Modern society is now greatly dependent on certain technologies, and one of the great unsung heroes of our civilization is the valve actuator. This relatively simple—and ubiquitous—device is found everywhere from home heating systems to large-scale industrial water treatment plants, performing the critical task of regulating fluid flow in a safe, efficient, and precise manner.
Valve actuation, which refers specifically to machinery that mechanically controls the flow of liquids or gases, can be performed in one of several different ways. At Aberdeen Dynamics, our focus is on ensuring that our clients are utilizing the best technology for the specific requirements of their equipment. In the following article, we’ll discuss manual, pneumatic, and electro-hydraulic methods of valve actuation and which applications are best suited for each.
Valve Actuators: The Basics
For most industrial applications, smooth and effective operation depends on the reliable and accurate flow of various fluids. For example, controlling the flow of natural gas in an industrial oven must be maintained at a certain consistent level to achieve the necessary temperatures. This is only possible with a well-constructed and properly installed device for the control of the valve itself.
In many types of valve installation, the valve actuation technology must be able to provide reliable operation as well as incredible amounts of force to cycle a valve. For example, the valves used to regulate the flow in a refined product pipeline frequently have several hundred thousand barrels of gasoline constantly flowing through the pipeline per day. Controlling that flow without doing harm to the valve requires a sturdy and powerful actuation system.
The underlying principle behind fluid regulation is fairly simple: a valve utilizes a valve stem to open and close. The actuator is the device that moves the stem from the open position into the closed one, and vice-versa. There are two ways for this process to occur: by rotational or linear motion. While those are the basics, there are dozens of different permutations of these fairly simple concepts.
Manual Actuators
The most basic method of fluid control is through manual actuation. With this method, the valve is opened and closed by the turning of a lever or a handwheel. Levers are generally used for smaller-scale piping that doesn’t face a great deal of force. For larger valves, handwheels are ideal because they can generate a considerable amount of torque to open and shut valves that are under high pressure.
Manual valves are the simplest method of actuation and are suitable for less complex systems or those that are easier for a human operator to access. Due to the lack of moving parts, they are also the most inexpensive type of valve actuation. However, they are not able to be automated, which makes them impractical for technologies that require constant, continuous usage, and they can pose potential safety issues. In certain cases, manual valves can be integrated with various technologies to allow for a greater degree of control over the system; however, for more advanced applications, other methods are necessary.
Pneumatic Actuation
For larger-scale or industrial applications, pneumatic actuation is a popular choice, using compressed air to operate the valve stem through pneumatic actuators. Pneumatic actuators are capable of applying more force than a human operator can provide. For this reason, they can be used in systems that are larger scale than those that utilize manual actuation. They are controlled through a signaling device, meaning they can be installed on valves that are not easily accessible by an operator.
There are several types of pneumatic actuator technologies, including:
- Double-acting rotary piston or diaphragm
- Double-acting linear piston or diaphragm
- Spring-return rotary piston or diaphragm
- Spring-return linear piston or diaphragm
Pneumatic actuators are typically controlled with a solenoid valve (signaling device) and are mounted on the actuator or close to the actuator. The solenoid valve can be remotely or locally operated. The solenoid valve directs fluid pressure—in this case, compressed air—into the actuator’s piston or diaphragm, causing the actuator to rotate or move in a linear motion to operate a valve.
One of the key benefits of a pneumatic actuator is safety: For spring-return actuators, if the air supply is vented from the actuator, whether because of an emergency or for another reason, a spring will return the valve to a closed (or open) position. This limits the possibility of the system suffering from a catastrophic failure in a way that may place workers at risk.
Electro-Hydraulic Actuation
For valve actuator systems that require extreme amounts of force or fast open/close speeds, or where clean, dry compressed air is unavailable, electro-hydraulic actuation may be the best valve actuation method. Similar to pneumatic actuation, electro-hydraulic systems use a fluid medium to control valve motion. Instead of compressed air, however, hydraulic actuation technology uses liquid fluid. In most cases, pressurized oil provides the necessary power to open and close the valve.
Pressurized oil can be generated from a hydraulic pump coupled with an electric motor, gasoline/diesel engines, or even from compressed air. The oil pressure in an electro-hydraulic actuator is typically much higher than compressed air. Since pressurized oil can be 20 to 30 times higher, electro-hydraulic actuators are able to provide greater force (torque/thrust) and cycle at much faster speeds than pneumatic actuators.
This makes electro-hydraulic actuators ideal for pipeline valves, refinery/petrochemical plant valves, power plant valves, paper mill valves, water/wastewater plant valves, and many more industries where valves require high torque or thrust, fast operating speeds, or where clean, dry compressed air is not available.
Choosing the Best Technology for Your Needs
At Aberdeen Dynamics, we specialize in integrating various technologies to provide the most powerful and versatile options for industrial applications. With the top designers in both electric and hydraulic actuation technology, we are equipped to help you achieve your specific operational needs. Furthermore, we understand that many of our clients will have needs that are unique to them. That’s why we work closely with you to create custom versions of the technologies we offer. If you have a project that requires advanced valve actuation, contact us today. We can discuss your needs with you so the end result is a more efficient and effective operation.