All About Hydraulic Directional Control Valves
They go by a couple different names but they are generally all the same: Control Valves, Directional Control Valves, Hydraulic Control Valves or Hydraulic Directional Control Valves.
Control Valve Purpose in Life
If you're a control valve, your main purpose in life is to direct hydraulic force to do work. Hydraulics 101 tells us that while hydraulic force is very powerful, it isn't all that intelligent.
Oil will always follow the path of least resistance!
Inside a control valve, the tolerances are extremely tight - 0.0005" or better. Five ten-thousands of an Inch. Or half of a thousandth of an inch. This is a fraction of the width of a human hair! This diagram gives you a visual on the tolerances inside a hydraulic control valve.
The tolerances are so tight because a metal-to-metal fit must hold back hydraulic oil at 4500 psi or more. Variable or fixed displacement pumps create the flow to be directed through the control valve. Any scoring or imperfection on the spool will create a path of lower resistance. The oil will choose to leave the spool or go back to tank instead of doing the work the machine operator needs.
Control Valves in Heavy Equipment
Control Valves can be found in all kinds of heavy equipment including: excavators, bulldozers, aerial lifts, and cranes. Anything that moves multiple functions hydraulically... there is a good chance it uses a control valve.