Differentiating Regulators and Minimizing Valves

This article aims to clarify the distinctions between pressure-reducing valves and regulators in fluid power systems. Although the valves may seem straightforward, their terminology and function can cause confusion. In pneumatic systems, the valve is referred to as a regulator, while in hydraulic systems, it is known as a pressure-reducing valve. Both valves, despite sharing the same symbols, serve a similar purpose but operate with different mediums - gas for regulators and liquid for pressure-reducing valves.

Typically, both valves are of the normally open type, with a spring at the bottom. When tracing the flow on a schematic, the spring pushes the arrow up to keep the valve open. However, the valve needs to partially close to reduce pressure. This is achieved by calculating the downstream pressure and transmitting it to the top of the arrow, causing it to be pushed down and partially closing the valve. The equilibrium between spring tension and air/hydraulic pressure results in pressure reduction.

In pneumatic systems, the regulator is the primary pressure control, capable of decreasing the inlet pressure. It stabilizes the pressure to a safe and usable level, opening and closing as needed to maintain a steady pressure. In contrast, hydraulic pressure-reducing valves lower the system pressure for circuits requiring less pressure than the maximum system pressure, thus conserving energy and prolonging the life of lower-pressure circuits.

Pneumatic regulators are mostly of the relieving type, offering the advantages of reducing system pressure and releasing any excess pressure if it exceeds the spring tension. However, unlike non-relieving regulators, trapped air may hinder pressure reduction. In hydraulic systems, the corresponding valve is called a pressure-reducing relieving valve. This valve ensures downstream pressure never surpasses the spring setting, but it may shift into its relieving mode when opposing forces momentarily elevate pressure.

Both hydraulic pressure-reducing valves and pressure-reducing relieving valves feature an external drain line, which must remain unobstructed to allow oil bypassing the internal spool to flow to the tank. Troubleshooting these valves involves inspecting the check valve trash to ensure it is not stuck open, as this can impede pressure control.

In summary, understanding the distinctions between pressure-reducing valves and regulators is essential for efficient fluid power system operation, as they play crucial roles in controlling pressure and flow rates in pneumatic and hydraulic systems.