July 28, 2021

Plant engineers and technicians in the process industry continuously strive to make systems more efficient and productive. They are faced daily with making decisions on what type of equipment to use. Valve automation is a huge part of the process control industry. There are many valve actuator manufacturers to choose from and therefore it may not always be easy to make the best economical and technical choice.
The choice of pneumatic or electric actuators involves an evaluation of performance, cost, productivity, and safety. Each type of valve actuator has inherent advantages and disadvantages. The decision on how to automate a valve is usually based on the following factors:

Electric Actuators Pneumatic Actuators
Power source
First and foremost in the selection of an actuator type is to determine the most effective power source for the actuator which is largely based on the power source availability.
Electric power supply only

Much lower total power consumption compared to pneumatic actuators thanks to their high efficiency.
Pressurized air AND electric power are required (pneumatic pressure is usually supplied by an electrically driven compressor)
⇒ Need larger infrastructure
– Compressor
– Electric power
– Air lines
Torque output
Torque output needs to be tailored to the line size and the CV (flow coefficient) of the valve. CV is calculated based on input & output pressure, temperature, medium, and flow. If you are unsure of the CV value you can use this valve calculator for help.
Less powerful than pneumatic actuators Provide more force than any other actuator technology, except hydraulics
Speed of Operation
How fast the valve moves: time per turn, time from open to close.
High speeds possible.

Electric actuators use gearing to transfer rotary motion of the motor into valve movement. Unless the motor is changed (entirely new actuator), faster valve operation therefore goes hand in hand with lower torque output.
High speeds possible.

Force and speed are easily adjustable and are independent of each other
Plant Environment & Location Hazardous Location – providing explosion-proof actuators for hazardous or harsh environments (traditionally pneumatic actuators are more widely used in hazardous locations, but if compressed air is not available or if a pneumatic actuator will not provide the operating characteristics required, then an explosion-proof classified electric actuator can be used)

Inaccessible or remote valve location (automation with electric actuators is preferable here, as they require much less maintenance than pneumatic actuators) Temperature range: Both pneumatic and electric actuators may be used in a wide temperature range
Size of Actuator
Becoming of more and more importance as system requirements are become stricter.
Constant new developments for compact sized but strong electric actuators. This will make automation systems simpler, lighter, and more efficient Pneumatic actuators are much bigger and bulkier than electric actuators for the same torque output and performance standards
Lifetime costs
Make sure to consider cost per unit, as well as costs for maintenance and operation.
High initial per unit cost

Low maintenance cost

Low operating cost
Low per unit cost

High maintenance cost

High operating cost (pneumatic actuators have a constant energy draw from system leakage and positioned bleed )
Purpose Modulation – for precision applications using multi-turn actuators. (electric actuators are preferred for multi-turn valves as they are much more precise than pneumatics).

On/Off – for opening and closing the valve in 90 degree or 180 degree increments. (Electric and pneumatic actuators are equally suitable)
The control method is mainly based on the purpose of the actuator (modulating vs on/off). Secondary considerations include integration with any other equipment present, and the options available at the installation site.
4-20 mA control signal: most popular and widely used analog signal. For modulating, precise and proportional control.

TTL Control: used for on/off control, one of the earliest logic standards and therefore widely available and compatible.

Modbus control: transmitted over serial lines between devices. Can be used for both on/off and modulating control, and open-source.
Valves failing to an open, closed or last position at power/system failure
Electric actuator manufacturers are continuously introducing new and reliable fail-safe options to their product selection.

Not as widely known as pneumatic fail-safe actuators.
Pneumatic fail-safe actuators are widely available
Technical Support The importance of readily available, efficient, and effective technical support is often forgotten or overlooked when buying products for new systems. Finding a manufacturer who offers great technical support will save a lot of stress, time and money in the long run.

Take away points and summary of pneumatic vs. electric actuators:

Pneumatic Actuators:

The most practical pneumatic actuators utilize an air pressure supply of 40 to 120 psi (3 to 8 bar).Pneumatic actuators provide high force and speed at a low unit cost in a small footprint. Force and speed are easily adjustable and are independent of each other.

While pneumatic component costs are low, maintenance and operating costs can be high, especially if a serious effort has not been made to quantify and minimize those costs. Maintenance and operating costs include replacement cylinders, air line installation and maintenance, and electricity for the compressor.

Electric Actuators:

Electric actuators are often used with a 12-24 VDC or a 110-240 VAC power supply. The biggest difference is that electric actuators provide precise control and positioning of valves and can help adapt machines to flexible processes. Speed and torque are often related based on the functioning principle of an electric actuator, meaning speed is surrendered for torque and vice versa. This is an important distinction from pneumatic cylinders. Electric actuators are also quieter during operation, so they will reduce the noise of the production line.

The high initial cost of electric actuators often deters users. However savings that will result in low operating and maintenance costs compared to pneumatic actuators are often not thoroughly considered or analyzed. The annual cost of electric actuators is comparable to that of pneumatic actuators when considering replacement costs, operating costs and process efficiency.