Symbol

The symbol of a directional control valve contains all the information regarding its operational characteristics.

  • BOX AND LINES

The number of positions identifies the number of squares. For valves with two positions the square on the right identifies the position at rest; the other square indicates the position when the valve is actuated.

Inside each square the continuous lines indicate the passage of air and the arrows the direction of flow. The ways in which the air is closed off are identified by perpendicular dashes.

Outside of each square, dashes continuous identify the connection of a supply or exhaust.

  •  NUMBERS

Legislation provides that the inlet duct is always identified with the number 1 and is always indicated in the square which defines the rest position (right square). The outlet duct is always identified with the number 2 in the same square. If the valve has more than one outlet (for example a 5/2 valve), the outlets will always be indicated with successive even-numbered (outlet 2 indicated by the number 4, etc.).

The exhausts associated to each outlet are identified with odd numbers (3 identifies the exhaust of the first outlet, 5 identifies the exhaust of the second outlet, etc.).

On the right of the symbol, a pair of numbers indicates the flow of air in the rest position (10 means the flow is closed; 12 means the flow goes to the outlet).

On the left of the symbol, a pair of numbers indicates the flow of the air in operating position.

  •  ACTUATION AND RETURN INTO REST POSITION

The actuating mode and the type of return into the rest position are identified with special symbols, as shown in the figure below.

  • EXAMPLES

3/2 NO

The symbol is a 3-way valve (1 = inlet 2 = outlet, 3 = exhaust) and 2 positions (two squares). The valve is normally open as in the right square the inlet is connected to the outlet. The changeover takes place at the push of a button and the return is with a spring. In the operating mode (left square) the inlet is closed and the outlet discharges directly into the atmosphere.

3/2 NC

The symbol is a 3-way valve (1 = inlet 2 = outlet, 3 = exhaust) and 2 positions (two squares). The valve is normally closed as in the right square the inlet is closed and the outlet discharges directly into the atmosphere. The changeover takes place at the push of a button and the return is with a spring. In the operating mode (left square) the inlet is connected to the outlet.

5/2

 

The symbol is a 5-way valve (1 = inlet, 2 = first outlet, 3 = exhaust first outlet, 4 = second outlet, 5 = exhaust second outlet) and two positions (two squares). In the rest position the inlet is connected to the first outlet, and the second outlet discharges directly into the atmosphere. The changeover takes place at the push of a button and the return is with a spring. In the operating mode the inlet is connected to the second outlet and the first outlet discharges directly into the atmosphere.