| 摘要 |
PURPOSE:To prevent reduction of pressure in a furnace and to enable control of early restoration, by a method wherein an addition value signal in which a proportional integration value of a value by a pressure in a furnace is added to a forced draft fan moving vane control signal is switched to a main fuel trip control signal during the occurrence of a main fuel trip, and is switched to an internal pressure abnormal reduction control signal during abnormal reduction of an internal pressure. CONSTITUTION:When pressure in a furnace is sharply reduced to a value lower than that set by a furnace internal pressure setter SG51 for override, it is compared with an output from an SG53 at a set value 0% by means of a low value selector 52 to output a proportional control signal 73, by which a deviation signal is selected, to an AD 55. The signal is added togetherwith a PI control signal 71 and a signal 72, rendered effective only during MFT, the result is compared with a PI control signal 71 by means of an LS 56, and a value, being on the lower side, i.e. an override control signal 74, is selected. By closing an IDF moving vane 10 through an ASW 58, restoration of reduction of a pressure in a furnace is controlled. During the occurrence of MFT, on MFT generating signal 67 is immediately triggered, an ASW 44 is switched to the side (a), and the signal 72 is rendered effective from 0% of an SG45. |
