Analysis and comparison of electric butterfly valve valve drive mode

Analysis and comparison of electric butterfly valve valve drive mode

In the field of environmental protection, water conservancy, petrochemical, metallurgy, papermaking, electric power, aerospace, pipeline, industrial equipment, industrial processing and other fields need to use a large number of valves to control fluid movement. As a control valve open, close or part of the switch drive device is usually called a valve actuator or valve actuator. Actuator as a valve control of the terminal actuator, its reliability, controllability and functionality of the advantages and disadvantages, will have a direct impact on the regulation, control of the results of the success or failure and the safety of the equipment, and constraints on the overall level of automation to improve.

Traditional actuators are divided into electric, pneumatic and hydraulic three kinds, and the derivation of gas-liquid joint, electro-hydraulic joint drive. Each drive has its own advantages and disadvantages, this article briefly explains the electric, pneumatic, hydraulic three drive advantages and disadvantages, to facilitate a quick understanding.

I: electric actuator

Electric actuator, as the name suggests, is powered by electricity, the use of single-phase or three-phase motor drive gear or worm gear output linear or rotary motion. Electric actuator can output a relatively constant driving force, strong resistance to deviation, control accuracy is higher than the pneumatic actuator, without the aid of other auxiliary systems can be automatically retained. Electric actuator has a simple operation, easy to realize long-distance control and other characteristics, but its structure is complex, easy to load the failure, often low positioning accuracy, over-open and overload, motor burnt, gear box wear, etc., the maintenance cost is very large. Too frequent regulation will cause motor heating, gears are easy to wear. In addition, the electric actuator runs slowly, it is difficult to realize large driving force, and there are problems such as over-protection realization difficulties and bad position.

Analysis and comparison of several types of valve drive

Second: pneumatic actuator

Pneumatic actuator to compressed air as a driving force, has a simple structure, maintenance is more convenient and so on, but the volume is large, the need for a gas source and air purification devices; pneumatic actuator actuator and regulator is a unified whole, its actuator has a thin film type, piston, toggle fork and rack and pinion type. Adopting gas as power medium has the advantage of high safety and low requirements on the use environment. However, due to the compressibility of the gas, the relatively low stiffness of the pneumatic actuator response is slow, poor resolution, low control accuracy, weak resistance to deviation, applied in the dynamic force or friction in the case of a large number of situations, it is very easy to cause undesirable vibration of the equipment. And its energy to weight ratio is poor, low power density, large driving force of the pneumatic actuator is extremely complex, bulky and expensive.

Three: hydraulic actuator

Ordinary hydraulic actuator to high-pressure oil as a driving force, with a large load capacity, high regulation accuracy, but need to be equipped with a huge independent oil supply equipment, maintenance workload is relatively large. Hydraulic actuator structure has a vane structure, rack and pinion type, spiral actuator. The three have their own advantages and disadvantages. Vane-type structure of small load-bearing capacity, oil leakage; rack and pinion type large load-bearing capacity, simple structure, large volume, spiral positioning accuracy, high processing difficulty. The following figure shows the rack and pinion actuator installed on the valve. Existing hydraulic actuator usually need to use a hydraulic station, resulting in a huge volume, long hydraulic piping, and throttling loss, maintenance is not convenient.

Four: electro-hydraulic actuator

Electro-hydraulic actuator as a hydraulic actuator derived from a power device, a collection of hydraulic, control, electromechanical, computer, communications and other technologies, can be fast, stable position of the controlled object for accurate control, used in a variety of valve drive, control. Electro-hydraulic actuator integrates hydraulic power module and control module. Electro-hydraulic actuator integrates the simplicity of electric operation, the power of hydraulic fast, reliable electric control board, with fast response speed, high control accuracy, high output power, compact structure and other advantages; at the same time, electro-hydraulic actuator overcomes the pneumatic actuator's control accuracy is low, electric actuator controllability is poor and other issues. Electro-hydraulic actuator can be roughly divided into two kinds: one is controlled by servo valve, that is, the traditional electro-hydraulic servo actuator, open hydraulic system, through the control of the servo valve to adjust the direction of the hydraulic oil flow and flow size, to achieve the regulation of the controlled object; a motor-controlled, closed hydraulic system, through the adjustment of stepper motors or servomotor steering and rotation speed to control the bi-directional pump pressure oil output direction and Flow rate. Precise regulation of the controlled object.

The new electro-hydraulic actuator structure is simple, compact, small size, smooth transmission, can obtain a large output torque, speed adjustment is convenient, easy to control, easy to prevent overload and other advantages, there is an overall inexpensive, easy to maintain, applicable to a wide range of characteristics.

Analysis and comparison of several types of valve drive control box integrated hydraulic micro-power unit and control board, making the entire actuator intelligent, miniaturized. Electro-hydraulic actuator is an important control element of the industrial automatic control system, can be adjusted to the valve pressure, flow, temperature, etc., a large number of applications in the chemical industry, petroleum, metallurgy, electric power, coal and other industrial process control systems. Electro-hydraulic actuator development towards small, lightweight, energy efficient, high reliability trend.