# Project scheduling and control with CPM & PERT

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The best known and most widely used project scheduling and control method is called PERT, or Program Evaluation and ReviewTechnique. PERT is an analytical method which is designed to aid in the scheduling and control of complex projects which require that certain activities be performed in sequence

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• *LARGE SCALE PROJECTSProject scheduling and control with PERT / CPM The best known and most widely used project scheduling and control method is called PERT, or Program Evaluation and ReviewTechnique. PERT is an analytical method which is designed to aid in the scheduling and control of complex projects which require that certain activities be performed in sequence .

• *PERT has been used for many kinds of construction activities, for building bridge and unusual buildings such as stadiums etc. Project planning method, also called network planning methods, were initially developed independently by two different groups. As an internal project for any companies , Critical Path Methods ( CPM ) were developed to plan and control the maintenance of chemical plant, assembly plant or any big projects.

• *The immediate success of both the CPM and PERT methodologies may be gauged by the following facts. DuPonts application of the CPM technique to a maintenance project works resulted in a resulted in a reduction in downtime for maintenance from 125 to 78 hours.

• *The PERT technique was widely credited with helping to shorten by two years the time originally estimated for the completion of the engineering and development program.

• *PERT and CPM are based substantially on the concepts. As originally developed, PERT was based on probabilistic estimates of activity times that resulted in a probabilistic path through a network of activities and a probabilistic project completion time.

• *PERT CHARACTERISTICS AND DEFINITIONSACTIVITYAn activity is a part of the total work to be done; it consumes time and resources and has starting and ending points. EVENTAn event is a milestone; it marks the beginning or the end of an activity. In drawing a PERT network, events are symbolized as circle or nodes. Events are also numbered, with those at the tail of an activity having lower numbers than events at the head of each activity arrow.

• *Activity TimePERT uses three estimates of the amount of time an activity might take to complete. These estimates are obtained from people who have knowledge about the work and how long it will probably take. They are:Optimistic Time: The time the activity will take if everything goes well and no delays are encountered.Or The shortest time required for completion of the activity assuming that no hurdles or completions are encountered.

• The most likely time or Realistic Time: The time the activity will most likely take under normal conditions, allowing for usual delays.ORThe time in which the activity is most likely to be completed .This estimate takes into consideration normal circumstances, making allowance for some unforeseen delays.

*

• *Pessimistic Time The time the activity may take if more than usual delays are encountered.ORThe longest time required to complete the activity assuming that unusual complications and /or unforseen difficulties would arise.PERT weights these three estimates to obtain an expected time for an activity by:

• *Expected activity time = Optimistic Time + ( 4 x Realistic Time ) + Pessimistic Time 6Thus if an activity in a PERT network for building a building were pour the concrete foundation and it had estimates of 2, 4, and 12 days, its expected duration would be:2 =Optimistic time,4 =Realistic time and 12 =Pessimistic timeExpected activity time = 2 + (4x4) + 12 / 6 = 5 days.

• FLOATActivities that are not critical are called non-critical activities.These activities have a certain amount of spare time or float available.Thus, non critical activities can be delayed or advanced (depending on the extent of float availability)without affecting the overall completion date.*

• Earliest expected completion time of events (TE)Latest allowable time or latest finish time of events*

• *PERT data

1

2

3

4

5

6

7

8

9

10

Activity

Immediate

Precedence

requirements

Event

Begin End

Opti-

Mistic

time

Real-

Istic

time

Pesi-

Mistic

time

Expected

time

Start

ES LS

Finish

EF LF

Total

slack

A

None

1 2

3

4

5

4

0 0

4 4

0

B

A

2 3

4

7

10

7

4 16

11 23

12

C

B

3 7

2

7

12

7

11 23

18 30

12

D

A

2 4

3

5

13

6

4 19

10 25

15

E

D

4 7

1

5

9

5

10 25

15 30

15

F

A

2 5

7

8

21

10

4 4

14 14

0

G

F

5 6

1

7

7

6

14 14

20 20

0

H

G

6 7

---

---

---

---

20 30

20 30

10

I

C, E, G

7 8

10

10

10

10

20 30

30 40

10

J

G

6 8

15

20

25

20

20 20

40 40

0

K

L, I, J

8 9

2

7

12

7

40 40

47 47

0

L

A

2 8

10

15

20

15

4 25

19 40

21

• *PERT DATA WITH EXPECTED TIME(1)Activity(2) Immediate precedence requirement(3) Events Begins End (4) Optimistic time (5) Realistic time (6) Pessimistic time (7) Expected time (8) Start ES LS (9) FinishEF LF (10) Total slack A B C D E F G H I J K LNone A B A D A F G CEG G LIJ A 1 2 3 2 4 2 5 6 7 6 8 22 3 7 4 7 5 6 7 8 8 9 83 4 2 3 1 7 1 -- 10 15 2 10 4 7 7 5 5 8 7 --- 10 20 7 155 10 12 13 9 21 7 ---- 10 25 12 20Expected time = Optimistic Time + ( 4 x Realistic Time ) + Pessimistic Time 64 7 7 6 5 10 6 --- 10 20 7 154 7 7 6 5 10 6 --- 10 20 7 15

• *PROJECT SCHEDULINGData on the activities in the Print Project

ACTIVITY

DESCRIPTION

TIME REQD.

PREDECESSORS

A

Widen access door

3

-----

B

Build compressor housing

3

A

C

Remove old printing press

1

-----

D

Move other machines to create more space

2

C

E

Re-lay concrete floor

8

A,D

F

4

-----

G

Lay new electrical cabling

1

F

H

4

----

I

Operators go on training course

12

C

J

Install new printing press

6

B,E,F,G,

K

Commission new press

4

H,I,J,

• *NETWORK DIAGRAM FOR PRINTING PRESS PROJECTNodes with activity0ACDHB331FKEG846 114JI1286 6264 44

• *NETWORK DIAGRAM FOR PRINTING PRESS PROJECTPriority activity013482A3B361257E8F4J6 C1G1H41110I12E8J6 J6D2J6K4 K4K4

• *FLOW OF CALCULATION FOR EARLY START, ES, AND EARLY FINISH, EF, TIMES.20EARLY FINISHPriority Activities013482A3B361257E8F4J6 C1G1H41110I12E8J6 J6D2J6K4 K4K440843010311131136313117111713126405410411521172121EARLY START

• *Precedence Chart Showing Activities Their Required Sequence, and Time Requirements for the New Product Introduction ProjectTable

Activity Code

Description

Immediate Processor

Activity

Time

weeks

A

Organize Sales Office

------

6

B

Hire Sales people

A

4

C

Train Sales People

B

7

D

A

2

E

D

4

F

E

10

G

Design Package

----

2

H

Set Up Packaging Facilities

G

10

I

Package initial Stocks

H, J

6

J

Order Stock from Manufacturer

----

13

K

Select Distributors

A

9

L

Sell Distributors

C, K

3

M

Ship Stock to Distributors

I,L

5

• *Network Diagram for New Product Introduction Project0ACB647DEHJFG241021013KLI669335M5Nodes with activity

• *Network DiagrammingA network is developed that takes account of the precedence relationships among the activities; it must be based on a complete, verified, and approved activity list.The important information required for these network diagrams is generated by the following three questions:

• * Which activities must be completed before each activity can be started. Which activities can be carried out in parallel. Which activities immediately succeed other activities.

• *ARCS NETWORK DIAGRAM FOR THE NEW PRODUCT INTRODUCTION PROJECT.012Start (0)A (6)3B (4)4C(7)8D(2)5G(2)6H(10)J(13)7I(6)K(9)L(3)10M(5)9E(4)F(10)11FINISH(0)Priority Activity

• *FLOW OF CALCULATION FOR EARLY START, ES, AND EARLY FINISH, EF, TIMES.012Start (0)A (6)3B (4)4C(7)8D(2)5G(2)6H(10)J(13)7I(6)K(9)L(3)10M(5)9E(4)F(10)11FINISH(0)00201221301913608612822121061710156201725202525EARLY0;00;0EARLYPriority Activities

• *FLOW OF CALCULATION FOR LATE START, LS, AND LATE FINISH, LF, TIMES.012Start (0)A (6)3B (4)4C(7)8D(2)5G(2)6H(10)J(13)7I(6)K(9)L(3)10M(5)9E(4)F(10)11FINISH(0)0;00;02;40;20;00;0LATEEARLYStartFinishEARLYLATE12;142;413;140;16;60;010;106;614;1410;108;116;912;158;1115;176;8 22;2512;1525;2525;2520;2017;1725;2520;2019;2013;14

• *PROJECT GRAPH OF ACTIVITIES ON NODESA,6B,4C,7L,3M,5K,9D,2E,4F,10J,13G,2H,10I,6Finish,0A,6Critical PathActivity CodeTime, Weeks

• *123475689A 4B 7C 7D 6E 5F 10G 6H 0I 10J 20K 7PERT NETWORK WITH ACTIVITY TIMEContinue from slide # 38

• *PERT data(1)Activity(2) Immediate precedence requirement(3) Events Begins End (4) Optimistic time (5) Realistic time (6) Pessimistic time (7) Expected time (8) Start ES LS (9) FinishEF LF (10) Total slack A B C D E F G H I...