Resource Leveling Vs. Critical Mass
Industrial plant maintenance shutdowns / turnarounds are very demanding from a project management standpoint. They offer significant differences from civil/construction projects (see our Turnarounds vs. Projects white paper). One difficulty project managers face with managing turnarounds is balancing resource management and schedule management in the face of a constantly changing scope.
At inception, the scope of a turnaround project is only partially known. The scope usually grows as vessels are opened, inspections are performed and repair work is identified, planned and scheduled. Field supervisors require flexibility in directing crews to work assignments as obstacles to working the schedule are normal and expected (equipment breakdown, missing/misplaced tools/materials, vessel conditions worse [or better] than expected, weather, etc.).
Resource Leveling is Counter Productive
Resource leveling algorithms employed by many critical path and critical chain scheduling tools level the schedule. They effectively add invisible soft logic links to force schedules into sequencing resources according to a fixed availability. Some resource leveling algorithms even adjust the duration/crew loading ratio to fit tasks. This may work when schedules are fairly static in nature or are executed in a less compressed timeframe (where the reporting cycle allows the project team to adjust to changes easily).
But when the scope in a schedule has great fluctuations, resource leveling may lead to schedules that vary greatly from one update to the next. In a turnaround, this destroys confidence in the schedule and leads to abandonment from the front line in the field. In addition, field supervision rarely have the time to study shift schedules every shift to identify changes to the crew loadings on tasks. They are apt to assign crews to the work as originally planned, so changes to the crew loadings by resource leveling algorithms are not likely to match field execution.
Furthermore, within the context of a turnaround project, time is usually the most critical goal. Managers need to maintain focus on jobs that are critical and near critical based upon hard logic (required dependencies). Non-critical jobs that require critical resources can always be cut from the scope and tabled for a future opportunity. Sometimes more resources can be requisitioned to address them as well. Resource leveling obscures the critical and near critical jobs by scheduling non-critical work as critical when resources are constrained.
Critical Mass - A Practical Approach
Leveling the schedule is not the only approach (or even the optimal approach) to managing resource criticality for turnarounds. Instead of leveling the schedule, ATC Professional tracks, measures and analyzes Critical Mass to ensure that non-critical jobs do not become resource critical. Critical Mass analysis forecasts potential problems in resource criticality based upon progress trends for every resource. Managers are alerted to potential problem areas long before they pose a danger of impacting the critical path. This allows suffient time to make decisions necessary to effect the best possible outcome within the existing circumstances.
By leveling resource requirements only during reporting, the schedule retains only the sequencing logic applied by the planner (that have been reviewed and approved by the field supervision) and does not fluctuate wildly as the scope changes from update to update. This instills confidence in the schedule and encourages cooperation and buy-in from the field. Field supervision retains flexibility in their ability to manage their labor pool in the face of multiple issues that may prevent schedule compliance (equipment breakdowns, tool and material availability, etc.).
The Critical Mass approach to managing resources offers many advantages over resource leveled schedules for turnarounds:
- It allows management to focus on the true critical and near critical jobs
- It allows greater flexibility in managing resources, the scope and schedule
- It instills greater confidence in the schedule
- It encourages better cooperation and adoption of the schedule
InterPlan Systems has developed the Critical Mass approach for turnaround management in the ATC Professional Shutdown / Turnaround Management System.
Authored by Bernard Ertl, Vice President, InterPlan Systems
Bernard Ertl has a bachelor’s degree in Computer Science and extensive field experience planning and managing turnarounds in the oil refining and petrochemical process industries.