VALVE ACTUATORS:
Valve actuator is a mechanical device fitted on the valve to operate it from
remote location (Control room or field panel).
WHEN IT IS USED?
- — When force required for valve operation is too high for manual operation
- — When manual valve operation time is high.
- — When valve is to be operated frequently.
- — When valve is located in “Inaccessible area”.
- — When valve is ‘Interlocked’ for control.
- — When ‘Remote’ valve operation is needed.
WHAT ARE ITS TYPES?
— MANUAL
- Operated
MANUALLY by gear box
— PNEUMATIC
- Operated
by AIR pressure
— HYDRAULIC
- Operated
by OIL pressure
— ELECTRICAL
- Operated
by ELECTRIC motor
MANUAL ACTUATORS:
- — They are operated manually by a Hand wheel or a Handle mounted on a gear box.
- — The gear box is mounted on the valve which multiplies the torque.
- — Valve can be positioned accurately.
- — Normally used with butterfly valves.
PNEUMATIC ACTUATORS:
- — They are operated by air pressure.
- — They are direct acting.
- — They are linear actuators.
- — They may be of following two types:
(I)
Piston type
(II)
Diaphragm type
PISTON TYPE ACTUATORS:
- — They consist of a Piston and Cylinder arrangement.
- — Air pressure is used for piston movement.
- — Piston rod is attached to valve stem.
- — Used only on Motorized Valves
- — May be either Single acting or Double acting type
DIAPHRAGM ACTUATORS:
•
They consist of a Diaphragm and spring
arrangement.
•
Air pressure is used on the diaphragm
for stem movement.
•
Used on Control Valves
•
May be either Forward acting or Reverse acting
type.
