Valve actuators are devices used to operate valves in piping systems to control the flow of fluids. They are used to regulate the flow of liquids, gases, slurries and other media through pipes in various industrial applications. Valve actuators open and close valves, or adjust their position to vary the flow rate.
There are several types of valve actuators, including electric actuators, pneumatic actuators, hydraulic actuators, and manual actuators. Electric actuators use electric motors to operate valves, while pneumatic actuators utilize air pressure and hydraulic actuators employ hydraulic fluid to generate force. Manual actuators like handwheels, levers and gears are used by humans to physically adjust valves.
Valve actuators are selected based on the type of application, valve being used, nature of the flow medium, precision of control required, speed of actuation, cost, and environment. They provide the means to control valves that regulate flow for the efficient operation of piping systems found in water treatment facilities, chemical plants, mining operations, and other industrial processes. Various manufacturers like KMC, Honeywell, and Hayward Flow Control produce valve actuators to suit different valve types, applications and budgets.
Types of Valve Actuators
Electric actuators operate valves using electric motors that run on AC or DC power. Models like the KMC Controls QStart series provide reliable control of valves in water and wastewater applications. KMC valve actuators are also well-suited for controlling valves in hazardous locations that require explosion-proof devices. However, they can be more expensive than other options and require electrically powered control systems.
Pneumatic actuators use pressurized air to actuate valves. Honeywell valve actuators offer a range of compact pneumatic actuators that provide accurate positioning of control valves. Pneumatic actuators generate high torque and can operate at high speeds, but require a source of clean, dry air and compatible control systems. They are low-cost, durable, and suitable for difficult environments, so they are commonly used for industrial control applications.
Hydraulic actuators function by employing hydraulic pistons or motors, which are powered by pressurized hydraulic fluid. Due to the high pressures attained, these actuators can efficiently manage substantial valves, making them especially suitable for high-torque applications such as pipeline valves. While they offer precision, it’s important to note that their implementation can be more costly due to the inclusion of high-pressure hydraulic hoses, pumps, and specialized fluid. Additionally, their operational speeds are generally lower when compared to their electric and pneumatic counterparts.
Manual actuators such as handwheels, levers and gears are the simplest actuators. Handwheels and levers translate rotational or linear hand movements into valve adjustments. They are low-cost but can be time-consuming to operate and do not provide automated control. Gears can be used to translate the motion from an actuator like an electric motor into the large rotational movements required for some valves. While manual actuators lack precision control, they continue to serve some niche applications where power sources are unavailable.
Valve Actuator Applications
Valve actuators are commonly used to precisely control the flow rate and pressure in pipelines through control valves. By adjusting control valves, actuators regulate flow to match changing process conditions and demands. Precise positioning is required to achieve consistent flow control, so electric, pneumatic or hydraulic actuators are typically used for these applications.
Actuators are also used to fully open or close butterfly valves and ball valves for on/off flow control. These valve types can handle large volumes of liquids or gases, so they require actuators capable of generating sufficient torque to operate them, such as pneumatic, hydraulic or electric actuators. Though precise positioning is not necessary, accurate seating and tight shutoff may still be required.
Valve actuators have many applications in chemical plants, wastewater treatment facilities, mining operations, and other industrial processes. In chemical plants, specialized actuators are used to precisely control the flow of chemicals through control valves and also open or close isolation valves for maintenance. At wastewater treatment plants, actuators open and close valves to control the flow of wastewater through the various treatment stages before discharging to the environment. In mining, heavy-duty hydraulic actuators operate large valves used in processing ore and controlling the flow of wastewater and chemicals.
Other applications include HVAC systems, where actuators control the flow of heating and cooling fluids, gas pipelines, where valves regulate the flow and distribution of gases, and food/beverage processing, where hygienic actuators are required to operate valves. There are many new applications for valve automation emerging with the development of smart actuators that can be remotely monitored and controlled as part of automated process control systems.
Comparing Valve Actuator Options
There are several factors to consider when comparing valve actuators. Cost can vary significantly based on the type of actuator. Pneumatic and hydraulic actuators typically have lower upfront costs than electric actuators, but require supporting systems that can impact overall cost. The amount of torque generated depends on the power source, with hydraulic actuators producing the highest torque, followed by pneumatic and then electric actuators.
Speed of actuation also depends on the power source and components, with electric actuators operating the fastest, followed by pneumatic then hydraulic actuators. Electric actuators such as the Hayward Flow Control valve actuators typically offer the most precise control. Environmental suitability depends on the location, with pneumatic and hydraulic actuators well-suited for outdoor conditions, while electric actuators require protection from weather and potential hazards.
The application requirements determine which factors take priority for actuator selection. High-torque on/off applications may focus on cost and torque, while precise control applications require speed and precision. Hazardous environments may require pneumatic or hydraulic options. Some applications may demand a combination of characteristics, narrowing selection to more robust electric or electrohydraulic actuators, despite their higher costs.
In summary, comparing valve actuators based on factors such as cost, torque, speed, precision, and environment helps determine which is optimal for a specific application. The most suitable actuator may be one that satisfies several key requirements, even if some compromise is needed. With many options available, there are actuators to suit virtually any valve automation need.
In summary, the main types of valve actuators discussed include electric actuators, pneumatic actuators, hydraulic actuators and manual actuators. These actuators are used to operate valves for controlling the flow of fluids in piping systems and processes such as water treatment, chemical plants, mining, food processing, and HVAC.
The choice of actuator for a given application depends on several factors, including the type of valve and flow medium, the precision and speed of control required, the amount of torque needed, environmental considerations, and budget. By reviewing the operating principles, characteristics, applications and options from brands like KMC Controls, Honeywell and Hayward Flow Control valve actuators, the most suitable solution for a particular set of needs can be determined. There are many possibilities for automating valves, so any process control requirements can be achieved.