If you are not familiar with the process of defining relationships between tasks in Microsoft Project, then this blog may be of use to you. These examples are shown using Microsoft Project 2013, however these steps are the same in most recent versions of Microsoft Project.
Once you have defined your tasks and task durations in Microsoft Project 2013, the next process of connecting tasks with relationships is important for finding the true length of the project. This article describes how to use the various capabilities in Microsoft Project to apply relationships to your tasks, so you can compute the overall length of the project.
Before we begin defining task relationships, let’s first make certain we understand the precedence diagramming method. The precedence diagramming method is implemented to show task dependencies. In this method rectangular bars represent tasks, and arrows between bars show task dependencies. There are four types of relationships you can use to define the inner workings between tasks.
- Finish-to-Start (FS): This is the most common type of relationship where one task cannot start until another associated task has finished. A mechanical example is a pipe insulation task cannot start until the pipe installation inspection task is complete.
- Start-to-Start (SS): This is a relationship where one task cannot start until another task has begun. An example is that remove damaged piping task cannot proceed until the safety plan is commenced.
- Finish-to-Finish (FF): In this relationship one task cannot finish until another related task has finished. A possible example from the research industry is that documentation cannot complete until experimental testing described by that documentation has finished.
- Start-to-Finish (SF): In this not so common relationship one task cannot finish until another task has begun. An example is the run generator task cannot cease until the power is activated.
Lags and Leads
Lags and leads also have a significant impact on the length of the schedule. A lag describes a required time between tasks. In the FS relationship this means that the second task cannot commence until a scheduled period of time has elapsed after the completion of the first task. The most common example is concrete, in which a lag is inserted between tasks to allow the concrete time to cure before the successor task can proceed. A lead has the opposite effect on the schedule. A lead is the amount of time that a task can start before the completion of the first task. Many schedulers refer to lead as a negative lag. Note that the use of leads is discouraged by scheduling guidelines.
Repair & Improve Piping Schedule
This article describes a Repair & Improve Piping project to show how to use the various features in Microsoft project to model relationships between tasks. The list of tasks and corresponding durations for our Repair & Improve Piping project is displayed in Figure 1.
Note the milestone tasks Notice to Proceed, Project Start, and Project Complete. Also, note the summary tasks Demolition Piping, Installation Piping & Thrust Block, and Quality Assurance. These summary tasks are elements of the work breakdown structure, and will not have assigned relationships.
Assigning Start-to-Start Relationships
The first relationship we want to assign is a Start-to-Start relationship between tasks Notice to Proceed and Project Start. Highlight Project Start then select the Task tab, Properties ribbon group, and Information icon, Figure 2.
In the corresponding Task Information dialog select the Predecessors tab, Figure 3.
The predecessor of Project Start is Notice to Proceed, so in the Task Information dialog we want to set Notice to Proceed as the predecessor of Project Start. Notice to Proceed is the first task, so type in 1 for Notice to Proceed in the ID column. The Task Name should default to Notice to Proceed in the Task Name column. Select Start-to-Start (SS) from the drop down menu in the Type column, Figure 3. This relationship assignment has no lag, so leave the lag as 0d. Click OK, and the relationship assignment between Notice to Proceed and Project Start will be as displayed in Figure 4.
Now repeat this process to insert a Start-to-Start relationship between Project Start and Drain Piping System, Figure 5.
The relationship assignment between Project Start and Drain Piping System will be as shown in Figure 6.
Assigning Finish-to-Start Relationships
The process for assigning the standard Finish-to-Start relationship is less involved. Highlight Drain Piping System and Remove Damaged Piping task. Next select the Task tab, Schedule ribbon group, and link icon, Figure 7.
That’s it. Your Finish-to-Start relationship for these two tasks is applied as displayed in Figure 8.
Repeat this process to assign a Finish-to-Start relationship between Remove Damaged Piping; Install Pipe, Fittings, & Couplings; and Test Piping at Pressure, Figure 9.
Again, your tasks with the Finish-to-Start relationship will be as shown in Figure 10.
This process is repeated again to insert Finish-to-Start relationships between Test Piping System at Pressure, Set Forms, Pour Concrete, and Strike Forms, Figure 11.
The result is in Figure 12.
Assigning Concrete Cure Time Lag
Now we want to assign a lag between Pour Concrete and Strike Forms to give the concrete thrust block time to cure before we remove the forms. To insert a standard lag time type a number followed by the letter “d” in lowercase in the Lag column of the Task Information and Predecessors tab dialog. This is the input for the standard business time lag.
However, our lag is not standard. Our lag describes the cure time of concrete, which happens “round-the-clock” 24-hours a day. Microsoft Project has an elapsed time lag for modeling this type of “round-the-clock” lag. In the Lag column of the Task Information dialog for Predecessors, Figure 13, type in 5ed, which stands for five elapsed days.
Click OK, and your elapsed time lag will be as displayed in Figure 14.
Assigning a Finish-to-Finish Relationship
Now we are going to assign two tasks a Finish-to-Start relationship, and edit it to make the relationship Finish-to-Finish. Assign Strike Forms and Insulate Piping a Finish-to-Start relationship, Figure 15.
Next double click on the Gantt chart relationship arrow connecting the two tasks, and the Task Dependency dialog shall appear, Figure 16.
Simply change the type to Finish-to-Finish (FF), and the relationship will be as displayed in Figure 17.
As displayed in Figure 17, access the Task Information dialog to assign the additional Finish-to-Start relationship between Test Piping at Pressure and Insulate Piping. The Insulate Piping task and associated relationships will be as shown in Figure 18.
So the Insulate Piping task may commence after the completion of the Test Piping System at Pressure task and completes shortly after the completion of the Strike Forms task. The Finish-to-Finish (FF) relationship allowed us to begin insulation of the piping while waiting for the concrete to cure. It, thus, enabled us to compress the schedule by performing tasks in parallel, which is called fast tracking.
Round Out the Schedule
Complete the schedule by assigning a Finish-to-Start relationship between the remaining tasks, Figure 18. The project with assigned relationships will be as displayed in Figure 19.
Now select the Format tab, Bar Styles ribbon group, and Critical Tasks to display the schedule with critical path, Figure 20.
You now have the true length of the schedule, which is compressed slightly via the tasks performed in parallel.
Microsoft Project provides four types of relationships between tasks, allowing you to model tasks both in series and parallel. Parallel tasks allow you to shorten the schedule through the use of parallel task assignments. Lags allow you to model delays between tasks, and the elapsed time lag, in particular, enables you to describe such things as cure time delays.
The standard Finish-to-Start relationship is the most common relationship type and Microsoft Project provides an icon button to insert this relationship. Insertion of the other types of relationships may require invoking the Predecessor tab in the split screen view.
Of course, another approach is to create a Finish-to-Start relationship and then edit it by doubling clicking on the Gantt chart relationship arrow, which brings up the Task Dependency dialog. So there is more than one way to insert a relationship in Microsoft Project. With practice you will find the quickest and most convenient way to create relationships for you and hope that this article will assist you in doing this.