Project Management - Network Analysis - Critical Path Method

PROJECT MANAGEMENT 

Network Analysis

Critical Path Method

 

Part A: Discussion about -

(1) Definition of Critical Path,

(2) Determination of Critical Path, and

(3) Determination of Normal Project Duration.

Part B: YouTube link for the video on above discussion including solution of one illustration.

Part A

Definition of Critical Path

Critical path is the longest path of activities to be performed from start to finish of a project which can be located and depicted in the Network Diagram drawn before the construction of the project is started.

 

All the activities on the critical path are called “CRITICAL ACTIVITIES”, whereas other activities of the project are called “NON-CRITICAL ACTIVITIES”.

 

Determination of Critical Path

Step: 1 – Draw the Network with ES and LF

Draw the network diagram as above.

Fill up the nodes as stated. Earliest Starts (ES) will be found by Forward Pass Calculations and Latest Finishes (LF) will be found by Backward Pass Calculations. Forward Pass Calculations will start at the first event of the network and will finish at the last event of the network. Backward Pass Calculations will start at the last event of the network and will finish at the first event of the network.

During Forward Pass, start at the first event with ‘0’ earliest start and keep on adding the activity durations for the earliest starts of the rest of the events. During Backward Pass, start at the last event with the earliest start of the event as the latest finish of the event and keep on subtracting the activity durations for the latest finishes of the rest of the events.

 

During forward pass, take the highest earliest start time for a ‘merge event’ and during backward pass, take the lowest latest finish time for a ‘burst event’.

 

Step: 2 – Find the Critical Path

Following rules apply in locating the critical path of a network:

Rule 1: Necessary Condition

If, for an activity, the ES time equals the LF time at both the head of the arrow and the tail of the arrow, the activity is possibly a critical activity, lying on the critical path.

 

Rule 2: Sufficient Condition

If the first condition is met and the difference between the ES time at the head of the arrow and the ES time at the tail of the arrow is equal to the duration of the activity, then the activity is critical and lies on the critical path.

 

In the above network diagram the critical path is:

1 – 3 – 6 – 8 (Node number wise)

 

Normal project duration:

7 + 10 + 5 = 22 days (assuming that activity durations are in days)

 

 Part B

 

YouTube Link for the Video on above discussion including solution of the following illustration:

 

Please click on the following YouTube Link:

Project Management - Critical Path Method

 

Illustration:

Information on the activities required for a project is as follows:

Name of Activities	Activities by Node(ij)	Duration (days)
A	1 – 2	2
B	1 – 3	7
C	1 – 4	8
D	2 – 5	3
E	3 – 5	6
F	3 – 6	10
G	3 – 7	4
H	4 – 6	6
I	5 – 7	2
J	6 – 8	5
K	7 – 8	6

 

Draw the network diagram and determine the critical path and normal project duration.