Pneumatic vs Electric Actuators

If you’re using a general-purpose actuator for an application, various factors might affect your choice. These include your application’s requirements for speed, accuracy, repeatability and force, as well as the complexity of the actuator’s design and the environments in which you want to use it. Pneumatic and electrical actuators both have their pros and cons, so consider carefully which type would best suit your intended application.

Speed

Pneumatic actuators are typically capable of higher speeds than electrical ones. Both types can be fast in performance, but a pneumatic actuator offers higher duty cycles and faster reaction times. Pneumatic actuators usually take from 0.5 to 1.0 seconds to open or close a valve and also offer adjustable operating speeds.

Accuracy And Repeatability

Pneumatic actuators currently offer lower accuracy and repeatability than electrical ones. This is because controlling air pressure is harder than controlling electric current and/or voltage. For extreme precision with pneumatic actuation — with control valves, for example — you may need to install an electro-pneumatic positioner to achieve accurate motion control.

Force

Pneumatic actuators are capable of generating significantly higher force than electrical ones, which depends on the design and capacity of their mechanical components.

Design

Pneumatic actuators are simpler in design — compact and with fewer components. They’re easier to install but may require more overall space to house peripherals. The components of electrical actuators, such as electric motors and ball screws, are more complex.

Environment

Pneumatic actuators are designed to withstand higher pressures and temperatures, as they’re often used in harsh and hazardous environments. The delicate components in electric actuators require a greater level of protection to withstand high pressures and temperatures, as well as vibration and the ingress of moisture, dirt or dust. They might not function properly in hazardous environments, for which numerous certifications such as IP ratings are required.

Efficiency And Cost

When comparing pneumatic and electrical actuators, pneumatic systems are typically cheaper to install and initiate. But their long-term running costs may eventually exceed those of electrical actuators, once replacement parts and energy costs are taken into account. You don’t need a motor to run a pneumatic actuator, but you will need electricity if you’re using a pilot valve or solenoid directional control valve. Electrical actuators are more expensive to purchase, but their long-term running costs are usually lower and energy savings are more achievable.

Failsafe

Many manufacturers offer double-acting pneumatic actuators with a built-in failsafe device, which you’d normally only find in spring-return models. A failsafe installed in a durable double-acting actuator kicks in if you lose power, signal or air pressure. In this event, it automatically engages built-in springs to return a control valve or other device to the normal or “safe” position. Failsafe features are available for electric actuators, but they’re not so easy to implement.

Pneumatic Or Electrically Actuated Ball Valves

You might be comparing pneumatic or electrical actuators for specific situations such as flow control. When you need to control the flow of any media like air, gas or fluids, you might be looking at ball valves. In this circumstance, both types of actuation serve the same purpose.

Pneumatically Actuated Ball Valves

Pneumatically actuated ball valves work with the two most common types of pneumatic actuators — the double-acting or the spring-return. Both are of reliable and durable rack and pinion design. Double-acting pneumatic actuators are likely to be up to 70% smaller than comparable industry-standard electrical versions.

Electrically Actuated Ball Valves

Electrically actuated ball valves are also called rotary or motorised ball valves. They’re commonly powered by a motor, which will probably be of 12DC, 24DC or 120AC voltage, plus a gear train to generate the torque required for cycling the valve. They’re cheap to operate, offer flexible motion control and make minimal noise. On the downside, you’ll find them initially more expensive, slower than pneumatic actuation and lacking in failsafe options.

What Are The Essential Differences Between Pneumatic And Electric Actuators?

The essential differences between pneumatic and electric actuators boil down to available space, power source, operating temperature, lifespan and cost.

Space

When space is limited, you’ll need an electric or double-acting pneumatic actuator. Electrical models are typically about 30% larger overall and pneumatic spring-return models are much wider than the double-acting type.

Power Source

You’ll need a compressor to provide a 60–125 PSI air supply to run a pneumatic actuator. If it has a solenoid directional control valve, this will require AC or DC voltage supply. If air compression isn’t feasible for your application, use an electric actuator.

Operating temperature

Pneumatic actuators are much more flexible concerning operating temperature. They can be rated to work at anywhere between -20°F and 350°F. Pneumatic actuators are also resistant to explosion, though you should be careful if a flush-mounted solenoid valve is installed.

High-temperature environments are more likely to cause overheating in electrical actuators, which are typically rated between 40°F and 150°F. They’re designed to comply with common NEMA ratings for specific operating environments, such as wet, dirty or hazardous areas. In all cases, ratings will depend on the specific product and the manufacturers’ rating criteria.

Lifespan

Top-quality pneumatic actuators of the rack and pinion type can last up to around a million cycles when used within spec. Electric actuators are application-dependent, but mostly achieve only about a quarter of that.

Cost

Depending on your application, you’ll generally find pneumatically actuated ball valve models less expensive than their electrical counterparts. As long as you use them within the prescribed specifications, they’ll last longer and may offer better overall value.

Should I Choose Pneumatic Or Electrical Actuation?

Go for electrical actuators if you have no access to pressurised air or your application requires a slower cycle time. The rapid cycle times achievable with pneumatic actuators are inefficient in high-flow applications with liquid media. If you require greater speed and force, you should go for the more affordable pneumatic actuators. They’re simple to use, reliable, durable and resistant to most environments.

Originally published at https://www.rowse-pneumatics.co.uk.