Page 54 - PNEUMATIC SYSTEM INSTRUMENT

Three-way valves may also be used in pairs to operate a double acting

cylinder, thus replacing a four-way valve. Consider using paired three-

way valves instead of a four-way when high cylinder speeds are

necessary. Close coupling of three-way valves to the cylinder ports

reduces cylinder back pressure and pressure drop in the lines,

permitting higher cylinder velocities. The valves are also used to save

compressed air in highly cyclic applications or when intermediate

positions are required.

 A three-way valve has a pressure port 1(P), an outlet port 2(A)

and exhaust port 3(R).

 In normal condition, the pressure port is connected to the

compressed air source and the outlet port is connected to the

actuator.

 The exhaust port is open directly to the atmosphere.

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