German II-VI valves II-VI models II-VI prices

II-VI valves are used in industrial automation process control fields. They are the final control elements that change process parameters such as medium flow, pressure, temperature, and liquid level by accepting control signals from the regulation control unit and using power operation. They generally consist of an actuator and a valve body. According to stroke characteristics, control valves can be divided into linear stroke and angular stroke. According to the power source used by the associated actuator, they can be classified into pneumatic control valves, electric control valves, and hydraulic control valves. According to their function and characteristics, they are divided into linear characteristics, equal percentage characteristics, and parabolic characteristics. Control valves are suitable for media such as air, water, steam, various corrosive media, slurry, and oil products.

II-VI valve working principle

Control valves are used to regulate the flow, pressure, and liquid level of the medium. Based on the signal from the control point, the valve opening is automatically controlled to achieve regulation of medium flow, pressure, and liquid level. Control valves are divided into electric control valves, pneumatic control valves, and hydraulic control valves. A control valve consists of an electric or pneumatic actuator and the control valve body. Control valves are typically divided into straight-through single-seat control valves and straight-through double-seat control valves. The latter features high flow capacity, low unbalanced force, and stable operation, making it particularly suitable for applications with high flow rates, high pressure drops, and minimal leakage.

II-VI valve structure

Valve body types: There are many types of control valve bodies. Common types include straight-through single-seat, straight-through double-seat, angle type, diaphragm type, low-flow type, three-way, eccentric rotary, butterfly, sleeve type, and ball type. For specific selection, consider the following: 1) Valve core shape and structure Mainly considered based on selected flow characteristics and unbalanced forces. 2) Wear resistance When the fluid medium is a suspension containing high concentrations of abrasive particles, the internal materials of the valve must be hard. 3) Corrosion resistance Since the medium is corrosive, choose valves with simple structures whenever possible. 4) Medium temperature and pressure When the medium temperature and pressure are high and fluctuate significantly, select valves where the valve core and seat materials are less affected by temperature and pressure changes. When the temperature is ≥250℃, a heat sink should be added. 5) Prevention of flashing and cavitation Flashing and cavitation occur only in liquid media. In actual production processes, flashing and cavitation cause vibration and noise, shortening the valve's service life. Therefore, valve selection should prevent flashing and cavitation. Control valve actuators: To ensure normal operation of the control valve, the associated actuator must generate sufficient output force to ensure tight sealing and valve opening. For double-acting pneumatic, hydraulic, and electric actuators, there is generally no return spring. The magnitude of the force is independent of its direction of motion. Therefore, the key to selecting an actuator is to determine the maximum output force and the motor's rotational torque. For single-acting pneumatic actuators, the output force is related to the valve opening. The forces appearing on the control valve will also affect motion characteristics, requiring force balance across the entire opening range of the control valve. After determining the actuator output force, select the appropriate actuator based on process environment requirements. For sites with explosion-proof requirements, pneumatic actuators should be selected. From an energy-saving perspective, electric actuators should be selected whenever possible. If high regulation precision is required, hydraulic actuators can be chosen, such as for speed regulation of transparent machines in power plants or temperature regulation control of catalytic reactor units in refineries. The action mode of a control valve applies only when selecting pneumatic actuators. The action mode is formed by combining the direct/reverse action of the actuator with the direct/reverse action of the valve. There are 4 combinations: direct-direct (air-to-close), direct-reverse (air-to-open), reverse-direct (air-to-open), and reverse-reverse (air-to-close). These four combinations result in two control valve action modes: air-to-open and air-to-close. Selection of the control valve action mode is mainly considered from three aspects: a) Process production safety; b) Medium characteristics; c) Ensuring product quality with minimal economic loss.

II-VI valve classification

Control valves can be divided by stroke characteristics into: linear stroke and angular stroke. Linear stroke includes: single-seat valves, double-seat valves, sleeve valves, cage valves, angle valves, three-way valves, and diaphragm valves. Angular stroke includes: butterfly valves, ball valves, eccentric rotary valves, and multi-functional ultra-light control valves. Control valves can be divided by drive method into: manual control valves, pneumatic control valves, electric control valves, and hydraulic control valves. This includes pneumatic control valves powered by compressed air, electric control valves powered by electricity, and hydraulic control valves powered by liquid medium pressure (such as oil). By regulation form, they can be divided into: regulating type, shut-off type, and regulating/shut-off type. By flow characteristics, they can be divided into: linear, logarithmic (percentage), parabolic, and quick-opening.

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