An overview article on Actuators
pd11in23g > 11-24-2021, 07:44 AM
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.