How does a pressure reducing valve work?

In simple terms, a pressure reducing valve is an "automatic pressure regulator". Its core task is to reduce and stabilize the higher and unstable inlet pressure from the gas source (such as gas cylinders or pipelines) to a lower and required outlet pressure. Moreover, when the inlet pressure or downstream flow changes, it can automatically maintain the stability of the outlet pressure. 

Its working principle is mainly based on force balance. The most common types are diaphragm pressure reducing valves or piston pressure reducing valves. We take the diaphragm type as an example: 

Core components: 

Adjusting knob (handwheel): Users set the desired outlet pressure through it. 

Main spring (adjusting spring): Connected to the knob, it provides a downward force. 

Diaphragm (membrane): A flexible membrane that divides the valve into upper and lower chambers. 

Valve disc and valve seat: Components that control the flow of gas or liquid by opening and closing. 

Exhaust hole (safety valve): There is usually a small hole above the membrane in the chamber, which is used to safely release excess pressure when it is too high. 

Work process: 

Non-working state (closed): When the adjusting knob is loosened counterclockwise, the main spring relaxes and the pressure on the diaphragm decreases. At this point, the valve disc is tightly pressed against the valve seat under the action of the intake pressure from below, and the valve is closed with no gas flowing out. 

Set pressure (opening and balancing): 

When you turn the adjustment knob clockwise, the main spring will be compressed, exerting a downward force (Fspring) on the film. 

This downward force pushes the film and the attached valve flap downward, away from the valve seat, opening the passage. 

High-pressure gas flows into the low-pressure chamber from the inlet, and the outlet pressure begins to rise. At the same time, this outlet pressure is transmitted to the chamber beneath the diaphragm through a small internal channel (feedback channel), exerting an upward force (F pressure) on the diaphragm. 

When F pressure = F spring, the system reaches dynamic equilibrium. The valve disc will remain at a certain open position, maintaining a stable outlet flow and pressure. 

Automatic voltage stabilization process (core function): 

When the gas consumption downstream increases (such as when an additional device is turned on), the outlet pressure shows a tendency to drop. At this point, F pressure < F spring, and the balance is disrupted. The spring force pushes the diaphragm and the valve disc further downward, increasing the opening and allowing more gas to pass through, thereby restoring the outlet pressure to the set value. 

When the gas consumption downstream decreases (such as when equipment is shut down), the outlet pressure tends to rise. At this point, F pressure > F spring, the diaphragm is pushed upwards, driving the valve disc to move upwards, reducing the opening, restricting the gas flow, and thus bringing the outlet pressure back to the set value. 

When the inlet pressure fluctuates (such as when the pressure in the gas cylinder gradually decreases), the principle is the same as above. The valve will automatically adjust its opening to compensate for the changes in the inlet pressure and strive to maintain the stability of the outlet pressure. 

In summary, a pressure reducing valve is like an automatic "tap" controlled by a spring and air pressure. It constantly adjusts its opening degree by sensing changes in the outlet pressure, thereby achieving pressure stabilization.