Pilot-to-open check valves are hydraulic valves designed to allow flow in one direction while blocking flow in the opposite direction until a specific pilot pressure is achieved. They are commonly used in hydraulic systems to control the direction and flow of fluid.
The pilot valve in a pilot-to-open check valve serves the purpose of controlling the opening and closing of the main check valve. It is responsible for initiating and regulating the flow of fluid that acts on the main valve to either allow or block the flow in the desired direction. The pilot valve typically consists of a smaller valve mechanism that is connected to a control signal, such as hydraulic or pneumatic pressure. When the control signal is applied, the pilot valve opens, allowing the fluid to flow through it and act on the main check valve.
The primary function of the pilot valve is to provide the necessary force or pressure to overcome the resistance of the main check valve and open it. It ensures that the main valve remains closed and prevents fluid flow in the undesired direction until the pilot valve is activated.
When there is no fluid flow or pressure difference, the pilot-to-open check valve is in a closed position. The main valve is closed, and the pilot valve is also closed.
When fluid flow is initiated in the desired direction, the pressure at the inlet side of the pilot valve starts to rise. As the pressure exceeds a predetermined value, typically set by an adjustable spring or a separate pilot pressure source, it triggers the opening of the pilot valve.
With the pressure exceeding the predetermined value, the pilot valve opens, allowing fluid to flow into the pilot chamber. The fluid pressure in the pilot chamber then acts on the main valve.
As the fluid pressure in the pilot chamber increases, it overcomes the force of the spring or any opposing pressure on the main valve. This causes the main valve to open, allowing fluid to flow in the desired direction.
Once the main valve is open, fluid flows freely in the intended direction, maintaining the desired flow rate.
If the pressure at the inlet side of the pilot valve drops below the predetermined value, which could happen due to a decrease in upstream pressure or flow reversal, the pilot valve begins to close.
As the pilot valve closes, it cuts off the flow of fluid into the pilot chamber.
Without the pressure in the pilot chamber, the main valve is forced closed by the spring or any opposing pressure. This prevents backflow or reverse flow of the fluid.
