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What is the difference between the regulating valve and the flow valve?
Sep 12, 2018

Regulating valve
Regulating valve, also known as control valve, in the field of industrial automation process control, by accepting the control signal output from the control unit, by means of power operation to change the final control element of the process parameters such as medium flow, pressure, temperature, liquid level. It usually consists of an actuator and a valve. According to the characteristics of the stroke, the regulating valve can be divided into straight stroke and angular stroke; according to the power used by the actuator, it is divided into linear characteristics, equal percentage characteristics and parabolic characteristics according to its function and characteristics. The regulating valve is suitable for air, water, steam, various corrosive media, mud, oil and other media. English name: controlvalve, the bit number usually starts with FV. Regulating valves are commonly classified: pneumatic regulating valves, electric regulating valves, hydraulic regulating valves, and self-operated regulating valves.
Regulator basic information
The regulating valve, also known as the control valve, receives the control signal output from the regulating control unit.
The regulating valve changes the fluid flow by means of a power operation. The regulating valve is generally composed of an actuator and a valve. If the power used by the actuator is matched, the regulating valve can be divided into three types: pneumatic regulating valve, electric regulating valve and hydraulic regulating valve. In addition, according to its function and characteristics, linear characteristics, equal percentage characteristics and parabolic characteristics Kind.
Body type
There are many types of valve bodies for regulating valves. Commonly used valve bodies are straight-through single-seat, straight-through two-seat, angular, diaphragm, small flow, three-way, eccentric rotation, butterfly, sleeve, and spherical.
In the specific choice, you can make the following considerations:
(1) Spool shape structure
Mainly based on factors such as selected flow characteristics and imbalance forces.
(2) Wear resistance
When the fluid medium is a suspension containing a high concentration of abrasive particles, the internal material of the valve is tough.
(3) Corrosion resistance
Due to the corrosive nature of the media, try to choose a simple valve.
(4) Temperature and pressure of the medium
When the temperature and pressure of the medium are high and the change is large, the valve and the material of the valve seat should be selected to be small in temperature and pressure change. When the temperature is ≥250°C, the radiator should be added.
(5) Prevent flashing and cavitation
Flashing and cavitation are only produced in liquid media. In the actual production process, flashing and cavitation will form vibration and noise, shortening the service life of the valve, so the valve should be prevented from flashing and cavitation when selecting the valve.
Regulating valve actuator
In order for the regulating valve to work properly, the actuator used must generate sufficient output force.
To ensure a high degree of sealing and opening of the valve.
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 travel. Therefore, the key to selecting an actuator is to clarify the maximum output force and the rotational torque of the motor. For a single-acting pneumatic actuator, the output force is related to the opening of the valve. The force appearing on the regulating valve will also affect the motion characteristics. Therefore, it is required to establish a force balance across the opening range of the regulating valve.
After determining the output force of the actuator, select the corresponding actuator according to the requirements of the process environment. For explosion-proof requirements on site, pneumatic actuators should be used. In terms of energy saving, electric actuators should be selected as much as possible. If the adjustment accuracy is high, the hydraulic actuator can be selected. Such as the speed regulation of the power plant transparent machine, the temperature regulation control of the catalytic converter of the refinery.
The mode of action of the regulating valve is only when the pneumatic actuator is selected, and its action mode is formed by the combination of the positive and negative action of the actuator and the positive and negative action of the valve. There are 4 kinds of combination forms, namely, positive (gas-off type), positive and negative (air-open type), anyway (air-open type), anti-reverse (air-closed type), and the regulating valve formed by these four combinations has a gas function. Both open and closed.
The choice of the mode of operation of the regulating valve is mainly considered from three aspects: a) process production safety; b) medium characteristics; c) product quality and economic loss.
Flow valve
The flow valve is suitable for water system that needs flow control. It is especially suitable for flow control of non-corrosive liquid medium such as heating and air conditioning. Installed in the water system, the system flow can be automatically constant after one adjustment before operation. At the required set value. Automatically eliminate the hydraulic imbalance caused by various factors in the water system, maintain the flow required by the user, overcome the "uneven heating and cooling", improve the heating, air conditioning room temperature, improve system energy efficiency, achieve energy saving, is the realization of heating and air conditioning systems The ideal accessory product for “metering and charging”.
Flow valve function
The function of the flow valve is to adjust the flow rate by adjusting the throttle port area between the valve body and the valve body and the local resistance generated by the valve when the pressure difference between the inlet and the outlet of the valve is changed, thereby controlling the moving speed of the actuator. The flow rate through which the passage is maintained is constant, so that the flow rate of the controlled object (such as a loop, a user, a device, etc.) in series with it is maintained constant. The flow valve is applied in the pipe network, and the flow can be set directly according to the design. The valve can automatically eliminate the flow deviation caused by the residual head and pressure fluctuation of the pipeline under the action of water pressure. The name of the flow valve is more, such as self-operated flow balance valve, constant flow valve, dynamic balance valve, etc. Various types of flow valves have different structures but work similarly.

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