Benefits and Drawbacks of Electric Valve Actuators in Process Control

Electric actuators use electricity to operate a valve. While most of the basic principles utilized in electric actuators have been present since the 1930s, decades of incremental progress have considerably enhanced their capability while lowering their cost. These advancements have reached a tipping point in recent years, making electric actuators the preferred choice for many applications. 

There are many advantages to electric valve actuation. Electricity is relatively cheap, simple to control, and usually available at most industrial sites. Electric actuators often have a lower capital cost per equivalent unit of torque/thrust production. They are also more environmentally friendly and safer to use. Electric actuators can provide higher positioning accuracy for control or modulating valve tasks and options for extensive process monitoring, data logging, and information feedback. Electric actuators include all necessary control functions, lowering capital expenditures. By enabling distributed control, the electric actuator's considerable cost in wiring is cut—through efficient and straightforward control logic through integrating control commands and feedback into customer SCADA or DCS systems. (Traditional electromechanical control systems require a distinct wire for each command and feedback signal, resulting in cable bundles with at least seven cores for each actuator.

On the other hand, a standard bus system can use one twisted pair wire in a daisy chain configuration to transport all required input and output signals.) Electric actuators weigh less and have smaller footprints than pneumatic actuators as torque and thrust requirements increase. Finally, electric actuators can generate exceptionally high output thrust and torque values in conjunction with external gears. 

There are also some disadvantages to electric valve actuation to note. Except for a few specific combinations, electric actuators cannot ensure a fail-safe stroke. Still, they will "fail in the last position"  - the ability of an actuator to move a valve to a specified safe position when power ceases is known as fail-safe stroke. Electric actuators contain more sophisticated and delicate components than other forms of actuators. Electronic technology likewise necessitates regular updating to stay up with component changes and advances. Compared to pneumatic and hydraulic actuators, electric actuators are less cost-effective and have operating speed restrictions beyond a specific size/torque range. Electric actuators require more rigorous certifications and construction features to be regarded safe for usage in hazardous regions with potential exposure to explosive process material. 

For more information about electric valve actuation, contact Swanson Flo. Call them at 800-288-7926 or visit their web site at https://swansonflo.com.

Electric Valve Actuation

Electric Valve Actuator in Service (Limitorque)

Electric actuators use electrical power to actuate a valve. While most of the basic technology used in electric actuators has been around since the 1930s, decades of incremental improvement have significantly increased their functionality while dramatically reducing their cost. In recent years, these advances have reached a tipping point that makes electric actuators the first choice for a wide variety of applications.

Electric Valve Actuation Advantages

• Electric power is relatively inexpensive, easy to manage, and normally available to most industrial sites. The capital cost of electric actuators is typically cheaper per equivalent unit of torque/thrust output. They’re also cleaner and safer to operate.
• Electric actuators can provide superior positioning accuracy for control or modulating valve functions, which can include provisions for a high degree of process monitoring, data logging and information feedback.
• All necessary control functions are integral to electric actuators, reducing capital costs.
• Electric actuators significantly reduce control wiring costs by enabling distributed control. They simplify control logic by integrating control commands and feedback into customer SCADA or DCS systems. (Traditional electromechanical control systems require a dedicated wire for each command and feedback signal, leading to cable bundles with seven or more cores as minimum for each actuator. By contrast, a typical bus system can use one twisted pair wire in a daisy chain configuration to carry all required input and output signals.)
• As torque and thrust requirements increase, electric actuators weigh less and have smaller footprints compared to pneumatic actuators.
• Electric actuators may be combined with external gearboxes to produce extremely high output thrust and torque values.

Electric Valve Actuation Disadvantages

• With the exception of a few specific configurations, electric actuators can’t guarantee a fail-safe stroke but will “fail in the last position.” (Fail-safe stroke refers to an actuator’s ability to move a valve to a predefined safe position when power fails).
• Electric actuators have more complex and sensitive components than the mechanical parts used in other types of actuators. Electronic technology also requires periodic refreshing to keep pace with component changes and improvements.
• Beyond a certain size/torque range, electric actuators are less cost-effective and generally have limitations in operating speed when compared to pneumatic and hydraulic actuators.
• In hazardous areas with potential exposure to explosive process media, electric actuators require more specific certifications and construction features to be considered safe for use.

Recommended applications for electric actuation.

Electric actuation is the first choice for most oil and gas applications. They’re ideal for general process valve automation, non-critical applications, and light-duty modulating applications (generally up to 1200 starts per hour), although some can modulate continuously up to 3600 starts per hour.

For more information about electric valve actuation, contact Swanson Flo. Call them at 800-288-7926 or visit their web site at https://swansonflo.com.

Reprinted with permission from Flowserve Limitorque.