Hydraulic Directional Control Valves
Directional controls valves have the ability to permit flow in more than one direction, so they have a component that shifts or rotates to accommodate the number of ports. Some directional valves are also
check valves, self-activating safety valves that allow fluid to flow in only one direction so as to prevent contamination. Hydraulic directional control valves may be constructed from a metal such as brass, bronze, copper, cast iron or
stainless steel as well as plastic or composite materials. They are generally an average around three inches in length although they can be smaller than a pencil tip or larger than a bowling ball. Specifications such as diameter, pressure and temperature are important to consider so they might achieve the maximum result. Common uses for control valves include process control, oil or fuel, sanitary, wastewater, water, irrigation, gas or air, steam, fire service, cryogenic, refrigeration, chemicals and laboratory or medical within industrial, manufacturing and labor industries.
Directional control valves types include globe, diaphragm, pinch, knife or gate, needle, butterfly, ball and plug. They are usually
electronically controlled though they can also be operated manually by rotating a handwheel or turning a switch at least 90°. Inside the valve, a piston or other component (depending on the specific kind of valve) allows fluid flow through or around itself until a signal is given to close off one side while another opens. Some automatically change when the fluid pressure behind the piston or part exceeds the pressure below it. One of the most common kinds of directional control valves is the
hydraulic ball valve. This valve is widely used and utilizes a spherical element with holes bored through it. When rotated, a different hole lines up with the corresponding pipes or tubes and the fluid changes direction. Standard ball valves have only one hole that allows for straight-through flow with a simple quarter turn shutoff. When used for directional control, ball valves often have holes that form a T; one or all three passageways may be shutoff. Some directional control valves are faster than others; the speed and tightness of the seal depends on the mechanical strength of the part, the precise degree of machining and the method by which it is activated.
