Project Management in the Oil and Gas Industry

3.5.6 Example
The following example will illustrate the relationships between activities 
and how can you create them through the precedence diagram.
The example in the following table shows the activities for a cast con-
crete foundation under machine package and connects the machine with 
piping to the facilities, which is a simple example of knowing how to 
arrange activities, account for the overall time of the project, and identify 
the critical path.

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Pitfalls in Time Schedule Planning 99
In the above table, the first column contains the item number or the 
code for that item according to the project and its activities and the sub 
activities. Also, the main activity code may be 100 and the sub activity may 
be 110 and so on, but the above example is a simple case.
The second column is the name of the activity, which describes the 
activity, and the third column is the time period for each activity in days.
The fourth column specifies the relationships between activities. As 
for activity No. 200, which is the excavation, it is constrained by activity 
No. 1. Activity No. 6, which is setting the wooden form, is related to two 
activities, No. 300 and 500, meaning that the setting of the wooden form 
depends on finishing the preparation of the wooden form (item No. 300) 
and pouring the plain concrete (item No. 500).
Figure 3.7 shows the precedence diagram and in each diagram there is a 
number with its time duration. Figure 3.8 shows the early start and finish 
for each activity by using the following equation:
EF = ES + D,
where EF is early finish, ES is early start, and D is duration.
Start with activity number 100. The early finish (EF) of this activity is 
three days. Transfer this value to activities 200 and 400 in the early start 
(ES) rectangle zone.
Item number 800 depends on 600 and 700, so it will take the higher 
value in the early finish (EF), which is 23 days. Put this number as the early 
start (ES) for activity 800.
For the last activity, which has an early finish at 25 days, transfer this 
value to the latest finish (LF) rectangular zone.