Gas Turbine Hot Gas Path Inspection Checklist Guide
By Willam Jerry on October 21, 2026
The hot gas path of an industrial gas turbine lives at 1,400-1,600°C firing temperature behind a thermal barrier coating that measures in hundreds of microns. Every HGPI window the plant opens a casing, pulls combustion hardware, lowers the aft section and looks at parts the OEM has priced in the hundreds of thousands. This checklist standardizes what the inspector looks at, how damage is classified, and what gets logged against each part so the next inspection has a baseline, not a memory. OXMAINT AI is the AI-powered gas turbine maintenance software that holds the HGPI checklist, pins every finding to the part serial, scores the thermal-damage severity and keeps the repair-versus-replace decision on the same record the next outage inherits.
GAS TURBINE HOT GAS PATH INSPECTION CHECKLIST · HGPI · 2026
Gas Turbine Hot Gas Path Inspection Checklist Guide
Four hot-section sections, 44 inspection items, native checkboxes. OXMAINT AI assigns each walk, logs every finding against the part serial, scores thermal-damage severity on a four-tier scale and keeps the repair-vs-replace decision on the same record.
Three inspection tiers escalate in scope. The hours below are OEM-dependent — GE Frame 7 / 9, Siemens SGT, Mitsubishi M-series each publish their own; the shape of the ladder is universal.
COMBUSTION INSPECTION
CI · ~8,000 fired hours
Combustion liners, caps, flow sleeves, transition pieces pulled; borescope-only on buckets/vanes. 7-14 day outage. Smaller scope.
HOT GAS PATH INSPECTION
HGPI · ~24,000 fired hours (or ~900 starts)
Combustion plus turbine section opened; stage-1 and stage-2 buckets and nozzles pulled, inspected, repaired or replaced. 21-30 day outage. The subject of this checklist.
MAJOR INSPECTION
MI · ~48,000 fired hours (or ~2,400 starts)
Full teardown including compressor section, bearings and rotor; HGP plus everything else. 45-60 day outage. The capital event.
Section 1 · Combustion Liner & Cap Checklist
Twelve items. Each one ticks against a specific part serial so the finding ties to that liner's history.
Section 2 · Transition Piece Checklist
Eleven items. The transition piece sees the hottest gas and often drives the HGPI calendar.
Section 3 · Turbine Bucket / Blade Checklist
Eleven items per stage. S1 buckets usually drive the economics; the checklist runs the same way for S2 and S3.
Section 4 · Nozzles, Vanes & Shrouds Checklist
Ten items. Stationary hardware takes the gas-side pressure load; its damage pattern is different from the rotating buckets.
Thermal-Damage Severity Scale — T1 Through T4
A finding without a severity score is a photo in a drawer. The four-tier scale aligns findings across inspectors, outages and plants.
T1
Cosmetic / within spec
Minor discoloration, light coating wear, surface deposits. No action; log for trend; part returns to service.
T2
Repairable in-place
Minor cracking, partial coating loss, light erosion within OEM limits. Addressed in current outage without pulling part.
T3
Repair at vendor shop
Significant cracking, major TBC loss, dimensional change. Part shipped to OEM or approved vendor for strip, repair and recoat.
T4
Scrap / replace
Damage beyond repair criteria; cumulative repair count exceeded; dimensional out-of-tolerance. New or refurbished part installed.
Repair-vs-Replace Decision Matrix
A severity score drives a decision. The matrix below documents the typical path per component group; OXMAINT AI uses it as the recommendation default while leaving the plant to confirm per serial.
Component
T1
T2
T3
T4
Combustion liner
Reinstall
Weld / recoat
Vendor refurb
Replace
Transition piece
Reinstall
Weld / recoat
Vendor refurb
Replace
S1 bucket
Reinstall
Blend repair
Strip & recoat at OEM
Replace — capital
S1 nozzle
Reinstall
Weld / braze
Vendor repair
Replace — capital
Shroud & honeycomb
Reinstall
Segment replace
Ring refurb
Full ring new
The Serial Is The Record. The Record Is The Decision.
Every finding logged against the part serial means the next HGPI starts with the full history of this bucket, this liner, this nozzle. OXMAINT AI binds the serial-level record, the severity score and the repair-vs-replace decision on the same screen.
The right NDE method for the finding is a decision, not a reflex. The matrix below pairs the common HGPI damage types with the methods that size them. OXMAINT AI pre-fills the NDE recommendation when a severity is logged.
FPI (fluorescent penetrant)
Surface cracks on cooled hardware — liners, transition pieces, platforms. The HGPI workhorse.
Eddy current
Sub-surface indications on thin-wall components; depth sizing of linear indications found by FPI.
Phased-array UT
Depth sizing on thicker sections; crack-growth tracking inspection-over-inspection.
Blue-light / 3D scan
Dimensional check on airfoils; creep bow and twist against as-new.
Borescope video
In-situ interim-period checks between CI/HGPI; drives decision to open on cadence or defer.
Deposit analysis
Vanadium, sodium, sulfur deposits sampled from vanes to lab; feeds fuel-chemistry program.
How OXMAINT AI Runs The HGPI Program
The 44-item checklist, part-serial register, severity scoring, repair-vs-replace decision, NDE routing and shop-tracking logs all live natively in the OXMAINT AI gas turbine maintenance software — open a free account and load the HGPI checklist into OXMAINT AI.
Serial Register
Every liner, transition, bucket, nozzle as a sub-asset with fired-hours, cycles, prior repairs and cumulative-life position.
44-Item Checklist
Four-section mobile checklist with native checkboxes, photo capture per item and signoff against the part serial.
T1-T4 Severity Scoring
Severity assigned per part; T3-T4 auto-raise a shop-dispatch WO; T4 auto-flags the inventory replacement path.
R/R Decision Pin
Repair / recoat / replace decision pinned on the serial record; the next inspection sees the full history, not the memo.
Shop Tracking
Parts out for vendor repair tracked by serial, dispatch date, scope, return date and cycle-life credit.
Outage-to-Outage Trend
Thermal-damage trend per serial across HGPIs — the leading indicator for retirement planning.
Frequently Asked Questions
How much of the HGPI schedule is driven by hours vs starts?
OEM-dependent. Baseload units typically run on fired hours; peaking and cycling units run on an equivalent-operating-hours formula that weights starts and trips heavily — a hot start can equal 10-30 fired hours depending on the OEM. OXMAINT AI stores the OEM formula per unit so the next HGPI date is always current.
Can a part be repaired indefinitely?
No. OEMs publish cumulative repair limits — typically 2-3 strip-and-recoat cycles for S1 buckets, more for stationary parts. OXMAINT AI tracks the repair count per serial and flags a part approaching its cumulative limit before the next HGPI opens the casing.
What's the single biggest cost lever on an HGPI?
S1 bucket set. New S1 buckets are the capital line that dwarfs everything else on an HGPI. A disciplined serial-level record that defers an unneeded T4 call by one more cycle is where the real money lives — and where a sloppy inspection record costs the most.
How does fuel chemistry affect the HGPI?
Materially. Vanadium, sodium and sulfur in liquid fuel accelerate hot-corrosion attack on vanes and buckets, shorten repair intervals and change the dominant damage mode. OXMAINT AI stores the lab-sampled deposit record alongside the fuel-chemistry log so the correlation is visible, not implied.
Every Finding, Every Part, Every Outage — One Record.
Load the HGPI checklist into the OXMAINT AI gas turbine maintenance software — serial register, 44-item mobile walk, T1-T4 severity scoring, R/R decision pin, NDE routing and vendor-shop tracking. The next HGPI inherits the full history.
