Butterfly Valve Actuation Methods
Figure 1: A pneumatically actuated butterfly valve installed in a power plant
A butterfly valve actuator determines which power source is used to operate the valve. This impacts the valve's response time, actuation pressure rating, environmental suitability, and more. Sometimes selecting the proper actuator depends on the power source(s) available for the application. This article closely examines the various actuator types for users who have some flexibility in which type to get. Read our article on actuator types to learn how different actuator types work with industrial valves.
Table of contents
- What is a butterfly valve
- Selecting a butterfly valve actuator
- Butterfly valve actuator types
- Standards for industrial valve actuators
- Actuator specific applications
- Butterfly valve symbols
View our online selection of butterfly valves!
What is a butterfly valve
A butterfly valve is a control valve that regulates fluid flowing through a section of pipe. This valve is similar to a ball valve in operation, with a quick shut-off feature. A butterfly valve has a disc mounted to a rotating stem. When the valve is fully closed, the disc blocks the fluid flow. Conversely, when the valve is fully open, the disc is rotated a quarter turn to allow a nearly unrestricted fluid flow. The disc's position between fully closed and fully open allows for proportional flow characteristics. Butterfly valves are used for their simplicity, reliability, and relatively low cost.
Selecting a butterfly valve actuator
Selecting the correct type of actuator for a butterfly valve depends on specific system components and requirements. A butterfly valve can be actuated manually, electrically, pneumatically, or hydraulically.
- Frequency of use: Manually operated butterfly valves are suitable for relatively small butterfly valves that open and close infrequently. For larger sizes, the valves will come equipped with a gearbox so a user can actuate it manually.
- Cost: Although there is significant variability depending on the valve's model and construction material, butterfly valves order from least expensive to most expensive in the following way: manual, electric, pneumatic, and hydraulic. Pneumatic and hydraulic actuators require compressed air or a hydraulic system, increasing their initial costs.
- Valve size: A hydraulic actuator may be necessary for huge butterfly valves to produce enough force to open or close the valve.
- System pressure: Hydraulically actuated butterfly valves may be necessary for applications with very high system pressure.
- Response time: Pneumatically actuated butterfly valves have a very fast response time for applications that require it.
- Power source: Manual butterfly valves are the only type not requiring an external power source, making them the most straightforward type to install and use.
- Environment: Electrically actuated butterfly valves are unsuitable for moist or explosive environments.
Butterfly valve actuator types
There are four primary methods for actuating a butterfly valve: manually, electrically, hydraulically, and pneumatically. For electric, hydraulic, and pneumatic butterfly valves, there is often an option to also have a manual method of actuation for the butterfly valve to use if needed.
Manual butterfly valve
Manual actuation is the simplest way to actuate a butterfly valve. The most basic design uses a lever to turn the valve stem, which rotates the valve's disc to open or close the valve. Larger butterfly valves can have a handwheel that connects to a gearbox. This is the easiest way to generate enough force to manually open or close the valve. The primary benefit of manual actuation is that an external power source is not required. However, since a user needs to open or close the valve, this actuation style is not ideal for applications requiring frequent butterfly valve actuation.
Electric butterfly valve
An electric actuator converts electrical energy into mechanical torque. This torque rotates the valve's stem to open or close the valve. Electrically actuated butterfly valves are versatile because they can be programmed to respond to specific signals and can be controlled remotely. Electric actuators are relatively energy efficient and simple to maintain. However, they are not suitable for high-moisture or explosive environments.
Figure 2: An electric butterfly valve with a handwheel and gearbox to assist in the event of manual operation
Hydraulic butterfly valve
Butterfly valve hydraulic actuators use fluid pressure to create mechanical force. The hydraulic pump pressurizes the fluid, typically oil, which moves a piston inside the cylinder. The piston movement transfers to the valve's stem, opening or closing the valve. Hydraulic actuators can generate a large amount of force and operate large valves or valves in high-pressure applications. However, the necessary hydraulic power unit and fluid reservoir increases the system's complexity and cost.
Pneumatic butterfly valve
Pneumatic actuators create mechanical motion using air pressure. Pressurized air in the actuator moves a piston or diaphragm, which rotates the valve stem. Butterfly valves with pneumatic actuators are fast-acting, reliable. They can be used in hazardous environments because they do not create sparks. There is a need for a compressed air source, though, and the actuation speed is more difficult to control than that of electric or hydraulic actuators.
Figure 3: A series of pneumatic butterfly valves
Standards for industrial valve actuators
When selecting an actuator for a butterfly valve, it's essential to ensure that the actuator meets standards set by the international community. Valve actuators that fail to meet these standards are at risk of premature breakage, which can cause damage to a system and endanger personnel. Some common standards for industrial valve actuators are:
- ISO 22153: ISO 22153 provides basic requirements for electric valve actuators for industrial valves.
- ISO 5211: ISO 5211 provides the requirements for any type of actuator used on a part-turn valve, defined as a valve with a stem that rotates less than 360° for the valve to open or close fully. This standard includes actuators with or without a gearbox.
- BS EN 15714: This standard provides requirements for any pneumatic actuator for a part-tun valve.
Actuator specific applications
The following examples are applications typically suitable to one type of butterfly valve actuation method. Use the examples to help determine which type of actuator a different application may require.
- Manual butterfly valve: Manual butterfly valves work well in small-scale water treatment plants. The valve controls the flow of water through different treatment process stages. Operators can use manual operation to adjust the valve and control water flow depending on treatment needs. Ideally, this valve will not be adjusted frequently.
- Electric butterfly valve: Electric butterfly valves work very well in large-scale HVAC systems in commercial buildings. HVAC systems typically require precise airflow control to maintain the optimal indoor environment. The building management system typically operates the electric butterfly valve to provide this control. The system automatically adjusts the valve based on temperature and air quality sensor feedback.
- Pneumatic butterfly valve: Pneumatic butterfly valves work well in gas processing plants where safety is essential. Using a valve that operates via air pressure rather than electricity reduces the risk of sparks which can cause explosions.
- Hydraulic butterfly valve: Hydraulic butterfly valves work well in hydroelectric power plants. The valve controls flow in the penstock leading to the turbine. This is a high-pressure application that other actuator types likely could not produce enough force to work under.
Butterfly valve symbols
|Manual butterfly valve|
|Electric butterfly valve|
|Hydraulic butterfly valve|
|Pneumatic butterfly valve|
How do I choose an actuator for a butterfly valve?
Choose a butterfly valve's actuator based on the available power source (e.g., manual, electric, pneumatic, and hydraulic) and the design elements of the application.
What are the different types of butterfly valve actuation methods?
A butterfly valve can be actuated manually, electrically, pneumatically, or hydraulically.