Abstract: Single annular membrane type of pneumatic positioner associated with a servo control comprising a cylinder-piston assembly, feedback connected to the positioner, which includes a hollow body, internally of which there is provided at one side a reverse feedback spring controlled by the servo control, and at the other side a slide or distributing valve is provided, the inner cavity of the pneumatic positioner being separated by a single annular membrane, capable of being displaced under the action of an adjusting signal, said annular membrane being provided at the center with a hole through which a stem of the slide or distributing valve frictionessly slides, which stem bears against a dish-like member resting on the reverse feedback spring, while at the opposite side the slide or distributing valve bears on a low load spring.

Abstract: Method for automating and optimizing the phases of the working cycle in adsorption gas dehydration plants of the "heatless" type, having two tanks storing an adsorbing medium and alternating with each other in the regeneration, repressurization, inversion, adsorption and decompression steps. The method according to the invention provides that the repressurization and inversion operations are driven by a single pneumatic pulse of simultaneous control by a programmer providing and removing only one signal at preselected intervals with respect to the servocontrol of an inversion valve, the shutter of which changes over only under the condition of balance between the force or bias of the servocontrol and the differential pressure between the two tanks.