Valve Magazine - Winter 2010

ACTUATORS & CONTROLS
The Basics of Choosing Actuators

BY ED HOLTGRAVER

For those of us who have been around for a number of years, this article on valve actuators will be too simplistic— but it’s meant to be. The seasoned professional has had ample experience—and knows what works and what is required. Other than staying up to date on new developments, he or she can readily specify the appropriate actuator for each application. But for those new to the scene, there are a few factors that need to be learned and considered before tackling actuator selection.

Logically, a newbie could turn to an experienced colleague for advice, thereby following proven practices while gaining personal insight. However, this approach works well only if all of that experience was not eliminated via an economically inspired cutback or a retirement!

Here is some of the basic information we all need to know:

VALVE TYPES

There are three basic valve types: those that employ linear motion, those using rotary motion and certain hybrids that both lift and turn. Obviously, an actuator must exhibit the same motion as the valve. Past that, there are conditions that will lead to certain actuator selections for each application.

Manual vs. Automated

Regardless of valve type, the first consideration is whether the valve will be operated manually (actuated by human muscle) or automated (actuated by a device that does not employ human muscle). Some of the conditions that affect this decision are:

; Valve size, which affects the ability of a human to provide sufficient input force

; Quantity of actuators versus available personnel to operate

; The on/off or control application— how often the valve must be repositioned and whether it must respond rapidly to system variables

; Location and whether the valve is accessible

; Environment—temperature, radiation, noise, potential to be explosive, whether chemicals are present

; Economics—the lesser purchase cost of a manual device versus the cost of operating personnel

; Speed or whether the operation is exceptionally fast or exceptionally slow

Manual Operation
If the decision is to use manual opera-
tion, you have a choice of handle, locking
handle, gearbox or chainwheel for valves
located above and beyond normal opera-
tor reach (Figures 1, 2, 3 and 4).

Automated Operation

If the decision is to automate the operation, the power source needs to be defined: electric, compressed gas or hydraulic pressure? Then, additional factors to consider include: