Difference between regulating valves and control valves

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Hi, I’m the Industrial Control Assistant. I’m here as promised, bringing with me the knowledge I believe I have in this field. Today’s topic is control valves, which are widely used in industry. In China, there isn’t really a clear distinction between control valves and regulating valves; these terms are often used interchangeably. Valves that come equipped with actuators are generally referred to as regulating valves, while the concept of control valves hasn’t yet become well-established. If you look at websites related to control valves online, you’ll find that they also refer to control valves as regulating valves. Today, I’ll simply help you distinguish between them. The definition of a control valve should be: In process control industry, the most commonly used terminal control element is the control valve. Control valves regulate the flow of fluids such as gases, steam, water, or chemical mixtures in order to compensate for load disturbances and keep the controlled process variable as close as possible to the desired setpoint. Sensors feed signals such as pressure, temperature, and flow rate back to the regulator. The regulator compares these measured signals with set values, and then outputs control signals to the control valve based on the results of these calculations. The control valve adjusts the degree of opening of the valve, thereby enabling automatic regulation of parameters such as temperature, pressure, and flow rate. According to this definition, a valve must form a control loop together with sensors and controllers (PLCs, DCSs, or simple regulators), whether it is a single-loop or multi-loop system, in order to achieve control over process variables; only then can it be called a control valve. Therefore, all pneumatic, electric, and hydraulic valves equipped with actuators should be referred to as control valves, including solenoid valves, as they can all form a control loop with a control system to achieve automatic control. Regardless of whether they receive digital signals or proportional signals, the control principle remains the same. And all manual valves are not control valves. Some valve manufacturers also use the term \"self-control valve\", whose definition should be the same as that of a control valve.  A control valve is essentially a throttle valve; its purpose is to create a pressure drop and reduce flow rate, which is why it can have a valve seat with a diameter significantly smaller than that of the valve’s passage. Throttle valves are designed to create a pressure drop in order to reduce linear pressure, flow rate, and temperature, whereas on-off valves are structured to allow fluid to pass through freely without causing a significant pressure drop. Valves such as O-ring ball valves, butterfly valves, and pipe clamp valves all have very low flow resistance; the pressure drop generated when the fluid passes through them is minimal. Therefore, they are suitable for on/off control but not for throttling control. Throttle valves need to have appropriate flow characteristics as well as valve stem and seat diameters designed in accordance with the requirements of the process, whereas on-off valves do not require this. A throttle valve equipped with an actuator becomes an electric, pneumatic, or hydraulic control valve. Therefore, in a narrow sense, control valves are limited to just a few types of throttling valves such as single-seat valves, double-seat valves, sleeve valves, angle valves, three-way valves, V-ball valves, etc. (which is why the term \"manual control valve\" is also used in the industry).  It can be said that all control valves are regulating valves, but not all control valves are regulating valves. As for self-acting control valves, they should not be classified as control valves, because whether it is a self-acting pressure control valve or a valve for controlling temperature or flow, it is the medium itself that drives the valve; the control parameters still need to be set manually, and such valves cannot form a control loop together with a control system. They should be classified as automatic valves along with safety valves, steam traps, pressure relief valves, hydraulic control valves, etc. That’s all for today. If you have any questions or anything you’d like to know, feel free to leave a message. Updates will continue, so please stay tuned.