How to plan work around a fixed outage or shutdown window
Plan work around a fixed outage or shutdown window on a Gantt chart: fix the window's start date, make the preparation finish before it, see a conflict early and check that the work fits inside.
An outage window is a date you are given, not a date you choose, so the plan has to show whether everything else can be ready for it. This guide shows how to fix the window, check that the preparation can finish first, and size the work inside it.
The short version
- Give the window its own task and fix only its Start; let everything else be calculated.
- Link every preparation task to the window, so a late delivery shows up as a conflict, not a surprise.
- Treat the operator's approval as a wait you enter, not a task you control.
- Size the work inside the window as a chain whose total matches the window's length.
- A chart can show whether the dates fit; it cannot make the work safe or the approval come.
A fixed date in a flexible plan
Most tasks in a schedule start when the work before them is done. An outage or shutdown window does not. The circuit, line or plant is only out of service on the days someone with authority has agreed, and that agreement is often made long before and for a short time. The plan then has two jobs: make sure everything the window needs is ready when it opens, and make sure the work fits inside the days it lasts.
In a Gantt chart this is one fixed date and a set of ordinary dependencies. The window gets its own task with a fixed Start. Everything that must happen first, such as the equipment arriving, the approval wait and the switching plan, is linked to it. The chart schedules forward from the earliest fixed date. If the preparation cannot finish by the window date, the window task is flagged with a conflict that names the earliest date its dependencies allow. That is the early warning: you see the gap while you can still ask for a different window or change the preparation.
The example below builds the substation upgrade template in stages. In its illustrative numbers the equipment is the slow part: it is on site 56 working days into the plan, and the outage approval wait ends on day 20, so the wait has room. The window task is 12 working days, and the five tasks inside it add up to exactly 12, which is why they are linked in a chain with no spare time. All durations are illustrative: replace them with your supplier's lead time and what the operator tells you.
A timeline schedules the work. It does not make any isolation, switching or test safe, permitted, certified or compliant, and it cannot tell you whether an operator will approve a window or how long they will take. Keep permits, safety documents and sign-offs as tasks with named owners, and use the chart to show whether the dates you have been given can be met.
A substation upgrade around a fixed outage window, built in stages
Twenty-two tasks and four milestones in four groups. Durations are illustrative; set your own. Open the spreadsheet panel to see the rows behind each stage.
The preparation that sets the earliest window
"Define upgrade scope and outage constraints" (3 working days) leads to "Complete detailed design" (8) and "Write equipment specification" (4). "Place transformer and switchgear orders" (2) needs "Design approved" and the specification. "Manufacture transformer and switchgear" (35), "Run factory acceptance tests" (3) and "Deliver equipment to site" (5) end at "Equipment on site", 56 working days in.
An external wait beside the equipment
"Submit outage request" (2) follows the scope task, and "Outage approval wait" (15) follows it, ending on day 20. The wait is the operator's, so you enter their number. Here it finishes long before "Equipment on site", so it has room; with a longer wait it could become the slowest path.
The window, fixed and checked
"Outage window" (12 working days) waits for "Prepare switching and commissioning plan", "Equipment on site" and "Outage approval wait". Give it a fixed Start on the agreed date. If any of the three cannot finish before that date, the window is flagged with the earliest date its dependencies allow.
Work that fits inside the window
"Isolate and earth the circuit" (1) starts with the window through a start-to-start link. Then "Remove the old equipment" (2), "Install new transformer and switchgear" (4), "Terminate cables and connect protection" (2) and "Run protection and site acceptance tests" (3). One plus two plus four plus two plus three is 12, the whole window.
Re-energise, then return to normal
"Circuit re-energised" is a milestone after the tests. "Monitor under load" (3) follows, then the "Return to normal operation" milestone and "Update records and close out" (3). A longer "Monitor under load" or close-out moves only the tasks after it, never the fixed window, but only if nothing inside the window was left undone.
What happens inside the window: the permit to work, with its loops
A Gantt chart gives "Isolate and earth the circuit" a length. It cannot draw the checks and repeats inside it. The permit to work process can.
Is a permit needed, and does the job clash?
"Does the task need a permit to work?" splits into "Permit required" and "Normal control". A permitted job moves from "Write the method statement and task risk assessment" to "Clash with other work or plant status?". A clash goes to "Re-time the job or cross-reference the other permit" and back to the check.
Prove the isolation, or isolate again
"Apply the isolations and lock off stored energy" leads to "Isolation proved and secured?". The "Re-isolate" branch goes back to the isolation step. Only "Proved" reaches "Record isolations on the isolation certificate". In the Gantt chart this whole loop is the one day of "Isolate and earth the circuit".
Work inside the permit, with changes
"Do the work inside the permit scope" is followed by "Conditions, scope or plant status changed?". "Suspend" goes to "Stop work, make safe and suspend the permit" and back to the worksite check. "Overruns" goes to "Sign the shift handover and set a new expiry" and returns to the work.
Hand back and reinstate
"Sign hand-back that the work is complete" leads to "Worksite clear and plant ready to reinstate?". "Unfinished" returns to the work; "Ready" leads to "Remove the isolations and reinstate the plant", "Test the plant and accept it back into service" and "Cancel the permit and close the certificates".
Permit to work process flowchart (issue, suspend, hand back)
How it works
Add the window as its own task
Create a task named for the window, such as "Outage window", with a length equal to the days you have been given. Do not fold the window into the first work task: it is the date, and the work is what happens in it.
Fix the window's Start
Enter the agreed date in the window task's Start. Fix the Start of the first task as well, on the day you begin, so the plan has a starting date. Leave every other date to be calculated from lengths and dependencies.
Link everything the window needs
In the window's Depends on, list the equipment milestone, the approval wait and the switching plan. If one cannot finish before the Start, the window is flagged with the earliest date its dependencies allow. Read that date before you ask for a different window.
Enter the operator's wait as a task
Add "Submit outage request" and a task for the wait, with the number of working days the operator gives you. Replace it when they answer. The chart does not contact anyone; it moves the dates when you change the length.
Chain the work inside the window
Link the first work task to the window with start-to-start so it opens with it, then link each task to the next. Make the total match the window's length. If it is longer, the window must be longer or the method must change.
Add a margin, owners and share
Add any spare time as its own task or lag, not hidden in a duration. Put owners in People, share the chart with the contractor and the operator's planner, and export a PDF or PNG for the outage meeting.
Mistakes to avoid
Fixing every date
If every task has a fixed Start, nothing can move and a late delivery cannot push anything. Fix the window and the first task only; let the rest follow from lengths and dependencies.
Hiding the margin in durations
Padding each work task by a day makes the chain longer than the window with no one seeing why. Keep the lengths honest and add margin as a separate task or lag you can point to.
Letting the window open before the paperwork is done
Switching programmes, permits and sign-offs belong in the chart as tasks that the window depends on. A timeline only schedules them; it does not make them valid. See the permit to work process at /templates/permit-to-work-process.
Planning the loops as lines
A Gantt chart cannot draw a repeat. If isolation may need to be proved twice, give the task a duration that allows for it, or draw the loop in a flowchart and link to it.
Open the substation upgrade Gantt chart
Open the substation upgrade template, fix the window on your date and see whether the preparation finishes in time.
Related guides
Frequently asked questions
How do I show that work must finish before a shutdown?
Link every preparation task to the shutdown task with Depends on, and fix the shutdown's Start. If anything cannot finish in time, the shutdown task is flagged with a conflict and the earliest date its dependencies allow.
What does the conflict flag tell me?
That the fixed Start is earlier than the dependencies allow. The flag names the earliest date they do, so you can compare it with the window and decide whether to move the window, shorten the preparation or accept the later date.
Can the work inside the window overrun?
The chart schedules what you enter. If the chain is longer than the window, the work will end after it, and you can see how many days over. It does not stop the work or extend the window; that is a decision for the people who own it.
Does the chart know whether the outage is approved?
No. It shows when you plan to submit the request and how long you expect to wait. Change the length of the wait task when you hear back and the dates after it move.
Where do I find the equipment side of this plan?
In the guide on long-lead equipment at /guides/long-lead-equipment-gantt-chart, and the test and energisation side at /guides/commissioning-and-energisation-gantt-chart.