Abstract: A vacuum control system and method for dewatering felts or fabrics on a papermaking machine including a suction pipe and a centrifugal exhauster connected to the suction pipe to supply a variable vacuum level. The fabric is passed over a slot in the suction pipe so that suction applied therethrough will dewater the fabric. A variable drive device is connected to the centrifugal exhauster for its operation with the variable drive device being responsive to an increase in the vacuum level in the suction pipe as fabric permeability decreases to correspondingly increase the speed of the centrifugal exhauster so as to increase the vacuum level in the suction pipe as a function of the decrease in felt permeability.

Abstract: A deliquefying system including at least one drainage device having a wear surface and being connected to a source of suction open to the wear surface. A wet web of material to be deliquefied is passed over the wear surface so that liquid is removed from the wet web of material by the drainage device. A liquid deckle is at each exposed end of the drainage device in position to prevent air from entering the drainage device through the end zone and thereby restricting the flow of air to passage through the wet web into the drainage device.