Chapter 6 Scheduling CPM PERT Classes.pdf

Scheduling
Project Management-CPM/PERT
1

Project
 A project is composed of Jobs, Activities, Functions
or Tasks that are related to one to the other in some
manner, and all of these should be completed in order
to complete the project.
Main Objectives of a Project
 The project should be completed with a minimum of
elapsed time.
 It should use available manpower and other resources
as carefully as possible, without delay.
 It should be completed with a minimum of capital
investment, without delay. 2

3
Characteristic of a project
 An unique, one-time operational activity or
effort.
 Requires the completion of a large number of
interrelated activities.
 Established to achieve specific objective.
 Resources, such as time and/or money, are
limited.
 Typically has its own management structure.
 Requires leadership.

Examples
 constructing houses, factories, shopping malls,
athletic stadiums or arenas.
 developing military weapons systems, aircrafts,
new ships.
 launching satellite systems.
 constructing oil pipelines.
 developing and implementing new computer
systems.
 planning concert, football games, or basketball
tournaments.
 introducing new products into market.
4

What is project management?
 The application of a collection of tools and
techniques to direct the use of diverse resources
towards the accomplishment of a unique,
complex, one time task within time, cost and
quality constraints.
 Its origins lie in World War II, when the military
authorities used the techniques of operational
research to plan the optimum use of resources.
 One of these techniques was the use of
networks to represent a system of related
activities. 5

 Project Planning
 Project Scheduling
 Project Controlling
Project Management Process
6

Work breakdown structure
 A method of breaking down a project into individual
elements ( components, subcomponents, activities and
tasks) in a hierarchical structure which can be scheduled
and given 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 durations.
 It can be used to identity the tasks in the CPM (Critical
Path Method) and PERT (Project Evaluation and
Review Technique).
7

Project Planning
 Resource Availability and/or Limits
 Due date, late penalties, early completion
incentives.
 Budget
 Activity Information
 Identify all required activities.
 Estimate the resources required (time) to
complete each activity.
 Immediate predecessor(s) to each activity needed
to create interrelationships.
8

Project Scheduling and Control Techniques
 Gantt Chart
 Critical Path Method (CPM)
 Program Evaluation and Review Technique
(PERT)
9

Project Network
 Network analysis is the general name given to certain specific
techniques which can be used for the planning, management and
control of projects.
 Use of nodes and arrows
 Arrows  An arrow leads from tail to head directionally.
 Indicates ACTIVITY, a time consuming effort that is
required to perform a part of the work.
 Nodes  A node is represented by a circle.
 Indicates EVENT, a point in time where one or more
activities start and/or finish.
10

11
 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.

 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
using nodes and arrows.
Project Network
Eve
nt
Eve
nt
Eve
nt
Eve
nt
Eve
nt
Activity
Fig: Network Diagram

Event
The commencement or completion of an activity is called as an
EVENT.
Representation of Events
Circular Square Rectangular Oval
Specifying the Events
Tail Event : Marks the beginning of an activity.
Head Event: Marks the ending of an activity.
Dual Role Event : Head event to some activity and tail event to other.
activity.
10
Activity Activity
10
Activity
10
Activity
Tail Event Head Event Dual Role Event
13

Example
1
4
2
3 5
A
E
D
B
C F
Event 1: Tail Event for Activities A and B
Event 2: Head Event for Activity A, Tail Event for Activity D
Event 3: Head Event for Activity B, Tail Event for Activities
C and E
Event 4: Head Event for Activity C, Tail Event for Activity F
Event 5: Head Event for Activities D, E, F
14

Successor Events
The event or events that follow another event.
Immediate Successor Events
The event or events that immediately follow another event without any
intervening ones.
Predecessor Events
The event or events that occur before another event.
Immediate Predecessor Events
The event or events that immediately come before another event without any
intervening ones.
1
4
2
3 5
Example;
Events 2, 3, 4 and 5 are Successor events to 1
Events 2, 3 and 4 are Immediate successor events to
1
Events 1, 2, 3 and 4 are predecessor event to 5
Events 2, 3 and 4 are Immediate Predecessor event
to 5 15

Activity
An Activity is the actual Performance of a task.
Representation and Identification
3
2
6
5
3
2
Representation of Activity
Activity (2,3)
Activity P
Identification of Activity
[Activity (2,3)]
Install Machine
Description of Activity
16

Parallel Activity
Those activities which can be performed simultaneously and independently to each other.
Serial Activity
Those activities which are to be performed one after the other, in succession.
3
A
B
3
P Q
Excavate
Foundations
Concrete
Foundations
Parallel Activities Serial Activities
Activities A and B are parallel
activities since they can taken up
concurrently and executed
simultaneously.
Activities P and Q are serial activities.
Activity Q cannot be started, unless
activity P is completed.
Activity P is known as Preceding Activity, while
Activity Q is known as Succeeding Activity, in
relation to each other.
17

Dummy
A dummy is a type of operation in the network which neither requires any time nor any
resources, but is merely a device to identify a dependence among operations.
1 2 3
4 5 6
Set 1
Set 2
Set 1: A. A wait for delivery of new machine.
B. Installing new machine.
A B
C D
Set 2: C. Removing Existing machine.
B. Disposal of existing machine.
Activities A and B of set 1 and C and D of Set 2 are to be performed
serially.
Both the sets are performed simultaneously.
However, from practical considerations, activity D of set 2 cannot be
performed unless activity A of set 1 is completed.
Hence a dummy link is used, joining node 2 to node 5, indicating that
activity D cannot be started unless event 2 is over.
18

Network Diagram
Activity-On-Node (AON)
Nodes represent activities, and arrows show
precedence relationships.
19
AOA Project Network for House
3
2 0
1
3
1 1
1
1 2 4 6 7
3
5
Lay
foundation
Design house
and obtain
financing
Order and
receive
materials
Dummy
Finish
work
Select
carpet
Select
paint
Build
house

AON Project Network for House
1
3
2
2
4
3
3
1 5
1
6
1
7
1
Start
Design house and
obtain financing
Order and receive
materials
Select paint
Select carpet
Lay foundations Build house
Finish work
20
Activity-On-Arrow (AOA)
Arrows represent activities and nodes are events for
points in time.

Situations in Network Diagram
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 C must finish before either of B 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.
21

Example
Draw the network for a project having four activities labeled A, B, C and D, and
related as below:
1) Activity A and Activity B can be done concurrently
2) Activity A is the immediate predecessor of activity C, and so is the
relation between B and D
3) Accomplishment of C and D marks the completion of the project.
1
3
2
4
A
B D
C
22

CPM Calculation
Path
 A connected sequence of activities leading
from the starting event to the ending event.
Critical Path
 The longest path (time); determines the
project duration.
Critical Activities
 All of the activities that make up the
critical path.

Forward Pass
 Earliest Start Time (ES)
 earliest time an activity can start.
 ES = maximum EF of immediate predecessors.
 Earliest finish time (EF)
 earliest time an activity can finish.
 earliest start time plus activity time.
 EF= ES + Time
Latest Start Time (LS)
Latest time an activity can start without delaying critical path
time.
LS= LF - Time
Latest finish time (LF)
Latest time an activity can be completed without delaying
critical path time.
LS = Minimum LS of immediate predecessors
Backward Pass
24

CPM analysis
 Draw the CPM network.
 Analyze the paths through the network.
 Determine the float for each activity.
 Compute the activity’s float.
 Float = LS - ES = LF - EF
 Float is the maximum amount of time that this activity
can be delayed in its completion before it becomes a
critical activity, i.e., delays completion of the project.
 Find the critical path is that the sequence of activities and
events where there is no “slack” i.e.. Zero slack
 Longest path through a network.
 Find the project duration is minimum project completion
time.
25

CPM Example:
CPM Network
a, 6
f, 15
b, 8
c, 5
e, 9
d, 13
g, 17 h, 9
i, 6
j, 12
26

Activity Time Immediate
predecessor
Earlier Start
(ES)
Earlier
Finish
(EF)
Latest
Start
(LS)
Latest
finish
(LF)
Float ( LS-
ES = LF-EF)
a 6 0 6 3 9 3
B 8 0 8 0 8 0
C 5 0 5 7 12 7
D 13 b 8 21 8 21 0
E 9 c 5 14 12 21 7
F 15 a 6 21 9 24 3
G 17 a 6 23 10 27 4
H 9 f 21 30 24 33 3
I 6 g 23 29 27 33 4
J 12 d,e 21 33 21 33 0 27
a, 6
f, 15
b, 8
c, 5
e, 9
d, 13
g, 17 h, 9
i, 6
j, 12
EF= ES +
Time
LS= LF -
Time

Critical Path
a, 6
f, 15
b, 8
c, 5
e, 9
d, 13
g, 17 h, 9
i, 6
j, 12
28

29
Example Activity Immediate
Predecessors
Duration
a --- 2
b --- 5
c --- 4
d b 5
e a 7
f a 3
g b 3
h c , d 6
i c , d 2
j e 5
k f , g , h 4
l f , g , h 3
m i 12
n j , k 8
29

Example
• The network for a certain project is shown in the figure
below along with the estimated time of completion of each
activity marked. Compute the activity times and float for
each activity. Locate the critical path on the network.
1
2
3
A
D 8 9 10
4 7
5
6
B C
E
F
G
H
I
J
K
L
M
36
4 2
2
10
15
4
9
9
9
8
20 20
30

Critical Path
1
2
3
A
D 8 9 10
4 7
5
6
B C
E
F
G
H
I
J
K
L
M
36
4 2
2
10
15
4
9
9
9
8
20 20
31

Example
Activity Immediate
Predecessors
Duration
a --- 5
b --- 4
c a 3
d a 4
e a 6
f b,c 4
g d 5
h d,e 6
i f 6
j g,h 4 32

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