[SAG] Concepts (5) - A Process for Creating and Maintaining ReliableSchedules

Capture all activities

Using the work breakdown structure as a basis, all activities are captured in the schedule, including all work necessary by the owner and contractors. The schedule should reflect all effort necessary to accomplish the deliverables described in the WBS. Depending on how much is known, some sets of activities will be scheduled in detail and others will be planned in long-duration planning packages.

▶ WBS를 기준으로 누락되는 Scope이 없도록 Activity를 작성

Create logically sequenced activity network

Activities are listed in the order they are to be performed and are joined with logic to create predecessors and successors. Logic relationships are not made overly complex and date constraints and lags are minimized.

▶ Activity의 선후행 관계를 고려하여 Logic을 작성. Logic는 너무 복잡하지 않게 하고, Constraint 및 Lag의 사용은 최소화

Estimate work and durations and assign resources

In accordance with rolling wave planning, estimates of work, duration, and effort are created for activities and resources are assigned. Budgets for direct labor, travel, equipment, material, and the like are assigned to both detail activities and planning packages so that total costs to complete the program are identified.

▶ Resource Loading. EPC 프로젝트 경험 상 제일 어려운 일 이다. 수많은 Activity에 관련 된 수많은 Resource를 정의하고 계량하여 입력하는 게 보통일이 아니다. 이 책에는 원론적인 이야기가 적혀 있으니, 실제 현장에서는 적용이 매우 어려워, Manhour, Weight Value, Quantity 정도는 입력하고 있으나, 이 정도 정보가 resource loading의 본래 목적을 충족할 수는 없을 거 같다. 이 문제는 향후에도 스케줄러로서 업무를 수행하는 게 계속되는 숙제 일 거 같다.

Validate critical path and reasonable total float

The critical and longest paths are identified and validated by the schedulers, management, and subject matter experts. Estimates of total float are examined for reasonableness and extreme values of float are confirmed after validating the network logic. Date constraints causing negative total float are examined and justified.

The initial plan or updated schedule may need to be optimized. Strategies for recovery and acceleration can be used to allocate resources more efficiently and to meet time or cost constraints. Recovery options are created for significant forecasted delays

 

Analyze schedule risk

Data about program schedule risks are incorporated into a statistical simulation to predict the level of confidence in meeting a program’s completion date; determine the contingency, or reserve of time, needed for a level of confidence; and identify high-priority risks and their mitigation plans.

A schedule risk analysis is performed on the schedule before a baseline is set and periodically as the schedule is updated to reflect actual progress on activity durations and sequences.

▶ Baseline 작성을 완료하기 전에 Risk Analysis가 필요한 것으로 이 책에선 설명하고 있다. 맞는 말인 것은 사실이나, 실제 수행 한 적은 거의 없었던 것 같다. 프로젝트 착수 후 2~3개월 내에 Schedule 제출을 해야하는데, Risk Analysis를 위한 Workshop을 실시하고 Risk Register를 작성하고, 관련 된 Activity를 Define 하고, 영향 및 Mitigation Plan을 수립하는 게 현실 적으로 어려웠다. 하지만 보다 Develop 된 스케줄 작성을 위해선 필요한 과정으로 생각 되어 향후 개선 방법을 모색해봐야겠다.

Verify and validate traceability

The schedule’s traceability, horizontally and vertically, is verified. Horizontal traceability ensures that products and outcomes are linked to associated activities. Vertical traceability ensures that data are consistent between different levels of the schedule.

▶ Horizontally : 프로젝트 시작부터 끝이 잘 연결되어야 함.

Vertically : WBS에 맞게 Activity들 Define 되어 있어, Summary와 Detail에 일관성이 있어야 함. 즉 WBS에 엉뚱한 Activity가 포함되어 있어, Summary schedule에 왜곡 된 결과가 나오지 않도록 해야 함.

Set and document baseline

The baseline schedule is designated the target schedule and is subjected to configuration management control. A corresponding basis document explains the overall approach to the program and documents and justifies features of the schedule

▶ EPC Schedule의 경우 2~3개월내 제출 및 승인을 득하여야 하며, Baseline Schedule setup 후 Progress Report 등이 정상적으로 이뤄질 수 있어, 프로젝트 초기 매우 중요한 Milestone 이다.

Update, revise, and manage change

Progress updates and logic provide a realistic forecast of start and completion dates for activities. The true status of the program is reflected through the integrity of the schedule logic. Performance is measured, monitored, and reported against the baseline schedule. The schedule is monitored to reveal when forecasted completion dates differ from baseline dates and whether schedule variances will affect downstream work.

Trend analysis provides insight into program performance. Strategies for recovery and acceleration can be used to allocate resources more efficiently and to meet time or cost constraints. Recovery options are created for significant forecasted delays.

▶ EPC Project에서는 보통 Monthly 단위로 업데이트가 이뤄지며, 그 결과를 발주처에 제출한다. Project  기간에 영향을 줄 수 있는 Event가 발생할 경우, Change Order를 통해 공기 영향에 대해 보고 및 승인이 이뤄지면 Baseline Schedule Revision을 추진하게 되며, 그 외의 경우에 Baseline Schedule이 변경되는 경우는 거의 없다.