Erosion slowly removes material from turbine parts and your performance margins. Whether you are operating a combined cycle plant or baseload steam unit, a simple edge of blade erosion can manifest as more fuel burned, a worse heat rate, and/or added loading on components.
Follow https://pmc.ncbi.nlm.nih.gov/articles/PMC11477678/ for more information.
This article discusses the origins of erosion, early detection methods, and actions to control it.
What Causes Erosion in Turbines?
In essence, erosion begins when hard solids or droplet collisions impact metal at fairly high velocities. In gas turbines, dust bypassing the inlet filtration will impact and sandblast the leading edges and nozzles. In the case of steam turbines, wet steam and carryover from the boiler or condenser reservoirs produces droplet impacts that chip away at the last stages.
Chemical issues, such as salts and oxides, can exacerbate the wear process to further combine erosion and corrosion. Inadequate drain management, cycling, and misaligned sprays all add risk elements to erosion wear. Good condition monitoring will allow you to make the connection of the erosion cause and the trends before it advances to damage.
Common Erosion Hotspots
Erosion would be great if it were distributed evenly, but it’s not and instead following flow direction or pressure and where the particles achieved their first hard turn. Familiarizing yourself with the usual suspects will allow you to be prepared with focused inspections and allow a more efficient outage time.
- Inlet guide vanes and first-stage nozzles where particles first accelerate
- Leading edges and pressure sides of early-stage rotor blades
- Shrouds, tip seals, and endwalls that trap recirculating debris
- Steam turbine low-pressure last-stage blades hit by wet-steam droplets
- Stationary diaphragms downstream of spray attemperators or carryover sources
Detecting Erosion Early
Erosion is best caught when it is still only a surface scar, and not yet a measurable change in profile. Borescope inspection can be performed between major outages to check leading edge, the platform, and both surfaces of the blade tip seal, without needing to tear down the unit. You can often pair visual inspection with vibration analysis to check for banging from a changing stage impact or growing imbalance. Non-destructive testing options such as dye penetrant (see here for more) or phased-array ultrasonics can be done on exposed parts during the outage or major inspection when the part is accessible, to check for cracks that have developed since the visual inspection or previously to being put in service.
Performance data is just as useful. Track compressor/steam mass flow, exhaust temperature spreads, and stage pressure ratios for small, steady drifts. Set simple triggers in your condition monitoring software so trend breaks generate a work order, not just a report. For gas turbines, schedule hot gas path inspection services during planned outages to size the damage, confirm coating condition, and prioritize parts for repair or replacement.
How Erosion Impacts Efficiency
Effectively, erosion is changing the shape of the blade that you paid for in performance. Even a small amount of metal loss along the leading edge, or the tip clearance has widened, will alter the lift-to-drag balance that that stage (or overall) relies on the get the performance you expect. So over time, you may notice you are using more fuel, or the plant just feels “tired” with the same load.
- Increased heat rate as air or steam leaks past worn seals and tip clearances
- Lower efficiency at the stage due to the leading-edge bluntness and rough leading-edge surfaces
- Added exhaust temperature and temperature spread that stresses downstream parts
- Increased fouling, re-entrainment from rough profiles that trap and accumulate debris
- Increased imbalance in the rotor and increased clearances that generate vibration and added risk
When effects stack up, a steam path assessment across the parts or a performance-based assessment typically demonstrates both a measurable loss of output, as well as the speed of recovery of performance will often be contingent on repair of the part.
Solutions for Erosion Issues
Begin with what’s entering the machine. Upgrade gas turbine inlet filtration—pre-filters to final HEPA as possible—and upgrade housekeeping around air intakes. In steam service, remedy wetness sources: tune sprays, repair attemperator leaks, restore moisture separator drains, and address chemistry to prevent salts from plating out. Fix drains in low points to keep slugs out of the last-stage buckets.
Next is protection and restoration. Erosion resistance coatings applied to leading edges together with nozzles exist where OEM or qualified aftermarket is available. Replace any worn tip seals and honeycomb to close gaps, apply weld build-up or laser cladding on eligible parts to restore profiles during a planned outage, and modify operating practices (softer/longer ramp rates and smarter water injection) to minimize particle and droplet impingement. Finally, lock in a predictable inspection cadence that separates visual checks, focused NDE, and performance trending to allow early intervention and robustness.
