Failure analysis and also the principal mechanisms by that boiler tubes fail in. Photographs displaying a the site of failure replacement tube welded in and b submitted portions of the failed tube. The thermal analysis is compared with previous studies on the cleanliness of boilers. Analysis of tube failure in water tube boiler ijirset. Waterside corrosion also can result from low or high boiler water ph values and high levels of certain salts. Recovery boiler water treatment figure 2 objectives of. Insitu metallography was used to survey the neighbouring regions to assess the conditions of the failed tube and neighbouring tubes.
Failure of tubes in boiler of the power plants may occur due to various reasons. Boiler tube failures are the leading cause of steam plant reliability issues. Recovery boilers are particularly vulnerable to short term overheat failures of superheater tubes during startup due to the potential for fouling and the suppression of heat transfer of these surfaces and the need to quickly restart these units in order to minimize downtime. Effective boiler tube integrity management, preventing. Tube failures in the lower furnace can cause deadly explosions from smeltwater. At times, the cause of a failure cannot be readily determined, making it difficult to determine the appropriate corrective action. Tube failure management renew tubes wholesale typically at planned outage on basis of known wastage rate to optimise maintenance strategy for reliability. Critical failure analysis of superheater tubes of coalbased. Failure analysis of the boiler waterwall tube sciencedirect. Reducing boiler tube failures requires a twopronged approach. Care and maintenance of circulating fluidized bed boilers. Determining the failure mechanism is the first step of the failure reductionelimination process. Oxygen pitting occurs with the presence of excessive oxygen in boiler water. Micrographs of the neighbouring tubes to the failure.
Therefore, it is necessary not only to identify and repair it in the case of failure but also to eliminate the root cause of this problem. This paper presents failure analysis of final superheater tube in ultrasupercritical. Aggressive localized boiler tube corrosion and loss of tube wall. Boiler tube failures are generally recognized as the major cause of forced outages of fossil power generating units for us electric utilities. At the last international boiler tube failure conference in. Pdf on jan 1, 2015, eaugen furamera published boiler tube failure analysis find, read and cite all the research you need on. Usually this change is wrought throuah some combination of corrosion and erosion acting on the boiler tube to weaken it. Failure analysis of a boiler tube in usc coal power plant frontics. Boiler tube failure mapping and root cause analysis boiler tube failure reduction plan with boiler quality inspection and overhauling. Also failure of superheater tubes has a significant negative impact. Manual for investigation and correction of boiler tube. A primary cause of this is the uneven distribution of hot gases across the face of the tube sheet. Guidance on boiler tubing, headers, and drums can be used by members to establish a boiler tube failure.
In almost all cases of serious availability losses, the boiler tube failures are repeat in nature and result in multiple forced outages. Boiler tube failures are leading cause of forced outages in fossilfired boilers. Several examples of boiler tube failures are given and explained using the thermal analysis. The investigation into the causes of a boiler tube failure is very important to prevent future. Shortterm overheat failures are most common during boiler startup. Damage mechanisms causes premature failures in boiler tubes. Workshop on boiler tube failures causes and remedial measures. Tube failures in high pressure boilers bright hub engineering. Boiler tube failure handbook pdf boiler tube failures continue to be the major cause of forced outages. Fireside mechanisms understand how and why tubes fail, and apply these preventive measures to avoid costly downtime, joseph colannino, colannino consultants oiler tube failure is an expensive problem, requiring valuable time and capital to correct. Water tube boiler a type of boiler that contains waterfilled tubes that allow water to circulate through a.
Depending on materials, fuel used, and operation practices. Boiler boiler is the main part in the power generation. The fuel used in this boiler is low grade bituminous coal having a calorific value of 4204kcalkg. Final report, author lamping, g a and arrowood, jr, r m, abstractnote the manual is for use by electric utility power plant personnel during the investigation into the cause of a boiler tube failure and during the evaluation of corrective actions to prevent future boiler tube failures. Quite often they are related to dew point corrosion, an insidious condition that can penetrate up to 0. Introduction case study 1waterwall tube burst in a cfbc boiler. Can be influenced through fouling and gas laning within the stage. Thin walled tubes that normally last 10 years can become badly pitted during shutdown, and replacement tubing becomes an unanticipated expense. To our luck, all the load variations could be seen. Analysis of boiler tube failure international journal of innovative. Failure investigation and analysis case histories 110. It must be kept in mind that a failure of a tube is generally a sign of another problem, and it needs complete evaluations and investigations.
Straight tube, shelland tube waste heat boilers frequently develop tube and tube sheet failures due to the imposition of unequal stresses. They can be analyzed and corrective and preventive action can taken. The performance of this boiler was conducted by calculating thermal efficiency and heat losses of pulverized fuel boiler. The failure of water wall tube is essentially due to hydrogen damage leading to formation of fissures and microcracks that weakened the tube matrix at failure location. Boiler tubes are subjected to various failure mechanisms driven by temperature, stress and environmental hazard, depending on. Two factors which greatly influence the pro pensity for tube nipple cracking are, the.
The present paper reports various problems such as agglomeration, slagging, fouling, caustic. The failure had been cut up into pieces prior to submission. Boiler tube failure management prevent boiler tube failures, one of the major causes of unplanned outages, by taking a proactive, costeffective approach to boiler tube management. Superheater tubes located near the boiler outlet that increase superheat the temperature of the steam, p. The outage results in lost production and lost revenue. Failure analysis of cracked boiler tube page 4 of 10 figure 1. Barry dooley the current state of boiler tube failures. Failure of boiler tubes is a very common phenomenon in a power plant. Boiler tubes failure causes and remedies a case study of. Oct 01, 2017 failure analysis of the boiler waterwall tube is presented in this work.
Both courses will be of value to anyone concerned with maintenance or operational aspects of boiler tube failures, and have been. Some designs are susceptible to waterside corrosion problems and tube failures may be prevalent. Boiler tube failures main cause of forced outages and availability in steam generating boilers. The effective boiler tube failure management oneday course is aimed at engineers directly involved in the strategic management of boiler tubes, whether operationally or commercially. Improve boiler availability through fewer boiler tube failures. Different case studies of boiler tube failures in thermal and gas power plants. Avoiding short term overheat failures of recovery boiler. The adjacent, mirrored tube had leaked and been replaced several years before. Two of the most prevalent refractory failures are thermally induced failures and anchoring system. Pdf this paper assesses boiler tube failures btfs, especially in boiler water wall tubes 14 kurita handbook of water treatment kurita water industries. For boilers that have been previously operat ing, some chanoe must occur to effect tube failure.
The boiler tubes are interacted at a harsh environment through inside steam and outside flue gases. The cost of boiler tube failures is comprised of three main components. Waterside deposits in boiler tubes raise tube metal temperatures and can lead to tube failures from overheating and waterside and fireside corrosion. Following is the summary of observations and operational modifications carried out. Boiler tube failures are the leading cause of forced outages of fossilfired power plants. Boiler tubes are a vital component in the steampower cogeneration plants. Pits can act as stressconcentration sites which can be initiation points for stressrelated corrosion mechanisms. Nonetheless, failures do happen, and of particular concern are tube failures, which are not uncommon. Reduce risk of inservice failures in tubes, headers, and drums. Depending on process and steam system considerations, varied boiler designs and pressures are utilized. Pdf boiler tubes are a vital component in the steampower cogeneration plants. Boiler is a sealed vessel in which water is converted into steam. Good operating and maintenance practice reduces tube failures.
Depending on materials, fuel used, and operation practices, different failures could occur. Water tube boiler a type of boiler that contains waterfilled tubes that allow water to circulate through a heated firebox, p. One common reason of the boiler tube failure is higher the. A tube failure may cause a forced outage, usually at the most inopportune time. Understand the root cause of failure tube failures predict. A detailed examination of the failure and associated operating data is usually helpful in identifying the mechanism of failure so that corrective action may be taken. It can occur during operation as a result of inleakage of air at pumps, or failure in operation of preboiler water. Tube failures in boiler accessories occur due to various reasons and major reasons for failure among the various reasons are flue gas erosion, long term. Failure analysis of high temperature superheater tube hts. These include failures due to creep, corrosion, erosion, overheating and a host of other reasons.
Routine sampling for condition assessment can help monitor the. An overview of problems and solutions for components. The hydrogen damage occurred due to underdeposit corrosion at localized region. The failures could have been avoided by proper field inspection. Recent experience in boiler header tube nipple failures. A boiler tube fails when the structural integrity of the tube is compromised. P63 boiler life and availability improvement program. Boiler tubes, overheating, welded joints, welded steel, joiningrelated failures, hydrogen damage and embrittlement. At the high temperatures found in a boiler, deposits are a serious problem, causing poor heat transfer and a potential for boiler tube failure. Contents boiler boiler accessories boiler tube failures case study on boiler tube failures. Superheater tube failure is listed among the major causes of a fossilfuelfired boiler outage. Introduction in the normal operation of a steam generator, regardless of the temperature or pressure, steam or water will react with steel to form iron oxide. The current state of boiler tube failures in fossil plants introduction at the last international boiler tube failure conference in 1991 1, the conference participants ranked the following areas as being of the highest priority to improve the overall area of boiler tube failures btf. Dec 21, 2017 in engineering applications, there are various types of boilers such as water tube boilers, fire tube boilers, packaged boiler, fluidized bed combustion boiler, pulverized fuel boiler and waste heat boilers.
Failure analysis and investigation methods for boiler tube. The performance of this boiler was conducted by calculating thermal efficiency and heat losses of pulverized fuel boiler by indirect method. Waste heat boilers whb generate steam while cooling a process fluid. Tube failures during the initial operation period, the normal operation period, and after ten to fifteen years operation show different trends. Boiler acts as a medium in which water is converted into steam by using the heat released in the process of combustion of coal in the presence of oxygen. To prevent tube failures, which causes temporary shutdown of the power plant, assessment of the tubes are always conducted according to power plant preventive maintenance practices 78. In order to examine the causes of failure, various techniques including visual inspection, chemical analysis, optical microscopy, scanning electron microscopy and energy dispersive spectroscopy were carried out. The process environment of fossilfired boilers and hrsgs, along with operation errors during engineering, fabrication, erection, operation, and maintenance will always result in occasional boiler tube failures. Most failures have been documented for boilers in service for a period of more than 15 years. Refractory used in circulating fluidized bed boilers includes brick, block, tile, plastic rammed, castable and gunned refractory.
This paper assesses boiler tube failures btfs, especially in boiler water wall tubes bwwts for a natural circulation highpressure fossil natural gas drum. Barry dooley the current state of boiler tube failures peter. The power plant had been in operation for a total period of 326 hrs. The case studies presented herein are categorized as, failures occurring in high temperature steam tubes and in lower temperature water carrying tubes. How to use the handbook the visual appearance of a failed boiler or hrsg tube provides valuable information regarding the mechanism of failure. Failure analysis, and the principal mechanisms by which boiler tubes fail in service, will be examined in this introductory survey. As this is an introductory survey, the reader is referred to two excellent reference texts covering the field of boiler failures for more detailed information. Boiler tube failure reduction program technical report.
In almost all cases of serious availability losses, the boiler tube failures are repeat in nature and result in. Workshop on boiler tube failures causes and remedial. Failures result in a ductile rupture of the tube metal and are normally characterized by the classic fish mouth opening in the tube where the fracture surface is a thin edge. The goal is for to reduce the forced outage with zero chemistry related failures.
These failures risk equipment damage, personnel exposure and downtime on the recovery boiler. Recovery boiler water treatment figure 2 objectives. Modern demands on hrsgs has effectively driven them to see many of the tube failures that occurred on radiant boilers, with some differences. During periodic shutdowns of the boiler unit, tube failures can occur. Therefore, it is necessary not only to identify and repair it in the case of failure. Learn from previous failures and our extensive experience of boiler plant worldwide to implement the right maintenance strategy and improve reliability and availability. Critical failure analysis of superheater tubes of coal. There are twentytwo primary reasons for tube failures in a boiler, which can be classified under six major groups.
The mechanism of tube failure could be found out in this visit. Boiler tube failure thermohydraulic analysis the boiler hopper tubes at an eskom power station suffer from continuous mechanical failures that lead to frequent unplanned maintenance. Both courses will be of value to anyone concerned with maintenance or operational aspects of boiler tube failures. The boiler tubes are under high pressure andor hightemperature conditions. Introduction case study 1waterwall tube burst in a. The boiler tubes in natural circulation boilers may suffer tube burnout because of rapid changes in boiler operating variables such as over firing, drum pressure, flame impingement, and steamwater ratio. The current state of boiler tube failures in fossil plants. Understanding corrosion fatigue and developing solutions. Waste heat boiler a device that uses waste heat from a process to produce steam, p. They are subject to potential degradation by a variety of.
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