A good percentage of these failures are due to long term overheating. Pulverized coal fired boiler persistent superheater tube. Epri is at the center of a quickly evolving energy landscape. Aggressive localized boiler tube corrosion and loss of tube wall.
Boiler feed pump failure root cause analysis duration. The tube failures investigated in this study occurred in the hopper section of the boiler. These best practices have realized not only the reliability of equipment but also the safety of the people that use them. Identifying the root cause and implementing corrective action is essential to avoiding repeat boiler tube failures and the costs and downtime incurred with those failures. Apr 18, 2019 they introduced codes, standards, and checklists to ensure that boiler safety is secondnature. These include failures due to creep, corrosion, erosion, overheating and a host of other reasons.
Prior to removing a failed tube, mark and photodocument the tube gas flow direction, fluid flow direction, row number, elevation, boiler section, etc. Various corrosion mechanisms contribute to boiler tube failure. The aware boiler integrity module is in use at over half the boilers in north america to improve reliability, availability and safety. These failures can be avoided when we understand the reason and operate the boiler accordingly. In order to help prevent boiler tube failures, in 1985 the electric power research institute epri developed the model for a boiler tube failure reduction btfr program. Standard tube failure and inspection reports are provided for all of the boiler pressure parts. Tube failures during the initial operation period, the normal operation period, and after ten to fifteen years operation show different trends. The first impression report from designer, analysis by designers and final evaluation and corrective action are. Only one half of the four boiler hopper walls were modelled as this forms a representative region of the complete. Explain four reasons why large number of repeat boiler tube failures. Long term overheating failures are due to the fact that the operating metal temperature of the boiler tubes going above the allowable limit.
In the literature, a comprehensive modeling for fire tube boilers. However, work conducted in the last 5 years has started to provide. Boiler tube failures are the leading cause of steam plant reliability issues. A thinlipped rupture at failed region was observed in superheater tube.
Good operating and maintenance practice reduces tube failures. Failure assessment of astm a2t12 superheater boiler tubes. The superheater overheat protection shop system is a proprietary technology that helps mitigate the risk of superheater tube failure due to shortterm overheat during boiler startups. The service uses ultrasonic technology and proprietary software to accurately measure the thickness of the deposit layer. Boiler tube failure reduction programme interteks boiler tube failure reduction programme and services can help power plants improve reliability and avoid costly outages. Shop assists operators in the management of boiler startups by enabling the detection of superheater tube clear events tces. This calls for immediate action as it can often cause a shutdown of the boiler, leading to loss of production and downtime. Failure mode determination can distinguish the various tube failure mechanisms such as creep, shortterm overheat, corrosion, erosion, or fatigue. Apr 04, 2014 ntpc, unchahar boiler explosion what is boiler explosion reasons behind ntpc boiler explosion duration.
One is the boiler machinery bm coverage for the pressure side, meaning the tubes, drums, water level controls and safety relief valves. Failure analysis of the steam tubes was carried out by optical and scanning electron microscopy examinations, chemical analysis of the tube material and the results showed that the scales were formed in. Is your boiler tube failure reduction program showing improvement when compared to programs at peer plants. Deterioration and loss of material due to chemical attack. Tube metal temperatures reach combustion gas temperatures of 1600f 870c. Unexpected boiler tube failure is the major factor causing unreliability in utility boilers. Boilers are generally one of three main types firetube boilers, watertube boilers, and electric boilers. Failure analysis of waste heat boiler tubes april 26, 2017 abdulmohsen alsahli, avtandil khalil bairamov, abdulaziz almeshari, gys van zyl, and ali alshawaf. 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. With tangent tube construction a failed tube can be plugged and the boiler operated normally without further attention. Failures result when the tube metal temperature is extremely elevated from a lack of cooling steam or water flow.
This makes maintenance easier and reduces associated costs. Tube temperature distribution in water tube boiler a. How to use the handbook the visual appearance of a failed boiler or hrsg tube provides valuable information regarding the mechanism of failure. The remaining wall thickness decreases due to the formation of scale which eventually causes failure of the boiler tubes.
The reader is cautioned to refer to the latest edition and addenda of the asme boiler and pressure vessel code for current requirements table i initial creep temperature. During periodic shutdowns of the boiler unit, tube failures can occur. Boiler tube failure analysis applied technical services. Boiler maintenance workstation supplements formal prevention programs to dramatically reduce tube failure. Look to the industry leader for comprehensive tube. Engineers guide to boiler tube inspections engineering360. Since 1969, webco has provided seamless carbonalloy and welded carbon tubing products for pressure tube applications in petrochemical, commercial fire and water boiler service, and requirements in a variety of other industries.
Justin will discuss the aspects of whe tube failure, api 521 evaluations, and sru pressure buildup. The aware boiler integrity software provides the tools necessary to record, view, and report tube failures by displaying them on plantspecific interactive cad drawings providing total quality assurance. A tube failure may cause a forced outage, usually at the most inopportune time. 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.
Boiler tubes are susceptible to certain damage mechanisms, including. Consequently, the internal oxide layer led to a series of metallurgical degradation and the loss in mechanical strength of the boiler tubes. Barry dooley the current state of boiler tube failures peter. Once the damage mechanism has been identified, recommendations can be made to mitigate similarly affected tubes within the boiler via subsequent nondestructive testing or additional tube sampling. Failure of tubes in boiler of the power plants may occur due to various reasons. The boiler tubes are operated continuously at high temperature and pressure. 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. The second part of a boiler s insurance is the property coverage, which covers the fire side, such as the fuel train, firebox, and refractoryrelated issues. Better yet, let us help put together a complete condition assessment program to help eliminate tube problems before failures occur. After a tube failure is suspected it is necessary to decide to run or stop boiler if unit did not trip, then after boiler is shut down the correct location of failure, collecting tube sample, and ensuring all inspection is complete before repairing the failed area are very important. Such failures are less frequent than boiler tube failures, but the damage resulting can be enormous. Stress corrosion cracking scc hydrogen damage sulphur corrosion graphitization thermal fatigue waterside corrosion fatigue soot. Easy access to all internal areas of the boiler including tubes, burner, furnace, and refractory, is available from either end of the boiler.
The technical knowledge of boiler tube failures btf has improved dramatically in the past 10 years and has most recently been compiled in a threevolume book. Boiler tube failures continue to be the leading cause of downtime for steam power plants. Barry dooley the current state of boiler tube failures. Boiler tube failures are the number one cause of forced outages in fossilfuel power plants. The advantus is a twopass counter flow fire tube commercial boiler for hydronic heating and hot water supply. P63 boiler life and availability improvement program. It can occur during operation as a result of inleakage of air at pumps, or failure in operation of preboiler water.
Intertek s boiler tube failure reduction programme and services can help power plants improve reliability and avoid costly outages. There are twentytwo primary reasons for tube failures in a boiler, which can be classified under six major groups. Thermohydraulic analysis can reveal boiler tube failure mechanisms not apparent with other methods, helping reduce the frequency of tube failure. As we collect, analyze, interpret and study our findings, ats indepth failure analysis experience plays a major contributing role in delivering accurate conclusions. The visual condition of nearby tubes and the proximity of the damaged tubing to attachments, sootblowers, etc. Recent experience in dissimilar metal weld failures. Wall thinning and creep damage analysis in boiler tube and. An examples of our root cause tube failure analysis and diagnostic capabilities may be found here. Tube failures form a major portion of the forced outages of boilers. Understanding corrosion fatigue and developing solutions. Those who work in power plants understand that boiler tube leaks can ruin a weekend or holiday for the plant staff. The statistics the statistics encompass a wide range of boiler inspection and failure analysis reports from all over subsaharan africa.
Failure analysis of superheater tube sciencedirect. In this work, the modeling of the heat transfer between flue gas and water in a fire tube boiler is considered. Effective boiler tube failure management course uniper. Pits can act as stressconcentration sites which can be initiation points for stressrelated corrosion mechanisms. Fly ash erosion, is a significant boiler tube failure concern, occurs in the regions with high local flue gas velocities, with high ash loading, and with abrasive particles such as quartz corrosion. Your unit can be running along at full load, seemingly problemfree. The failures were in the platen superheater which hung above the furnace and acted as the first stage of the superheater. In almost all cases of serious availability losses, the boiler tube failures are repeat in nature and result in multiple forced outages. Boiler life and availability improvement program program 63. A well planned and executed boiler chemistry control program is essential to prevent tube failure. Alternatively the tube can be plugged at either end, but refractory materials must be placed over the failed tube to protect the insulation behind it. Boiler tube failures are generally recognized as the major cause of forced outages of fossil power generating units for us electric utilities. Map tube failures, repairs, thickness and oxide scale data.
Boiler maintenance and upgrades attacking tube failures. For most failure mechanisms, a few simple practices can proactively manage tube failure risk. Introduction boiler tube failures have been cited as the primary cause of fossilfired plant forced out. May 09, 2009 part 2 flow accelerated corrosion fac. Drawing upon a full century of experience and expertise, boiler tube company of america bta manufactures replacement pressure boiler components and related auxiliary industrial boiler parts for all sizes and styles of boilers, regardless of original oem. Creep and creep failures national board of boiler and. Quite often they are related to dew point corrosion, an insidious condition that can penetrate up to 0. Reducing boiler tube failures requires a twopronged approach. Boiler tube failure reduction program technical report. Serving thousands of customers around the country, bta has earned the trust of. Today, webco is the only fullline manufacturer of welded boiler tubing in the united states.
Using this service allows for a more accurate chemical cleaning strategy chemical cleaning cycles could be extended and the lifespan of your boiler can be. From table 1 it can be seen to be the second most common cause of failure in the sample of fire tube boilers. Boiler tubes can undergo sudden failures by rupture or leakage and is usually detected while in operation rather than during a hydro test or other inspection activities. Boiler tube scale deposit measurement reduces energy cost and. There are many factors responsible for boiler tube failure. Top ten boiler and combustion safety issues to avoid. This blog is the second in a series discussing boiler tube condition. Valmets boiler tube scale deposit measurement program is an effective inspection service that will enhance your program and help us better understand the deposition within your boiler. Thin walled tubes that normally last 10 years can become badly pitted during shutdown, and replacement tubing becomes an unanticipated expense. Effective use of boiler tube failure outages course uniper. By measuring the tubes wall thicknesses far from failed region, nonuniformity was seen. At ats our program for determining the cause of failure incorporates laboratory testing and empirical. Boiler tube failure is the major cause of unscheduled shutdowns in the coal fired boiler plants, which is responsible for production loss. Ats focus on boiler tube failure analysis begins with examining the conditions that resulted in the failed component and collecting the pertinent data for reliable information.
This paper reports that boiler tube failure btf is such a common experience over 4000 occurrences are reported each year to the north american electric reliability council that plant managers have developed a variety of methods to aid tube repair and replacement. Louis plant, leaving three people dead and several others seriously injured. During operation, scales are formed in boiler tube due to tube geometries. The outage results in lost production and lost revenue. A typical example is when superheater tubes have not cleared of condensation during boiler startup, obstructing steam flow.
This case study follows the investigation of a leak in a lateral water wall tube from a coalfired boiler. This section forms the bottom part of the boiler where the systems water arriving from the economizer is still in its subcooled phase. Steam boiler inspections using remote field testing. Boiler tube failures, especially in coalfired power plants, continue to be the major cause of boiler forced outages. For superheaters and reheaters, the scale that forms is essentially. The effective boiler tube failure management course is a one day training course intended principally for engineers who are directly involved in the strategic management of boiler tubes, whether operationally or commercially, but it is of value to anyone concerned with maintenance or operational aspects of boiler tube failures. Software is also available for documenting and analyzing the problem of premature tube leaks. Top five fundamental integrity issues for sru waste heat. As reported by yates 1999 somewhere between 8% and 12% of fire tube boilers in the uk have been found to be affected. Dont let those boiler tubes fail again power engineering. Boiler tube failures are still the leading cause of forced outages in coalfired boilers.
To get your boiler back on line and reduce or eliminate future forced outages due to tube failure, it is extremely important to. Routine sampling for condition assessment can help monitor the health of a boiler, thereby preemptively mitigating damage mechanisms before they become problematic. It features thermal efficiencies of up to 99% and turndown ratios of. A pulverized coal fired industrial boiler experienced several superheater tube failures about six months after commissioning resulting in several boiler shut downs. The visual appearance of a failed boiler or hrsg tube provides valuable information regarding the mechanism of failure. High pressure boilers long term overheating tube failures. Cycle chemistry influenced failure and damage in the ptz of the lp steam turbine include stress corrosion cracking and corrosion fatigue.
The data includes a record of all tube failures and repairs, ultrasonic test readings, their. Use features like bookmarks, note taking and highlighting while reading the nalco water guide to boiler failure analysis, second edition. Oxygen pitting occurs with the presence of excessive oxygen in boiler water. However, if a tube leak is detected early more severe damage to surrounding. Design boiler has the required capabilities and diagnostic resources to undertake root cause analysis of boiler tube failures and related issues that occur on boiler plants. The current state of boiler tube failures in fossil plants powerplant chemistry 198 powerplant chemistry 2000, 24 corrosion fatigue corrosion fatigue has been the leading single cause of availability loss in fossil plants for over 20 years. These exercises in life expectancy can be facilitated by use of computer software developed for this purpose. Procedures for boiler tube failure analysis at times, the cause of a failure cannot be readily determined, making it difficult to determine the appropriate corrective action. Download it once and read it on your kindle device, pc, phones or tablets. May 22, 2015 however, in the event of tube failure, a welded repair must be carried out. The fire tube boilers covered a steam production range of 120 thr at pressures from 10 to 20 bar.
Boiler tube failures btfs in natural circulation high. The nalco water guide to boiler failure analysis, second edition kindle edition by nalco chemical company. The analysis determined the failure mechanism that caused the leak and identified possible operating conditions that would have caused this type of failure. Because the boiler water is relatively unbuffered, total volatile programs are more affected by.
The nalco water guide to boiler failure analysis, second. With significant challenges facing the electric industry and the world, we are always seeking top talent with handson experience to address issues as they relate to the generation, delivery, use, management and environmental responsibility of global electricity. One of the biggest challenges for maintenance and operations personnel is the prevention of tube failures in boilers and heat exchangers without causing significant loss to the company. The failure analysis of a ruptured superheater tube after 20 years service in the oilfueled boiler, as the typical problems in power plants, was investigated. Look to the industry leader for comprehensive tube assessment boiler tube failures continue to be the leading cause of forced outages in fossilfired boilers. The effective use of boiler tube failure outages course is a one day training course intended principally for engineers who are directly involved in the repair of boiler tubes during forced outages, but it is of value to anyone concerned with maintenance or operational aspects of boiler tube failures. They can be analyzed and corrective and preventive action can taken. Full text of boiler tube failure see other formats boilertube failer,prevention and control sundaraveerraju.