WATER FEED CONTROL DEVICE DURING FCB OF DRUM BOILER

摘要

PURPOSE:To prevent the excessive increase of a drum level due to the excessive feed of water by a method wherein simultaneously with the starting of FCB, a regulating valve for the feed of steam to a turbine for driving a boiler water feed pump is rapidly controlled for opening operation, and after the starting of the rise of a drum level, the valve is throttled according to a load and then returned to normal control. CONSTITUTION:A steam feed regulating valve 13 is rapidly controlled for opening to a set specified opening simultaneously with FCB (forced load cutoff). Lowering phenomenon of a drum level is stopped, and converted into a rise. A differentiator 40 raptures the rise phenomenon to control a switching device 42. A change rate controller 45 outputs a target value signal, outputted according to a load from a function generator 43, and an opening signal, corresponding to a rate of change single outputted according to a load from a function generator 44, to a steam feed regulating control derive part 12, and the opening of the regulating valve is controlled according to restoration of a drum level. When the drum level is restored to a value within an allowable deviation based on a given set value, an H/L monitor 41 raptures the restoration to switch a switching device 7, and transfer to drum level single element control corresponding to a drum level signal is effected.