It features thermal efficiencies of up to 99% and turndown ratios of. Download it once and read it on your kindle device, pc, phones or tablets. Boiler tube failure reduction program technical report. Dont let those boiler tubes fail again power engineering. There are many factors responsible for boiler tube failure. Top ten boiler and combustion safety issues to avoid.
A pulverized coal fired industrial boiler experienced several superheater tube failures about six months after commissioning resulting in several boiler shut downs. Boiler tube installation new boiler tubes manufactured to meet or exceed specifications are installed, rolled, beaded and sometimes welded in the hot pass. Boiler life and availability improvement program program 63. For superheaters and reheaters, the scale that forms is essentially. A typical example is when superheater tubes have not cleared of condensation during boiler startup, obstructing steam flow. 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. This makes maintenance easier and reduces associated costs.
However, if a tube leak is detected early more severe damage to surrounding. 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. Better yet, let us help put together a complete condition assessment program to help eliminate tube problems before failures occur. Understanding corrosion fatigue and developing solutions. The nalco water guide to boiler failure analysis, second. Your unit can be running along at full load, seemingly problemfree. Barry dooley the current state of boiler tube failures peter. The visual appearance of a failed boiler or hrsg tube provides valuable information regarding the mechanism of failure. When the high payoff activities are executed routinely, such as performing thorough visual boiler inspections, targeting ut measurements, and monitoring online operational cues like tube temperature excedances, boiler tube forced outages will decrease. Boiler tube scale deposit measurement reduces energy cost and. The service uses ultrasonic technology and proprietary software to accurately measure the thickness of the deposit layer. Failure analysis of superheater tube sciencedirect. Recent experience in dissimilar metal weld failures. With tangent tube construction a failed tube can be plugged and the boiler operated normally without further attention.
The analysis determined the failure mechanism that caused the leak and identified possible operating conditions that would have caused this type of failure. 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. Look to the industry leader for comprehensive tube assessment boiler tube failures continue to be the leading cause of forced outages in fossilfired boilers. Only one half of the four boiler hopper walls were modelled as this forms a representative region of the complete. Boiler tube failures btfs in natural circulation high. During periodic shutdowns of the boiler unit, tube failures can occur. Boiler tube failure analysis applied technical services. Such failures are less frequent than boiler tube failures, but the damage resulting can be enormous. Determining the failure mechanism is the first step of the failure reductionelimination process. During operation, scales are formed in boiler tube due to tube geometries. Aggressive localized boiler tube corrosion and loss of tube wall. Boiler tubes are susceptible to certain damage mechanisms, including. The boiler tubes are operated continuously at high temperature and pressure. 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.
Because the boiler water is relatively unbuffered, total volatile programs are more affected by. The aware boiler integrity module is in use at over half the boilers in north america to improve reliability, availability and safety. Top five fundamental integrity issues for sru waste heat. 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. Oxygen pitting occurs with the presence of excessive oxygen in boiler water. Consequently, the internal oxide layer led to a series of metallurgical degradation and the loss in mechanical strength of the boiler tubes. How to use the handbook the visual appearance of a failed boiler or hrsg tube provides valuable information regarding the mechanism of failure. Apr 04, 2014 ntpc, unchahar boiler explosion what is boiler explosion reasons behind ntpc boiler explosion duration.
They can be analyzed and corrective and preventive action can taken. As reported by yates 1999 somewhere between 8% and 12% of fire tube boilers in the uk have been found to be affected. 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. A well planned and executed boiler chemistry control program is essential to prevent tube failure. This case study follows the investigation of a leak in a lateral water wall tube from a coalfired boiler. 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.
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. These best practices have realized not only the reliability of equipment but also the safety of the people that use them. Reducing boiler tube failures requires a twopronged approach. The visual condition of nearby tubes and the proximity of the damaged tubing to attachments, sootblowers, etc. Intertek s boiler tube failure reduction programme and services can help power plants improve reliability and avoid costly outages.
These exercises in life expectancy can be facilitated by use of computer software developed for this purpose. Thin walled tubes that normally last 10 years can become badly pitted during shutdown, and replacement tubing becomes an unanticipated expense. An examples of our root cause tube failure analysis and diagnostic capabilities may be found here. Serving thousands of customers around the country, bta has earned the trust of. Justin will discuss the aspects of whe tube failure, api 521 evaluations, and sru pressure buildup. Tube temperature distribution in water tube boiler a. Effective boiler tube failure management course uniper. 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.
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. Epri is at the center of a quickly evolving energy landscape. This calls for immediate action as it can often cause a shutdown of the boiler, leading to loss of production and downtime. The advantus is a twopass counter flow fire tube commercial boiler for hydronic heating and hot water supply. 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. Boiler tube failures continue to be the leading cause of downtime for steam power plants. 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. 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. Software is also available for documenting and analyzing the problem of premature tube leaks. The outage results in lost production and lost revenue. 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. However, work conducted in the last 5 years has started to provide.
This blog is the second in a series discussing boiler tube condition. Tube failures form a major portion of the forced outages of boilers. 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. Look to the industry leader for comprehensive tube. Thermohydraulic analysis can reveal boiler tube failure mechanisms not apparent with other methods, helping reduce the frequency of tube failure. Engineers guide to boiler tube inspections engineering360. Boiler maintenance workstation supplements formal prevention programs to dramatically reduce tube failure. Failure of tubes in boiler of the power plants may occur due to various reasons. Quite often they are related to dew point corrosion, an insidious condition that can penetrate up to 0. Boiler tube failure is the major cause of unscheduled shutdowns in the coal fired boiler plants, which is responsible for production loss. 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. Pulverized coal fired boiler persistent superheater tube.
The nalco water guide to boiler failure analysis, second edition kindle edition by nalco chemical company. Boiler tube failures are the leading cause of steam plant reliability issues. In almost all cases of serious availability losses, the boiler tube failures are repeat in nature and result in multiple forced outages. These failures can be avoided when we understand the reason and operate the boiler accordingly. A tube failure may cause a forced outage, usually at the most inopportune time. 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. Apr 18, 2019 they introduced codes, standards, and checklists to ensure that boiler safety is secondnature. Failures result when the tube metal temperature is extremely elevated from a lack of cooling steam or water flow. The failures were in the platen superheater which hung above the furnace and acted as the first stage of the superheater. Failure mode determination can distinguish the various tube failure mechanisms such as creep, shortterm overheat, corrosion, erosion, or fatigue. 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. Failure assessment of astm a2t12 superheater boiler tubes.
Explain four reasons why large number of repeat boiler tube failures. Boiler tube failures are generally recognized as the major cause of forced outages of fossil power generating units for us electric utilities. Some asme boiler and pressure vessel code requirements may have changed because of advances in material technology andor actual experience. 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. Is your boiler tube failure reduction program showing improvement when compared to programs at peer plants. Unexpected boiler tube failure is the major factor causing unreliability in utility boilers. Boiler tube failure reduction programme interteks boiler tube failure reduction programme and services can help power plants improve reliability and avoid costly outages. Long term overheating failures are due to the fact that the operating metal temperature of the boiler tubes going above the allowable limit. Use features like bookmarks, note taking and highlighting while reading the nalco water guide to boiler failure analysis, second edition.
May 09, 2009 part 2 flow accelerated corrosion fac. As we collect, analyze, interpret and study our findings, ats indepth failure analysis experience plays a major contributing role in delivering accurate conclusions. Steam boiler inspections using remote field testing. The remaining wall thickness decreases due to the formation of scale which eventually causes failure of the boiler tubes. Failure analysis of waste heat boiler tubes april 26, 2017 abdulmohsen alsahli, avtandil khalil bairamov, abdulaziz almeshari, gys van zyl, and ali alshawaf. Stress corrosion cracking scc hydrogen damage sulphur corrosion graphitization thermal fatigue waterside corrosion fatigue soot. Today, webco is the only fullline manufacturer of welded boiler tubing in the united states. 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.
A good percentage of these failures are due to long term overheating. Boiler tube failures are the number one cause of forced outages in fossilfuel power plants. In the literature, a comprehensive modeling for fire tube boilers. 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.
Boiler feed pump failure root cause analysis duration. 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. The first impression report from designer, analysis by designers and final evaluation and corrective action are. The tube failures investigated in this study occurred in the hopper section of the boiler. May 22, 2015 however, in the event of tube failure, a welded repair must be carried out. 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. Those who work in power plants understand that boiler tube leaks can ruin a weekend or holiday for the plant staff. Boilers are generally one of three main types firetube boilers, watertube boilers, and electric boilers. Good operating and maintenance practice reduces tube failures. Tube metal temperatures reach combustion gas temperatures of 1600f 870c.
Map tube failures, repairs, thickness and oxide scale data. Introduction boiler tube failures have been cited as the primary cause of fossilfired plant forced out. Boiler tube failures, especially in coalfired power plants, continue to be the major cause of boiler forced outages. Deterioration and loss of material due to chemical attack. 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 statistics the statistics encompass a wide range of boiler inspection and failure analysis reports from all over subsaharan africa. A thinlipped rupture at failed region was observed in superheater tube. Standard tube failure and inspection reports are provided for all of the boiler pressure parts. Wall thinning and creep damage analysis in boiler tube and.
Cycle chemistry influenced failure and damage in the ptz of the lp steam turbine include stress corrosion cracking and corrosion fatigue. Easy access to all internal areas of the boiler including tubes, burner, furnace, and refractory, is available from either end of the boiler. It can occur during operation as a result of inleakage of air at pumps, or failure in operation of preboiler water. Various corrosion mechanisms contribute to boiler tube failure. Boiler tube failures are still the leading cause of forced outages in coalfired boilers. At ats our program for determining the cause of failure incorporates laboratory testing and empirical. Effective use of boiler tube failure outages course uniper. Shop assists operators in the management of boiler startups by enabling the detection of superheater tube clear events tces. Routine sampling for condition assessment can help monitor the health of a boiler, thereby preemptively mitigating damage mechanisms before they become problematic. The data includes a record of all tube failures and repairs, ultrasonic test readings, their. Barry dooley the current state of boiler tube failures. The fire tube boilers covered a steam production range of 120 thr at pressures from 10 to 20 bar. To get your boiler back on line and reduce or eliminate future forced outages due to tube failure, it is extremely important to.
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. Prior to removing a failed tube, mark and photodocument the tube gas flow direction, fluid flow direction, row number, elevation, boiler section, etc. Louis plant, leaving three people dead and several others seriously injured. Pits can act as stressconcentration sites which can be initiation points for stressrelated corrosion mechanisms. 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. Tube failures during the initial operation period, the normal operation period, and after ten to fifteen years operation show different trends. Boiler maintenance and upgrades attacking tube failures. There are twentytwo primary reasons for tube failures in a boiler, which can be classified under six major groups. From table 1 it can be seen to be the second most common cause of failure in the sample of fire tube boilers. One is the boiler machinery bm coverage for the pressure side, meaning the tubes, drums, water level controls and safety relief valves. 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. By measuring the tubes wall thicknesses far from failed region, nonuniformity was seen.
For most failure mechanisms, a few simple practices can proactively manage tube failure risk. These include failures due to creep, corrosion, erosion, overheating and a host of other reasons. In this work, the modeling of the heat transfer between flue gas and water in a fire tube boiler is considered. 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. Full text of boiler tube failure see other formats boilertube failer,prevention and control sundaraveerraju. 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.
P63 boiler life and availability improvement program. This section forms the bottom part of the boiler where the systems water arriving from the economizer is still in its subcooled phase. Creep and creep failures national board of boiler and. 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.