industrial pneumatic circuit advanced

1. INDUSTRIAL PNEUMATIC CIRCUIT

2. Sequence solution methods
 The main solutions tosolving
sequencesare:
 Cascade(pneumatic)
 Shift register (pneumatic)
 Electro-pneumatic
 PLC (Programmable logic
controller)
 Cascadecircuits providea
standard method of solving any
sequence. Itusesa minimumof
additional logic hardware (one
logicvalve pergroupof
sequential steps)
 Shift registercircuitsaresimilar
tocascade butuseone logic
valve foreverystep
 Electro-pneumaticcircuits use
solenoid valves and electro-
mechanical relays
 PLC. The standard solution for
medium tocomplex sequential
systems (exceptwhere electrical
equipmentcannot be used)

3. Cascade two group
 The A+ B+ B- A- circuit is solved
by the twogroupcascade
method
 Thesequence isdivided at the
point where B immediately
returns
 The twoparts areallocated
groups l and ll
 Gp l A+ B+ / Gp ll B- A-
 Twosignal supplies are provided
from a 5/2 valveone is available
only in group l the other is
availableonly in group ll
14 12
 Becauseonlyonegroupoutput
is available at a time it is not
possible to haveopposed signals
 A standard 5/2 doublepressure
operated valve is the cascade
valve
Group l Group ll
4 2
Select l 5 1 3 Select ll

4. Cascade (two group)
A B
b0
a1
a0 a1 b0 b1
Run/End
a0 b1
Sequence
Gp l A+ B+ Gp ll B- A-
Gp l
Gp ll

5. Cascade (two group)
A B
b0
a1
a0 a1 b0 b1
Run/End
a0 b1
Sequence
Gp l A+ B+ Gp ll B- A-
Gp l
Gp ll

6. Cascade (two group)
A B
b0
a0 a1 b0 b1
Run/End
a1
a0 b1
Sequence
Gp l A+ B+ Gp ll B- A-
Gp l
Gp ll

7. Cascade (two group)
A B
b0
a0 a1 b0 b1
Run/End
a1
a0 b1
Sequence
Gp l A+ B+ Gp ll B- A-
Gp l
Gp ll

8. Cascade (two group)
A B
a0 a1 b0 b1
Run/End
a1
a0
Sequence
Gp l A+ B+ Gp ll B- A-
Gp l
Gp ll
b0
b1

9. Cascade (two group)
A B
a0 a1 b0 b1
Run/End
Sequence
Gp l A+ B+ Gp ll B- A-
Gp l
Gp ll
b1
b0
a1
a0

10. Cascade building blocks
 A twogroup building block
consistsof a levervalve torun
and end thesequence plus the
5/2 double pilot operated
cascadevalve
 Fora twogroupsystem
consisting of any numberof
cylinders this building block
and the cylinder building
blocksareall that is required
tosolve thesequence
2
4
5 1 3
14 12
2
3 1
12
10
Gp l
Gp ll
Sel l
Sel ll
Run/End

11. Cascade building blocks
 This threegroup
building block
establishes an
interconnecting
pattern thatcan be
extended toany
numberof groups
Gp l
Gp ll
Sel l
Sel ll
Gp lll
Sel lll
Run/End

12. Dual trip building blocks
 When a sequence has a
cylinderoperating twice in
oneoverall sequence adual
trip building block may be
required foreach of the two
feedback valves
 The supply will be from
differentgroupsand the
outputgo todifferent
destinations
 Example is forfeedback valve
a1 of cylinderA when A is sent
+ both in Groupx and Groupy
A+ in
Group x
A+ in
Group y
a1
Send A+
a1 in x
a1 in y
Note: can often be rationalised to less
than these three components

13. Cascade rules
Establish thecorrectsequence
Divide the sequence in to groups.
Always start a sequence with the
Run/End valve selecting group l e.g.
R/E | A+ B+ | B- C+ | C- A-
Select thecylinderbuilding
blocks
Select thecascade building block
Select dual trip building blocks if
required
Interconnect the blocks as follows:
The first function in each group is signaled
directly by thatgroup supply
The last trip valve operated in each group is
supplied with main supply air and selects
the nextgroup
The remaining trip valves are supplied with
air from their respective groups and initiate
the next function
The “run/end” valve will control the
signal from the last trip valve to be
operated

15. 5/3 Valve
 5/3 valves havea third mid
position
 Thevalvecan be tri-stablee.g. a
detented leveroperatoror
mono-stablee.g. a doubleairor
double solenoid with spring
centre
 Thereare threecommon
configurationsforthe mid
position:
 All ports blocked
 Centreopen exhaust
 Centreopen pressure
 The majorityof applications are
actuatorpositioning and safety
4 2
14 12
14 12
5 1 3
4 2
14 12
5 1 3
4 2
5 1 3

16. 5/3 Valve actuator control
 Thevalve illustrated has “all
ports blocked” in the mid
position
 Wheneverthe mid position is
selected the pressure
conditions in thecylinderwill
be frozen
 This can be used to stop the
piston at part stroke in some
positioning applications
 Flowregulators mounted close
to the cylinder to minimise
creep
2
4
5 1 3
14 12

17. 5/3 Valve actuator control
 Thevalve illustrated has “all
ports blocked” in the mid
position
 Wheneverthe mid position is
selected the pressure
conditions in thecylinderwill
be frozen
 This can be used to stop the
piston at part stroke in some
positioning applications
 Flowregulators mounted close
to the cylinder to minimise
creep
2
4
5 1 3
14 12

18. 5/3 Valve actuator control
 Thevalve illustrated has “all
ports blocked” in the mid
position
 Wheneverthe mid position is
selected the pressure
conditions in thecylinderwill
be frozen
 This can be used to stop the
piston at part stroke in some
positioning applications
 Flowregulators mounted close
to the cylinder to minimise
creep
2
4
5 1 3
14 12

19. 5/3 Valve actuator control
 Thevalve illustrated has “all
ports blocked” in the mid
position
 Wheneverthe mid position is
selected the pressure
conditions in thecylinderwill
be frozen
 This can be used to stop the
piston at part stroke in some
positioning applications
 Flowregulators mounted close
to the cylinder to minimise
creep
2
4
5 1 3
14 12

20. 5/3 Valve actuator control
 Thevalve illustrated has “all
ports blocked” in the mid
position
 Wheneverthe mid position is
selected the pressure
conditions in thecylinderwill
be frozen
 This can be used to stop the
piston at part stroke in some
positioning applications
 Flowregulators mounted close
to the cylinder to minimise
creep
2
4
5 1 3
14 12

21. 5/3 Valve actuator control
 Thisversionof a 5/3 valve is
“centreopen exhaust”
 Thesupplyat port 1 is isolated
and the cylinder has power
exhausted when this centre
position is selected
 Theversion illustrated showsa
mono-stableversiondouble
pilotoperated spring centre
 Thecylinderwill be pre-
exhausted when changing
from the mid position
2
4
5 1 3
14 12

22. 5/3 Valve actuator control
 Thisversionof a 5/3 valve is
“centreopen pressure”
 The supply at port 1 is
connected to bothsides of the
cylinderand theexhaust ports
isolated when this centre
position is selected
 Can be used to balance
pressures in positioning
applications
 The version illustrated is
mono-stable, doublesolenoid,
spring centre
14 4 2 12
5 1 3

23. INDUSTRIAL PNEUMATIC CIRCUIT