ABSTRACT
All fluid power circuits incorporate valves. Many authors, e.g., [1], state that there are three categories of valves. These are directional control, pressure control, and flow control. A simple application of a directional control valve would be the valve controlled manually by an operator that determines which end of a cylinder is connected to a pump. The most commonly encountered pressure control valve is the pressure relief valve used to protect components from excess forces caused by overloads or actuators reaching the end of their travel. A flow control valve is used to route oil to a secondary circuit in such a fashion that flow rate remains approximately constant even when pressure is varying.
