Sequence the steps of a planned shutdown or tie-in, track the running clock, add a contingency buffer, and see whether it fits inside the maximum allowable out-of-service window. Runs entirely offline; everything persists in this browser via localStorage.
Use limits: The window is a hard constraint set by whatever actually governs — customers' tolerable outage, hours of storage in the tanks, a boil-water threshold, a permitted lane-closure or night-work window, a contractual milestone. Name it, and be honest about the durations: the unknown condition of the existing valve or pipe is the classic overrun, which is what the buffer is for. This plans a serial sequence; you can't backfill before you test.
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Planned duration (steps)
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Contingency buffer
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Committed (planned + buffer)
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Max allowable window
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Slack against the window
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Projected return to service
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Must be back in service by
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How the Numbers Are Derived
The clock and the go/no-go
Steps run in sequence, so the planned duration is just their sum, and each step's start and end clock times accumulate from the planned start. The committed duration is planned × (1 + buffer%). Slack is window − committed: positive is go, negative is the amount you'd blow the window by. The timeline draws the steps end to end with the buffer appended and the window line marked — if the bars cross into the shaded zone past the line, the plan doesn't fit.
Field notes
The buffer isn't optional padding — it's the plan for the valve that won't seat, the coupling that's the wrong size, the pipe that's a different material than the record says. Serial work has no slack of its own to absorb that.
Hold points have their own clocks that manpower can't shorten: a pressure test holds for its full duration, disinfection sample results come back when the lab runs them, an inspector arrives when they arrive. Sequence around them.
Set a go/no-go decision time — the point of no return where, if you're not at a given step, you abort and restore service on the old configuration rather than run past the window.
Have a real plan B for restoring service: temporary service connections, a bypass pump, or a valve that lets you re-pressurize the old alignment. “We'll hurry” is not a contingency.
The window is someone's promise to customers or a regulator. Beating it quietly is fine; blowing it is a notification, a boil-water advisory, or a claim — which is why the buffer lives inside the window, not outside it.
References
The utility's / owner's shutdown and outage procedures, and the customer-notification or boil-water policy that sets the allowable duration (governing).