Follow the fuel path from the supply line to the combustion chamber. Contaminated gas first crosses the upstream piping and filtration, then the fuel manifold and burner nozzles. A clogged nozzle is the stopping point, not the initiating fault. Cleaning the burners without correcting particle ingress only resets the failure cycle.
Where does the contamination stop?
Layer one first: identify every physical boundary between the gas source and the flame. Sand-sized particles should be intercepted before reaching the burner nozzles. Material found at the nozzles therefore calls for inspection of both the filters and any piping that can release contamination downstream of them.
| Path position | Expected function | Failure to check | Proof |
|---|---|---|---|
| Fuel-gas supply and upstream piping | Deliver clean gas | Entrained particles, sand, or debris remaining after construction or maintenance | Inspect collected samples and low points using the approved site procedure |
| Fuel-gas filter | Capture particles before the turbine | Damaged, bypassed, incorrectly installed, overloaded, or unsuitable element | Inspect the element, housing, seals, bypass condition, and differential-pressure indication |
| Downstream piping and manifold | Carry filtered gas to each burner | Residual debris or internal contamination downstream of the filter | Inspect or clean the isolated section under the manufacturer-approved procedure |
| Burner nozzle | Meter and distribute fuel | Partial or complete restriction | Borescope inspection followed by an approved nozzle inspection or flow check |
| Combustion and turbine sections | Receive combustion products | Particles passing burners and damaging protective surfaces | Borescope inspection of accessible hot-gas-path components |
Do not treat particles that pass a burner as harmless. They continue toward expensive hot-gas-path components and can erode protective coatings. The check before proceeding is a documented contamination boundary: identify the first clean point and the first dirty point in the fuel path.
Is nozzle fouling actually causing the symptom?
Confirm the restriction before selecting a cleaning method. Flame instability can result from uneven fuel distribution, but the same symptom can originate in supply pressure, valves, instrumentation, ignition, or combustion hardware. DLN systems are particularly sensitive to differences among nozzles because small distribution errors disturb the intended fuel split and flame pattern.
- Review the operating trend at the time instability appeared. Compare fuel conditions, load, combustion indications, and individual exhaust thermocouple values with a known acceptable run.
- Plot each exhaust thermocouple reading by circumferential position. A radar-style plot makes a changed exhaust-temperature profile easier to see than an average value.
- Use a borescope to inspect the suspected burners and accessible combustion areas. Record deposits, blocked passages, foreign material, and hardware condition.
- Check whether the temperature-profile change aligns with the location of a visibly fouled burner. A mean exhaust temperature can hide a local hot or cold sector.
The proof is agreement between two independent observations: visible nozzle contamination and a repeatable combustion or exhaust-temperature pattern. If they disagree, continue upstream and through the combustion diagnostics rather than declaring the nozzle to be the sole fault.
Are filtration and purge controls blocking new ingress?
A clean burner will clog again if the filter housing passes debris or if downstream piping still contains particles. Read the installed filter element identification and its required service limits from the equipment documentation; do not infer the capture rating from appearance. Differential pressure alone is insufficient because a damaged or bypassed element can show little restriction while passing contamination.
- Isolate the fuel system under the approved plant and turbine procedure.
- Inspect the element for damage, incorrect seating, collapse, contamination loading, and seal problems.
- Inspect the housing and bypass arrangement for a path around the element.
- Examine downstream piping, drains, low points, and the manifold for retained particles.
- Review whether the specified fuel-line purge is completed between starts and whether its discharge path removes debris instead of carrying it toward the nozzles.
Purge sequence, medium, direction, and acceptance limits must come from the turbine and fuel-system documentation. The check is a clean downstream sample or inspection point after the filter has been returned to its correct configuration.
Can reverse blowout clean the burners in place?
Do not repeat an improvised reverse blowout as the primary remedy. A previous attempt used combustion-chamber pressure at full-speed no-load, reported at about 12 bar, and produced little improvement. Chamber pressure is not automatically the pressure differential across each blocked nozzle; the actual reverse flow depends on manifold pressure, valve positions, restrictions, and the available return path.
| Method | What it can establish | Principal limitation | Decision |
|---|---|---|---|
| Reverse blowout in the assembled turbine | May dislodge loosely held material if a defined reverse path exists | Unknown distribution among nozzles; debris destination is uncontrolled; compressor or turbine blade rubbing can occur | Use only with a written manufacturer procedure for the exact machine configuration |
| Borescope inspection | Confirms visible fouling without immediate burner removal | Cannot prove that internal metering passages are clear | Use for diagnosis and post-work inspection |
| Burner removal and cleaning | Provides access for controlled cleaning and inspection | Requires an outage and handling time | Follow the manufacturer’s stated remedy |
Operating outside written recommendations can also affect warranty and insurance treatment. The check at this stage is written authorization: if no approved in-place procedure defines valve lineup, pressure limits, debris collection, and inspection criteria, stop the in-place attempt and schedule removal.
How should removal and cleaning be commissioned?
The manufacturer has directed removal of all burners for cleaning. Treat that direction as the controlling maintenance path. A spare clean burner set can reduce outage duration when replacement is coordinated with another planned turbine outage, such as a crank-wash window.
- Record burner positions and the pre-maintenance exhaust thermocouple profile so that location-specific findings can be correlated later.
- Shut down, isolate, cool, and release the turbine for work under the applicable site and manufacturer procedures.
- Remove the burners using the prescribed sequence and handling controls. Preserve position identification for every unit.
- Clean and inspect each burner by the approved process. Obtain the manufacturer’s acceptance criteria for internal cleanliness, damage, and any required flow comparison.
- Inspect the combustion section and accessible turbine surfaces for transported particles or erosion before closing the machine.
- Correct the filter, housing, purge, or piping defect that admitted contamination before installing the cleaned or spare set.
- Reinstall the burners with the specified parts, settings, and inspection records from the turbine documentation.
The check before startup is a signed mechanical completion record tying every burner position to its inspection status and confirming that the upstream contamination source has been removed.
How is end-to-end recovery verified?
Verification must follow the same path as the fault: clean supply, functional filtration, unrestricted distribution, stable combustion, and an acceptable exhaust pattern. A successful start alone does not prove that all nozzles are clear.
- Inspect the restored filter installation and confirm the expected differential-pressure indication.
- Complete the documented purge and startup sequence.
- Trend fuel conditions, flame stability, combustion indications, and every exhaust thermocouple through the permitted operating range.
- Recreate the circumferential exhaust-temperature plot and compare its shape with the pre-maintenance plot and an accepted baseline.
- Investigate any persistent local deviation by burner position; do not hide it in an averaged temperature.
- At the next permitted inspection opportunity, borescope the burners and accessible hot-gas-path surfaces to check for renewed deposits or transported debris.
The final acceptance check is stable operation with an acceptable individual-thermocouple profile and no renewed contamination at the downstream inspection points.
FAQ
Can I clean gas turbine burner nozzles without removing them?
Only use an in-place method when the manufacturer supplies a written procedure for the exact turbine configuration. The attempted reverse blowout at about 12 bar and full-speed no-load gave little improvement, so burner removal remains the directed remedy.
Does a normal average exhaust temperature rule out a clogged burner?
No. Compare every exhaust thermocouple by circumferential position; averaging can conceal a local hot or cold sector. Correlate a changed profile with borescope findings.
Can I restart after cleaning the burners but not the gas line?
Not as a completed repair. Inspect the filter, housing, purge path, downstream piping, and manifold first, then perform the final verification through stable combustion, the individual exhaust-temperature profile, and downstream cleanliness checks.