The Test of Inner-flue Tube Wall Temperature of Superheater Based on the Power Plant SIS
Superheater and reheater tube failures were mostly due to excessive temperature, the inner-flue tube wall temperature of superheater make certain of tube thermal stress, material creep status and residual lifespan of tubes. So investigation of superheater safety began with experimentation of inner-flue tube wall temperature of superheater. In order to precisely learn inner-flue tube wall temperature of superheater of 600MW supercritical boiler, new measuring points are set on the superheater tube wall inner the flue. Since the working condition of 600MW supercritical boiler is quite severe, the temperature measuring points can only be used for short-term test. The data acquisition can be carried out automatically and a data storage system is required. The testing method in this paper transmit the measuring signal to the database of the thermal power control system through the redundant channel of the system. This method only requires new measuring points (thermocouple). The test data can be loaded directly from the SIS database, which saves not only money but also the work.
Test and Correlative Formula of Boiler Superheater Inner-Flue and Outer-Flue Tube Wall Temperature
In order to monitor tube wall temperature of boiler superheater, a new method was put forward to observe inner-flue tube wall temperature by long-term measuring outer-flue tube wall temperature. The method was based on the relation between inner-flue tube wall temperature and outer-flue tube wall temperature that was build up through testing data. The testing points were settled on the inner-flue and the outer-flue of same tube. According to the experimental data, the inner-outer flue tube wall temperature relation modeling was build up and checked.
Life Assessment of Superheater/Reheater Tubes in Fossil Boilers
Creep rupture failure of superheater(SH)/-reheater(RH) tubes is a major cause of forced outages of power boilers. A methodology developed recently by EPRI researchers has helped utilities make more informed run/replace decisions for tubes by judiciously combining calculational, nondestructive and destructive evaluations. In this methodology, the tubes/tube assemblies at risk are identified by ultrasonically measuring the thickest steamside oxide scale and thinnest wall thickness in the tubes. The remaining life of each tube/tube assemblies is predicted using a computer code known as TUBELIFE, thus achieving a further level of focus on the tubes/assemblies in the highest risk category. Sacrificial tube samples are then removed from the select locations and subjected to laboratory metallurgical evaluation and isostress rupture testing to refine the remaining life estimates. Research has further refined this methodology by validating the ultrasonic technique for scale measurement, identifying the appropriate stress formula and oxide growth laws and evaluating the limitations of creep damage summation rules and isostress rupture test procedures. This paper provides an overview of the research in the field, and establish a road map for assessing the remaining life of SH/RH tubes.