome is described in this case report. 80-year-old female with dementia and multiple co-morbidities presented from a nursing home with complaints of hematemesis and bleeding around PEG tube. Clinically she was noted to be tachycardic (HR 113 bpm), febrile (100.6 degrees). Blood work revealed anemia (Hgb 6.8 gm/dl) and high Blood Urea Nitrogen. On exam, a 22 Fr balloon PEG (15 cc balloon) with dried blood in and around the tubing was observed with melena on rectal exam. EGD revealed a large gastric ulcer with a visible vessel at the point of contact with an overinflated balloon. The internal balloon of the PEG tube appeared to be overinflated (at least 25 cc in a 15 cc balloon), compressing and ulcerating the stomach wall at the area of contact between the balloon and the gastric wall (Figure 1). Successful hemostasis was achieved endoscopically and a new bumper PEG tube placed under endoscopic guidance. Overinflated PEG tube balloon resulting in a large gastric pressure ulcer is an uncommon etiology of upper GI bleeding. This report can be used to emphasize the importance of following the PEG tube manufacturers recommendations and exercise proper technique and caution.Figure: Internal balloon of PEG appeared to be overinflated and compressing the stomach wall in area of ulcer.

Airflow Error Measurement Due to Pneumotachograph Mask Rim Leaks

Airflow during speech production is recorded using a pneumotachograph system wherein typically a mask is placed upon the face. Accurate measures of airflow require mask calibration and a complete seal of the mask rim to the face. Literature frequently cites mask rim leaks as causing flow measurement inaccuracies, but quantitative studies of the inaccuracies are needed. The purpose of this study was to determine the degree of inaccuracy of flow measurement using a Glottal Enterprises aerodynamic system for a variety of mask rim leak conditions. Air was pushed and pulled through the Glottal Enterprises mask system over a wide range of airflow with leaks simulated by small metal tubes of various cross-sectional areas placed between the mask rim and a face-like calibration mold. Two leak locations, single versus multiple leaks, and two different leak tube geometries were used. Results suggest that (1) as leak area increases, the amount of leak flow increases; (2) the amount of flow leak is relatively independent of location; (3) given equivalent leak areas, multiple leak locations provide less leak flow; and (4) quasi-elliptical tubes were more resistive to airflow than rectangular tubes. A general empirical equation was obtained that relates the leak flow between the mask rim and the face, the size of the leak region, and the amount of the upstream airflow toward the mask: Leak(cm3/s) = 0.33 × Area(cm2) × Flow(cm3/s) for the range of ±2000 cm3/s. This equation may provide researchers and clinicians with a tool for generalizing airflow leak effects.

Total Laparoscopic Approach for Transhiatal Esophagectomy and Gavriliu's Esophagoplasty in Children with Caustic Esophageal Injuries.

Esophageal repair after caustic injury is a surgical challenge in children. The aim of this study was to report the first results of a total laparoscopic approach in transhiatal esophagectomy and esophageal replacement by an anisoperistaltic gastric tube. A retrospective review of data from children operated on with a laparoscopic approach for transhiatal esophagectomy and Gavriliu's esophagoplasty between 2011 and 2015 was performed. Surgical techniques were related with variations for 2 cases, 1 case with robotic assistance and 1 with thoracoscopic assistance. Seven patients were operated on. The median weight was 16 kg. Median duration of mechanical ventilation was 2 days. Total esophagectomy was achieved in all cases. Two patients could eat after a barium swallow 7 days after surgery. The most frequent immediate complication (57%) was anastomotic or gastric tube leakage treated successfully in 100% of the cases with self-expanding metallic stent placement. Seventy-one percent of children presented with stenosis, which responded to pneumatic dilatation in 67% of the cases. Redo surgery was required in 43%, either for anastomosis revision or nonfunctioning gastric tube. With an average follow-up of 51 months, 85.7% of children achieved oral feeding. Total laparoscopic approach for esophagectomy and esophageal replacement by Gavriliu's anisoperistaltic gastric tube is a feasible technique allowing to shorten the postoperative mechanical ventilation duration and save parietal damage often present in these patients requiring multiple surgery. It appears to have a good long-term tolerance, although the immediate postoperative complication rate remains as high as the open technique.

Compliance and Quality Control Monitoring of Diagnostic X ray Facilities in Dar es Salaam City, Tanzania

The compliance evaluation and quality control measurements on 14 diagnostic X ray units were carried out. The results on legal compliance show that 43 % of X ray facilities operated without or with an expired license. The rest of the centers were new and had already applied for license and others had valid licenses. For basic requirements, the results shows that 57 % of X ray facilities did not have the changing cubicles, 36 % of X ray facilities did not post radiation warning sign and symbols also 64 % of units were found either without protective gear or operated by unqualified personnel. The QC test results showed that 93 % had X-ray tube voltage within the tolerance limit of 10 % and HVL ≥ 2.3 mmAl, at 80 kV was observed in all 14 units whereas 100 % of exposure had acceptable kV reproducibility within the tolerance limit of 5 %. Of the X-ray generators assessed, 86 % had tolerable mAs linearity. 79 % and 93 % had acceptable beam alignment and light beam diaphragm. Of the assessed units, 57 % had tube leakage 10 µSv/hr were recorded at viewing windows, walls and doors of control cubicles and behind the doors of changing cubicles. These dose rates indicating higher health risk to workers and member of public.

Volume guaranteed? Accuracy of a volume-targeted ventilation mode in infants

ObjectivesVolume-targeted ventilation (VTV) is widely used and may reduce lung injury, but this assumes the clinically set tidal volume (VTset) is accurately delivered. This prospective observational study aimed to determine...

Experimental study on spray flash evaporation under high temperature and pressure

Most leakage problems from pipe system breaches result in the formation of spray flash evaporation. In this study, a variety of experiments were carried out in the high temperature and high pressure (HTHP) steam-water test loop to study spray flash evaporation related to tube leakage problems. The focus of our study was on the flash evaporation from the highly superheated jet (the superheat degree can be up to 200K) with a small injection rate. The temperature and relative humidity variations in the region of interest were measured in the experiment. As the transient relative humidity changes can enable better reflection of the characteristic of flash evaporation, non-dimensional relative humidity (NDRH) and the critical time of the relative humidity variation was proposed and used to analyze the flash evaporation. The effects of injection rate, injection direction, initial water temperature, and injection pressure were investigated. The experimental results showed that the increase of the injection rate and initial water temperature enhanced the flash evaporation. The corresponding critical time increased with the increase of spray angle. The injection pressure was found to result in better atomization and evaporation of the water on the premise that the injection pressure guaranteed complete flash evaporation.

Thermal Spraying with Diode Lasers

AbstractBoiler tubes in biomass and incineration plants are exposed to extreme operating conditions. To create vapor pressure within the pipes that makes an effective drive of the power‐plant turbines possible, flue gas temperatures of up to 1000 °C must be realized within the combustion chamber of the boiler. No pipe‐material will sustain the chemical processes induced in this way for very long. Already at temperatures of 350 °C, the chlorine in the flue gas increasingly reacts with the iron of the ferritic pipe materials. A rapid and progressive oxidation process begins and reduces the wall thickness of the pipes, which can lead – using unprotected pipes – to tube leakage in some cases within less than one year (Fig. 1). In order to improve the lifetime of pipes, many power plant operators count on metallic or ceramic corrosion‐protection coatings. With their help, the material decomposition process can be delayed and the lifetime of the pipes can be tripled or even quadrupled. However, the investment in a coating in most cases is profitable already if lifetime of pipes is doubled because the exchange of corroded pipes requires new tubes plus a temporary shutdown of the whole boiler system.

Acoustic radiation and cold point defect in boiler tube arrays based on phononic crystals theory

The structure of heat exchangers is similar to two-dimensional phononic crystals in boilers. In this study, with the given tube array parameters of the heat exchanger, we investigate the effects of sound source location and different frequencies on acoustic radiation. Based on phononic crystals theory, the Plane Wave Expansion method is used to calculate the band gap structure, and the Finite Element method is used to study the acoustic insertion loss and radiation characteristics. In the simulations, constant boundary conditions are imposed on the boundary between the air and steel boards, the radiation boundary conditions are applied to all boundaries of the air domain cell, and the free triangular is used in the simulated domain. When there is tube leakage, a cold point defect exists in the tube arrays. We also study the sound transmission characteristics of the cold point defect at a different location. This study can provide an innovative concept and method for leakage location and sonic soot cleaning in boiler tube arrays.

CANDU pressure tube leak detection by annulus gas dew point measurement: a critical review

Abstract In the event of a pressure tube leak from a small through-wall crack during CANDU reactor operations, there is a regulatory requirement – referred to as Leak Before Break (LBB) – for the licensee to demonstrate that there will be sufficient time for the leak to be detected and the reactor shut down before the crack grows to the critical size for fast-uncontrolled rupture. In all currently operating CANDU reactors, worldwide, this LBB requirement is met via continuous dew point measurements of the CO2 gas circulating in the reactor's Annulus Gas System (AGS). In this paper the historical development and current status of this leak detection capability is reviewed and the use of moisture injection tests as a verification procedure is critiqued. It is concluded that these tests do not represent AGS conditions that are to be expected in the event of a real pressure tube leak.

A novel plugged tube detection and identification approach for final super heater in thermal power plant using principal component analysis

During startup or normal operations, tube monitoring systems for steam boilers can considerably improve efficiency and reliability in thermal power plants (TPPs). Although several attempts have been made to detect and locate boiler tube leaks, what seems to be lacking is the study for tube plugging, one of the fundamental causes of the leaks and other tube failures. Scale and deposit formations on inner surfaces of tubes cause the tubes to be plugged. Although the formations can be suppressed and removed by chemical treatments for boiler water and steam blowing during startup procedures, it is still difficult to monitor and prevent tube plugging during startup or normal operations. In this paper, a novel plugged tube detection and identification approach is proposed for final super heater (FSH) tube banks. Principal component analysis is applied to tube temperature data for plugging detection and identification. The data are collected from thermocouples installed on the FSH outlet header section. To identify plugged tubes, contribution analysis and the characteristics of plugged tube temperatures are employed. To verify the performance of the proposed method, tube temperature data from an 870 MW supercritical coal-fired TPP are used. The experiment results show that the proposed method can successfully detect and identify plugged tubes. The proposed method can help to decide how many times steam blowing should be performed, whether startup procedures should be delayed or stopped, and which tubes should be maintained. Furthermore, severe tube failures can be prevented by avoiding damage from overheating due to tube plugging.