The core difference between pressure reducing valves and regulating valves

Although both pressure reducing valves and regulating valves belong to the category of pressure control valves, their core positioning, working logic, and structural design are completely different: Pressure reducing valves are "self-operated passive pressure regulating valves," requiring no external control and only stabilizing upstream high pressure to downstream low pressure, with a single function; regulating valves are "controlled active parameter adjusting valves," relying on external signals to precisely adjust multiple parameters such as pressure, flow rate, and temperature, adapting to dynamic process control. The two differ clearly in their working principles, structural composition, and core components, and can be directly and intuitively distinguished through appearance and accessories. The following detailed explanation covers the three core issues you are concerned with: principle, structure, and structural differentiation.

I. Working Principle: The Essential Differences in Core Logic

Pressure reducing valve: self-operated passive pressure stabilization, "fixed pressure reduction + downstream pressure maintenance" The pressure reducing valve is a self-operated valve that does not require external power/control signals. It relies entirely on the pressure energy of the medium itself to drive the valve disc to move. Its core function is to stabilize the unstable high pressure upstream to a constant low pressure downstream. It belongs to the passive control of "one-time pressure reduction and continuous pressure maintenance". It can only control one parameter, the downstream pressure, and the adjustment is open-loop (no feedback and cannot be remotely intervened).

Core Process:

1. High-pressure medium enters the valve body from upstream, pushing the valve disc to open. The medium flows downstream after being

throttled and depressurized through the valve port.

2. Downstream pressure is fed back to the diaphragm/piston (power component) of the pressure-reducing valve through the pressure 

guide tube/built-in channel, balancing with the spring force on the diaphragm.

3. If the downstream pressure increases, the feedback force is greater than the spring force, causing the valve disc to move towards the

closing direction, reducing the flow cross-sectional area and decreasing the medium throughput, thus lowering the downstream pressure.

4. If the downstream pressure decreases, the spring force is greater than the feedback force, causing the valve disc to move towards the opening direction, increasing the flow cross-sectional area and increasing the medium throughput, thus raising the downstream pressure.

5. The entire process is completed automatically, always maintaining the downstream pressure at the set value. When the upstream pressure 

fluctuates slightly, the downstream pressure remains essentially unchanged (the set value can be finely adjusted via the valve top adjusting screw). Key Features: Only controls downstream pressure; no precise adjustment accuracy; suitable for "fixed pressure requirements".

Control valve: Controlled active regulation, "Multi-parameter dynamic precise control of pressure/flow/temperature" The control valve is an externally controlled valve, requiring external power (pneumatic/electric/hydraulic) and control signals (4-20mA electrical signal/0.02-0.1MPa pneumatic signal). Its core function is to precisely adjust any process parameter within the system, such as pressure, flow rate, temperature, and liquid level, according to process requirements. It is an active control that "dynamically follows the setpoint," capable of controlling multiple parameters, and the regulation is closed-loop (with monitoring instruments for real-time feedback and precise correction).

Core Process:

1. The system's monitoring instruments (pressure/flow/temperature transmitters) acquire process parameters in real time and transmit the 

signals to the control system (DCS/PLC);

2. The control system compares the actual parameter values with the process setpoints, calculates the deviation, and outputs a regulating 

signal to the actuator of the regulating valve;

3. Upon receiving the signal, the actuator drives the valve stem to move the valve core/disc up and down/rotate, changing the flow 

cross-sectional area of the valve port;

4. The change in the flow cross-sectional area directly alters the medium's throughput, thereby correcting process parameter deviations 

(e.g., when controlling pressure, opening the valve port wider → pressure decreases, closing the valve port narrower → pressure increases);

5. The monitoring instruments continuously acquire the corrected parameters and feed them back to the control system, forming a closed-loop 

control that ensures the parameters always accurately match the setpoints. The setpoints can be adjusted remotely/on-site at any time with extremely high accuracy. Key Features: Manages multiple parameters such as pressure, flow, and temperature; high adjustment accuracy; adaptable to conditions with dynamic changes in process parameters.

II. Structural Composition: Clear Differences in Core Components

Both valves consist of a valve body and a power/control section, but due to their different working principles, their core components and supporting parts differ greatly. The pressure reducing valve has a simpler structure (no external components), while the regulating valve has a more complex structure (relying on external components). A detailed disassembly is as follows:

Pressure reducing valves (taking the most commonly used piston/diaphragm type pressure reducing valve as an example) are integrated self-operated structures with no external supporting components. All power, feedback, and regulation components are integrated into the valve body. The core components consist of only two parts, with no actuator and no positioner:

1. Valve Body: Valve shell, valve seat, valve disc, throttling orifice (core pressure-reducing component), inlet and outlet channels;

2. Self-operated Control Components: Diaphragm/piston (power core, receiving downstream pressure feedback), pressure regulating spring 

(providing balancing force, setting pressure), pressure guide channel/pressure guide tube (downstream pressure feedback channel), 

adjusting screw (fine-tuning the set pressure), valve stem (connecting the diaphragm/piston and valve disc). 

Additional Features: Some pressure reducing valves include a filter (pre-positioned to prevent impurities from jamming the valve) 

and pressure gauges (one at the inlet and one at the outlet, displaying the pressure before and after). These are auxiliary components, 

not core control components.

Control Valve (Taking the most commonly used pneumatic diaphragm control valve as an example)

It belongs to a combined external control structure, with three core components, all of which must be paired with external detection/control 

accessories. Each component is indispensable, including an independent actuator and a positioner (core precision component):

1. Valve Body: Valve shell, valve seat, valve core/disc (throttling and regulating component, available in different shapes to suit different regulating characteristics), valve stem, stuffing box (sealing the valve stem);

2. External Control Actuator: Pneumatic diaphragm head/electric actuator (power core, receiving external signals), spring (for reset), independently mounted on top of the valve body, is the most prominent feature of the control valve;

Precision Control Component: Valve positioner (core, converting control signals into precise valve stem stroke to ensure regulation accuracy), 

mounted on the actuator, is the "brain" of the control valve; External Accessories (Required): Pressure/flow/temperature transmitter 

(detection instrument), DCS/PLC control system, air source device (for pneumatic valves)/power supply (for electric valves), 

signal cables/air pipes. Additional features: Auxiliary components such as solenoid valves, filters, pressure reducing valves, and handwheel 

mechanisms can be added according to operating conditions.

Quick On-Site Judgment Formula

Check the top: If there is an actuator + positioner, it is a regulating valve; otherwise, it is a pressure reducing valve. Check the wiring/air pipe: If there is a signal line/air pipe, it is a regulating valve; otherwise, it is a pressure reducing valve. Check the pressure gauges: If the valve body has built-in inlet and outlet dual pressure gauges, it is a pressure reducing valve; otherwise, it is a regulating valve.

Core Summary

1. Principle: Pressure reducing valve → self-operated, passive, open-loop, only stabilizes downstream low pressure; Control valve → externally 

controlled, active, closed-loop, precisely adjusts multiple parameters;

2. Structure: Pressure reducing valve → integrated, no actuator/positioner, no external accessories; Control valve → combined, 

with actuator/positioner, relies on external detection/control accessories;

3. Differentiation: The most crucial distinguishing feature is whether there is an actuator + positioner on the valve body. This is the most 

significant and easily identifiable difference in appearance between the two.