How does an air pressure regulator works?
The air pressure regulator is also known as pressure-reducing valves. It maintains a constant output pressure regardless of variations in input pressure or output flow. In pneumatic instrumentation systems, instrument air is required to power valve actuators and other instruments like transmitters, controllers, control valves etc. Examples of air pressure regulators are Masoneilan and Fisher.
The figure shown above is fisher air regulator. As the pressure rises, it pushes the diaphragm closing the inlet valve and preventing the instrument air from entering regulator. As the air is drawn out through the outlet side, the pressure inside the regulator falls.
The working principle of the air pressure regulator
• The main air supply which is connected to the air inlet port passes through the filtering chamber.
• The filter removes the dirt particles from the air which may block nozzles etc. The air then goes into the valve assembly.
• The valve assembly is moved by the range spring pressing on the diaphragm.
• The range spring holds the valve assembly until the output pressure is high enough to lift the diaphragm. At this point the small spring in the valve assembly closes the valve.
• The air now passes through a hole at the center of the diaphragm and out of the vent. This is how the pressure is balanced across the diaphragm.
• When the output pressure becomes more than the pressure set by the range spring, the air will go out through the vent. When the outlet pressure becomes less, the valve assembly opens up to reach the set pressure. This pressure will exit the regulator through the outlet air port.
• If the outlet pressure is below the pressure set by the range spring the valve assembly will stay open until the set pressure is reached.