The working principle of the control valve with electric actuator

Control valves with electric drives are used for automating manufacturing processes and in building engineering systems (heating, ventilation, cold and hot water supply). The control valve shuts off the pipeline, opens it, or restricts the water flow by partially closing the passage opening. The valve is operated automatically, according to signals from the control system.

As a rule, control valves are used together with electric drives connected to the automation system controller. In industrial installations and production facilities, pneumatic or hydraulic drives may be used to control the regulating valve.

Principle of Operation of the Control Valve

The automation system measures the controlled parameter (room temperature, water volume, water temperature, etc.), and when this parameter deviates from the set value, it sends a signal to the electric drive to open/close the control valve. The drive receives the signal and moves the valve shutter to the position set by the automation system.

Changing the flow in the pipeline where the control valve is installed should affect the parameter controlled by the automation system. More detailed information about control valve installation schemes can be found in the 'Installation Schemes' section.

Optimal operation of the control valve, which periodically operates in the mode of partial closure of the passage opening, is possible only when maintaining a constant pressure difference between its inlet and outlet nozzles. Stabilizing the pressure difference ensures the valve operates according to the hydraulic characteristic specified by the design of its shutter (linear, logarithmic, or parabolic – more details are in the section describing the Characteristics of Control Valves). Therefore, control valves are usually installed together with differential pressure regulators. The principle of operation of a control valve with an electric drive in combination with a differential pressure regulator is described on this page.

The position of the control valve shutter depends on the signal received by the electric drive from the automation system and the availability of electrical power.

All types of control valves, according to their operating principle, can be divided into those that restrict, mix, or separate the flow of the working medium. Valves that restrict water volume are called two-way valves, while mixing valves are four-way and three-way.

Two-Way Control Valve

The two-way control valve has two flanges for connecting to the pipeline and is designed to restrict the volume of water. Depending on the design of the shutter, valves are divided into seat, ball, and gate types. Gate and seat control valves require drives with reciprocating rod motion, while ball control valves use rotary electric drives.

Two-way control valves are used to control heat exchangers in hot water supply systems and independent heating systems, manage mixing processes in thermal points connected to the heat network, and act as an executive element for volume, pressure, or indirect pressure differential regulators.

Operation of the Control Valve during Power Loss

If there is no electrical power, some valves remain in the position in which the shutter was at the moment of power off, some may fully open, and others may completely close. The action of the valve during power loss depends on the electric drive installed on it and the design features of the valve itself. The choice of valve and electric drive with the action that meets the requirements of the automation system during power loss is determined during the system design stage.

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