Abstract: An actuator for a pilot valve, including a housing, a piston movably mounted in the housing and an actuator chamber defined between the piston and the housing. The actuator includes a control fluid feed for introducing a fluid into the actuator chamber to control fluid pressure, with the fluid pressure acting on the piston. The actuator also includes an actuation member for acting on the pilot valve and a loading spring between the piston and the actuation member. The loading spring is arranged to bias the piston against the fluid pressure in the actuator chamber. The control fluid feed controls the fluid pressure so the fluid pressure acts on the piston against the bias of the loading spring to control the biasing force.

Abstract: A device for controlling the flow of a fluid through a conduit from an upstream side of the device to a downstream side of the device is provided. The device includes an upstream valve casing defining an inlet, a downstream valve casing defining an outlet aperture, and a valve core secured between the upstream valve casing and the downstream valve casing. The upstream valve casing, the downstream valve casing and the valve core are formed as discrete parts. The valve core includes a housing defining a control volume. The valve member is mounted on the housing and positioned on the upstream side of the outlet aperture, the valve member being arranged to move reciprocally to selectively open and close the outlet aperture, thereby controlling flow of the fluid through the outlet aperture.

Abstract: A device is provided for controlling the flow of a fluid through a conduit from an upstream side to a downstream side of the device. The device includes a valve aperture, a cylindrical mounting member on the downstream side of the valve aperture, a valve member on the outside of the cylindrical mounting member that moves reciprocally to open and close the valve aperture, a control volume defined between the cylindrical mounting member and the valve member, an arrangement for introducing a control pressure into the control volume, and a seal between the outer surface of the cylindrical mounting member and the inner surface of the valve member that substantially seals the control volume. The valve member is acted on by the pressure of the upstream side (P1) and the control pressure (P4) so as to be moved by the difference between these pressures.