Turnaround Project Planning Primer
Planning & Scheduling
Planning and scheduling is the process of defining numerous activities or tasks, and organizing them into a logic network (usually called a "logic diagram", "arrow diagram" or "precedence diagram"). Relationships or dependencies ("restraints") are used to indicate how activities are influenced by other activities in the logic network. This graphic representation of the turnaround scope serves to organize the schedule information and to present it in such a manner as to make it visible and understood by all involved. Most project management software offer the ability to display logic relationships in the schedule.
After the logic network has been defined and reviewed by all involved, the schedule must be calculated to determine the overall duration, the critical and near-critical paths, and the general timing of the work orders to coincide with the planned shut down sequence and safety release of the plant equipment.
At this stage, and prior to the shutdown, as many changes to the logic and estimates may be made as required to optimize the schedule to fit all of the required work within the time limitations.
One way to optimize schedule logic is through the scheduling of work crews. This is accomplished by selecting a group of equipment, i.e. heat exchangers, and through the use of restraints, connect the logic in such a manner as to reflect the sequence that will be followed by one or several crews in blinding, unheading, pulling bundles, etc.
Using this method, we can determine how many crews can be used effectively. The same method should be used to schedule a crew of pipe fitters, electricians, instrument fitters, tower tray specialists, etc. This will result in the best possible schedule, in particular if the work is sequenced after a preliminary critical path analysis, so that priorities can be better determined.
To arrive at a good, workable schedule, several evaluations (computer "runs") may be required. The first calculation will identify the initial critical path and overall duration. After some sequencing and restraining, another evaluation becomes necessary to see if the overall duration has been affected by the changes. After some more modifications and "fine tuning" of the schedule logic, another evaluation ("run") must be made to verify that the overall schedule is still within the acceptable limits of time, manpower and priorities.