Pneumatic actuators rely on compressed air or gas as the primary power source. These actuators don&#;t require a motor, but electricity is necessary when paired with an integral solenoid valve which is commonly referred to as a pilot valve.

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Remote piloting can also be achieved utilizing the air supply port(s). The solenoid (pilot) valve receives an electric signal which energizes its coil and allows air to flow either in or out of the pneumatic actuator, subsequently opening/closing the ball valve.

Two types of pneumatic actuators are available: double-acting and spring-return. Both utilize a rack and pinion design, which is well known for its reliability and durability.

• Double-Acting Pneumatic Actuated Ball Valves
  Double-acting uses air to move internal pistons (racks) in two directions, which rotates the actuator pinion 90°. The pinion is connected to the ball valve stem and opens or closes the ball valve as it rotates. Double-acting actuators will return to the normal position when power is lost and can be configured as either normally open or normally closed. In the event that air supply is lost, double-acting actuators will stay in their current position.
• Spring-Return Pneumatic Actuated Ball Valves
  Spring-return uses air to move the internal pistons in one direction and springs in the other. These actuators are normally supplied as an air to open, spring to close operation, but can be supplied as air to close, spring to open. The mechanical springs can be susceptible to spring fatigue, making double-acting a better choice for high-cycle applications. Spring-return actuators will fail to the normal position in the event of either power failure or loss of air supply.
• Double-Acting with Failsafe
  Gemini Valve now offers an industry first double-acting pneumatic actuator with failsafe. This combines the durability of a double-acting actuator with the failsafe normally only offered by spring-return models. The actuator operates in a double-acting configuration until power or air pressure is lost, and springs engage automatically to return the valve to the normal position.

Pros & Cons of Pneumatic Actuators Pros Cons

• Low Cost
• High Durability
• Fast Cycle Time
• Spring-Return Failsafe Available
• Resistant to Overheating & Moisture
• Double-Acting Models Are Up to 70% Smaller Compared to Industry Standard Electric Actuators

• Higher Operating Costs
• Compressed Air Required
• Fast Cycle Time

Electric actuators (sometimes known as motorized or rotary ball valves) are powered by a motor and gear train. These are the most popular choice for ball valve automation. If no air supply is available to power pneumatic devices, electric actuators are used.

The most common motors are supplied in 120AC, 24DC and 12DC voltages. The motor, when supplied with voltage, engages a gear train which produces the torque necessary to cycle the ball valve.

In the case of Gemini Valve&#;s electrically actuated ball valves, this torque rotates a shaft that is connected to the stem of the ball valve. An external SPDT (Single Pole Double Throw) switch or device is used with the electrically actuated ball valve to control the position, either open or closed.

With the Gemini Model 600, starting with the ball valve in the closed position and applying power to &#;terminal 2&#; on the internal actuator terminal strip, the actuator shaft rotates 90° at which time an internal cam switch shuts off the motor. The ball valve is now in the open position. Using the external SPDT switch, the power is then applied to &#;terminal 3&#;, causing the actuator shaft to rotate 90° at which time another internal cam switch shuts off the motor. The ball valve is now in the closed position. This cycling process takes approximately 6 seconds. Gemini&#;s electric actuator also features a fold out manual override handle to enable the valve to be operated in the event of loss of power.

Pros & Cons of Electric Actuators Pros Cons

• Compressed Air Not Required to Operate
• Low Operating Costs
• Minimal Noise
• Flexible Motion Control 
• Slower Cycle Time Than Pneumatic Actuation

• Failsafe Options Not Widely Available
• Generally Higher Cost
• Slower Cycle Time Than Pneumatic Actuation

Power Source

The biggest difference between electric and pneumatic actuators is the driving force of their operation. 

Pneumatic actuators require an air supply of 60 to 125 PSI. The solenoid (pilot) valve is controlled by either an AC or DC voltage.

When no air supply is available, electric actuators are used.

Component Size

Double-acting pneumatic actuators are up to 70% smaller in size compared to electric actuators.

Speed

To open or close the valve, pneumatic actuators take 1&#;2 a second to 1 full second, depending on the model. Gemini&#;s electric actuators take approximately 6 seconds, while other manufacturers can take upwards of 25 seconds or more.

Temperature

Pneumatic actuators are suitable for a wide variety of ambient temperatures, and are rated to operate in temperatures between -20°F and 350°F. Electric actuators can be at risk of overheating in high temperature applications and are often rated between 40°F and 150°F. However, the temperature restrictions will vary depending on the product and the company&#;s guidelines for rating their products. 

Durability & Longevity

High quality rack & pinion style pneumatic actuators can cycle on or off up to 1,000,000 +/- times when used within specifications. Electric actuators have cycles of 250,000 +/- but are application dependent.

NEMA Ratings

The National Electrical Manufacturers Association (NEMA) sets guidelines for the use of actuators in specific environments, like hazardous areas or locations affected by water and debris. 

Pneumatic actuators are explosion proof, though care must be taken when paired with a flush mounted solenoid valve. Electric actuators are designed to the following most-common NEMA ratings:

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• NEMA 4: Water-tight and intended for indoor or outdoor use. This rating sets a level of protection against dirt, water and ice. 
• NEMA 4X: Similar to NEMA 4, with an additional level of protection against corrosion.
• NEMA 6: Submersible, with design dependent on the specified conditions and time.  
• NEMA 7: Designed for indoor applications and certain hazardous environments. Capable of withstanding pressure from internal explosions.

Spring-Return

A safety feature for valve actuators is a spring-return or failsafe option. In the event of a power or signal failure, the spring-return sets the valve to the &#;safe&#; position determined by the operator. 

Spring-return failsafe options are widely available for pneumatic actuators. However, this feature is not as easily implemented with electric actuators. 

Cost

Pneumatic ball valves generally have a lower purchase price than electric ball valves. When used within specifications, they have a longer lifespan and may deliver the best overall value depending on your application.

Pneumatic Actuators Electric Actuators Power Source

• Air Supply of 60 to 125 PSI 
• Solenoid Valve Controlled By AC or DC Voltage

• Voltage of 120AC / 24DC / 12DC

Common Component Sizes

• 2.66&#; x 3.41&#; x 3.63&#; (Double Acting)
• 2.86&#; x 8.11&#; x 3.63&#; (Spring Return)

• 7.70&#; x 6.45&#; x 4.75&#; 

Open/Close Speed

• 1&#;2 a Second to 1 Second

• 6 Seconds

Temperature Range

• -20° to 350° F

• -40° to 150° F

Lifespan/Cycles

• 1,000,000 +/- When Used Within Specifications

• 250,000 +/- Application Dependent

Spring-Return Options

• Widely Available

• Not Widely Available

Industry Examples

• Oil & Gas
• Automotive
• Pharmaceutical
• Food & Beverage
• Power Processing
• Chemical Admixtures & Treatment

• Food Service Equipment
• Irrigation
• Vehicle Wash Systems
• Water Treatment Equipment
• Manufacturing Facilities

Pneumatic Actuators

If your facility has access to compressed air, you can explore the following pneumatic actuators: 

• Double-Acting Pneumatic Actuated Ball Valves

These are intended for low to high-cycle applications that require a power outage failsafe and compact design.

• Spring-Return Pneumatic Actuated Ball Valves

This option is designed for moderate-cycle applications that require a failsafe in the event of compressed air or power loss.

• Double-Acting Pneumatic Actuated Ball Valves (with Failsafe)

Use these actuators for high-cycle applications that require a failsafe in the event of compressed air or power loss.

Electric Actuators

If your facility or OEM equipment doesn&#;t have access to pressurized air, pneumatic actuators won&#;t be an option. Electric actuators are also popular in applications where a slower cycle time is required. The fast ½ second cycle times offered by pneumatic actuators can be a detriment in high flow applications due to water (or other liquid media) hammer caused by the abrupt stop of media when cycling the valve. 

Gemini Valve is happy to help you find the perfect ball valves for your project. Just contact us to get started.

Electric vs. Pneumatic Actuators: Which One is Right for You?

The choice between pneumatic and electric actuators is not always an easy one. However, the two technologies are so different that one can rarely be a replacement for the other. Many variations exist to meet the demands of the compressed air market. There are a few key points that can help you to decide between electric and pneumatic actuators. 

This decision becomes easier by evaluating performance, productivity gains, component costs, and system costs. Whether you choose electric or pneumatic actuators will largely depend upon the applications that are required for your system. The technologies are quite different. They have their own distinct advantages and disadvantages. In best-case scenarios, both technologies are utilized by capturing the major advantages of each. 

Pneumatic Components 

Pneumatic actuators provide high force and speed in a low unit cost that has a small footprint. Force and speed are easily adjustable and independent of each other. The typical pneumatic application employs over-sized cylinders as a safety factor. This is common because pneumatic cylinders are inexpensive. Stepping up to the next larger diameter is feasible and practical. 

Advantages

• Low cost: Pneumatic actuators are less costly than electric actuators&#;. Pneumatic systems generally have long operating lives and require little maintenance.  
• High force and speed: Due to their simple design, pneumatic actuators can provide rapid movement and high force as long as adequate compressed air pressure and flow are available 
• Simplicity of operation: Pneumatic systems are easier to design and use than their electrical counterparts in many applications. Pneumatic cylinders and actuators provide a quick path to linear motion.  
• Sophisticated transfer mechanisms are not required: Fluid power systems require air or fluid to transmit energy. Pneumatic systems use the atmosphere as the source of their fluid. 
• Tolerance to overloads, up to a full stop: Pneumatic system components do not burn or get overheated when overloaded.  
• High reliability of work: Pneumatic systems offer a long service life, reliability, and are low maintenance.  They can withstand extreme temperatures, shock and vibration. 
• Explosion and fire safety: Being pneumatically powered they can be used in hazardous environments without causing fire or explosion.  When properly configured they can withstand most damage and resist corrosion.
• Pneumatic system components are&#;very durable: They are reliable and not easily damaged.  
• Ease of assembly: Due to its straightforward design, installation of a pneumatic actuator is a relatively quick process.

Disadvantages

• Difficult to attain mid-stroke positioning: Mid-stroke positioning requires adding hardware to hit the third position.  
• This results in positional performance that is not very accurate or repeatable. 
• Difficult to maintain uniform and constant speed: Due to compressibility, it is not always possible to have&#;a uniform and constant speeds. 
• Difficulties in performance at slow speeds: Due to the compressibility and pressure loss of the air, the pneumatic system has less efficiency as compared to other techniques.  
• Requires clean, dry air for maximum performance and life expectancy: Minimizing costs could produce a compressed air system that is contaminated by water, oils, particulates, or micro-organisms. This can lead to higher expenses for equipment maintenance and replacement. 
• High maintenance and operating costs of the compressed air system: Approximately 25% of the cost of compressed air is due to maintenance, equipment, and installation. More than 75% is due to electricity costs. 

Electric Components 

Electric actuators provide precise control and positioning, help adapt machines to flexible processes, and have low operating costs.  They are most economical when deployed on a moderate scale.  This is especially true in processes where their performance advantages can be a benefit.  They are economical when the electronics are separate from the actuator, to segment and minimize replacement costs. 

Advantages

• Precise control: Electric actuators offer outstanding precision and repeatability. They perform fast and powerful movements with flexible positioning. 
• Multiple positioning: Electric actuators&#;can precisely and accurately control velocity as well as acceleration and deceleration throughout the motion profile. They can be changed from one speed to another without stopping or over-running position.
• Low operating costs: An electric system is energy efficient and can provide you with cost savings. 
• They help adapt machines to flexible processes: Not only do Electric actuators provide accurate control and positioning, operation can easily be modified by making simple program changes.
• Minimal maintenance: They can offer reduced maintenance and costs of ownership since they don&#;t require a compressed air system and don&#;t suffer air leaks.
• Easy to set acceleration and deceleration: Electric actuators&#;can precisely and accurately control velocity as well as acceleration and deceleration throughout the motion profile. They can be changed from one speed to another without stopping or over-running position. 

Disadvantages

• Higher cost: Component costs are usually higher for an electric actuator system versus a pneumatic one.
• Sensitivity to vibration: Vibration can cause part fatigue and breakage, component wear, loss of performance, and damage to accessories.
• Technology is more complex: This can lead to higher production costs than the alternatives. 
• High speeds, less thrust: Electric actuators tend to lack the speed and thrust associated with pneumatics. Thrust must be sacrificed to achieve high speeds and vice versa. 

The goal of any industry&#;s air compressor system is to increase process efficiency while minimizing costs. 

This can only be attained by ensuring that the appropriate equipment is integrated relative to system demands.  Pneumatic actuators have advantages in cost, size, and thrust.  On the other hand, electric actuators are best when speed, accuracy, flexibility, and control are required.  An assessment of your needs and equipment can help you to find the right balance while increasing performance and reliability. 

What if I have questions about Electric and/or Pneumatic Actuators? 

At JHFOSTER, one of our technicians would be happy to speak with you about choosing the right Actuator for your process. Our expertise is in working with our clients to help them achieve optimal efficiency in their facilities. JHFOSTER is a leading distributor of automated systems and robotics. 

A JHFOSTER representative is available at 651.998. or 855.688. 

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