Pneumatic vs. Electric Valve Actuators for Centrifugal Compressors

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Compressor Control Valves

Control valves play an important role in centrifugal compressor operation. Typical valves supplied with a compressor package include the inlet valve, discharge check valve, and, when required, a shut-off valve. The inlet and unloading valves are automatically controlled by the compressor control system and help maintain safe and efficient operation across varying demand conditions.

Each valve requires an actuator to provide the force needed to open, close, or position the valve. Pneumatic and electric actuators are the two most common options used on centrifugal compressors. Both technologies are widely used in industry, but their performance characteristics differ in several key areas. Understanding these differences can help operators and engineers select the most suitable solution for their application.

How Valve Actuators Operate

Pneumatic Valve Actuators

Pneumatic actuators use compressed air to move a piston or diaphragm, converting air pressure into mechanical motion. A current-to-pneumatic (I/P) transducer receives a signal from the compressor control system and adjusts the actuator position accordingly.

Their straightforward design has made pneumatic actuators a common choice across a wide range of industrial applications. Fast response times, proven reliability, and simple fail-safe configurations are among the reasons they continue to be widely used on centrifugal compressors.

Electric Valve Actuators

Electric actuators use a motor and gearbox assembly to position the valve. The actuator receives a signal directly from the compressor control system, allowing precise positioning without the need for a compressed air supply.

Many facilities choose electric actuators when precise control and integration with plant automation systems are priorities. Because they contain additional electronic and mechanical components, maintenance requirements and operating characteristics may differ from those of pneumatic systems.

Valve Comparison

Below lists a table of detailed analyses of the comparisons.

Comparison	Electric	Pneumatic	Comment
Force Availability	Extremely High but smaller size	High larger size	No impact
Explosion Proof	Need to build per safety code compliance	Does not generate sparks or heat	Pneumatic is a safer option
Overload Ability	High risk of overload shutdown from motor heat protection; Risk of gearing wearing out	Normally designed with larger margin for overloading	Pneumatic will be a better option for instantaneous overloading
Lifespan	Relatively shorter but adequate	Excellent especially for frequently varying loads	Not a big difference
Fail Safe	Feasible but cost is higher	Common and low cost (Spring return option)	Pneumatic is a better option
Responding Time	Relatively slower; Could be faster but with an impact on cost	Excellent response with low cost	Pneumatic is a better option and more economic
Hazardous Conditions	Delicate electronic components. Requires certifications for specific environments.	Rugged, can withstand higher pressures and temperatures.	Pneumatic offers more options in hazardous environments.
Control Efficiency	Operation is approximately 80% efficiency	Greater than 80% when coupled with PID control efficiency.	Both offer excellent efficiency during operation.
Reliability	More complex design; Good for design conditions	Simple and mature design; Robust and better reliability	Pneumatic is more mature and reliable
Lead Time	Around 12 weeks	Around 12 weeks	No impact
Maintenance	Complex for service; usually need replacement	Simple and easy service for the actuator, but not for electrical accessories	Pneumatic is more convenient for service
Control Integration	Direct Signal	I/P Transducer	Not big impact
Utility Requirement	Electricity only	Electricity and air	Not big impact for most industries
Noise Level	Good	Slightly higher noise	No impact
Dimensions	Compact	Slightly Bigger	No impact
Weight	Slightly heavier	Good	Not big impact
Price	Less expensive	More expensive	Electric may cost less initially, but have higher maintenance costs

Selecting an Actuator for a Centrifugal Compressor

Actuator selection depends on the operating requirements of the compressor and the environment in which it operates. Factors such as response time, fail-safe operation, maintenance requirements, environmental conditions, and integration with plant controls should all be considered during the evaluation process.

Electric actuators can be a suitable option when precise positioning and direct electrical integration are primary requirements. Pneumatic actuators are often selected when rapid response, overload tolerance, fail-safe functionality, and operation in demanding industrial environments are higher priorities.

The comparison table highlights that both technologies can perform effectively in centrifugal compressor applications. The most suitable choice depends on the goals and operating conditions of the facility.

Pneumatic and electric valve actuators each offer advantages depending on the application. Electric actuators provide accurate positioning and eliminate the need for a dedicated air supply, while pneumatic actuators offer fast response, straightforward serviceability, and a long history of use in industrial compressor systems.

FS-Elliott’s compressors are supplied with pneumatic actuators as the standard configuration due to their dependable operation and quick response during changing compressor conditions. Electric actuators are also available when application requirements call for them.

For additional information about compressor upgrades and performance improvements, download our inlet upgrade guide or contact your authorized FS-Elliott channel partner.

Operating Centrifugal Compressors