What is the purpose of the adjustment spring in a pressure regulator?

The adjustment spring in a pressure regulator plays a crucial role in maintaining the desired downstream pressure by exerting a force that holds the valve in a closed position when the downstream pressure reaches the setpoint. As the downstream pressure builds and approaches this desired level, the force exerted by the adjustment spring balances with the pressure acting on the poppet (valve), effectively keeping the valve closed and regulating the flow of fluid.

When the downstream pressure is equal to the set pressure, the balance allows the system to stabilize, preventing further fluid from flowing through the regulator and thereby maintaining the designated operating pressure. The effectiveness of a pressure regulator relies heavily on this mechanism, ensuring consistent and reliable pressure control in hydraulic systems. By contrast, the other options either describe functions that don’t accurately reflect the purpose of the adjustment spring or involve actions unrelated to the spring's primary role in regulating and maintaining downstream pressure.