Understand how scheduling tools works-Draw network diagram yourself

Understand how scheduling tools works-Draw network diagram yourself

All PlanningPlanning and scheduling procedures. Read more ... » Engineers, and most of projectWhat to do when your project slips. Read more ... » managers can create a Gantt ChartExcel Gantt chart by excel: Step by Step Guide Tutorial. Read more ... » (Bar Chartwhat is the time schedule and what is the types of the schedules. Read more ... ») using different schedulingPlanning and scheduling procedures. Read more ... » tools such as PrimaveraWhat are activity duration types and their use in Primavera P6.. Read more ... » and Microsoft ProjectDifferences Between Primavera P6 and MS Project in planning. Read more ... ». However, only few of them really know how the scheduling software is calculating the network diagram in order to estimateMethods to estimate task and activity duration. Read more ... » the project durationMethods to estimate task and activity duration. Read more ... », project floats, and critical path.


In this topic we will discuss how any software is calculating the network diagram in order to estimate project duration, float, and the critical path. Using the following figure of network diagram we will see how is the calculation works.

network diagram


Each circle represent a taskMethods to estimate task and activity duration. Read more ... », each line between tasksWhat to do when your project slips. Read more ... » represent the relationshipClaim Digger Baseline Schedule V.S Revised Schedule Comparison Tool. Read more ... ». For example Task S  need to be finished before task A can start, and Tasks B and C should be finished before task F can start and so on.

First of all, you need to draw a rectangular for each task as per the following figure.

TaskES = Early start

EF= Early finishHow primavera calculates dates of those activities whose predecessor has the actual start or actual finish.. Read more ... »

ID = task ID

Slack= Total FloatProject Management General Definitions. Read more ... »

E= Task durationMethods to estimate task and activity duration. Read more ... »

LS= Late start

LF= Late finish


If we assumed the duration (E) for each activityWhat are activity duration types and their use in Primavera P6.. Read more ... » as per the following:

Task Task Duration E
A 7
B 11
C 12
D 9
E 2
F 10
G 3
H 2
I 6
J 8

In order to calculate the values is each rectangular (task), you should first fill the duration (E), calculate Early Start (ES) and Early Finish (EF). This process is called Forward Calculation EF = (ES + D) – 1

After you Finish all the tasks, from the last one you need to go back and calculate the Late Finish (LF), Late Start (LS), and the Total Float (Slack). This process is called Backward Calculation LS = (LF – D) + 1

You should have a shape something like the following figure

network diagram

The Green color represent the Forward Calculation EF = (ES + D) – 1, and the yellow color represent the Backward Calculation LS = (LF – D) + 1


Try to solve this network diagram by yourself, this will help you to develop a common sense when you are dealing with scheduling software such as Primavera or Microsoft Project. when you finish you will be able to find the project total duration, which will be founded on task J Early Finish or Late Finish, and you will be able to define the critical Path.

Assuming that the project duration is 30, and the critical path is ACGHI, useWhat are activity duration types and their use in Primavera P6.. Read more ... » both of them as a password 30ACGHI to open the following link and add your name to honor board :)

Add your name to the honor board from the following link: http://www.planningengineer.net/network-diagram-honor-board/


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