VACUUM CONTROL SYSTEM AND METHOD FOR DEWATERING A WEB OF PAPER

摘要

A vacuum control system for the flat box section (20) of a papermaking machine includes a plurality of serially arranged boxes (21, 22, 23, 24, 25) interconnected by a header (27). Vacuum controllers (41) are connected to a predetermined number of the boxes for controlling and producing desired vacuum conditions at the boxes. A web is passed over the boxes for dewatering purposes. A vacuum pump (35) supplies vacuum to the boxes and dewaters the web passing thereover. Controls (38, 37) are provided which are connected to at least the last box (25) and to the vacuum pump (35) and responsive to a change in vacuum level or air flow demand on the last flat box to correspondingly adjust the speed of the vacuum pump and obtain desired vacuum at at least the last box. The pump is stopped if pressure or flow limits are conceded. IMAGE