Reliability of power plants is one of the primary concerns in power industry. Usually the reliability of boilers is calculated on the basis of analysis of long-term operation data or using the data of short tests by extrapolating them to long-term operation. Short tests in laboratory conditions can provide the data for initial determination of boiler reliability by the method of extra polation, but finally reliable data must be confirmed by industrial operation. Data on unit operation are obtained during the warranty period, which started after provisional acceptance conditions have been met, when the unit starts normal operation. The failures of components of CFB boilers that became evident during the warranty period are analyzed in this article.