Schedule Assessment Guide(SAG) - CONCEPTS (1)

플랜트 EPC Project에서 Schedule이 잘 만들어졌는지를 어떻게 평가할 수 있을까?

이에 대한 답을 찾는 첫 번째 과정으로 GAO(U.S Government Accountability Office)에서 2015년에 발간 한

를 공부해 보고, 내용을 정리해 보고자 한다.

[CONCEPTS] 

Ten Best Practices

The ten best practices associated with a high-quality and reliable schedule and their
concepts are as follows.

 

1. Capturing all activities 

The schedule should reflect all activities as defined in the program’s work breakdown structure (WBS), which defines in detail the work necessary to accomplish a project’s objectives, including activities both the owner and the contractors are to perform.

▶ WBS 정의에 따라 모든 Activity를 포함해야 한다. WBS는 프로젝트의 목적 달성을 필요한 과업(Work)을 상세히 정의한 것으로, 발주처(Owner)와 계약자(Contractor)가 수행해야 할 모든 Activity를 포함한다. 

2. Sequencing all activities 

The schedule should be planned so that critical program dates can be met. To do this, activities must be logically sequenced and linked—that is, listed in the order in which they are to be carried out and joined with logic. In particular, a predecessor activity must start or finish before its successor. Date constraints and lags should be minimized and justified. This helps ensure that the interdependence of activities that collectively lead to the completion of activities or milestones can be established and used to guide work and measure progress.

▶ 모든 Activity가 논리적으로 순서화 및 연결 되어야 한다. 선행 Activity는 후행 Activity보다 빨리 시작하거나 끝나야 한다. Constrains 및 Lag 의 적용은 최소화.

 

3. Assigning resources to all activities. The schedule should reflect the resources (labor, materials, travel, facilities, equipment, and the like) needed to do the work, whether they will be available when needed, and any constraints on funding or time. 

 

4. Establishing the duration of all activities. The schedule should realistically reflect how long each activity will take. When the duration of each activity is determined, the same rationale, historical data, and assumptions used for cost estimating should be used. Durations should be reasonably short and meaningful and should allow for discrete
progress measurement. Schedules that contain planning and summary planning packages as activities will normally reflect longer durations until broken into work packages or specific activities.

 

5. Verifying that the schedule can be traced horizontally and vertically. 

The schedule should be horizontally traceable, meaning that it should link products and outcomes associated with other sequenced activities. Such links are commonly referred to as “hand-offs” and serve to verify that activities are arranged in the right order for achieving aggregated products or outcomes. The schedule should also be vertically traceable—
that is, data are consistent between different levels of a schedule. When schedules are vertically traceable, lower-level schedules are clearly consistent with upper-level schedule milestones, allowing for total schedule integrity and enabling different teams to work to the same schedule expectations.

6. Confirming that the critical path is valid. 

The schedule should identify the program’s critical path—the path of longest duration through the sequence of activities.
Establishing a valid critical path is necessary for examining the effects of any activity’s slipping along this path. The program’s critical path determines the program’s earliest completion date and focuses the team’s energy and management’s attention on the activities that will lead to the project’s success.

 

7. Ensuring reasonable total float. 

The schedule should identify reasonable total float (or slack)—the amount of time a predecessor activity can slip before the delay affects the program’s estimated finish date—so that the schedule’s flexibility can be determined. The length of delay that can be accommodated without the finish date’s slipping depends on the number of date constraints within the schedule and the degree of uncertainty in the duration estimates, among other factors, but the activity’s total float provides a reasonable estimate of this value. As a general rule, activities along the critical path have the least total float. Unreasonably high total float on an activity or path indicates that schedule logic might be missing or invalid.

 

8. Conducting a schedule risk analysis. 

A schedule risk analysis starts with a good critical path method schedule. Data about program schedule risks are incorporated into a statistical simulation to predict the level of confidence in meeting a program’s completion date; to determine the contingency, or reserve of time, needed for a level of confidence; and to identify high-priority risks. Programs should include the results of the schedule risk analysis in constructing an executable baseline schedule.

 

9. Updating the schedule using actual progress and logic. 

Progress updates and logic provide a realistic forecast of start and completion dates for program activities. Maintaining the integrity of the schedule logic is necessary to reflect the true status of the program. To ensure that the schedule is properly updated, people responsible for the updating should be trained in critical path method scheduling.

 

10. Maintaining a baseline schedule. 

A baseline schedule is the basis for managing the program scope, the time period for accomplishing it, and the required resources. The baseline schedule is designated the target schedule and is subjected to a configuration management control process. Program performance is measured, monitored, and reported against the baseline schedule. The schedule should be continually monitored so as to reveal when forecasted completion dates differ from baseline dates and whether schedule variances affect downstream work. A corresponding basis document explains the overall approach to the program, defines custom fields in the schedule file, details ground rules and assumptions used in developing the schedule, and justifies constraints, lags, long activity durations, and any other unique features of the schedule.