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PERT :

Basic Network Terminology Rules forDrawing Network

PRESENTATION BY:

!R!"enkates#

$$A%$A&'('

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Introduction

Any project involves planning, scheduling and controlling anumber of interrelated activities with use of limitedresources, namely, men, machines, materials, money and

time.

The projects may be extremely large and complex such asconstruction of a housing , a highway, a shopping complexetc.

introduction of new products and research and developmentprojects.

It is required that managers must have a dynamic planningand scheduling system to produce the best possible results

and also to react immediately to the changing conditionsand make necessary changes in the plan and schedule.

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A convenient analytical and visual technique of PERTand )P* prove extremely valuable in assisting the

managers in managing the projects.

!"T stands for Pro+ect E,aluation an- Re,iewTec#ni.ue-e,elo/e- -uring $01&2s! T#e tec#ni.ue wasdeveloped and used in conjunction with the planning and

designing of the olaris missile project.

#$ stands for )ritical Pat# *et#o- w#ic# was-e,elo/e- 3y DuPont #ompany and applied %rst to theconstruction projects in the chemical industry.

Though both !"T and #$ techniques have similarity interms of concepts, the basic di&erence is, !"T is used foranalysis of project scheduling problems. #$ has single timeestimate and !"T has three time estimates for activities anduses probability theory to %nd the chance of reaching the

scheduled time.

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)O*PONENTS of PERT4)P*NET5OR%

!"T + #$ networks contain two major

componentsi. Activities, andii. !vents!ctivity:An activity represents an action and consumptionof resources (time, money, energy( required to complete aportion of a project. Activity is represented by an arrow,

'igure -.(.

"vent:An event (or node) will always occur at the beginning andend of an activity. The event has no resources and is representedby a circle. The ith event and jth event are the tail event and headevent respectively, 'igure -./(.

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*erge an- Burst E,ents

0ne or more activities can start and end simultaneously at an event'igure -.1 a, b(.

Prece-ing an- Succee-ing Acti,ities

Activities performed before given events are known as precedingactivities 'igure -.2(, and activities performed after a given event areknown as succeeding activities.

Activities A and 3 precede activities # and 4 respectively.

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Dummy Acti,ity

An imaginary activity which does not consume any resource and time is

called a dummy activity. #ummy activities are simply used torepresent a connection bet$een events in order to maintain a logicin the network. It is represented by a dotted line in a network, see igure-.5.

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ERRORS TO BE A"OIDED IN )ONSTR6)TIN7 A NET5OR%

a. Two activities starting from a tailevent must not have a same end

event. To ensure this, it is absolutelynecessary to introduce a dummyactivity, as shown in igure -.6.b. 7ooping error should not be formedin a network, as it representsperformance of activities repeatedly

in a cyclic manner, as shown below inigure -.8.

c. In a network, there should be onlyone start event and one ending eventas shown

below, in igure -.-.

d. The direction of arrowsshould )ow from left to rightavoiding mixing of direction asshown in igure -.9.

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R6ES IN )ONSTR6)TIN7 A NET5OR%

$! No single acti,ity can 3e re/resente- more t#an once ina network! T#e lengt# of an arrow #as no signi8cance!

9! T#e e,ent num3ere- $ is t#e start e,ent an- an e,entwit# #ig#est num3er is t#e en- e,ent! Before an acti,itycan 3e un-ertaken all acti,ities /rece-ing it must 3ecom/lete-! T#at is t#e acti,ities must follow a logical

se.uence ;or < interrelations#i/= 3etween acti,ities!

>! In assigning num3ers to e,ents t#ere s#oul- not 3e any-u/lication of e,ent num3ers in a network!

'! Dummy acti,ities must 3e use- only if it is necessary tore-uce t#e com/le?ity of a network!

1! A network s#oul- #a,e only one start e,ent an- one en-e,ent!

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:ome conventions of network diagram are shown inigure -.; 'a(, 'b(, 'c(, 'd( below