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Comparison and difference between electric actuators and pneumatic actuators

Electric actuators and pneumatic actuators are both commonly used equipment in our current actuators. The main difference can be seen from the name, which is the difference in driving methods. One is electric drive and the other is pneumatic drive. Because of the difference in the driving mode, the performance and usage modes of the two actuators are different. Now let's take a look at the comparison and difference between electric actuators and pneumatic actuators along with the manufacturer of Oldron actuators!

1: Comparison of electric actuators and pneumatic actuators

1. Anti-overload capability and service life

Electric actuators can only be used for intermittent operation, so they are not suitable for continuous closed-loop operation. The pneumatic actuator has the ability to resist overload and is maintenance-free throughout its service life. No oil change or other lubrication is required. Its standard service life is up to one million switching cycles, so pneumatic actuators are superior to other valve actuators.

2. Security

Pneumatic actuators can be used in potentially explosive situations, especially in the following situations:

Explosion-proof valves are required. Valves or valve islands need to be installed outside the explosive area. Pneumatic actuators used in explosive areas must be driven by air pipes; electric actuators are not easy to use in potentially explosive situations and have high costs.

3. Anti-overload ability

In the case of the need to increase the torque or have special requirements for the force, the electric actuator will quickly reach the torque limit. Especially when the valve actuator is opened irregularly or closed for a long time, the advantage of the anti-overload capability of the pneumatic actuator is obvious, because deposits or sintered objects will increase the starting torque. Using pneumatic components, you can easily increase the working pressure and force or torque.

4. Economy

In water and sewage treatment technology, most valve actuators are operated in an on/off mode or even designed to be manually operated. Therefore, pneumatic components have created an important prospect for rationalization. Compared with pneumatic actuators, if electric actuators are used, monitoring functions such as over-temperature monitoring, torque monitoring, switching frequency, and maintenance intervals must be designed in the control and test system, which results in a large number of line inputs and outputs . In addition to terminal position sensing and air supply processing, pneumatic actuators do not require any monitoring and control functions. The cost of pneumatic actuators is very low, so manual valve actuators should be automated.

5. Assembly

Pneumatic technology is very simple. The installation of the pneumatic actuator on the valve drive head and the connection and drive of the air source processing device can be easily achieved. In addition, the maintenance-free design of the pneumatic actuator ensures that it is easy to use and run immediately.

6. Components

Pneumatic components have high vibration resistance, sturdiness, durability, and generally will not be damaged. Even high temperatures will not damage corrosion-resistant components. Electric actuators are composed of a large number of components, which are relatively easy to damage.

7. Technology

The linear actuator directly acts on the closing device, while the swing actuator only needs one piston and one drive shaft to convert the "linear compressed air force" into swing. The use of pneumatic actuators can also easily achieve slow motion, such as by using simple and low-cost flow control elements to achieve slow motion. When the electric actuator converts the supplied energy into motion, a large energy loss will occur. The first is because the electric motor converts most of the energy into heat, and the second is because the gearbox is used.

Two: Summary of the difference between electric actuators and pneumatic actuators

1. Electric actuator
Electric actuators are mainly used in power plants or nuclear power plants, because the high-pressure water system requires a smooth, stable and slow process.

The main advantages of electric actuators are high stability and constant thrust that users can apply. The maximum thrust generated by the actuator can be as high as 225000kgf. Only hydraulic actuators can achieve such a large thrust, but hydraulic actuators are more expensive than electric Much higher. The anti-deviation ability of the electric actuator is very good, and the output thrust or torque is basically constant, which can well overcome the unbalanced force of the medium and achieve accurate control of the process parameters, so the control accuracy is more than that of the pneumatic actuator high. If equipped with a servo amplifier, the positive and negative effects can be exchanged easily, and the signal-off valve position state (hold/full open/full close) can be easily set, and when a fault occurs, it must stay in the original position. This is Pneumatic actuators can't do it, and pneumatic actuators must rely on a set of combined protection system to achieve position retention.

The main disadvantages of electric actuators are: the structure is more complex, more prone to failure, and because of its complexity, the technical requirements for on-site maintenance personnel are relatively higher; the motor runs to generate heat, if the adjustment is too frequent, it is easy to cause The motor is overheated to produce thermal protection, and it will also increase the wear on the reduction gear; in addition, it runs slowly. It takes a long time from the output of a signal from the regulator to the movement of the regulating valve to the corresponding position in response. It is inferior to pneumatic and hydraulic actuators.

2. Pneumatic actuator

Nowadays, most of the actuators used in industrial control applications are pneumatic actuators, because pneumatic actuators are used for power, which is more economical than electric and hydraulic, and has a simple structure, which is easy to master and maintain. From a maintenance point of view, pneumatic actuators are easier to operate and calibrate than other types of actuators, and it is also easy to exchange positive and negative left and right in the field.

Its biggest advantage is safety. When using a locator, it is ideal for flammable and explosive environments. If the electrical signal is not explosion-proof or intrinsically safe, there is a potential fire hazard due to ignition. Therefore, although the application range of electric control valves is becoming wider and wider, in the chemical industry, pneumatic control valves still occupy an absolute advantage.

The main disadvantages of pneumatic actuators are: slow response, poor control accuracy, and poor anti-deviation ability. This is because of the compressibility of the gas, especially when using large pneumatic actuators, air fills the cylinder and needs to be emptied. time. But this should not be a problem, because many working conditions do not require a high degree of control accuracy and extremely fast response and anti-deviation ability.

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