A transducer with a lower housing assembly and an upper housing assembly is for connection to a fluid pressure source having a mechanism for setting a pneumatic output via an electrical input signal. The lower housing assembly comprises lower housing configured to receive a supply nozzle, which fluidly communicates with a supply port and intermittently fluidly communicates with an output port of the lower housing through an internal fluid passageway. The lower housing further comprises an exhaust nozzle fluidly communicating with an exhaust port and intermittently fluidly communicates with the output port of the lower housing through the internal fluid passageway. The upper housing assembly comprises an upper housing configured to receive a coil and an armature such that the upper housing, coil and armature define a latching electromagnetic circuit that provides alternating contact of the armature with the supply nozzle and the exhaust nozzle of the lower housing assembly.

The positioner having an air circuit including magnetism generating portions producing magnetism based on a current in accordance with a difference between a valve opening setpoint of a regulator valve and a measured value for the valve opening, to generate a pneumatic signal wherein the air pressure is adjusted based on the magnetism produced by the magnetism generating portions, where this pneumatic signal is supplied to an operating device of the regulator valve, where the magnetism generating portions are connected in parallel, and including a plurality of coils connected through magnetically additive coupling.

A fluid control system is provided for controlling flow of a process fluid through a pipeline. The fluid control system can include a valve, one or more instruments in fluidic communication with the valve, and a pressurized chamber. In one example, the pressurized chamber contains the one or more instruments. In one example, the pressurized chamber has a dynamically variable pressure, which corresponds to a pressure in a downstream portion of the pipeline, such as a natural gas pipeline. In another example, the pressurized chamber captures instrument gas bled/leaked from the instruments and reinjects the instrument gas into the downstream portion of the pipeline.

A hydraulic device having: a plurality of main piston-cylinder arrangements, each of the respective pistons having a fixed stroke length and configured for axial reciprocation within their respective cylinder; a plurality of flow control valves for switching between a lockdown state and an unlocked state of one or more of the plurality of main piston cylinder arrangements during operation of the hydraulic device; and one or more control valves for directing the plurality of flow control valves between their respective unlock and lock positions.