Actuator Types

The primary grouping of actuators by power source and range of motion permit some convenience in defining the actuator. The conversion of power to motion presents a large range of actuator designs. The different designs have distinctly different functional characteristics to consider 

Hydraulic and pneumatic piston and diaphragm actuators provide a linear output. These may be integrated with scotch yoke or crank arm mechanism to provide a quarter turn output. These two mechanisms have variations in the output torque over the stroke of the actuator. When integrated with a rack and pinion mechanism they may provide up to a full turn output. 

Hydraulic and pneumatic vane actuators provide a direct translation from the vane to a partial turn actuator output without the additional conversion mechanism required for a diaphragm or piston actuator. 

Hydraulic and pneumatic motor drives may be configured to provide a range of outputs based on gearing mechanisms. Gearing provides multiturn and partial turn outputs. The addition of a stem nut system permits translation to linear operation. 

Electric actuators have a range of output similarities to the hydraulic and pneumatic motor drives, but t5q)ically have a much higher level of complexity due to the additional functionality provided with the units. 

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Valve Application Technology Functional requirements and the properties of the controlled fluid determine which valve and actuator types are best for a specific apphcation. If demands are modest and no unique valve features are required, the valve-design style selection may be determined solely by cost. If so, general-purpose globe or angle valves provide exceptional value, especially in sizes less than 3-inch NFS and hence are very popular. Beyond type selection, there are many other valve specifications that must be determined properly in order to ultimately yield-improved process control. 

The compressor cylinder valves are of the spring-loaded, gas-actuated type in all but a limited number of portable compressors. This kind of... 

Actuator type Electro-hydraulic for fast response and accurate control. 

Functional requirements and the properties of the controlled fluid determine which valve and actuator types are best for a specific application. If demands are modest and no unique valve features are required, the valve design style selection may be determined solely by... 

The stem position feedback network converts stem travel to a useful form for the summer. This block includes the feedback linkage which varies with actuator type. Depending on positioner design, tKe stem position feedback network can provide span and zero and characterization functions similar to that described for the input conversion block. 

Remote actuated valves must be chosen to match process requirements. Design decisions include materials of construction, valve seat material, valve t q)e, actuator type and controls characteristics. The design must match utility supply levels (air pressure, hydraulic pressure, flow capacity) and tolerances with actuator design to provide the correct torque/thrust to the valve. The torque/thrust must be above breakaway requirements and must be below stress limits of the drive train. With some valves, the ratio of these values may limit the available operating safety factor. 

Two basic actuator types Out of Plane(parallel plate)... 

Each injection line or pressurizing line has a reliable hydraulic pressure valve actuated by the pressure difference between the RPV and CV to allow gravitational feed of CV water to the RPV. The hydraulic pressure valve which is directly connected to the RPV is a check valve of a spring actuation type and does not open until the design pressure difference (for example, 0.5 MPa) between the RPV and CV is reached. 

Abstract Function Type is a typecast for a function Actuator Type, Function Type and Sensor Type). It is instantiated to fulfill functional safety or non-safety requirements in the FN. The purpose of the usage of an Abstract Function Type cannot be foreseen. The instantiation becomes a safety related element by the context of application, but not the type. Therefore the Abstract Function Type is not a Safety Related Element. 

Solid-state actuators and actuators with controllable fluids show certain similarities piezo actuators and electrorheological fluids are driven with electrical fields whereas magnetostrictive actuators and magnetorheological fluids draw their actuation energy from a magnetic field. We will therefore consider the power electronics of these two superordinate groups, but still we will mention the differences between the two different actuator types of each group. 

Actuation type Tensile Tensile Tensile Tensile bending Bending Bending ... 

The combination of primary and secondary actuators varies with the specific application. Secondary actuators can be another solenoid or any of the other actuator types that have been previously discussed. 

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