It is not uncommon that you have two, or more, different projects that you want to connect together using external dependencies in P6. In certain scenarios you may find yourself with a project that is affected by another external project. You most likely want to link the projects together to model the inter-dependency between these projects. But is it possible to link separate projects together with an external dependency or cross-project link? In Primavera P6 Professional the answer is yes, it is feasible.
External Dependencies in P6
This article demonstrates a quick tip to model the inter-dependency between two projects by linking them together using a external dependencies in P6.
In our particular situation we have two contractors each providing a separate schedule for the installation of underground piping. But these two separate projects are interdependent, one project affects the other. The first contractor project provides for the trench excavation and installation of piping. The second contractor project schedules the back-fill and asphalt paving of roadway. The end of the first trench excavation & pipe installation project signals the beginning of the second back-fill & paving project.
We want each contractor to maintain their schedule, accordingly. And we want to model the inter-dependency between these projects with a cross-project link.
We proceed and open the first trench excavation and pipe installation project, Figure 1.
But we need both interdependent projects open to make the cross-project link. So we highlight both projects, right click, and select open project, Figure 2.
This opens both projects. Observe, Figure 3, that both projects are scheduled to commence on the data date (DD), which is not going to work.
The backfill & paving project must succeed the trench excavation & pipe installation project.
We continue and insert a cross-project link. In Figure 4, we highlight the End Pipe Installation activity and in the bottom details relationships tab and successors frame we click assign.
Then in the assign successors dialog we highlight the start backfill activity and click assign, Figure 5.
To view the effect of this cross-project link we click schedule (F9), Figure 6, to recalculate the schedule.
The resulting master schedule (two open schedules) displaying the cross-project link effect is displayed in Figure 7.
Note that start backfill commences after end pipe installation.
Let’s view the grand total impact of both projects together. In Figure 8 we select the group sort by feature.
Then in the group and sort by dialog we toggle on show grand totals, Figure 9.
Figure 10 then displays both open projects, and the grand total of both projects at the top.
The trench excavation & pipe installation project concludes on 18-Jul-2018. The back-fill & asphalt paving project concludes on 26-Jul-2018. At the top of the activity table we find the grand total finish date of both open projects is in fact 26-Jul-2018, Figure 10.
To demonstrate that both projects do not have to be open for the external dependency to take effect we close the trench excavation & pipe installation project. We then recalculate the back-fill & asphalt paving project, Figure 11.
The dates hold, as per the external dependency, Figure 12.
Let’s explore what happens when we remove the backfill & asphalt paving external dependency and recalculate the schedule, Figure 13.
The dates do not hold, Figure 14.
And we are right back to where we began with two unconnected projects.
Primavera P6 Professional makes possible the insertion of external dependencies. Creating cross-project links is a simple as opening both projects and connecting the two inter-meshing activities from each project with a relationship. And the projects do not necessarily have to be in the same enterprise project structure (EPS) node.
The project ID is specified in the cross-project link, which is included as part of the link definition. Identifying schedules with external dependencies is not so apparent. Schedulers will have to display the bottom details relationships tab and inspect the project ID to confirm that the project indeed has an external dependency.