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Procudure To Find The Earliest and Latest Expected Time Of An Event - Earliest And Latest Times

Posted On :  24.06.2018 12:08 am

Take the Earliest Expected Time of Occurrence of the Start Event as

Procudure To Find The Earliest Expected Time Of An Event

Step 1

Take the Earliest Expected Time of Occurrence of the Start Event as zero.

Step 2

For an event other than the Start Event, find out all paths in the network which connect the Start node with the node representing the event under consideration.

Step 3

In the “Forward Pass” (i.e., movement in the network from left to right), find out the sum of the time durations of the activities in each path identified in Step 2.

Step 4.

The path with the longest time in Step 3 gives the Earliest Expected Time of Occurrence of the event

Working Rule for finding the earliest expected time of an event:

For an event under consideration, locate all the predecessor events and identify their earliest expected times. With the earliest expected time of each event, add the time duration of the activity connecting that event to the event under consideration. The maximum among all these values gives the Earliest Expected Time of Occurrence of the event.

Procudure To Find The Latest Allowable Time Of An Event

We consider the “Backward Pass” (i.e., movement in the network from right to left).

The latest allowable time of occurrence of the End Node must be the time of completion of the project. Therefore it shall be equal to the time of the critical path of the project.

Step 1

Identify the latest allowable time of occurrence of the End Node.

Step 2

For an event other than the End Event, find out all paths in the network which connect the End node with the node representing the event under consideration.

Step 3

In the “Backward Pass” (i.e., movement in the network from right to left), subtract the time durations of the activities along each such path.

Step 4

The Latest Allowable Time of Occurrence of the event is determined by the path with the longest time in Step 3. In other words, the smallest value of time obtained in Step 3 gives the Latest Allowable Time of Occurrence of the event.

Working Rule for finding the latest allowable time of an event:

For an event under consideration, locate all the successor events and identify their latest allowable times. From the latest allowable time of each successor event, subtract the time duration of the activity that begins with the event under consideration. The minimum among all these values gives the Latest Allowable Time of Occurrence of the event.
Tags : Operations Management - Network Problems
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