Borescope or teardown: choosing the cheaper answer
An unplanned teardown costs weeks of production. A borescope costs a shift. The decision is about what you expect to find, not about how the machine is running.
Every flexible borescope inspection is a wager: a shift of lost production against the possibility of avoiding four weeks of it. The wager is worth taking when the inspection has a specific question to answer, and it is not worth taking when it is a general look around.
Questions a borescope can settle
- Is there a discrete foreign-object damage mark on a stage 1 or 2 bucket, and is it within the repair limit?
- Are the combustor liner cooling holes clear, or is there cracking between them?
- Is the tip clearance pattern symmetrical, or has a shroud segment moved?
- Is a rising vibration signature coming from the compressor or the turbine section?
If none of those questions is on the table, the scope will produce a set of ambiguous photographs and a recommendation to tear down anyway — in which case you should have simply torn down.
What each route actually costs
| Route | Duration | Production impact | Information gained |
|---|---|---|---|
| Borescope, hot section, no rotor turn | 6–12 h | one shift | combustors, transitions, stage 1 nozzle |
| Borescope with rotor turn, inlet + hot section | 1–3 days | 1–3 days | all stages, both vane rows, tips |
| Top-half / partial teardown | 1–2 weeks | 1–2 weeks | buckets removable, root inspection possible |
| Full teardown | 3–6 weeks | 3–6 weeks | complete rotor, bearings, alignment |
The evidence problem
A borescope result is only as good as its record. Ask for a numbered still frame for every location, with the inspection map marked so that position 14 on the map is a specific vane on a specific can. Without that, a later claim about crack growth has no reference photograph to grow from, and both the insurer and the OEM will push back.
Two inspections six months apart are worth ten times one inspection. It is the delta that tells you whether a crack is stable.
NDE lead, utility steam plant
The practical version of this is a fixed inspection map kept with the unit's permanent record. Inspect the same twenty points every time, on the same scope model, and the third interval starts to predict the fifth.
- Borescope
- NDE
- Turnaround
