[SAG] Concepts (3) - The Critical Path Method

The critical path method is used to derive the critical activities—that is, activities that cannot be delayed without delaying the end date of the program. The amount of time an activity can slip before the program’s end date is affected is known as “total float.”

 

Critical activities have the least amount of float and, therefore, any delay in them gener­ally causes the same amount of delay in the program’s end date. Activities with total float within a narrow range of the critical path total float are called “near-critical” activities, because they can quickly become critical if their small amount of total float is used up in a delay. Management must closely monitor critical and near-critical activities by using sound schedule practices.

▶ Critical Activity : 보통 "Total Float"가 0 activity로, Critical Activity의 지연은 곧 전체 Project (여기선 Program)의 지연으로 이어진다. 따라서 해당 Activity는 Project를 진행하는 동안 주의깊은 모니터링이 필요하다.

 

Unless the IMS represents the entire scope of effort and the effort is correctly sequenced through network logic, the scheduling software will report an incorrect or invalid critical path. That is, the critical path will not represent the activities affecting the program fin­ish date. With no accurate critical path, management cannot focus on the activities that will be detrimental to the program’s key milestones and finish date if they slip

▶ 불필요한 Critical Path가 생기는 것을 방지하려면 어떻게 해야할까? 

- network logic이 적절히 연결되어야 하며, 불필요한 Logic이 생기지 않도록 Logic을 연결할 때는 주의가 필요하다. Simple is best. Activity 당 연결되는 선후행 Logic은 최소 1개 이상이며, 1개씩만 연결하는 것이 베스트이나, 복잡한 EPC 프로젝트에 이는 거의 불가능하다. Activity를 상세히 작성할 수록 연결되는 Logic의 수를 줄일 수가 있는데, 이렇게 할 경우, EPC Projec에서 Activity개수가 2~3만개를 넘는 게 다반사이다. 어느 게 정답인지는 여전히 숙제로 남아 있다.