Abstract: A control apparatus for controlling the differential pressure between steam inlet and outlet lines of a web dryer and includes a selectively controllable outlet valve disposed in the outlet line for selectively controlling the flow of blow-through steam, condensate and non-condensible gases out of the dryer. A dryer speed sensor generates a first control signal and a condensing rate sensor senses the rate at which a layer of condensate builds up within the dryer. The condensate rate sensor generates a second control signal. A control device is operably connected to an outlet valve actuator for selectively energizing the actuator in response to the first and second control signals. The control device compares the signals to determine the optimum relative setting of the outlet valve so that flooding of the dryer with condensate is inhibited while the differential pressure between the inlet and outlet lines is maintained as low as possible.