 Welcome to the Numatic Directional Control Valve's video. A directional control valve, DCV, controls the direction of flow in a pneumatic circuit. Numatic DCVs can be divided into three main categories, two-way, three-way, and four-way valves. The number refers to the number of ports a valve has. We're going to be covering each of these categories with examples in this video. Two-way valves. A two-way valve has a pressure port, P, and an outlet port, A. The pressure port is connected to the compressed air source, and the outlet port is connected to the actuator. Pushing the valve button opens the valve to allow air to pass through. The spring causes the ports to be closed to air flow when the valve button is not pushed. Two-way valves are commonly used to start and stop flow in a particular line. Three-way valves. A three-way valve has a pressure port, P, an outlet, A, and an exhaust port, E. The pressure port is connected to the compressed air source, and the outlet is connected to the actuator. The exhaust port is opened directly to the atmosphere. When the button is pressed to move the valve against the spring, the pressure port and the outlet ports are connected, so flow will go from P to A. When the button is not pressed, the spring causes the valve to be in the position where the outlet and exhaust ports are connected, so flow will go from A to E. A common application for a three-way valve is to control a single-acting cylinder. When the cylinder is extending, air causes the piston to push against the spring inside the cylinder. The spring expands to retract the piston. Single-acting cylinders activate clamps and presses. Four-way valves. A four-way valve has a pressure port, P, two outlet ports, A and B, and two exhaust ports, E. The four-way pneumatic valve actually has five ports. It is called a four-way valve because the two exhaust ports are considered to have the same function. Both of them are opened directly to the atmosphere. When the button is pressed to move the valve against the spring, the following conditions occur. The pressure port and outlet port B are connected, so flow will go from P to B. Outlet port A and one of the exhaust ports are connected, so the flow will go from A to E. When the button is not pressed, the spring causes the valve to be in the position where the following conditions occur. The pressure port and outlet port A are connected, so flow will go from P to A. Outlet port B and one of the exhaust ports are connected, so flow will go from B to E. A common application for a four-way valve is to control a double-acting cylinder. The path air takes through the cylinder is demonstrated in the animation below. Congratulations! You have completed the pneumatic directional control valves video.