Turnaround Project Planning Primer
Interpreting a Gantt Chart
One of the most important aspects of managing a turnaround is the interpretation of the CPM schedule information.
A Gantt chart (Bar Chart) is the preferred mode of presenting the CPM schedule information. Graphs and charts convey information in a concise and easy to understand manner.
When studying a Gantt chart, the first thing to consider is whether it has been correctly updated, and what time scale / time line is being reported.
The most obvious item to study next is the critical path. It is usually highlighted in red, and shows no float or slack. Every activity on the critical path should be re-examined, in particular those which are in progress or soon to be started. Often it becomes necessary to re-estimate the duration and manpower requirements of activities on the critical path, as new information becomes available from inspection, etc.
If all activities are properly sequenced, and their estimates are as realistic as they can be made under the circumstances, then the end date should also be realistic.
Of particular importance is to examine what other activities are being scheduled concurrently during the same shifts or time periods, to detect any interferences with the work on the critical path. These interferences could be too many workers in the same workspace (inside a vessel, for example), sandblasting or x-ray activity which could cause workers to be forced to leave the area, safety considerations, competition for the use of lifting equipment, etc.
The Gantt chart is, above all, a tool to be used for thinking, discovering new and better ways to carry out the work, and for communicating the overall strategy to all involved. As changes are made, they should be posted on the bar chart, for all to see - in particular the planner, so he can incorporate the changes in his next schedule update.
The original Gantt chart is often posted and kept for referencing the initial baseline, but every updated Gantt chart should be posted in a visible place so everyone can become informed of the new priorities and deadlines.