A fluid control system includes a choke valve having a first connector shaft; an actuator having a second connector shaft; a collar disposed around the first and second connector shafts; and a spring disposed on the first connector shaft. The collar may have an internal taper and a plurality of engagement pins.

The present disclosure pertains to a valve for a refrigeration application, in particular a shut-off and/or regulating valve. The valve includes a bonnet connected to a housing with two fluid openings, a spindle fully penetrating the bonnet and reaching inside the housing, and a piston with an upper guiding and sealing portion with a seal section, a bottom closing portion for opening and closing a fluid passage between the two fluid openings, and a piston tube between the upper guiding and sealing portion and the bottom closing portion. The spindle engages the piston for moving it between a closed position and an open position of the valve and a pressure balancing chamber is provided above and within the piston. The piston is sealed against the bonnet at the upper guiding and sealing portion. An inner surface of the bonnet guiding the upper guiding and sealing portion and/or an outer surface of the piston has a smaller diameter at a bottom portion than at an upper portion.

A valve closing member for cooperating with a valve seat, comprising: a body a front circular face forming a central protrusion along a longitudinal axis of the body; a seal forming a ring fitted on the front circular face and around the central protrusion; and a retainer forming a ring surrounding the seal and attached to the body for retaining the seal on the body; wherein the seal shows a radially inner surface contacting a radially outer surface of the central protrusion, the radially inner surface and radially outer surface being both cylindrical, the radially outer surface showing at least one circular groove into which the seal is radially pressed by the retainer.