It is usually the case that as the project nears completion the project manager presses hard to make certain the project completes on schedule. It may, however, be prudent to put the brakes on to ensure the project comes to a successful end. Applying the brakes on a near completion project is exactly what the Finish No Earlier Than (FNET) constraint can facilitate.
Constraints place conditions on activities above and beyond their precedence relationships. Because constraints can interfere with the critical path, most scheduling guidelines recommend the limited use of constraints. So the preference is for task durations and network relationships to drive the schedule. Sometimes, however, you want to place a constraint on a date to define the importance of that date in the schedule.
The FNET constraint is a sibling to the Start No Earlier Than (SNET) constraint,which delays task commencement until an event has occurred. The FNET constraint in Microsoft Project 2013, being used in this blog, is flexible for the start of a task, but delays task completion to make sure, perhaps, a major event occurs before the end of that task. It may seem counter intuitive to delay task completion, but it just might be necessary to ensure adequate quality or a successful finish.
This article describes the insertion of a FNET task constraint in Microsoft Project, and when a FNET constraint is suitable for the schedule.
In Figure 1 we have a demonstration project. The main effort in this schedule is the mechanical, electrical, and plumbing (MEP) installation for a building interior.
Note that all three of these efforts begin together. Plumbing and Heating, Ventilation, and Air Conditioning (HVAC) are along the critical path, while Electrical is not. Commissioning occurs after the MEP tasks. Commissioning Mechanical is the inspection of both plumbing and HVAC systems.
When it comes to mechanical commissioning we are concerned about when permanent electrical power is energized at the finish of this task. Mechanical commissioning may proceed with plumbing inspection before permanent power, as most plumbing equipment does not require electricity. This is particularly the case if the hot water heater is gas fired.
So mechanical commissioning may commence with the inspection of plumbing. Commissioning of the HVAC system does require electrical power. We therefore do not want mechanical commissioning to end until after permanent power is energized for the site. This schedule situation may be defined using a FNET constraint on mechanical commissioning. The FNET constraint imposes a restriction on an activity’s early finish date. This activity cannot conclude earlier than its constrained finish date, although precedence relationships might cause the activity to finish later.
Let’s proceed and insert a FNET constraint in our demonstration schedule, and examine its influence. Note that all the activities in Figure 1 have a constraint type As Soon As Possible (ASAP). This specifies that the activity will proceed as soon as precedence relationships say it can, and no later. That’s fine!
Mechanical commissioning may commence when the network logic says it can. We do, however, want to ensure that mechanical commissioning does not end until after permanent power to the site is activated. This is where our FNET constraint comes in handy.
To include a FNET constraint on Commissioning Mechanical highlight Commissioning Mechanical and select the Task tab, Properties ribbon group, and information icon, Figure 2.
In the following Task information dialog, Figure 3, select the Advanced tab.
In the constraint type drop down menu select “Finish No Earlier Than”. Next, in the constraint date menu option select Friday, November 20th, as the constraint date, Figure 4.
Finally, select the Notes tab and enter the event note “Provide permanent electrical power to site”, Figure 5.
We see the effect of the FNET constraint on the schedule in Figure 6.
Well, the FNET constraint did not shift any of the tasks. We do note, however, in the information column that Commissioning Mechanical has a constraint and a note, Figure 7.
We know from the Constraint Type column that Commissioning Mechanical has a “Finish No Earlier Than” constraint, and the Constraint Date column tells us the date (11/20/2015). Thus, we have modeled and highlighted the importance of providing permanent power on Commissioning Mechanical.
The constraint allows mechanical commissioning to proceed before site power, but restricts mechanical inspection to conclude after permanent power activation. If Commissioning Mechanical duration is reduced to three days, Figure 8, its start date is delayed so that it completes on November 20th, after final activation of power.
It is best to let precedence relationships drive the schedule. Sometimes though, a started activity cannot properly conclude before an important event. This event may be a deliverable approval or as in our demonstration the activation of site power. Either event would require a FNET constraint to brake the activity to ensure its successful conclusion.
Again, because constraints require manual schedule checks and/or updates, there is cause for pause that limits the number of task constraints. Still, application of a FNET constraint’s flexible start and restricted early finish may provide the best description of an activity’s boundaries.