Best Practices to Analyze Failed Pressure Components From Power Boilers, Identify Failure Root Causes, and Assess Fixing and Preventive Actions
Ayag, Fatih (2019)
2019
Materials Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2019-01-09
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201901031009
https://urn.fi/URN:NBN:fi:tty-201901031009
Tiivistelmä
Circulating fluidized bed boilers which provide heating and/or power have proven their importance over the years and became very popular and economical energy supply facilities for today`s world. Their life time and performances based on the failures need a broad analysis to determine main reasons and possible preventive and mitigation measures. It should be noted that depending on the fuel combusted failures and their main causes vary and accordingly failure analysis methods applied will be different.
This thesis basically analyses best practices for the failures observed in circulating fluidized bed boiler pressure parts and suggests their preventive and mitigation measures as a result of different fuel combustions. Main fuel types considered in this study are waste, biomass and coal which have been widely used for combustion of such boilers. Due to various content and capacity of such fuels it is likely to see various failure types during operation of a boiler. Therefore, a proper investigation starting from the evidence collection and photo documentation to further metallographic analysis and final evaluation is required. Analysis of failed boiler parts should include the investigation of fuel, operational conditions, design parameters, material used within the structure. With the help of collected data it would be easier to anticipate the possible problems and reasons causing failures and accordingly methods to be pursued for the correct analysis would be clear. Sample preparation shall be performed adequately and correctly. Not only selecting the correct location but also cutting the sample and following further steps shall be done by using proper tools without destroying or modifying the evidences.
In the study, failure modes and their reason has been examined together with effect of such failures on the pressure parts. Based on these findings, thesis aims to discover controlling methods of such causes to improve the performance of a boiler under severe working conditions. Although theoretical background was given for three main fuel types, experimental part was performed on a waste fuel fired boiler. It was concluded that fuel type and working condition have a great influence for the failure and the total performance of a boiler. It is therefore, a critical task to understand the phenomena of the main reasons causing failures to reach a correct evaluation of failures observed in boilers.
This thesis basically analyses best practices for the failures observed in circulating fluidized bed boiler pressure parts and suggests their preventive and mitigation measures as a result of different fuel combustions. Main fuel types considered in this study are waste, biomass and coal which have been widely used for combustion of such boilers. Due to various content and capacity of such fuels it is likely to see various failure types during operation of a boiler. Therefore, a proper investigation starting from the evidence collection and photo documentation to further metallographic analysis and final evaluation is required. Analysis of failed boiler parts should include the investigation of fuel, operational conditions, design parameters, material used within the structure. With the help of collected data it would be easier to anticipate the possible problems and reasons causing failures and accordingly methods to be pursued for the correct analysis would be clear. Sample preparation shall be performed adequately and correctly. Not only selecting the correct location but also cutting the sample and following further steps shall be done by using proper tools without destroying or modifying the evidences.
In the study, failure modes and their reason has been examined together with effect of such failures on the pressure parts. Based on these findings, thesis aims to discover controlling methods of such causes to improve the performance of a boiler under severe working conditions. Although theoretical background was given for three main fuel types, experimental part was performed on a waste fuel fired boiler. It was concluded that fuel type and working condition have a great influence for the failure and the total performance of a boiler. It is therefore, a critical task to understand the phenomena of the main reasons causing failures to reach a correct evaluation of failures observed in boilers.