Tag Archive for: pneumatic actuator


Comparison of pneumatic actuator, electric actuator and hydraulic actuator

The valve actuators used in the regulating valve are nothing more than pneumatic, electric and hydraulic:

hydraulic actuator for marine valve

hydraulic actuator for marine valve

1. Nowadays, most of the actuators used in industrial control places are because they use air source as power, which is more economical than electric and hydraulic, and has a simple structure, which is easy to control and maintain. From a maintenance point of view, it is easier to operate and proofread than other types of actuators, and it is also easy to realize the call of positive and negative on the spot. 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 risk of fire caused by 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.

2. Electric actuators: 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 applied by users. The maximum thrust generated by the actuator can be as high as 225000kgf. Only hydraulic actuators can achieve such a large thrust, but the cost of hydraulic actuators is higher than that of electric Much higher. The anti-deviation ability of the electric actuator is very good, and the output thrust moment 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 higher than that of the pneumatic actuator . 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 it must remain in the original position when it fails. What the pneumatic actuator cannot do, the pneumatic actuator must rely on a set of combined protection system to achieve position retention.

Hydraulic actuator: When we need abnormal anti-deflection ability, high thrust and fast formation speed, we often choose hydraulic or electro-hydraulic actuator. Because of the incompressibility of hydraulics, the advantage of using hydraulic actuators is better anti-deviation ability, which is very important for regulating conditions, because when the regulating element is close to the valve seat, the throttle condition is unstable. The larger the pressure difference, the worse this situation is. In addition, the hydraulic actuator runs very smoothly and responds quickly, so high-precision control can be achieved. The electro-hydraulic actuator integrates the motor, the oil pump, and the electro-hydraulic servo valve. It can work as long as it is connected to the power supply and the control signal. The hydraulic actuator is similar to the cylinder, but it can withstand higher pressure than the cylinder. Work requires an external hydraulic system. The factory needs to be equipped with hydraulic stations and oil pipelines. In contrast, electro-hydraulic actuators are more convenient.

Valve actuator / actuation -(1)-introduction

The valve actuator is an indispensable part of the valve automatic control system. Its function is to accept the control signal sent by the controller, change the size of the controlled medium, so as to maintain the controlled variable at

21 manual-actuator-lever-handwheel-worm-gear-box

21 manual-actuator-lever-handwheel-worm-gear-box

the required value or within a certain range. According to their energy form, actuators can be divided into three categories: pneumatic, hydraulic and electric. Pneumatic actuators use compressed air as energy source. They are characterized by simple structure, reliable action, stable operation, large output thrust, convenient maintenance, fire and explosion prevention, and low price. Therefore, they are widely used in chemical, paper, and oil refining production processes. It can be conveniently used in conjunction with passive instruments. Even when using electric instruments or computer control, as long as the electric signal is converted into a standard pressure signal of 20-100kPa by an electric-pneumatic converter or an electric-pneumatic valve positioner, pneumatic actuators can still be used. The electric actuator has convenient energy access and rapid signal transmission, but the structure is complex and the explosion-proof performance is poor. The hydraulic actuator is basically not used in the chemical, oil refining and other production processes. It is characterized by a large output thrust.

Definition of valve actuator:
The actuator is a combination of the actuator and the control valve in the automatic control system. Its role in the automation control system is to receive the signal from the regulator or computer (DCS, PLC, etc.), and adjust the flow of the process medium based on its position and characteristics in the process pipeline, so that the controlled automation instrument is in production Within the range required by the process.

electric actuator for butterfly valve

electric actuator for butterfly valve

Basic composition of valve actuator:
Types of valve actuators:
In the process control system, the actuator is composed of two parts: the actuator and the automatic adjustment mechanism. The automatic adjustment mechanism directly changes the parameters of the production process through the actuator, so that the production process meets the predetermined requirements. The actuator accepts the control signal from the controller and converts it into the output of the drive adjustment mechanism (such as angular displacement or linear displacement output). It also uses appropriate actuators, but the requirements are different from the adjustment mechanism. The actuator is installed directly on the production site, sometimes with harsh working conditions. Whether it can maintain normal operation directly affects the safety and reliability of the automatic adjustment system.

The structure of the valve actuator:
A device in an automated control technology tool that accepts control signals and exerts a control function on the controlled object. According to the driving energy used, the actuators are divided into 3 categories: pneumatic, electric and hydraulic actuators.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Related news/knowledge:
Valve actuator / actuation -(2)-classification and working principle;
The matching function and principle of pneumatic valve accessories;
Valve installation instructions and process precautions;
Valve actuator / actuation -(3)-classifications