What to Choose for Valve Actuation: Pneumatic vs. Electric Actuators
Finding the right valve or valve actuator for a specific situation can be challenging. The team at BI-TORQ Valve Automation has been providing valves and valve actuators for a broad range of applications for over two decades now. Our valve offerings include a broad range of ball valves and butterfly valves.
To facilitate remote operation of our valves, we also offer a full product line of pneumatic and electric actuators. BI-TORQ is eager to assist our customers in identifying the appropriate valve actuator solution for their needs. The following page will provide basic background information on pneumatic and electric actuators.
A pneumatic actuator facilitates linear or rotary valve motion in automated processes. Pneumatic actuators function by forcing compressed air into a cylinder or actuator, which moves the mechanical components contained within and creates the necessary motion for valve actuation. There are three basic types of rotary pneumatic actuators that we will discuss here:
Scotch yoke actuators are piston style actuator that use a connecting shaft, yoke and rotary pin to deliver motion to a valve. This type provides a better torque curve at the opening and closing making them suited for larger valves. They are available in both air to open /air to close (double acting) and as air to open/spring to close (single acting)
Rack and Pinion
This piston style actuator utilizes a circular gear (pinion) that engages along linear gears (racks) as compressed air or liquid is introduced two ports for introducing compressed air into the cylinder. Advantages of this type of actuator include compactness, reliability and use for control. They are available in both air to open /air to close (double acting) and as air to open/spring to close (single acting)
Rotary vane pneumatic actuators operate similarly to a piston style actuator by providing two ports for introducing compressed air, though the housing is wedge-shaped rather than cylindrical. Rather than moving a piston, the pressure from the compressed air moves a paddle, which separates the two pressure chambers inside the housing. Movement of the paddle produces rotary motion actuation, allowing for variation in actuator rotation from 0 to 90 degrees.
Advantages of Pneumatic Actuator
Pneumatic actuators offer a broad range of benefits, such as:
- Low maintenance. Minimal maintenance is required if gearing is intact.
- Compact and lighter. Where space or weight limitations are critical, the smaller, lighter design of these actuators presents an advantage over other bulkier types.
- Fast cycle time. Pneumatic actuators work well in applications where rapid opening or closing is a necessity.
- Versatility. These actuators work well for a wide range of applications and operate well within a variety of environments, including those where temperature extremes can range from -40° F to 305° F.
- Easier to add accessories. ISO and NAMUR pads, adding accessories is easy.
BI-TORQ Pneumatic Actuators
BI-TORQ’s product line of pneumatic actuator solutions feature two different series:
PN Series Pneumatic Actuators
The actuators in this series include a durable rack and pinion system. Both single-acting and double-acting models are available, with spring returns of up to 13900 inch-pounds in spring end torque. Other features of the PN Series include:
- ISO and NAMUR compliant
- Inclusion of an anodized aluminum extrusion housing with epoxy coated end caps
- Support the setup of valves, solenoids, limit switches, positioners, and other automation accessories
SS Series Pneumatic Actuators
Like the PN series, the actuator models in this series also include a durable rack and pinion system and are available in single and double-acting styles. In contrast to the PN series, the construction of these models is stainless steel, making them a viable solution for marine, food and beverage, pharmaceutical, and other applications where limiting contamination or corrosion is critical. SS Series actuators also meet ISO and NAMUR standards and facilitate the setup of various automation accessories.
Electric actuators convert electrical power into kinetic energy for linear or rotary motion. These actuators increase process efficiency by offering automated control of a valve or damper. The popularity of electric actuators continues to increase as automation technology moves toward decentralization. Electric actuators work as follows:
- A motor provides the actual movement within an electric actuator with torque being increased through a series of gearing.
- The degree of opeing or closing is determined by switches and set of cams. Additional limit switches can be sued to provide position feedback.
Advantages of Electric Actuators
Electric actuators offer numerous advantages for various applications, including:
- Precision. Electric actuators allow for greater control precision.
- Lower operating cost. There are no compressors or pumps involved n operation.
- Quiet operation. Quiet operation is a distinguishing characteristic of an electric actuator.
- Data driven. When used with protocols, a lot of data can be mined about processes.
- Smaller footprint. The mechanical advantage of the gearing allows for a space saving actuation option.
BI-TORQ Electric Actuators
BI-TORQ provides a full line of electric actuators, including models with torque levels from 100-8,800 inch-pounds. These actuators are available in a variety of voltages, enclosures, and service options to meet the needs of a broad range of circumstances. Voltage options include:
- 115, 230, or 24VAC
- 12 or 24VDC
Customers may choose between modulating, jog, and on/off style service with fully adjustable limit switches for fine-tuning. Our electric actuators include ISO mounting and double star output for adapting to quarter turn valves. NEMA 4, 4X, and 7 casings are also available to support operation in harsh or explosive environments.
Which Actuator is Right for My Operating System?
Choosing between a pneumatic and electric actuator for your operating system can be a challenge. Examining the performance of each type of actuator in relation to various operational factors can help simplify your choice.
Both actuator types perform comparably in the following areas:
- Maintenance costs
Operational factors where pneumatic actuators have a performance edge over electric actuators include:
- High loading
- Versatility in operating environment
- Initial investment
Conversely, electric actuators excel over pneumatic actuators in areas such as:
- Control flexibility
- Position accuracy
- Long term operating cost
Pneumatic and electric actuators provide viable solutions for many valve automation applications. Each type of actuator has its own set of advantages when applied to different situations and circumstances. When making your choice, select the actuator with the best performance edge in the specific operational areas of your application.
BI-TORQ Valve Automation has the necessary expertise to help you with the valve and valve actuator selection process. We provide valves and automation systems for nearly any application and have the capability to retrofit existing valves with automation systems.