7/21/2019 Choosing Valve Actuator Power Source _ Instrumentationportal

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Choosing Valve Actuator Power Source

 Valve Actuator, based on the power source, falls into the three categories. Each power source of valve actuator has

unique characteristic which provide different advantage to make it suitable for specific application.

1. Pneumatic Actuator

Pneumatic actuator is the most commonly used type due to the cheapest price and availability of its power source

 i.e. compressed air. The use of natural gas is also applicable if it is not feasible to install air compressor system. It is

used both for control valve which operates in throttling mode or actuated valve which intermittently operates.

2. Hydraulic Actuator

The superiority of hydraulic actuators is its capability of supplying very high torques. Since hydraullic is considered

as non-compressible liquid it can provide fast stroking speed. A typical application of hydraullic actuators is for

 wellhead valves since very high torques and stroking speed become a concern.

3. Electric Actuator

Electric actuators has smooth operation, provide very high torque values, and retain thrust. In process platform,

motor operated valve is used in sea water intake line where large valve which requires high torque is operating in

on-off mode.

The selection of valve actuator type by its power source shall consider several issues as follow:

Service in process system

Mode of operation such as on-off or throttling operation. The requirement of valve closing or opening time.

Remote valve location

For pipeline in the middle of nowhere, pneumatic actuated valve with supplementary air or nitrogen bottle which

periodically inspected is the only posibility.

Fail-safe requirement

Process requirement of valve to fail open, fail close or fail last. Standard motor operated valve will be fail last when

loosing power supply.

 Valve operating torque

The actuator torque shall be larger than the required torque by valve in specified operating process and condition.

Safety factor shall be taken into account in selecting the size of the actuator.

Insig ht | actuated valve (SDV/BDV), control valve

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