Single function and double action is usually referred to as cylinder actuators.
Single action: cylinder movement through the instrument air pressure, returns by spring provide pressure. . ` e9 3 D) I "f - Z
Double action: cylinder movement and return are through the instrument air to provide the power.
Single acting torque than double acting much smaller. The double action are used for need large torque valve.
Single acting actuators general for security occasion, in the system fault (lose electric or loss of gas) through the spring ensure valve in a safe location (open or closed).
The difference is in and valve in snuff under the condition of the valve position!
When compressed air from A tube nozzle into pneumatic actuators, gas promote double piston to both ends (cylinder head end) linear motion, piston on the rack drive axis of rotation on the gear counterclockwise rotation 90 degrees, the valve is open. The pneumatic operation valve on both ends of the gas with B tube nozzle discharge. Conversely, when compressed air from B officer nozzle into pneumatic actuators ends, gas promote double plug to intermediate linear motion, piston on the rack drive axis of rotation on the gear clockwise 90 degrees, the valve is closed. The pneumatic actuators in the middle of the gas with A tube nozzle discharge. Above is standard transmission principle. According to the needs of users, pneumatic actuators can be device into and standard opposite transmission principle, namely, choose standard shaft clockwise to open valve, counterclockwise rotation to close the valve. Single action (spring reset type) pneumatic actuators A tube nozzle for inlet port, B tube nozzle for vent (B tube nozzle should be installed muffler). A tube nozzle inlet for open valve, snuff when rely on spring force close the valve.
Actuator according to the energy form is divided into pneumatic, electric and hydraulic three categories, each with characteristics, suitable for different occasions. Pneumatic actuators is actuator of a class. Pneumatic actuators can also be divided into single function and DOUBLE action two types: the implementation of the switch act through the air to drive execution, called DOUBLE ACTING (DOUBLE action). SPRING RETURN (single action) switch action only open source movement is driven, and shut when the movement SPRING reset.
In the pneumatic/electric actuator mounting to the valve before, must consider the following factors. * valve operating torque and the manufacturer's recommended security coefficient/according to the operation status. * actuator air pressure or the power supply voltage. * actuator type double action or single action (spring reset) and a certain air of the output torque or rated voltage output torque. * actuator steering and fault mode (fault open or fault closed) correct choose a actuator is very important, such as actuator is too large, the valve stem may be excessive force. Instead such as actuator is too small, side cannot produce enough moment to full operation of the valve. Generally speaking, we think that operation of the valve the moment from the valve metal parts (such as ball core, disc) and seals (seat) between friction. According to the valve use situation, using temperature, operation frequency, pipeline and differential pressure, flow medium (lubrication, drying, mud), many factors influence operating torque
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