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An overview article on Actuators
An actuator is a type of motor, typically operated by electric current, hydraulic
fluid or air pressure that's widely used in the Process Industry for moving or
controlling a mechanism or system.
How do actuators work?
Actuators take fluid, electric or some other source of power and convert it through
a motor, piston or other devices to perform work. Basic versions are used to move
Actuated Valves to either
fully opened or fully closed positions. While actuators for control or position
regulating valves are given a positioning signal to move to any intermediate position
with a high degree of accuracy.
Actuator types
There are four main types of actuators that are a combination of the type of power
applied and the type of movement required at the valve.
Pneumatic
Actuators are one of the most common and dependable configurations of actuators
and are capable of quickly operating very large valves. The main advantage of this type
of actuator is that all of the accessories are incorporated in the package and are
physically and environmentally protected. It has all the basic and advanced functions
incorporated in a compact housing which can be watertight, explosion-proof and in some
circumstances, submersible.
Electric
Actuators are very similar except that the final drive element is usually in one
quadrant that puts out a 90° motion. The newer generation of quarter-turn actuators
incorporates many of the features found in the most sophisticated multi-turn actuators.
They are compact, so can be used on smaller valves, and because of their lower power
requirements, they can be fitted with an emergency power source such as a battery to
provide failsafe operation.
Fluid power quarter-turn actuators are extremely versatile and can be used where
there is no readily available electric power or where simplicity and reliability are
essential. They can also withstand considerable mechanical abuse. The smallest can
deliver a few inch pounds of torque where the largest are capable of producing in excess
of a million inch-pounds of torque. Almost all fluid power actuators utilize a cylinder
and a mechanism to covert the linear motion generated in the cylinder to a quarter-turn
motion.
Fluid Power multi-turn actuators are frequently used when multi-turn output is
required to operate a linear type Pneumatic Valves (such as a gate or globe valve).
Electric actuators are often used for this type of valve but, if there is no electric
power supply readily available, pneumatic or hydraulic motors can be used to operate
multi-turn actuators.
Selecting a valve actuator
The correct type and size of
Valve Actuators can be determined by checking:
The Power source
The type of valve
The torque required by the valve
Remote control
One of the great advantages of an automated valve is that it can be remotely
controlled without having to physically go to the
Electric Valves
and give it an open or close command. A common method of positioning an actuator
is to feed it a proportional signal (such as 4-20 mA), so that the actuator can then
position itself in direct portion to the received signal.
If you have worked with any kind of fluid processing system, then you are familiar
with ball valves and the crucial job they do. Ball
Valves are quarter-turn valves that are
often made with full-bore designs. This means they can completely stop flow when closed
and will not hinder flow when opened. This is valuable with flow rate and pressure are
important to the application. Stainless steel is one of the strongest and most resilient
materials out there, with top-notch pressure and temperature resistances. There are too
many applications for stainless steel ball valves, but in this article we will look at
some of the most common. But first, what makes stainless steel so special?
What is Stainless Steel?
The reason there are so many uses for stainless steel
Ball Valves is that it is a
fantastic material. It is tougher than cast iron, ductile iron, brass, and copper when
it comes to pressure rating and temperature tolerance. Stainless steel competes with
carbon steel on many fronts, but beats it by a mile in corrosion resistance. For this
reason, applications for stainless steel ball valves are typically demanding in one or
more area (corrosion, temperature, pressure).
Stainless steel is a fantastic material that is difficult to beat, but it does have
one major drawback: price. There is a major price jump from iron valves to steel
Butterfly Valves, but
it is warranted! The price jump is reflected by a jump in quality from one material to
another. Stainless steel is the best of the best, with high pressure tolerance,
temperature limits, and corrosion resistance.
- Created: 10-11-21
- Last Login: 10-11-21