Network Planning Methods

8/6/2019 Network Planning Methods

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NETWORK PLANNINGNETWORK PLANNINGMETHODSMETHODS


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FLOW OF PRESENTATIONFLOW OF PRESENTATION

INTRODUCTIONINTRODUCTION

NETWORK PLANNINGNETWORK PLANNING

ESTIMATING TIMEESTIMATING TIME

CPM AND CRASHINGCPM AND CRASHING

PERTPERTGANTT CHARTSGANTT CHARTS


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Project ManagementProject ManagementProject :Project :

A project is an interrelated set of activitiesA project is an interrelated set of activitiesthat has a definite starting and ending pointthat has a definite starting and ending pointand that results in a unique product orand that results in a unique product or

service.service.

Project managementProject management::

Project management is a scientific way ofProject management is a scientific way ofplanning, implementing, monitoring &planning, implementing, monitoring &controlling the various aspects of a projectcontrolling the various aspects of a projectsuch as time, money, materials, manpower &such as time, money, materials, manpower &

other resources.other resources.


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Network Planning MethodsNetwork Planning Methods

What is network planning?What is network planning?

Methods used for network planning are:Methods used for network planning are:

CPMCPM

PERTPERT

Managing a project with network planning methodsManaging a project with network planning methodsinvolves four steps:involves four steps:

1.1. Describing the Project.Describing the Project.

2.2. Diagramming the Network.Diagramming the Network.

3.3. Estimating time of completion.Estimating time of completion.

4.4. Monitoring Project Progress.Monitoring Project Progress.


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Network DiagramNetwork Diagram

ConceptsConcepts

ActivityActivity Precedence relationshipPrecedence relationship

SuccessorSuccessor

EventEvent


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Guidelines for network diagramGuidelines for network diagram

1.1. Before an activity can begin, its precedingBefore an activity can begin, its precedingactivities must be completed.activities must be completed.

2.2. Arrows indicate logical precedence.Arrows indicate logical precedence.3.3. Flow of the diagram is from left to right.Flow of the diagram is from left to right.

4.4. Arrows should not intersect.Arrows should not intersect.

5.5. Dangling should be avoided.Dangling should be avoided.


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APPRAOCHES FOR NETWORKAPPRAOCHES FOR NETWORK

DIAGRAMDIAGRAMACTIVITYONARC(AOA):ACTIVITYONARC(AOA):Uses arcs to represent activities and nodes toUses arcs to represent activities and nodes to

represent events.represent events.

It is Event Oriented.It is Event Oriented.

1 876

54

3

2


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DUMMY ACTIVITYDUMMY ACTIVITYAOA approach requires the addition of aAOA approach requires the addition of a DummyActivityDummyActivity

to clarify the precedence relationships between theto clarify the precedence relationships between thetwo activities. It is a zero time activity and consumestwo activities. It is a zero time activity and consumesno resources.no resources.

Dummy Activity is used in two situations:Dummy Activity is used in two situations:

1)1) When two or more activities start and end at the sameWhen two or more activities start and end at the samenodesnodes

1 3

2


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2) When two or more activities share the same precedence2) When two or more activities share the same precedenceactivity but not all the precedence are shared.activity but not all the precedence are shared.

1 53

6

7

2 4


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ACTIVITY ON NODE(AON):ACTIVITY ON NODE(AON):Uses nodes to represent activities and arcs indicateUses nodes to represent activities and arcs indicate

precedence relationships between them.precedence relationships between them.

It is Activity Oriented.It is Activity Oriented.


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ESTIMATING TIME OFESTIMATING TIME OF

COMPLETIONCOMPLETIONPlanning the schedule of the projectPlanning the schedule of the projectTime estimates include:Time estimates include:

1)1) Total time for completion.Total time for completion.

2)2) ESES-- Earliest start time: the earliest time at which the activity canEarliest start time: the earliest time at which the activity canstart given that its precedent activities must be completed first.start given that its precedent activities must be completed first.

3)3) EFEF--Earliest finish time: equals to the earliest start time for theEarliest finish time: equals to the earliest start time for theactivity plus the time required to complete the activity.activity plus the time required to complete the activity.

4)4) LFLF-- Latest finish time: the latest time in which the activity can beLatest finish time: the latest time in which the activity can becompleted without delaying the project.completed without delaying the project.

5)5) LSLS-- Latest start time: equal to the latest finish time minus theLatest start time: equal to the latest finish time minus thetime required to complete the activity.time required to complete the activity.


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6)6) FORWARD PASSFORWARD PASS::The early start and early finish times are calculated byThe early start and early finish times are calculated by

moving forward through the network and consideringmoving forward through the network and consideringthe predecessor activities.the predecessor activities.

Considers maximumConsiders maximum

7)7) BACKWARD PASS:BACKWARD PASS:

The latest start and finish times are calculated by movingThe latest start and finish times are calculated by movingbackward through the network.backward through the network.Considers minimumConsiders minimum

8)8) SLACK TIME:SLACK TIME:

Slack time for an activity is the difference between itsSlack time for an activity is the difference between itsearliest and latest start time or between the earliest andearliest and latest start time or between the earliest andlatest finish time.latest finish time.

Critical path is the path of activities having zero Slack time.Critical path is the path of activities having zero Slack time.


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CRITICAL PATH METHODS(CPM)CRITICAL PATH METHODS(CPM)

HISTORYHISTORY ::It was developed by J.E.KELLY of REMINGTONIt was developed by J.E.KELLY of REMINGTON--RANDRAND

and M.R.WALKER of DU PONT and the emphasis was onand M.R.WALKER of DU PONT and the emphasis was on

the tradethe trade--off between the cost of project and its overalloff between the cost of project and its overallcompletion time. The first test was made in 1958,whencompletion time. The first test was made in 1958,whenCPM was applied to the construction of a new chemicalCPM was applied to the construction of a new chemicalplant.plant.

DEFINITIONDEFINITION::Critical path is the sequence of activities between aCritical path is the sequence of activities between aprojects start and finish that takes the longest time toprojects start and finish that takes the longest time tocomplete.complete.


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STEPS IN DETERMINING CRITICALSTEPS IN DETERMINING CRITICAL

PATHPATH Specify the individual activities.Specify the individual activities.

Determine the sequence of the activities.Determine the sequence of the activities.

Draw the network diagram.Draw the network diagram.

Estimate the activity completion time.Estimate the activity completion time.

Identify the critical path.Identify the critical path.

Update the CPM diagram.Update the CPM diagram.


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ADVANTAGESADVANTAGES

Provides a graphical view of the project.Provides a graphical view of the project.

Predicts the time required for completingPredicts the time required for completingthe project.the project.

Shows which activities are critical toShows which activities are critical tomaintaining the schedule and which aremaintaining the schedule and which are

not.not.


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DISADVANTAGESDISADVANTAGES

There can be potentially hundreds or thousandsThere can be potentially hundreds or thousandsof activities making the network diagramof activities making the network diagram

complex.complex.

Any changes introduced in the diagram makesAny changes introduced in the diagram makesthe calculation of critical path difficult.the calculation of critical path difficult.


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HISTORYHISTORY::

Pert (Pert (Program Evaluation and Review Technique)Program Evaluation and Review Technique)

was developed in 1958 by BOOZ ALLEN and HAMILTONwas developed in 1958 by BOOZ ALLEN and HAMILTONInc along with US Navy for planning and control ofInc along with US Navy for planning and control of

Polaris Missile Project and emphasis was on completingPolaris Missile Project and emphasis was on completingthe project in the shortest possible time.the project in the shortest possible time.

PERTPERT


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TIME ESTIMATESTIME ESTIMATES

oo Optimistic time (to)Optimistic time (to) It is the shortest time in which theIt is the shortest time in which theactivity can be completed.activity can be completed.

oo Most likely time (tm)Most likely time (tm) It is the probable time required toIt is the probable time required toperform the activity.perform the activity.

oo Pessimistic time (tp)Pessimistic time (tp) It is the longest estimated timeIt is the longest estimated timerequired to perform an activity.required to perform an activity.

oo Expected timeExpected time

te =te = to + 4tm + tpto + 4tm + tp

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STEPS IN PERTSTEPS IN PERT

1.1. Identify the specific activities.Identify the specific activities.

2.2. Determine proper sequence of the activities.Determine proper sequence of the activities.

3.3. Construct the network diagram.Construct the network diagram.

4.4. Estimate the time required for each activity.Estimate the time required for each activity.

5.5. Determine the critical path.Determine the critical path.

6.6. Update the PERT chart.Update the PERT chart.


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Advantages of PERTAdvantages of PERT Expected project completion time.Expected project completion time.

Probability of completion before a specified date.Probability of completion before a specified date.

The critical path activities that directly impact theThe critical path activities that directly impact thecompletion time.completion time.

The activities that have slack time and that can lendThe activities that have slack time and that can lendresources to critical path activities.resources to critical path activities.

Activity start and end dates.Activity start and end dates.


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LIMITATIONSLIMITATIONS The PERT Formula RequiresToo Much Work.The PERT Formula RequiresToo Much Work.

The network charts tend to be large and unwieldy.The network charts tend to be large and unwieldy.

Calculating the time estimates is very complex for all theCalculating the time estimates is very complex for all the

activities.activities.

Updating of the project is time consuming and requiresUpdating of the project is time consuming and requireshigh costs.high costs.

Emphasis is laid only on time factors and cost factors areEmphasis is laid only on time factors and cost factors areneglected.neglected.


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ApplicationApplication

oo Used for scheduling of aircrafts.Used for scheduling of aircrafts.

oo Pert techniques used in the administrationPert techniques used in the administrationof firms.of firms.


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Difference between CPM & PERTDifference between CPM & PERT

CPMCPM PERTPERT CPM works with fixedCPM works with fixeddeterministic timedeterministic time

PERT works withPERT works withprobabilistic timeprobabilistic time

CPM is useful for repetitiveCPM is useful for repetitive

and non complex projectsand non complex projectswith a certain degree of timewith a certain degree of timeestimates.estimates.

PERT is useful for nonPERT is useful for non

repetitive and complexrepetitive and complexprojects with uncertain timeprojects with uncertain timeestimates.estimates.

CPM includes timeCPM includes time--costcost

trade off.trade off.

PERT is restricted to timePERT is restricted to time

variable.variable.

CPMCPM-- for constructionfor constructionprojects.projects.

PERTPERT-- used for R&Dused for R&Dprograms.programs.


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Thank YouThank You

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Network Planning Methods