Electric actuators have different functions and types, which can be called electric valves when matched with valves. However, in the design and selection process, only focus on the parameters of the valve, and ignore or do not clearly define the relevant requirements of the electric actuator, which will not only make the electric valve performance poor, but also cause serious consequences in the process of use.
There are many kinds of electric actuators selected according to the type of butterfly valve, and their working principles are different. Generally speaking, the switching control is realized by rotating the valve plate angle, lifting the valve plate and so on. When matching with electric actuators, electric actuators should be selected according to the valve type first.
(1) The rotation of the output shaft of the angle-stroke electric actuator is less than one cycle, i.e. less than 360 degrees, usually 90 degrees, to control the opening and closing process of the valve. According to the different ways of installation interface, this electric actuator can be divided into direct connection type and base crank type.
(2) The output shaft of multi-rotation electric actuator rotates more than one cycle, i.e. more than 360 degrees. Usually, multiple revolutions are required to control the opening and closing process of the valve. This kind of electric actuator is suitable for gate valve, globe valve, etc.
(3) The motion of the output shaft of linear stroke electric actuator is linear motion, not rotation. This kind of electric actuator is suitable for single-seat regulating valve, double-seat regulating valve, etc. According to the production process control requirements, the control mode of electric actuator is generally divided into switching type and regulating type.
Pressure loss after the flow of the medium through the valve (the pressure difference before and after the valve) will occur. This is because the flow regulating valve has a certain resistance to the medium. The medium needs some energy to overcome the resistance of the valve. Consider the design and manufacture of the valve from the perspective of energy saving and emission reduction in order to minimize the resistance of the butterfly valve to the flowing medium.
Opening and closing forces and moments are the forces or moments that must be applied to open or close the valve. When closing the valve, it is necessary to apply closing force and torque between the sealing surfaces of the two halves of the valve seat with specific pressure, and between the packing and nut threads between the stem and stem end to overcome frictional components such as bearings and friction. The maximum values of opening and closing forces and opening and changing closing torques required during the opening and closing of high-performance butterfly valves are at the last moment of closing or the initial moment of opening. When designing and manufacturing the valve, efforts should be made to reduce the closing force and torque.
The lifting speed is used to open or close the valve to indicate the required movement time. The opening and closing speed of the valve is generally not important, but in some cases the opening and closing speed is required to be fast to prevent accidents, and in some cases the valve is required to close slowly to prevent water hammer, etc. This should consider the choice of valve type.
This refers to the sensitivity of the butterfly valve to changes in media parameters in order to make a corresponding response. For valves such as throttling valves, pressure reducing valves, valves used to regulate media parameters and safety valves, traps with specific functions, the sensitivity and reliability of the function are very important technical performance indicators.