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The principle and function of electric regulating valve

Electric regulating valve is an important execution unit instrument in industrial automation process control. With the increasing degree of automation in the industrial field, it is being used more and more in various industrial production fields. Compared with the traditional pneumatic control valve, it has obvious advantages: the electric control valve is energy-saving (only consumes electricity when working), environmentally friendly (no carbon emission), and quick and convenient installation (no complicated pneumatic pipelines and air pump workstations are required). The valve is divided into three types: linear characteristic, equal percentage characteristic and parabolic characteristic according to its function and characteristic according to the power used by its equipped actuator.

The electric control valve is mainly composed of an electric actuator and a control valve body. By receiving the signal from the industrial automation control system, it drives the valve to change the cross-sectional area between the valve core and the valve seat, and controls the flow, temperature and pressure of the pipeline medium. and other process parameters to realize remote automatic control. With equal percentage characteristics as the best, it has the characteristics of stable adjustment and good adjustment performance.

Structural features of electric regulating valve:

1. The servo amplifier adopts deep dynamic negative feedback, which can improve the automatic adjustment accuracy.

2. There are various forms of electric operators, which can be applied to 4~20 mA. DC or 0~10mA.DC.

3. The adjustable range is large, the inherent adjustable ratio is 50, and the flow characteristics are linear and equal percentage.

4. The electronic electric regulating valve can directly control the valve opening by the current signal, without servo amplifier.

5. The valve body is designed according to the principle of fluid mechanics, and the flow channel of equal section and low flow resistance is designed, and the rated flow coefficient is increased by 30%.

The electric regulating valve automatically controls the opening of the valve according to the signal of the regulating part, so as to achieve the adjustment of medium flow, pressure and liquid level. Taking the commonly used 4-20 mA current signal as an example, when the signal from the control system to the electric control valve is 4 mA, the control valve is in a fully closed state, and when it is given a 20 mA signal, the control valve is in a fully closed state. closed state. Different signal values in the middle of 4-20 mA correspond to different opening degrees of the regulating valve, that is, the opening degree of the regulating valve is 50% when the control system gives it a 12 mA signal. Select the appropriate flow coefficient according to your own working conditions, and you can calculate the flow and pressure corresponding to each opening of the control valve. So as to meet the adjustment requirements of the regulating valve for the working medium.

The principle of the electric control valve: by receiving the signal of the industrial automation control system (such as: 4~20mA), the valve is driven to change the cross-sectional area between the valve core and the valve seat to control the flow, temperature, pressure and other process parameters of the pipeline medium. Realize automatic adjustment function.

The function of electric regulating valve:

1. The air pressure switch is used to detect the air permeability of the filter. The dirtier the filter, the lower the air permeability, and the greater the pressure difference on both sides. When the pressure difference exceeds the set value of the differential pressure switch, the micro switch operates and an alarm signal is issued.

2. The driver is driven by a single-phase hysteresis synchronous motor, the valve spring is reset, and the valve is in a normally closed state when it is not working. When it needs to work, the thermostat provides an opening signal to make the electric valve connect to the AC power supply and act.

3. Open the valve, chilled water or hot water enters the fan coil unit to provide air-conditioning or heating for the room. When the room temperature reaches the set value of the thermostat, the thermostat will power off the electric valve, and the reset spring will close the valve, thereby cutting off the The water flow into the fan coil is closed and opened through the valve, so that the room temperature is always kept within the temperature range set by the temperature control.

4. The driver of the electric valve and the valve are connected by thread, and the driver can be installed after the valve is installed. On-site assembly, flexible and convenient wiring. The plane design of the driver can be installed close to the wall, occupying a small space, the product is reliable and durable, the working noise is low, and it can work reliably in the high temperature and high humidity environment that often occurs in the concealed fan coil unit.

5. When the temperature after the coil is lower than a certain limit, the low temperature protection differential pressure switch cuts off the power supply of the blower, so that the fresh air valve is closed to prevent the water in the coil from freezing and cracking the coil.

6. The electric regulating valve is used to control the opening or closing of the pipes of the cold water or hot water air conditioning system to achieve the purpose of controlling the room temperature.

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