Actuators

Piston Actuator (Fail Safe)

Can have a spring to give a fail safe position.

Piston Actuator Disadvantages

-A positioner is required if when used for control valves making them more expensive. -Piston seals and cylinder walls are subject to friction wear.

Diaphragm Actuator desirable characteristics

-Low maintenance -low friction

Diaphragm Actuator

-Pneumatic Range generally 20-100 KPa(3-15psi) -Low pressure device -Short stroke distance as neoprene diaphragm will stretch or break if over extended

Piston Actuator

-Usually used for On-Off Control as they have great closing and opening force. -normally used with greater pressure than what is used with diaphragm actuators. -They produce larger forces and thrust -High stroking speed and longer cylinders give the actuator better stroking capabilities.

The two types of Pneumatic Actuators

1. Diaphragm Actuators 2. Piston Actuator

Classifications of Actuators

1. Manual 2. Pneumatic 3. Electric 4. Electro-Hydraulic

Two Types of Electric Actuators

1. Solenoid 2. Electric Motor

Manual Actuator

Hand Operated

Actuator

Is an instrument that supplies force and motion to open or close a valve.

Pneumatic Actuator

Operate by gas pressure(usually air)