Pneumatic and electrical actuators offer a variety of benefits, but if you choose the wrong one for your application, you may suffer serious consequences. There is, however, a lot of confusion when it comes to choosing between them. The purpose of this article is to explain how pneumatic and electric actuators work, before comparing their features to help you decide which is best for you.
The valve actuator is an automation device that allows valves to be controlled remotely without the need for human intervention. Based on signals received, these devices generate motion to control valves. The valves to be controlled are controlled by actuators instead of manual levers. A valve’s mounting features vary depending on the actuator model.
As a general rule, valve actuators are classified according to how they generate torque – or force – when opening a valve. Electric actuators and pneumatic actuators are the most prevalent types of actuators based on this classification. Pneumatic valve actuators use compressed air to produce motion, while electric valve actuators use electricity. In addition to mechanical actuators, hydraulic actuators are also available but are less common.
Pneumatic actuators
Using pneumatics-controlled compressed air systems – pneumatic actuators produce the force required to operate valves. Compressed air may be used to control pistons or diaphragms on these actuators. More commonly, a piston is housed in a chamber in the piston-featuring type. Actuators may be single-acting or double-acting. Single-acting actuators, also known as spring return actuators, feature a loaded spring on one side of the piston that maintains the valve’s natural position. Pressurized air is supplied on the other side of the piston to open or close the valve, and the air pressure overcomes the spring’s force.
Air is supplied to both sides of the piston in double-acting actuators. The difference in pressure between the two sides keeps the valve in its desired position. In general, pneumatic actuators produce linear motion. Nevertheless, actuators such as butterfly valve actuators (which generate rotary motion) use motion conversion mechanisms such as rack and pinion and scotch yoke.
Electric actuators
An electric actuator converts electrical energy into a force that opens or closes a valve. It is possible for these devices to run on AC or DC power. A valve actuator with an electric motor produces the rotary motion that turns the valve. Quarter-turn actuators are used for quarter-turn valves, which require a 90° turn to open or close. Ball and butterfly valve actuators are examples of quarter-turn actuators.
The solenoid actuator is another type of electric actuator widely used in fluid control systems. In most cases, these devices are integrated with valves, forming a single unit.
Choosing between electric and pneumatic actuators
In different applications, electric and pneumatic valve actuators have specific advantages. It is important to analyze certain factors and characteristics of these actuators before selecting one for your application. Below are some of these factors and characteristics.
1. Precision
Valve precision is considered when they must operate partially closed or partially open in order to allow an exact amount of media to pass through. Pneumatic and electric actuators are both capable of providing precise control. For high precision control in applications such as chemical production, an electro-pneumatic positioner may be required when relying on pneumatic actuation to control a pneumatically operated device such as a control valve.
2. Force range
Pneumatic actuators provide greater force/torque per unit side than electric actuators. When large valves or valves with high operating pressure are involved, pneumatic actuators are preferred.
3. Speed
The speed of actuation is a crucial consideration in specific applications, such as flood control. In the same way that pneumatic actuators can be fast, electric actuators can also be fast. A pneumatic actuator, however, reacts faster and has a higher duty cycle. The operating speeds of pneumatic actuators can also be adjusted.
4. Lifespan
There are fewer parts in the pneumatic actuator. Thus, they are easier to maintain and last longer than electrical actuators, which have several parts that may need regular maintenance. Although the actuator unit may not require maintenance, other components such as the air compressor and FRL (Filter, Regulator, and Lubricator) may need it more often.
5. Cost
As pneumatic valve actuators are simpler to design than electric counterparts, they cost less than electric counterparts. The overall cost of a pneumatic actuation system increases when the accompanying pneumatic system is considered. By connecting multiple actuators to the same pressurized air supply system, this cost can be significantly reduced.
6. Fail safe
When a failure in the actuator can have severe consequences, the actuator should have a fail-safe mechanism. It is easier and cheaper to install a fail-safe pneumatic actuator. As spring return pneumatic valve actuators feature a natural fail-safe mechanism, the force of the spring will automatically return the valve to its natural position in the event of a failure.
7. Hazardous conditions
Often, electric actuators feature delicate components that may not function correctly under hazardous conditions. Furthermore, these actuators must be certified in numerous ways before they can be used in certain environments. Electric actuators need to be protected against high temperatures and pressures, dust, and moisture. In contrast, the pneumatic actuator can withstand higher pressures and temperatures than the electric actuator.
Conclusion
There are numerous industries that use pneumatic and electric actuators as efficient and highly functional automation devices. They each possess unique characteristics that make them suitable for different applications.
Aira Euro Automation is a leading types of pneumatic actuators manufacturer and supplier in India. We supply our pneumatic actuators in more than 20 countries including Gulf countries, Bangladesh, Sri Lanka, Nepal Etc. We have established a quality benchmark for Pneumatic Rotary Actuators.
Also, read In the Chemical Industry, There Are Various Types of Valves