(a) Valve actuation
• The valve can be actuated by number of ways. Symbolic representation of each is summarized here
Fig. Valve actuation symbols.
• Valves arecommonly described by a standard notation : x/y.]
Where x is number of ports
y is number of positions.
A two port and two position valve is described as a 2/2 valve.
A four port and three position valve is described as a 4/3 valve.
(b) Pilot operation: An operation in which the control valve is operated by an air signal itself is called pilot operation. In the pilot operation, the external operator acts on a small pilot valve which in turn switches the main valve pneumatically.