Thermal volume control for an actuator assembly

A valve actuator, comprising:

• a spring cylinder having a spring, a spring seat, and a hydraulic cylinder having an aperture in one end, wherein the spring biases the spring seat in a first direction;
• a rod member that is operably coupled to the spring seat, wherein translation of the rod member is configured to cause rotation of a valve shaft that is coupleable to the valve actuator;
• a ram member having a first portion that is positioned in the hydraulic cylinder and a second portion that is slidably positioned in the aperture;
• and
• a hydraulic system that is configured to contain a hydraulic fluid, wherein the rod member and the spring seat are configured to move together between a first position and a second position based, at least in part, on a pressure of the hydraulic fluid, and wherein an increase in the pressure of the hydraulic fluid when the rod member is in the second position is configured to cause the spring seat, but not the rod member, to move in a second direction that is opposite of the first direction,
• wherein the hydraulic cylinder is fluidly coupled to the hydraulic system.

A valve actuator, comprising:

• a spring cylinder having a spring and a spring seat, wherein the spring biases the spring seat in a first direction;
• a rod member that is operably coupled to the spring seat and positioned within a collar that is positioned between the spring seat and a ram member, wherein translation of the rod member is configured to cause rotation of a valve shaft that is coupleable to the valve actuator;
• an engagement member that is fastened to an end of the rod member and configured to maintain the end of the rod member within the collar;
• and
• a hydraulic system that is configured to contain a hydraulic fluid, wherein the rod member and the spring seat are configured to move together between a first position and a second position based, at least in part, on a pressure of the hydraulic fluid, and wherein an increase in the pressure of the hydraulic fluid when the rod member is in the second position is configured to cause the spring seat, but not the rod member, to move in a second direction that is opposite of the first direction;
• wherein, the ram member is moveable based, at least in part, on the pressure of the hydraulic fluid, and wherein the rod member is operably coupled to the spring seat in a manner that enables movement of the ram member in the second direction to cause movement of the spring seat in the second direction independent of the rod member.