Duration type in Primavera P6- A Comprehensive Guide.

In Primavera P6, the Duration Type is a key concept used to define how activity durations, resource assignments, and work quantities are calculated and updated when changes occur in the schedule. It determines how Primavera P6 handles changes in resources, durations, or units (work) for an activity, allowing project managers to control what remains constant and what adjusts when changes happen.

Choosing the right Duration Type is essential for effective resource management and maintaining a realistic project schedule, as it governs how Primavera P6 balances the relationship between an activity’s Duration, Units (work), and Units/Time (resource productivity).

Primavera P6 provides four different Duration Types:

Fixed Duration & Units
Fixed Duration & Units/Time
Fixed Units
Fixed Units/Time

Each Duration Type affects how changes in one component (e.g., duration, units, or productivity) influence the others. Let’s explore these types in detail:

1. Fixed Duration & Units

Fixed Duration & Units means that both the activity’s Duration and Total Units (work) remain constant when resource assignments change. This duration type is useful when the time frame for completing an activity and the total amount of work required are fixed, and you do not want either to change even if the number of resources working on the task fluctuates.

Key Features:

Duration remains fixed even when resources are added or removed.
Total Units (work) also remain fixed.
Units/Time (productivity rate) is recalculated based on changes to resource assignments.

Use Cases:

This type is typically used when you want to ensure that an activity will be completed within a set timeframe and with a predetermined amount of work, regardless of changes to resource productivity.

Example:

If a painting job is planned to take 10 days and requires 100 hours of labor, those values will remain constant even if additional painters are assigned. The productivity per painter would adjust accordingly.

2. Fixed Duration & Units/Time

In Fixed Duration & Units/Time, the activity’s Duration remains constant, and the Units/Time (resource productivity rate) remains unchanged. However, the Total Units (work) will vary when resource assignments change. This type is useful when the productivity rate (work per time unit) is fixed and the activity duration cannot be altered, but the total work can increase or decrease depending on how many resources are assigned.

Key Features:

Duration remains fixed regardless of changes to resources.
Units/Time (productivity) also remains fixed.
Total Units will adjust based on the number of assigned resources.

Use Cases:

This type is useful for tasks where the duration and productivity rate cannot change but the amount of total work required might vary depending on resource availability. It’s often applied in time-bound tasks where the rate of work needs to be stable, such as regular maintenance activities.

Example:

If you have a task like daily inspections that must be completed within a week, and the productivity rate is fixed at 5 inspections per day, the total work will increase if more inspectors are assigned to complete the job.

3. Fixed Units

Fixed Units means that the Total Units (work) remain constant even when the activity duration or resource productivity changes. This type is ideal when the total work (resource hours) is the most critical aspect, and you want to control that, while allowing the activity duration to adjust based on resource availability or productivity.

Key Features:

Total Units (work) remains fixed.
Duration and Units/Time will change based on resource assignments.
Adding more resources will decrease the activity’s duration.

Use Cases:

This duration type is best for tasks where the total amount of work is fixed, such as a construction activity requiring a specific number of labor hours, and the duration can adjust based on how many workers are assigned to the task.

Example:

If digging a foundation requires 200 labor hours, and you initially assign 5 workers, the task will take 40 hours. If you later assign 10 workers, the duration will drop to 20 hours, but the total work remains at 200 hours.

4. Fixed Units/Time

In Fixed Units/Time, the Units/Time (resource productivity rate) remains fixed, while the Total Units and Duration vary depending on resource assignments. This type is useful when you need to maintain a consistent work rate (e.g., specific hours of work per day), but both the activity’s duration and the total amount of work can change based on the number of resources assigned.

Key Features:

Units/Time remains constant.
Total Units and Duration adjust based on the number of resources assigned.
If more resources are added, the duration decreases, but the productivity rate per resource remains the same.

Use Cases:

This type is often used when managing teams where each resource works at a fixed productivity rate, and you want to maintain that rate across the project, even if the duration or total work may change. It’s common in projects where each worker performs at a fixed pace, such as repetitive tasks in a manufacturing process.

Example:

If a task involves loading 50 pallets per day, assigning more workers won’t change the productivity rate per worker (loading 5 pallets per day), but it will reduce the total duration needed to complete the task.

How to Choose the Right Duration Type?

Choosing the correct Duration Type depends on the nature of the work and the priorities of the project. Here’s a quick guide to help you decide:

Fixed Duration & Units: Choose this when both the duration and the total work are fixed, and you want the resource productivity rate to adjust with changes in resource assignments.
Fixed Duration & Units/Time: Select this when the duration and productivity rate must remain constant, but the total amount of work can vary based on resource changes.
Fixed Units: Use this when the total amount of work is fixed, and you want the duration and productivity rate to adjust depending on the resources.
Fixed Units/Time: Opt for this when you need to keep the productivity rate fixed, and you’re okay with the duration and total work fluctuating as resources are added or removed.

Conclusion

Duration Types in Primavera P6 provide a crucial mechanism for controlling how activities are scheduled and resourced, offering flexibility to project managers when planning, adjusting, and optimizing schedules. By mastering the use of Fixed Duration & Units, Fixed Duration & Units/Time, Fixed Units, and Fixed Units/Time, you can ensure that your project schedules remain realistic, accurate, and adaptable to changes in resource availability and project constraints.

Understanding and applying the correct Duration Type can help keep projects on track, improve resource management, and provide better control over schedule variations.