Below is a list of Hydraulic Valves manufacturers from Chicago, Illinois. Hydraulic valves are parts that control the flow and pressure of hydraulic fluid within a system. They allow hydraulic equipment to function properly and safely while allowing for precise control. Hydraulic valves are made up of a main casing, which is the outer enclosure that holds all the other components. The other components are a bonnet, or a removable section of the casing, a seat, which is the interior surface where the connection is made, and a disc that acts as the seal that prevents leaking at the seat.