### Directional control valves

```Pneumatics – Module 3
Objectives











Differentiate between the main types of directional control valves.
Explain the function of each type of directional control valves.
Demonstrate the function and uses of 3/2 way valve, (N/C) push
button actuated.
Demonstrate the function and uses of 3/2 way valve, (N/O) push
button actuated.
Demonstrate the function and uses of 3/2 way valve, (N/C) roller
lever actuated.
Explain the function and uses of 5/2 way valve, selector valve.
Explain the function and uses of 5/2 way valve, single pilot valve.
Explain the function and uses of 5/2 way valve, double pilot valve.
Use the FluidSIM software to build and simulate a pneumatic circuits
that contain DCV
Build a pneumatic circuit using DCV on the Festo trainer and check its
operation
Design simple pneumatic circuits for a given application.
Introduction
Directional control valves are devices which
influence the path taken by an air stream.
 The directional control valve is represented by two
numbers. The first number represents the number
of ports, and the second number represents the
number of positions.


Note:
These symbols do not provide any information
about the constructional design, but just indicate
the function of the valve.
Directional Control Valves
(DCV)
3/2 WAY
3/2 way
DCV (N/C)
5/2 WAY
5/2 way DCV
3/2 way DCV
(N/O)
5/2 way
Selector Valve
3/2 way
Roller Valve
5/2 way Single
Pilot
3/2 way
Selector Valve
5/2 way Double
Pilot
3/2 way DCV (Directional Control
Valve) – NC (Normally closed)
A 3/2-way valve has 3 ports (1, 2 and
3) and 2 switching positions (before
operating and after operating).
 It is represented by the normal
position.
 Normally closed means that
compressed air cannot flow
through the valve

3/2 way DCV
(Directional
Control Valve)
– NC
(Normally
closed)
Actuated
Actuating this valve
results in allowing the
flow from port (1) to port
(2) and blocking the
exhaust port (3).
Un-Actuated
In normally closed 3/2
disk seal blocks the air
flow from the air supply
port (1) to the working
port (2). The working port
(2) is connected with
exhaust port (3).
3/2 way DCV (Directional Control
Valve) – NO (Normally Open)
Normally open means that
compressed air flows through
the valve.
 When the pushbutton is
actuated the valve is closed,
thus stopping the air to flow
from port (1) to port (2).

3/2 way DCV
(Directional
Control Valve)
– NC
(Normally
closed)
Actuated
Actuating this valve results in
allowing the flow from port (2)
to port (3) and blocking the
supply air port (1).
Fig. (3.5.b) shows the ISO
symbol of 3/2 way valve
normally open (N/O) and spring
reset,

Un - actuated
In the normally open
3/2 way valve, a spring
exhaust port (3). The
air supply port (1) is
connected to the
working port (2).
3/2 way Roller Lever Valve (N/C)
The roller lever actuation way
is considered to be one of the
most important types of valve
actuation that is used for
automatic operation of the
pneumatic cylinders.
 It is generally known as
pneumatic limit switch.


This valve is actuated by pressing the
roller lever e.g. by means of cylinder
trip cam. The valve is returned to the
normal position via return spring after
releasing the roller lever.
3/2 way Roller
Lever Valve
(N/C)
3/2 way Selector Valve
5/2 way Directional Control Valve
This valve contains 5 ports and 2
positions.
 The 5/2 DCV could be actuated
manually or by using pressure
actuation (single pilot and double
pilot), or by electrical actuation
(solenoid).

5/2 way
Directional
Control Valve
Actuated
After operating the valve by
any method, the valve will be
shifted to the other position
and in this case, the flow will
be from port (1) to port (4)
while the exhaust will be from
port (2) to port (3)

Before Actuation
When the 5/2-way valve
is not actuated, the flow
will be from port (1) to
port (2) while the
exhaust will be from
port (4) to port (5)
5/2 way Selector Valve

This valve is used for
manual operation, and
you can control the
valve by selector
switch, and it is used
in simple applications.
5/2 way Single Pilot Valve

This valve is used for
automatic operation, and
you can control the valve
by a pneumatic signal and
a spring return.
5/2 way Double Pilot Valve
 This
valve is used for
automatic operation,
and you can control the
valve by two pneumatic
signals and this valve
keeps the last position
after removing the
applied signal, and it is
sometimes called
memory valve.
Valve Actuators
The pneumatic directional control valves can be
actuated (operated) in several ways
• MANUAL
• MECHANICAL
• ELECTRICAL
• PNEUMATIC
1. MANUAL Actuators
Manual
Push
Button
Foot
Pedal
2. MECHANICAL
Actuators
Roller
Idle
Return
Roller
3. ELECTRICAL
Actuators
Solenoid
Valve
4. PNEUMATIC
Actuators
Pneumatic Pressure
Actuation
Pneumatic Actuators
They are used to produce the
required forces in the pneumatic
systems.
Single
Double
Single
Single Acting Cylinder
acting
cylinder is
Single acting cylinder (SAC) is an output used to
produce
device. The function of the SAC is to
linear force
convert the pressure energy to mechanical in one
energy (linear motion).
direction
only
Double Acting Cylinder
double
acting
Double acting cylinder (DAC) is an output cylinder
is used to
device. The function of the DAC is to
produce
convert the pressure energy to mechanical linear
energy (linear motion).
force in
two
directions
.
PRACTICAL