logic representation

8/14/2019 Logic Representation

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F n i n l L iFunctional Lo ics

Systems designed to provide the safeSystems designed to provide the safestart up, shut down and operation ofstart up, shut down and operation of

units.units.

They use a system of locks and interlocksThey use a system of locks and interlocksthat prevent unsafe situations developing.that prevent unsafe situations developing.

A logic system consists of inputs andA logic system consists of inputs and

outputs, interconnected by gates andoutputs, interconnected by gates and

timers.timers.


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LogicLogic

SystemSystem

NeutralNeutral

StarterStarter

MotorMotor

InputInput InputInput

InputInput

OutputOutput


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Functional LogicFunctional Logic

Look like a series of boxes connected toLook like a series of boxes connected toother boxes via signal linesother boxes via signal lines

The lines connect inputs to gates, timersThe lines connect inputs to gates, timers

etc to the final element box.etc to the final element box.

The signals are based on the BinaryThe signals are based on the Binary

systemsystem

Signals are either 1 or 0Signals are either 1 or 0

Healthy Signal = 1Healthy Signal = 1


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Any signal failure for example dueAny signal failure for example dueto ato a

If a final element is a solenoid, theIf a final element is a solenoid, thesolenoidsolenoid

will be energised in normalwill be energised in normal

operation tooperation to When the solenoid is de-energisedWhen the solenoid is de-energisedthe systemthe system

will tri to rovide itswill tri to rovide its

31-XE-105

FUEL


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Logic sheets are read from leftLogic sheets are read from left

Logics sheets have coded circles andLogics sheets have coded circles andsymbolssymbols

connected off them.connected off them.


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A functional logic diagram mayA functional logic diagram mayencompass,encompass,

Each of these sheets is necessary toEach of these sheets is necessary toshow theshow the

interrelationship of a safeguarding logicinterrelationship of a safeguarding logic

The sheets must be integrated withThe sheets must be integrated with

Each sheet has an identifyingEach sheet has an identifyingnumber innumber in


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Signals that leave, enter, or transfer on aSignals that leave, enter, or transfer on asheet aresheet are

displayed by a circle with the sheetdisplayed by a circle with the sheetnumbernumber

The identifying number in a circle on theThe identifying number in a circle on the

logiclogicdiagram gives the identity of thediagram gives the identity of thefunctional logicfunctional logicsheet where the signal originates from,sheet where the signal originates from,


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A functional logic sheet may haveA functional logic sheet may haveseveralseveralinputs/outputs to other sheets.inputs/outputs to other sheets.

1414AASheet 13Sheet 13

1313AASheet 14Sheet 14

1212

CC

1414DD

Sheet 11Sheet 11

1111

CC

1111DD

Sheet 12Sheet 12

Sheet 14Sheet 14


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Fail Safe ConceptFail Safe Concept

Unhealthy 0Unhealthy 0

Healthy 1Healthy 1


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00

UnhealthyUnhealthy

OFOF

00


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11

HealthyHealthy

ONON

11


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EmergencyShutdown

31-HE-

Two Position Rotary SwitchTwo Position Rotary Switch

11

Signal is 1 when notSignal is 1 when not

Position1Position1


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EmergencyShutdown

Signal isSignal is 00 whenwhen

00

Signal out known asSignal out known as

the Y outputthe Y output

Position 2Position 2

31-HE-

Two Position Rotary SwitchTwo Position Rotary Switch


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31-LEA-2031-LEA-20

Range 4 to 20maRange 4 to 20ma

Trip value 63%Trip value 63%= 14.08 ma output= 14.08 ma output

TunedTuned

to trip theto trip the

contactscontacts..

In thisIn thiscase atcase at14.08m14.08m

>LL>LL

31-LEA-20

Level LegLevel Leg Input BoxInput Box

Tuned Relay 0 or 1 outputTuned Relay 0 or 1 output

11

Signal to Input boxSignal to Input box

Output 15maOutput 15ma

Output greater than Low LowOutput greater than Low Low

Condition HealthyCondition Healthy

Si


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31-LEA-2031-LEA-20



TunedTuned


contactscontacts..


>LL>LL

31-LEA-20



00


Output 14 maOutput 14 ma

Output lower than Low LowOutput lower than Low Low

Condition UnhealthyCondition Unhealthy

Si l I b


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31-LEA-2031-LEA-20



TunedTuned


contactscontacts..


>LL>LL

31-LEA-20



00


Output 14 maOutput 14 ma

Output lower than Low LowOutput lower than Low Low

Condition UnhealthyCondition Unhealthy

Relay TripsRelay Trips


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Input BoxInput Box

Final Element BoxFinal Element Box

Gates and TimersGates and Timers


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Device that performs a simple logic functionDevice that performs a simple logic function

>>X2X2

X1X1YY

GatesGates


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0 00 0

11 00

00 11

1 11 1

X1 X2 YX1 X2 Y

A Truth Table shows the Logic of the GateA Truth Table shows the Logic of the Gate


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0 00 0

11 00

00 11

1 11 1

X1 X2 YX1 X2 Y

A Truth Table shows the Logic of the GateA Truth Table shows the Logic of the Gate

>>X2X2X1X1

YY If X1 is 1If X1 is 1

11

Y is 1Y is 1

11

X2 is 0X2 is 0

00


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>>X2X2

X1X1YY

OR GATEOR GATE

0 00 0

11

00

00 11

1 11 1

X1 X2 YX1 X2 Y

Truth TableTruth Table

11

00

11

Needs X1 or X2 to be 1 for Y to be 1Needs X1 or X2 to be 1 for Y to be 1


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>>X2X2

X1X1YY

OR GATEOR GATE

0 00 0

11

00

00 11

1 11 1

X1 X2 YX1 X2 Y


11

00

11



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>>X2X2

X1X1YY

OR GATEOR GATE

0 00 0

11

00

00 11

1 11 1

X1 X2 YX1 X2 Y


00

11

11



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>>X2X2

X1X1YY

OR GATEOR GATE

0 00 0

11

00

00 11

1 11 1

X1 X2 YX1 X2 Y


00

00

00



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++X2X2

X1X1YY

EOR GATEEOR GATE (Exclusive OR gate)(Exclusive OR gate)

0 00 0

11

00

00 11

1 11 1

X1 X2 YX1 X2 Y


When X1 and X2 are both 1 signal = 0When X1 and X2 are both 1 signal = 0

00

11

11


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++X2X2

X1X1YY

EOR GATEEOR GATE (Exclusive OR gate)(Exclusive OR gate)

0 00 0

11

00

00 11

1 11 1

X1 X2 YX1 X2 Y


When X1 and X2 are both 1 signal = 0When X1 and X2 are both 1 signal = 0

00

11

11


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&&X2X2

X1X1YY

AND GATEAND GATE

0 00 0

11

00

00 11

1 11 1

X1 X2 YX1 X2 Y


Needs X1 and X2 to be 1 for Y to be 1Needs X1 and X2 to be 1 for Y to be 1


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&&X2X2

X1X1YY

AND GATEAND GATE

0 00 0

11

00

00 11

1 11 1

X1 X2 YX1 X2 Y


11

00

00


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&&X2X2

X1X1YY

AND GATEAND GATE

0 00 0

11

00

00 11

1 11 1

X1 X2 YX1 X2 Y


00

11

00


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&&X2X2

X1X1YY

AND GATEAND GATE

0 00 0

11

00

00 11

1 11 1

X1 X2 YX1 X2 Y


11

11

11


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XX YY

Invert Gate GATEInvert Gate GATE (or NOT Gate)(or NOT Gate)

00 11

11 00

X YX YTruth TableTruth Table

When X = 0 Y = 1When X = 0 Y = 1


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XX YY


00 11

11 00


00 11


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XX YY


00 11

11 00


11 00


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TimersTimers

Delay the acceptance of a healthy signalDelay the acceptance of a healthy signal

Extend recognition of a healthy signalExtend recognition of a healthy signal

Hold a healthy or unhealthy signal for aHold a healthy or unhealthy signal for a

period of timeperiod of time

Dela TimerDelay Timer


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t=XX YY

11

00XX

tt

11

00YY

TIMETIME

00

5sec5sec

5sec5sec

Delay TimerDelay Timer

1 signal starts timer1 signal starts timer

11

Output only after 5 seconds delayOutput only after 5 seconds delay


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OFFOFF

Start

Stop

5 Second Delay Timer5 Second Delay Timer


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OFFOFF

Start

Stop



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Start

Stop


Extension TimerExtension Timer


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t=

XX YY

11

00XX

tt

11

00YY

TIMETIME

00

5sec5sec

5sec5sec

Extension TimerExtension Timer


11

Output Continues for 5 secondsOutput Continues for 5 seconds

Double Acting TimerDouble Acting Timer


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t=XX YY

11

00XX

tt

11

00YY

TIMETIME

00

Double Acting TimerDouble Acting Timer


Output Continues for 5 secondsOutput Continues for 5 seconds

tt

5sec5sec

5sec5sec5sec5sec

11

Output only after 5 seconds delayOutput only after 5 seconds delay

Pulse TimersPulse Timers


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t=XX YY

11

00XX

tt1100

YY

TIMETIME

Pulse TimersPulse Timers

Output will pulse to either 1 or 0 for the time shownOutput will pulse to either 1 or 0 for the time shown

tt


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MOSMOS


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MOSMOSMaintenance OverideMaintenance Overide

31-HI-907 POSPOS 55

MaintenanceOveride

11

Outputs 1 when switch in overide positionOutputs 1 when switch in overide positionOtherwise signal output = signal inputOtherwise signal output = signal input

Used for Trip TestingUsed for Trip Testing

OOSOOS


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OOSOOS

Operational OverideOperational Overide

OVERIDE

OperationalOveride

Used for Start UpsUsed for Start Ups

NORMA

11

Outputs 1 when switch in overide positionOutputs 1 when switch in overide position

When in normal position signal output = signal inputWhen in normal position signal output = signal input

30-HI-32


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Final Element BoxesFinal Element Boxes


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Final Element BoxesFinal Element BoxesReceivingReceiving

K-3101

TRIP

Compressor is Tripped when signal is 0Compressor is Tripped when signal is 0

Logical 0Logical 0DEB.FEED

COMP.



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31-XE-105

FUEL GASTO F-3101

O

C

No Flow of gas to furnaceNo Flow of gas to furnace

Gas FlowGas Flow

Logical 0 Closes Fuel Gas ValveLogical 0 Closes Fuel Gas Valve

00



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31-XE-105

FUEL GASTO F-3101

Logical 1 Opens Fuel Gas ValveLogical 1 Opens Fuel Gas Valve

O

C

Gas FlowGas Flow

Valve opens and gas flows to FurnaceValve opens and gas flows to Furnace

11



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51-XE-113

Nitrogen Purge

C

O

Logical 0 Opens Nitrogen ValveLogical 0 Opens Nitrogen Valve

00

Nitrogen FlowNitrogen Flow



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Final Element BoxesReceivingReceiving

31-XE-105

FUEL GASTO F-3101

Logical 1 Opens Fuel Gas ValveLogical 1 Opens Fuel Gas Valve

O

C

Gas FlowGas Flow

Valve opens and gas flows to FurnaceValve opens and gas flows to Furnace

11



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Final Element BoxesReceivingReceiving

51-XE-113

Nitrogen Purge

C

O

Logical 0 Opens Nitrogen ValveLogical 0 Opens Nitrogen Valve

00



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ReceivingReceiving

51-XE-113

Nitrogen Purge

C

O


11

Logical 1 Closes Nitrogen ValveLogical 1 Closes Nitrogen Valve

Valve closes and Nitrogen flow stopsValve closes and Nitrogen flow stops


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SummarySummary


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Functional logics are used to quicklyFunctional logics are used to quicklyand safelyand safelyshutdown equipment where a failureshutdown equipment where a failure

Logics are also used to ensure plant is startedLogics are also used to ensure plant is startedsafelysafelyusing the correct procedure, e.g. start up ofusing the correct procedure, e.g. start up of

A knowledge of functional logic sheetsA knowledge of functional logic sheetsprovides a usefulprovides a usefultool to better understanding of thetool to better understanding of the

Try working through the logic sheets forTry working through the logic sheets foryour blockyour blockwith a colleague, this will help to reinforcewith a colleague, this will help to reinforce


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The EndThe End


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>>

Device that performs a simple logic functionDevice that performs a simple logic function

X2X2

X1X1

YY

OR GATEOR GATE


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O

C

51-XE-119


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Functional logic sheets look like a series of boxesconnected to other boxes via signal lines.

The lines connect inputs, to gates, timers etc, to theFinal Element Box.

The logical arithmetic is based on the binary system.This requires that the signals used be either 1or"O".


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Health

1


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Health

0kg


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Unhealth

1kg

Identifying numbersIdentifying numbers


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Identifying numbersIdentifying numbers

InputInput

Final ElementFinal Element

Circuits. (trip cards identifies numbersCircuits. (trip cards identifies numbers

AlarmAlarm

OverridOverrid

Gates,(a.) "AND",(b.) OR, (c.)Gates,(a.) "AND",(b.) OR, (c.)

Timers, "Delay", "Extension",Timers, "Delay", "Extension",

logic representation

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