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.
Life management of high-temperature piping and tubing in fossil power plants
Aging of power plants and competitive pressures to operate and maintain (O&M) these plants at reduced costs have heightened industry interest in life assessment and management technologies. Piping and tubing systems carrying high-pressure steam at temperatures exceeding 1000°F (530°C) have notably been the center of focus of many of these activities. Enormous progress has been made in understanding mechanisms of damage and their rate of evolution. Progressive application of improved calculational, nondestructive and destructive techniques have enabled optimum utilization of components at reduced costs. In addition, the efficacy of weld repair techniques to extend the lives of aged components has been investigated in detail. This paper will review the damage mechanisms encountered in fossil power plant boiler pressure parts and then describe in more detail life management tools that have been developed.
Use of Miniature Specimens for Creep-Crack-Growth Testing
Measuring the condition of high-temperature components after many years of service is an important part of remaining life assessment. Tests of miniature specimens have been utilized for this purpose because they require that only small samples he removed from the components, which minimizes or eliminates the need for costly repairs. Miniature-specimen techniques have been developed and validated for creep-rupture testing but not for creep-crack-growth testing. The objective of this research was to develop and validate a procedure for measuring creep-crack-growth behavior using miniature specimens. Based on a past study of Type 316 stainless steel, the single-edge-notch-tension (SENT) specimen configuration was chosen for the current work. SENT specimens were designed and prepared from both base metal and weldments of 2-1/4Cr-1Mo and 1-1/4Cr-1/2Mo steels. The base metal was ASME SA 387. Grade P22 and Grade P11 plate, respectively. The 2-1/4Cr-1Mo steel weldment was a seam-weld hot reheat steam pipe that had been in service for 106,000 hours, while the 1-1/4Cr-1/2Mo steel weldment was from a pipe that had been weld repaired after 244,200 hours of service. SENT specimens with test sections of 10×5×1.5 mm, 15×7.5×1.5 mm, and 20×10×1.5 mm were evaluated. Tests were conducted under constant weight loading or constant load-line displacement loading. Specimens were heated to 538°C using a standard laboratory furnace. Crack length was measured using the DC electric potential drop method. The test results were analyzed to produce creep-crack-growth rate (da/dt) as a function of the C * integral and compared with data from tests of half-size (1/2T-CT) and standard full-size (1T-CT) compacttension specimens. For both base metals, the 1/2T-CT and three sizes of SENT specimens gave results that agreed well with those of 1T-CT specimens. For the 2-1/4Cr-1Mo steel weldments, SENT specimens produced good results. However, SENT specimens of the 1-1/4Cr-1/2Mo steel weldments exhibited cracking blunting and no creep crack growth. The reasons for the differences in behavior are discussed and guidance for application of miniature specimens to creep-crack-growth testing is presented.