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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:
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
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”
1⁄2 a Second to 1 Second
Xingyu supply professional and honest service.
6 Seconds
-20° to 350° F
-40° to 150° F
1,000,000 +/- When Used Within Specifications
250,000 +/- Application Dependent
Widely Available
Not Widely Available
Oil & Gas
Automotive
Pharmaceutical
Food & Beverage
Power Processing
Chemical Admixtures & Treatment
Food Service Equipment
Irrigation
Vehicle Wash Systems
Water Treatment Equipment
Manufacturing Facilities
A valve actuator is defined as a mechanism that opens and closes a valve. By definition it seems simple but in reality there is nothing simple about them. There are two basic valve operating designs, linear and rotary. Therefore, basic actuator designs are linear, rotary and sometimes rotary linear. Typically, rotary operated design valves provide the best overall value in valve automation.
Valves that need to be opened, closed or throttled frequently are popular candidates for pairing with an actuator. Actuators are attached or built into a valve body to automatically adjust the flow of fluids, gases, steam, solids or slurries through a valve. If you’re in the market for an actuated valve, there are many things to consider before selecting the ideal one. First, there are several types of actuators, pneumatic, electric, water hydraulic, oil hydraulic and self-contained electro-hydraulic (oil). The two most often used types of actuators are pneumatic (air) and electric. These technologies are very different and understanding the benefits and limitations of each one is critical. In general, it’s important to consider the application, location and intended functionality. Throughout this article we explore the benefits of the two most popular actuator types: pneumatic and electric.
Pneumatic actuators typically provide high force and speed in a smaller footprint depending on available air pressure supply than electric actuators. The force and speed of these actuators are semi-independent from each other, the greater the force required, the larger the actuator size and therefore, slower operating speed ranges. These ranges are adjustable with air throttling mechanisms to accommodate different speed requirements.
There are several different designs of pneumatic actuators including diaphragm and piston-cylinder types for both linear and rotary valve operating designs. Rotary actuators have the most variety of designs. Piston-cylinder designs include scotch yoke, rack and pinion and modified scotch-yoke. Secondly, there are also vane and diaphragm type rotary designs. All of these provide air to open air close function. With the addition of a spring or springs a fail position on the loss of air supply can be provided. An electric solenoid valve is usually required to allow the actuator to shift air supply from open to closed and vice versa.
An important factor when determining price is the added compressor cost and added air tubing to each actuator cost. Although, pneumatic actuators are significantly less expensive in terms of upfront costs, they are most economical when appropriately matched with compressor size. Small compressors are economical only when they are used to power a small number of actuators. The same is true with larger compressors. Unused compressor capacity can be a waste of money therefore it is encouraged to only use a larger compressor when there is a need to power many pneumatic actuators.
Although initial pneumatic unit actuator price is considerably lower, compressor costs, tubing and solenoid wiring costs, maintenance and operating costs can be higher overall. These costs include replacing components that commonly wear out over time, like actuator cylinders, and paying for the electricity it takes to power compressors, which eventually adds up to more cost than most would expect. If there is already is a compressor at your facility and has capacity then, a pneumatic actuator can be the best value.
Electric actuators, also known as electric motor operators, are known for their precise control and positioning capabilities. Typically, they can be heavier but because of what it takes to achieve that precision, they can be substantial in cost. The accuracy comes from the high quality components. High precision screws and anti-backlash mechanisms can create positioning accuracy to ten thousandths of an inch and even standard components can generate exactness to a few hundredths or thousandths of an inch.
Electric actuators tend to not have the speed and thrust associated with pneumatic due to the nature of electric motors. Thrust must be sacrificed to achieve high speeds and vice versa. For any electric actuator, more thrust is available only at low speeds and less thrust will be offered at high speeds. Because of this, initial sizing of electric actuators is extremely important. If a thrust or speed increase is needed after installation, it will require replacing with a larger and more powerful actuator.
If you decide to go electric, make sure to understand its application in real conditions under load. With electric actuators, the cost between different sizes increases exponentially, so understanding specifications of your system will help in choosing the right actuator while minimizing cost. One area operators see lower costs with electric actuators is in operating expenses. Operating costs for these units come mostly from the power draw of the motors. When calculating cost versus benefit between pneumatic and electric, look past initial cost and remember to factor in operating time and costs.
It’s important to keep in mind, environmental regulations are getting tighter each year and strict emission laws are frequently being put in place. Electric actuators are currently gaining popularity because they do not require the use of supply gas and do not emit emissions. Installing a vapor recovery unit or using compressed air help cut down on emissions associated with pneumatic actuators.
Another case for electric actuators is automation. A significant benefit with electric actuators is they can control your valves from an offsite location. Automation is also possible with pneumatic but by only using an I/P valve controller which converts an electric signal to pneumatic. Ultimately adding another component to buy and maintain.
If it’s time to replace actuators or if you’re purchasing them for the first time, take some time to consider your system and the exact role the actuators will serve. Consider future expansion and your overall budget and always ask reputable experts for recommendations. Not only does Flomatic have the knowledge and experience but we take pride in helping every customer get the ideal product best suited to fulfill their valve needs.
Are you interested in learning more about Electro Pneumatic Valve? Contact us today to secure an expert consultation!