Chapter 2: The Different Types of Electric Actuators

Smart Linear Electric Actuator

There is a dislocation of linear output in this smart linear actuator. It has a high quality, stable precision material, and the design is durable and safe and can be used with a wide range of valve types, including butterfly and control valves.

Rotary Electric Cut Off Actuator

Standard signals can be integrated into these types of actuators. By converting the signals into equivalent angular displacements, they control the valve mechanically and achieve automatic modification.

Automatic change involves mechanical, physical, and bi-directional intrusion-free control of the regulatory system. There are two parts to it: the actuator and the servo amplifier. Control can be accomplished physically or rapidly at a distance.

Linear Electric Cut Off Actuator

The AC single-phase power supply and AC three-phase power supply are two types of power supplies available for this type of electric actuator. An electric actuator is established from the regulator control signal to achieve a prearranged linear reciprocating motion.

Electric actuator sequences are employed as regulating electric valve actuators. The control valve itself needs a variable change function, and the opening of the valve needs a signal function of the electric actuator. Therefore, it finds extensive use in metallurgical, power generation, papermaking, environmental protection, petrochemical, and light industries.

Rotary Electric Regulating Type Actuator

Full electronic actuators receive 4mA - 20mA or 1V - 5V dc input signals from the operator, PC, or regulator to work with a single-phase AC power supply and are available with servo systems. There is no need for an extra servo amplifier. An input component's controller accepts integrated circuits that are complex and mixed and is hardened by resin pouring and aging.

As a result, there is a high degree of inconsistency, and moisture and vibration are opposed. Once the base and crank are accepted for fitting, the crank zero ends can be determined randomly within 0 to 360 degrees Celsius. In addition, the electrical actuator has temperature, overload, and torque switch safety features. A product of high inconsistency and precision, with changeable mechanisms for angular travel, it is competent in determining the angular travel electric regulating valve.

SMC Electric Actuator

There are several advantages to these types of electric actuators; acceleration and speed can be controlled, and they can also be predicted. It is possible to achieve several positions with high accuracy and repeatability. Almost all forces can be automated. Since there is no need for condensed air, energy costs and infrastructure costs are reduced. Easy process and arrangement are the main focuses of these types of actuators.

Function parameters are fixed. Additionally, there is an easy mode that lets you operate quickly. Different types of SMC electric actuators include sliders, AC servo sliders, rods, guided rods, AC servo rods, slide tables, rotary, grippers, miniature, controllers, and drivers.

Comparison of Electric Actuators and Counterparts

In this section, electric actuators will be compared and contrasted with their mechanical counterparts.

Electric vs. Pneumatic Actuators

When comparing electric actuators with pneumatic actuators, the following is shown:

Power Source

There is a big difference between these actuators in terms of their diving force. An air supply of 60 - 125 PSI is required for pneumatic actuators. A solenoid valve (pilot valve) is controlled by either AC or DC voltage. When there is no air supply, electric actuators are used.

Component Size

Compared to electric actuators, double acting actuators are up to 70% smaller.

Actuator Speed

Depending on the model, pneumatic actuators close or open valves in half a second to a full second. On the other hand, electric actuators take approximately six seconds or more.

Pneumatic and Electric Temperature

It is possible to use pneumatic actuators at temperatures ranging from -20°F to 350°F and their rated temperature range is -20°F to 350°F. High temperatures can cause electric actuators to overheat in applications involving high temperatures, and they are often rated between 40 degrees Fahrenheit and 150 degrees Fahrenheit. There are however different temperature restrictions for different products, depending on the company's guidelines for evaluating their products.

Durability and Longevity

The cycle life of high quality rack and pinion pneumatic actuators is up to 1,000,000 +/- times when they are used according to specifications. It depends on the application whether electric actuators have a cycle of 250,000 or less.

Spring Return

For valve actuators, spring-return or failsafe options provide safety. If there is a power or signal failure, the valve is reset to the safe position by the spring return, which is determined by the operator. Pneumatic actuators are available with spring-return failsafe options. The implementation of this feature is not as straightforward with electric actuators.

Cost of Electric and Pneumatic

The cost of electric ball valves is generally higher than that of pneumatic ball valves. As long as they are used within specifications, pneumatic ball valves have a long lifespan and provide good overall value.

Electric vs. Hydraulic Actuators

Based on a comparison of electric actuators and hydraulic actuators, the following conclusions can be drawn:

Hydraulic Force

The force of hydraulic cylinders is equal to the pressure x the area. Even a 3-inch cylinder can achieve 15,000 lbf (66,723.3kN) at 2200 psi. Often, hydraulic cylinders are oversized, which obscures the application's actual force requirements. A hydraulic actuator must wait for pressure to build up before it can exert force.

In electric actuators, the current passing through the servo motor produces torque to drive the power screw and generate force. Many linear actuators use roller screws, which are excellent for transmitting force. The force applied by an electric linear actuator is instantaneous.

Providing Control

For simple end-to-end position applications, hydraulic actuators are a good choice. Complex motion profiles, however, may require expensive servo hydraulic systems. An electric actuator with a servo motor provides infinite control over position, acceleration, deceleration, velocity, output force, etc. It is possible to make adjustments on the fly. In comparison with hydraulic systems, the levels of accuracy and repeatability are much higher.

Hydraulic and Electric Velocity

A hydraulic actuator as well as an electric actuator can have difficulty delivering high forces. For a hydraulic cylinder to achieve high speeds at higher forces, there must be enough pressurized oil in the system to move the oil within the cylinder in the time required. In order to hold the pressurized volume, there may be a need for an accumulation system.

Electric actuation systems depend on motor RPM, torque, and screw characteristics to deliver high force. As the torque increases with the servo size, there is a limit in speed due to the decrease in RPM. Due to its control over the entire motion profile, the electric actuator does not have to stroke each cycle's entire length. Since it is able to execute shorter, more intelligent movements, the actuator may be able to deliver peak velocities.

Overall Footprint

The hydraulic cylinder has a compact footprint at the work point, but the hydraulic power unit, which regulates oil pressure and flow, requires a lot of floor space. Additionally, gauges, heat exchangers, accumulators, and cables may be required. In addition to the actuator, the drive, motor, cables, and cabinet, electric actuators have a small overall footprint. An electric servo mechanism takes up only a fraction of the space of a hydraulic cylinder with HPU.

Temperature Sensitivity

The temperature of hydraulic systems is very sensitive. As the oil gets thicker and slower moving in the cold, the engine performs sluggishly and inconsistently. The oil may be degraded or the seals ruined by high temperatures caused by overheating or environmental conditions. To maintain the operating temperature in the cold, a tank heater is added, while a heat exchanger mitigates overheating.

By adding either piece of equipment, the system costs increase. Temperature is less of a concern with electric actuation systems since they can be set to operate at a specific temperature for the amount of work required. For fast response in cold temperatures, electric actuators can be specified with extreme temperature grease.

Life and Maintenance

Properly maintained hydraulic cylinders provide long service life. Maintenance requires staff time, new seals, oils, and filters, as well as machine downtime. When the electric linear actuator is sized correctly for the application, there is no downtime since maintenance is not required. An accurate calculation of actuator life is the first step in selecting a proper electric rod.

Data Collection

Data collection and reporting are not available for hydraulic actuation systems. At the work point, only expensive, complex servo-hydraulic systems can track and monitor position, force, velocity, etc. Sensors are built into an electric actuator's servo system. Monitoring motor current tracks force and repeatability. Position and velocity are registered by the motor's feedback, and the PLC and drive report them.

Electricity Costs

Electricity is typically converted to motion by hydraulic systems at a rate of 40 to 50%. Linear actuators typically operate at 75 to 80% efficiency.

Environmental Impact

Leaks occur in hydraulic actuation systems. As a result of leaks, contaminant products are created, safety hazards are created, and the environment is polluted. Clean-up is expensive. Electric actuation is one of the cleanest technologies on the market. The grease on the roller screw is the only potential contaminant, and special greases can be specified.

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