Regulating valve is a key equipment used in industrial processes for precise control of fluid (gas, liquid or steam) flow rate. Its working principle is based on adjusting the flow rate by changing the cross-sectional area between the valve core and valve seat. The following is a step-by-step explanation of its core working principle:

1. Basic structure

A regulating valve usually consists of an actuator and a valve body:

Execution mechanism: Receive control signals (such as electric 4-20mA, pneumatic 0.2-1.0 bar) to drive the valve stem to move.

Valve body: It includes a valve core, a valve seat, and a flow channel. The position of the valve core determines the fluid flow and flow rate.

2. Workflow

Signal input:

The controller (such as PLC or DCS) sends control signals to the actuator according to process requirements.

Execution mechanism action:

Electric valve: The motor drives the valve stem to move up and down.

Pneumatic valve: The pressure of the air source drives the piston or diaphragm, which in turn drives the valve stem.

Valve core position adjustment:

The valve stem drives the valve core (such as ball valves, butterfly valves, sleeves, etc.) to move up and down, changing the opening between the valve core and the valve seat.

Flow regulation:

Opening degree increases → flow area increases → flow rate increases;

Decrease in opening → decrease in flow area → decrease in flow rate.

3. Key design factors

Traffic characteristics:

Curve describing the relationship between opening and flow rate, common types:

Linear characteristic: The opening is directly proportional to the flow rate.

Equal percentage feature: As the opening increases by the same percentage, the flow rate changes by the same percentage (suitable for fine adjustment of small openings).

Quick opening feature: When the opening is small, the flow rate changes greatly, making it suitable for quick response.

Valve core type:

Direct single seat valve: with low leakage, suitable for small flow rates.

Direct double seat valve: allows for a large pressure difference, but with a high leakage rate.

Sleeve valve: Good stability under high pressure difference, suitable for noise control.

Angle valve: suitable for high viscosity or granular media.

Selection of executing agency:

Pneumatic: Fast response, inherently safe, requires air source.

Electric: Convenient signal transmission, suitable for remote complex control.

4. Self operated regulating valve

No need for external energy, relying on the pressure changes of the medium itself to automatically adjust:

Self operated pressure regulating valve: sensing downstream pressure through a diaphragm, adjusting the opening to maintain the set value.

Self operated flow control valve: Built in flow sensor, dynamically balancing flow.

5. Application scenarios

Process control: closed-loop control of parameters such as temperature, pressure, and liquid level.

Safety protection: prevent overpressure or overheating (such as safety valves).

Energy management: Optimize fluid transportation efficiency and reduce energy consumption.

Summarize

The regulating valve drives the valve core to move through the actuator, changing the cross-sectional area of the fluid channel, thereby achieving precise control of flow rate. Its design requires comprehensive consideration of fluid characteristics, pressure difference, control accuracy, and process requirements, and is an indispensable terminal execution component in automation control systems.