On-line verifiable trip and throttle valve actuator

A method of fluid actuation, comprising:

• actuating a first moveable plate into sealing contact with a first end of an inner cylindrical housing having a first inner wall and a second end opposite the first end, wherein a piston in fluidically sealing contact with the first inner wall, the first inner wall, and the first moveable plate in sealing contact with the first end define a first fluid chamber;
• actuating the first moveable plate away from sealing contact with the first end;
• flowing fluid from the first fluid chamber to an annular cavity defined between the inner cylindrical housing and an outer cylindrical housing arranged at least partly about the inner cylindrical housing, the outer cylindrical housing having a third end, a fourth end opposite the third end, and a second inner wall;
• and
• actuating a second moveable plate into sealing contact with the second end wherein the piston, the first inner wall, and the second moveable plate in sealing contact with the second end define a second fluid chamber.

A fluid actuator system comprising:

• a fluid actuator comprising:
• a housing having an inner wall defining an interior cavity;
• a piston having a piston head configured for reciprocal movement within the interior cavity, the piston head contacting the inner wall and dividing the interior cavity into a first fluid chamber and a second fluid chamber;
• a first valve configured to control fluid flow between the first fluid chamber and a bypass conduit;
• and
• a second valve configured to control fluid flow between the bypass conduit and the second fluid chamber.

A method of fluid actuation, comprising:

• closing a first valve configured to block fluid flow between a first fluid chamber of a fluid actuator and a bypass conduit;
• opening the first valve to permit fluid flow between the first fluid chamber and the bypass conduit;
• closing a second valve configured to block fluid flow between a second fluid chamber of the fluid actuator and the bypass conduit;
• and
• opening the second valve to permit fluid flow between the second fluid chamber and the bypass conduit.

A trip and throttle valve comprising:

• a fluid actuator having an actuating piston configured to control operation of a turbine based on differential fluid pressure in a first fluid chamber and a second fluid chamber;
• means for controllably permitting and blocking fluid flow between the first fluid chamber and the second fluid chamber;
• and
• means for sequentially testing each element of the fluid actuator without tripping the turbine of a dump valve configured to protect the turbine.