The working principle of the electric control valve

- Oct 25, 2019-

The electric regulating valve uses electric power as the driving source to convert the kinetic energy of the motor into the displacement of the valve shaft through the output shaft, and stops the valve core at any opening required by the regulator through the control module, thereby realizing the flow rate, pressure and temperature. Control of parameters such as liquid level. The advantages of the electric control valve are that it is easy to use, saves energy, and has high control precision. In the case where explosion protection is required, only the explosion-proof actuator can be selected.


The working principle of the electric control valve:


Working power: DC24V, AC220V, AC380V and other voltage levels.

By receiving the signal of the industrial automation control system (such as: 4~20mA) to drive the valve 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. Implement automatic adjustment functions.

The principle of operation: motor power 220VAC or 380VAC, control signal 4~20mA, controller inside the controller, the controller converts the current signal into the angular stroke signal of the stepper motor, the motor rotates, and the gear, lever, or gear plus lever The stem operates to achieve a straight stroke or a quarter stroke.

Feedback: The motor runs through the gears. The three-joint sliding rheostat outputs the positioning signal of the valve. In addition, there are three line limit signals (full open, fully open, common line).


Features of electric control valve:


The electric regulating valve uses electric power as the driving source to convert the kinetic energy of the motor into the displacement of the valve shaft through the output shaft, and stops the valve core at any opening required by the regulator through the control module, thereby realizing the flow rate, pressure and temperature. Control of parameters such as liquid level. The advantages of the electric control valve are that it is easy to use, saves energy, and has high control precision. In the case where explosion protection is required, only the explosion-proof actuator can be selected.


 Advantages of electric control valve:



1. The number of links has been reduced, which has reduced the amount of maintenance work.

2. The use of power supply is convenient and economical, eliminating the need to establish a series of costs for the gas source station.

3. With the complicated method of “pneumatic valve + electric valve positioner + air source”, it not only increases the cost, but also brings about the decline of reliability (the more the link, the more the reliability is increased.

4. From the economic point of view, in addition to eliminating the cost of the gas source station, it also saves the cost of the electric valve positioner: now a good imported electrical valve positioner, usually more than 5000 to 6000 yuan, better At the price of 8000 ~ 10000, and this price can basically buy back the above highly reliable electronic actuators.



Application areas of electric control valves:


The electric control valve has the advantages of energy saving (power consumption only when working), environmental protection (no carbon emission), quick and convenient installation (no complicated pneumatic piping and air pump workstation), and is widely used in electric power, chemical industry, metallurgy, environmental protection, Industrial automation systems such as water treatment, light industry and building materials.


 Selection of electric control valve:

How to properly choose the type and specification of the electric control valve is crucial for the automatic control system. It determines whether the system can work normally and ensures that the various parameters of the system are controlled within the design range.

From the point of view of the water supply process, the smaller the pressure drop before and after the valve, the better, which can reduce the loss of the force and reduce the load on the feed pump. From the control process, the greater the pressure drop before and after the valve, the better the controllability. Under the trade-off, roughly 50% of the valve weight (the percentage of the pressure difference between the valve and the system relative to the system pressure drop) is usually chosen to be ΔP of 6 psi (about 4 meters of water column). After determining the Cv value, consult the product specifications of the electric control valve to determine the diameter of the regulating valve.


 Installation of electric control valve:



The installation of the electric control valve should be installed on the horizontal pipe, and should be considered to facilitate the maintenance and disassembly of the hand. When installing the regulating valve, it is generally considered to set the bypass pipe so that manual operation can be performed in case of failure of maintenance or self-control, without affecting The air conditioning system works normally.

After the electric control valve is installed, when the valve is at the maximum opening degree, the pipeline is cleaned to clean the dirt, so as to avoid the stuck phenomenon or damage the valve core and the valve seat during operation.

When the electric control valve is installed, the additional force to the regulating valve should be avoided to avoid deformation and damage of the adjusting valve flange due to the influence of temperature or self-weight. When the regulating valve is installed in a long place of the pipe, the supporting frame should be installed. Special use must be supplemented by support or appropriate vibration isolation measures in the case of severe vibration. When the large-diameter regulating valve is installed, it should avoid tilting. Because the self-weight of the valve core is large, it will be biased to one side, increase the mechanical wear between the valve core and the bushing, and the packing part is easy to leak. This should be paid special attention.

When installing the electric control valve, avoid the flow direction of the medium to the current valve body. If the nominal diameter of the valve is inconsistent, the tapered pipe fittings should be used. When installing, no loose clearance is allowed at the joint.

All electric control valves installed outdoors should be properly protected against explosion-proof sun and rain.