The short answer
In an unplanned boiler outage the first 24 hours decide the total duration. Cooling time, access, correct tube material and a qualified welder on site are the four constraints — and three of them can be prepared before the call comes.
A tube leak stops production immediately and without notice. The response is a logistics problem more than a technical one.
The four constraints
| Constraint | Can it be prepared in advance? |
|---|---|
| Cooling time | No — physics |
| Access and scaffolding | Partly — keep standard access designs |
| Correct tube material | Yes — hold critical spares |
| Qualified welder on site | Yes — retainer or framework contract |
Hour by hour
- 0–4 h — Controlled cooldown, isolate, drain. The contractor mobilises while the unit is still cooling.
- 4–8 h — Access built, leak located and confirmed. Verify it is a single failure, not the first of several.
- 8–16 h — Cut out, prepare, weld to approved WPS, NDT the joint.
- 16–24 h — Box up, test as the procedure requires, prepare for light-up.
Find the cause, not just the leak
A tube fails for a reason — erosion, overheating, corrosion or a weld defect. Replacing it without identifying the mechanism means the next failure is already scheduled. Photograph and retain the failed section.
Prepare before you need it
Plants that hold critical tube spares and keep a contractor on a framework agreement routinely restart a day earlier than plants that start sourcing after the trip.
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