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CPM/PERT

Project Planning and AppraisalM. Arch

SCET, Surat

Prof. BhaskER V. Bhatt

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ProjectA project is a series of activities directed toaccomplishment of a desired objective .

One definition of a project:A project is a temporary endeavor undertaken to create a "unique"product or service

Plan your work first..then work your plan

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What is ProjectManagement?

The application of a collection of tools and techniques todirect the use of diverse resources towards theaccomplishment of a unique, complex, one time task withintime, cost and quality constraints.

Its origins lie in World War II, when the military authoritiesused the techniques of operational research to plan theoptimum use of resources.

One of these techniques was the use of networks torepresent a system of related activities

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or rea ownStructure

A method of breaking down a project into individualelements ( components, subcomponents, activities andtasks) in a hierarchical structure which can be scheduledand cost

It defines tasks that can be completed independently of other tasks, facilitating resource allocation, assignment of responsibilities and measurement and control of the project

It is foundation of project planning

It is developed before identification of dependencies and

estimation of activity durationsIt can be used to identity the tasks in the CPM and PERT

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Work Breakdown Structure for Computer Order Processing System Project

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Project Scheduling and ControlTechniques

Network analysis is the general name given to certain specifictechniques which can be used for the planning, management andcontrol of projects.

Gantt Chart

Critical Path Method (CPM)

Program Evaluation and Review Technique (PERT)

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History

Developed in 1950s CPM by DuPont for chemical plantsPERT by U.S. Navy for Polaris missile

PERT was developed by the US Navy for the planning and control of the Polaris missile program and the emphasis was on completing theprogram in the shortest possible time. In addition PERT had theability to cope with uncertain activity completion times (e.g. for aparticular activity the most likely completion time is 4 weeks but itcould be anywhere between 3 weeks and 8 weeks).

CPM was developed by Du Pont and the emphasis was on thetrade-off between the cost of the project and its overallcompletion time (e.g. for certain activities it may be possible

to decrease their completion times by spending more money -how does this affect the overall completion time of theproject?)

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CPM - Critical Path Method

Definition: In CPM activities are shown as a network of precedence relationships using activity-on-nodenetwork construction

Single estimate of activity timeDeterministic activity times

USED IN : Production management - for the jobs of repetitive in nature where the activity time estimatescan be predicted with considerable certainty due tothe existence of past experience.

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Originated by H.L.Gantt in 1918

Gantt chart

Advantages- Gantt charts are quite commonly used.They provide an easy graphicalrepresentation of when activities (might)take place.

Limitations- Do not clearly indicate details regardingthe progress of activities

- Do not give a clear indication of interrelation ship between the separateactivities

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CPM/PERT

These deficiencies can be eliminated to a large extent byshowing the interdependence of various activities bymeans of connecting arrows called network technique.

Overtime CPM and PERT became one technique

ADVANTAGES:Precedence relationshipslarge projectsmore efficient

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The Project NetworkUse of nodes and arrows

Arrows An arrow leads from tail to head directionallyIndicate ACTIVITY, a time consuming effort that is required toperform a part of the work.

Nodes A node is represented by a circle- Indicate EVENT, a point in time where one or more activities

start and/or finish. Activity

A task or a certain amount of work required in the project

Requires time to complete Represented by an arrow

Dummy Activity Indicates only precedence relationships Does not require any time of effort

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Project Network Event

Signals the beginning or ending of an activity Designates a point in time Represented by a circle (node)

Network

Shows the sequential relationships among activities usingnodes and arrows

Activity-on-node (AON) Nodes represent activities, and arrows show precedence

relationships

Activity-on-arrow (AOA) Arrows represent activities and nodes are events for points in

time

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AOA Project Network for House

3 2 0

1 3

1 11

1 2 4 6 7

3

5

Lay foundation

Design house and obtain financing

Order and receive materials

Dummy

Finishwork

Select carpet

Select paint

Build house

AON Project Network for House

1 3

2

2

4 3

31 5

1

6 1

7 1Start

Design house and obtain financing

Order and receive materials Select paintSelect carpet

Lay foundations Build house

Finish work

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A B

C

A must finish before either B or C can

start A

B

C both A and B must finish before C can start

D

C

B

A both A and B must finish before either of C or D can start

A

C

B

D

Dummy A must finish before B can start

both A and C must finish before D can start

Situations in network diagram

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Concurrent Activities

2 3

Lay foundation

Order material

(a) Incorrect precedence relationship

(b) Correct precedence relationship

3

4 2

Dummy Lay foundation

Order material

1

2 0

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Critical Path

Is that the sequence of activities and events where there isno slack i.e.. Zero slack

Longest path through a networkminimum project completion time

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Benefits of CPM/PERT

Useful at many stages of project managementMathematically simpleGive critical path and slack timeProvide project documentationUseful in monitoring costs

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Questions Answered by CPM & PERT

Completion date?On Schedule?Within Budget?Critical Activities?How can the project be finished early at the least cost?

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For clarity, this list is kept to a minimum by specifying onlyimmediate relationships, that is relationships involving activitiesthat " occur near to each other in time".

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"What activities must be finished before this activity can start"

could we complete this project in 30 weeks?

could we complete this project in 2 weeks?

One answer could be, if we first do activity 1, then activity 2, then activity 3,...., then activity 10, then activity 11 and the project would then take the sumof the activity completion times, 30 weeks.

What is the minimum possible time in which we can complete this project ?

Before starting any of the above activity, the questionsasked would be

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We shall see below how the network analysis diagram/picture we constructhelps us to answer this question.

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CRITICAL PATH TAKES24 WEEKS FOR THE COMPLETION OF THE PROJECT

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Limitations to CPM/PERT

Clearly defined, independent and stableactivitiesSpecified precedence relationshipsOver emphasis on critical paths

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Thank you