What Is An Electric Three-Way Control valve?

Overview of Electric 3-Way Control Valves

Electric three-way regulating valves include regulating valves, throttle valves, and pressure-reducing valves, which are used to adjust the pressure, flow, and other parameters of the medium. The electric three-way regulating valve is composed of a linear electronic electric actuator and a three-way confluence (diversion) valve with a cylindrical thin-walled window-shaped valve core. It has a compact structure, lightweight, sensitive action, and precise flow characteristics. It can directly accept control signals such as (4-20mA DC 0-10mA DC or 1-5V DC) and single-phase power supply input from the regulating instrument to control the operation and realize automatic regulation and control of the fluid medium in the process pipeline. It is widely used in accurately controlling the process parameters of gas, liquid, steam, and other media such as pressure, flow, temperature, liquid level, and other parameters to maintain them at a given value. It is suitable for the working conditions of dividing a fluid into two outflows through a three-way valve or merging two fluids into one fluid through a three-way valve.

The electric three-way regulating valve relies on the pressure and temperature of the medium flowing through the valve as energy to drive the valve to work automatically, without the need for an external power supply and secondary instrumentation. This self-operated regulating valve uses the feedback signal (pressure, pressure difference, temperature) at the valve output end to be transmitted to the actuator through the signal tube to drive the valve disc to change the valve opening and adjust the pressure, flow, and temperature. This type of regulating valve is divided into two types: direct-acting and indirect-acting. The direct-acting type is also called the spring-loaded type. Its structure contains elastic elements such as springs, bellows, bellows-type temperature bags, etc., and uses the principle of balancing elastic force and feedback signals. The indirect-acting regulating valve adds a commander (pilot valve) which amplifies the feedback signal and then drives the main valve disc to move through the actuator to achieve the purpose of changing the valve opening.

Classification and Structure of Electric 3-way Control Valve

Electric three-way regulating valves are divided into two categories according to the action mode of the fluid: converging valves and diverting valves. Converging valves have two inlets, and the fluids flow out from one outlet after converging. Diverting valves have one fluid inlet, and the fluids flow out from two outlets after diversion into two streams. The structure of the converging three-way regulating valve is similar to that of the diverting three-way regulating valve. Its characteristics are as follows:

1. The electric three-way regulating valve has two valve cores and valve seats, and its structure is similar to that of the double-seat valve. However, in the electric three-way regulating valve, when the flow area between one valve core and the valve seat increases, the flow area between the other valve core and the valve seat decreases. In the double-seat valve, the flow area between the two valve cores and the valve seat increases or decreases at the same time.
2. The air opening and air closing of the electric three-way regulating valve can only be achieved by selecting the positive and negative action of the actuator. The change of the air opening and air closing of the double-seat valve can be directly reversed by installing the valve body or valve core and the valve seat.
3.  When the electric three-way regulating valve is used in a control system that requires fluid proportioning, it can reduce costs and installation space because it replaces an air-open control valve and an air-close control valve.
4. The electric three-way regulating valve is also used in bypass control places, for example, one fluid passes through the heat exchanger for heat exchange, and the other fluid does not exchange heat. When the electric three-way regulating valve is in front of the heat exchanger, a diversion three-way regulating valve is used; when the three-way regulating valve is installed after the heat exchanger, a converging electric three-way regulating valve is used. Since the fluid flowing through the three-way valve installed in front of the heat exchanger has the same temperature, the leakage is small; the fluid flowing through the three-way valve installed after the heat exchanger has different temperatures, and the expansion degree of the valve core and the valve seat is different, so the leakage is large. Usually, the temperature difference between the two fluids should not exceed 150℃.

The three-way regulating valve with a cage structure has a balancing hole and a cage guide. Therefore, the unbalanced force can be greatly reduced. Early three-way control valves used cylindrical thin-walled windows and were guided by the side of the valve core. Although this could reduce the unbalanced force, there was still a large unbalanced force when the fluid was close to closing (flow-off flow direction). Moreover, the unbalanced force changed with the change of valve opening. The cage structure with a balancing hole can eliminate the unbalanced force and has a damping effect, which is conducive to the stable operation of the control valve.

Since the leakage of the electric three-way control valve is large, in applications where a small leakage is required, two control valves (and two-way pipes) can be used to divert or merge the fluid, or to control the fluid ratio.

Function and Principle of Electric Three-way Regulating Valve

Regulating valves are used to regulate the flow, pressure, and liquid level of the medium. According to the signal of the regulating part, the valve opening is automatically controlled to achieve the regulation of the medium flow, pressure, and liquid level. The regulating valve consists of two parts: an electric actuator or a pneumatic actuator and a regulating valve. The regulating valve is usually divided into two types: a straight-through single-seat type and a straight-through double-seat type. The latter has the characteristics of large flow capacity, small unbalanced force, and stable operation, so it is usually particularly suitable for occasions with large flow, high-pressure drop, and less leakage. The valve is a control component in the fluid conveying system, with functions such as shutoff, regulation, diversion, prevention of backflow, pressure stabilization, diversion, or overflow pressure relief. The valves used in fluid control systems have a wide variety of varieties and specifications, from the simplest shut-off valve to various valves used in extremely complex automatic control systems. Valves can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal, and radioactive media. The nominal diameter of the valve ranges from a few mm instrument needle valve to a 10m industrial pipeline valve. The working pressure of the valve can range from 1.3×10-3MPa to 1000MPa. The working temperature ranges from -269℃ to 1430℃. The opening and closing of the valve can be controlled in a variety of ways, such as manual, pneumatic, electric, hydraulic, electric-pneumatic, or electric-hydraulic linkage and electromagnetic drive; it can also act according to the predetermined requirements under the action of pressure, temperature or other forms of sensor signals, or simply open or close. Nominal pressure or pressure level: PN1.0-32.0MPa, ANSI CLASS 150-1500LB, JIS10-20K Nominal diameter or caliber: DN10~500, NPS 1/2 ~36″ Connection: flange, butt welding, thread, etc. Applicable temperature: -196℃~700℃ Drive mode: manual, bevel gear drive, pneumatic, electric, hydraulic, gas-liquid linkage, electro-hydraulic linkage Valve body material: WCB, ZG1Cr18Ni9Ti, ZG1Cr18Ni12Mo2Ti, CF8(304), CF3(304L), CF8M(316), CF3M(316L), Ti. Different materials can be used for water, steam, oil, nitric acid, acetic acid, oxidizing medium, urea, and other media. This type of valve should generally be installed horizontally in the pipeline.

Features of Electric Three-way Control Valves

The electric control 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 traditional pneumatic control valves, it has obvious advantages: energy saving (only consumes electricity when working), environmental protection (no carbon emissions), and quick and easy installation.

Product features of electric three-way control valve

1. The direction of the fluid acting on the valve core is in the open state, so the working stability is good.
2. In addition to the bushing guide at the valve cover, the side of the valve core and the inner surface of the valve seat also have a guiding effect, with a large guiding area and reliable operation.
3. The servo amplifier adopts deep dynamic negative feedback to improve the adjustment accuracy.
4. The electric operator has various forms and can be applied to 4~20mA.DC or 0~10mA.DC.
5. The electronic electric control valve can directly control the valve opening by the current signal without the need for a servo amplifier.
6. Save automation investment. Compared with single-seat, double-seat, or sleeve control valves, the same system can save one valve, simplify the system, and save investment.
7. The bellows seal type forms a complete seal on the moving valve stem to prevent fluid leakage.
8. The three-way regulating valve is divided into T-type and L-type, which can divide and merge the medium. The selection should be determined according to the on-site working conditions.

Installation of Electric Three-way Control Valve

1. Before installation, you must read the instructions carefully, cut off the relevant power supply, and install it by professional technicians.
2. The water flow direction must be the same as the arrow direction on the valve body.
3. The valve body must be located above the coil water tray to ensure that water drips into the water tray.
4. The valve body and the driver must be installed within the vertical range of ±60°, and there should be at least 30mm space above for disassembly and assembly.
5. Sufficient maintenance and operation space must be maintained with surrounding pipes, equipment, and buildings, and it must be installed in a place that maintenance personnel can reach through the inspection hole.
6. The driver can only be installed after the valve body is installed and the pipeline passes the pressure test.
7. If the driver has been installed on the valve body, then during the installation and commissioning process, no force must be applied to the driver, otherwise the driver will be damaged.