Andy Le and Tom Mullins presented Optimizing Automated Valve Connectivity – Go Intelligent Electric Actuators at the 2023 Ovation Users Group Conference. Andy opened by showing the broad portfolio of valve actuators.
The electric-powered actuators include electric quarter-turn- and multi-turn, electric spring return, and small electric quarter-turn.
There are two main variations of the Bettis RTS design: a CM or compact multi-turn, a fail-last unit with a standard handwheel. And a failsafe version that can be configured for linear or quarter-turn operation with an optional handwheel.
Three primary methods to achieve a fail-safe stroke on losing main power to an electric actuator are supercapacitor, battery backup, and mechanical spring return. There are advantages and disadvantages to each method. The mechanical spring return is considered the most reliable method for fail-safe on an electric actuator.
Supercapacitors are one way to achieve a fail-safe stroke on losing primary power. Capacitors can store much energy in a small and lightweight package allowing the actuator to be compact. However, capacitors require recharge time which may prevent them from stoking again if power is intermittent. They also have a limited life and may require maintenance. Lastly and most critically, supercapacitors still use the motor and electric system within the actuator.
Battery backups are another method to achieve fail-safe on an electric actuator. We can also put backup electrical systems in this same category. The advantage is that a fail-safe position mid-stroke can be achieved with this technology. The disadvantages are the large size, extra cost, and effort required to source and set up a battery backup or redundant electrical system. Batteries also don’t last forever and must be maintained and replaced. This can be quite a task in remote applications.
And like the supercapacitor, a battery backup system still fundamentally relies on the motor and electrical system to operate in a fail-safe loss of power condition. So, if there was damage to that system, a battery backup may not cause the actuator to stroke.
The design of an actuator being either non-intrusive or conventional is a primary distinction in electric actuators. Actuators, known as non-intrusive, intelligent, smart, or electronic actuators, describe an actuator that generally has separate chambers for the line and control wiring and can be set up via a user interface without opening the covers. Other standard features of non-intrusive actuators are an LCD display, numerous sensors and diagnostic capabilities, and the ability to handle multiple types of service duty up to continuous modulation on some models. Due to their similarity to other industrial instrumentation, these actuators tend to be preferred by instrument technicians.
Conventional style actuators, by contrast, have a single chamber for all wiring, and setup requires opening the electrical enclosure. The wiring is generally point-to-point, with far fewer circuit boards. The unit may have a basic display, some sensors, and basic diagnostic capabilities. The actuator duty is typically S2 and S4—basic on/off service or simple modulating. These actuators tend to be preferred by electricians, given that the wiring style closely resembles other electrical equipment.
These two design styles can be likened to a classic car, the conventional style, and a modern car, the non-intrusive style. You could quickly work on the engine of a classic car, tuning the carburetor with a flat-blade screwdriver. In contrast, a modern vehicle has many more features, tuning, diagnostics, and an interface or software to maximize the technology benefits.
The DCMlink software collects data from electric actuators, providing connectivity to plant-level asset management systems. This software platform unifies Bettis electric and electro-hydraulic actuators, improving their commissioning and troubleshooting. It ensures seamless and convenient communication with actuators via wired and wireless connections.
Emerson’s electric actuator portfolio covers multi-turn, quarter-turn, and failsafe. The Bettis RTS Series spring-return electric fail-safe and control valve actuation may eliminate the need for air compressors in the future for maintenance and energy savings.
In these actuators, HART analog output technology enables two wires to each actuator, but with the ability to harvest preventative maintenance data without a special digital bus system. Using this HART communications protocol allows the use of existing tools for troubleshooting.
WirelessHART communications with Emerson Gateways allow actuator retrofit without adding control wiring at high costs. And the DCMlink Snap-On can be added to AMS systems and provide diagnostics on critical automated valves.
Visit the Actuators section on Emerson.com for more information on valve actuators’ complete suite and capabilities.