Every hydraulic system has a minimum number of basic components regardless of its design and function. The fundamental components of the hydraulic system include pump, reservoir, directional valve, check valve, pressure relieve valve, selector valve, actuator, and filter.
An open center system has fluid flowing, with any pressure in the system when the actuating mechanisms are idle. The pump disperses the fluid from the reservoir through the selector valves and return to the reservoir. The open center system may engage a several subsystems, with a selector valve for every subsystem. The selector valve of the open center system is connected in series with each other. In this arrangement, the system pressure line will go through each selector valve. The fluid is allowed free passage through the selector valve and return to the reservoir until one of the selector valves is ready to operate a mechanism.
When one of the selector valves is set to operate an actuating device, fluid is flowing from the pump through one of the working line to the actuator. When the selector valve is set in this position, the fluid flow to the reservoir is blocked. The system overcome the resistance by using the pressure build up in it and move the piston of the actuation cylinder, fluid from the opposite end of the actuator will returns to the selector valve and return to the reservoir. The operation of the system after actuation of the component will depends on the type of the selector valve that has been used. Many types of selector are used together with the open center system. One of the types is both manually engaged and manually disengaged. The valve is manually moved to an operating position. Then, the actuating mechanism reaches the end of the operating cycle, and the output of the pump continue until the pressure is relieves by the system relief valve. The relief valve dismount and allows the fluid to return to the reservoir. The system pressure remains at the relief valve set pressure until the selector valve is returned manually to the neutral position. It reopens the open center flow and let the system pressure to drop to line resistance pressure.