Every megawatt a gas turbine makes starts with the air going into the compressor, which means the inlet system is doing performance-critical work before combustion ever enters the picture. A dirty filter or a fouled cooling media doesn't trip the unit, it just quietly taxes it, showing up as higher heat rate and lower output long before anyone traces it back to the inlet house. Sign up to track filter pressure drop, cooling system readings, and inspection intervals across your fleet.
Why It Matters
A turbine's power output and heat rate are both directly tied to inlet air mass flow and temperature. Filter fouling raises pressure drop and starves the compressor of air, while a poorly maintained cooling system leaves output on the table on the hottest days of the year, which are usually when the grid needs that capacity most.
The Inlet System, Component By Component
Pre-Filters
First line of defense against coarse dust and insects, changed on a shorter cycle than the final stage
HEPA & High-Efficiency Filters
Final stage catching fine particulate that would otherwise foul compressor blades and drive up pressure drop
Evaporative Cooling Media
Wets and cools inlet air on hot days, checked for scaling, algae growth, and even water distribution
Fogging Nozzles & Chillers
Fine water mist or mechanical chilling pushed further below wet-bulb, inspected for nozzle clogging and carryover risk
Reading The Pressure Drop Gauge
Clean
Below 2 in. w.c.
Normal operation
Watch
2-3.5 in. w.c.
Trend it closely
Alert
3.5-4.5 in. w.c.
Schedule change-out
Alarm
Above 5 in. w.c.
Output loss underway
Exact thresholds vary by OEM and filter design, but the pattern holds everywhere: pressure drop rises slowly, then accelerates once the media starts loading unevenly, which is why a single spot-check misses more than a logged trend does.
Turn Pressure Drop Into A Trend, Not A Surprise
Oxmaint logs filter pressure drop, cooling system readings, and change-out history against every unit in your fleet, flagging the climb before it reaches alarm. Sign up for a free trial to bring inlet system tracking to your turbines, or book a demo to see it configured for your fleet.
Evaporative Cooling vs Fogging vs Chilling
| Factor |
Evaporative Cooling |
Fogging |
Mechanical Chilling |
| Cooling limit |
Down to wet-bulb temperature |
Wet-bulb, with some overspray potential |
Below wet-bulb, into the 45-50°F range |
| Best fit |
Hot, dry climates with low humidity |
Moderate climates, lower capital cost |
Humid climates or maximum output needs |
| Main upkeep risk |
Media scaling and algae growth |
Nozzle clogging and water carryover |
Chiller coil fouling and refrigerant system upkeep |
| Output gain |
Moderate, climate dependent |
Moderate to high, climate dependent |
Highest, largely independent of humidity |
Seasonal Inlet System Checklist
Trend Pressure Drop Weekly
A logged trend catches a fouling filter weeks before a spot-check would notice the same climb
Inspect Cooling Media Before Peak Season
Evaporative pads and fogging nozzles are checked for scaling, algae, and even distribution before summer demand hits
Test Water Quality
Poor water quality accelerates media scaling and raises the risk of carryover-related compressor fouling
4
Log Every Filter And Media Change-Out
Change-out dates, part numbers, and pre/post pressure drop readings build the history the next decision relies on
The Payoff
Compressor fouling from a neglected inlet system doesn't just cost output today, it drives up compressor wash frequency and accelerates blade erosion over time. Keeping filter and cooling data on a trend line rather than a memory is what keeps that cost from compounding across a fleet.
Frequently Asked Questions
Q
How much power does inlet fouling actually cost?
The exact number depends on the unit and how far pressure drop has climbed, but even a moderate rise in inlet loss measurably reduces mass flow through the compressor, which lowers both output and efficiency. The loss is gradual, which is exactly why it tends to go unnoticed without a logged trend.
Q
Should HEPA filters be changed on a fixed schedule or by condition?
Most operators use pressure drop as the trigger rather than a fixed calendar date, since dust loading varies by site and season. A fixed schedule is still useful as a backstop, but a filter reaching its alert threshold early should be changed regardless of how much time is left on the calendar.
Q
Can evaporative cooling and fogging carry water into the compressor?
Yes, if the media is scaled, unevenly wetted, or the fogging system is over-injected relative to what the air can absorb. Carryover water can erode early compressor stages and wash away protective coatings, which is why droplet size and saturation are checked as part of routine inspection.
Keep Filter And Cooling Data In One Place
Oxmaint logs pressure drop trends, cooling system checks, and change-out history for every unit in your fleet, so the next filter change is scheduled on data, not a guess. Sign up for a free trial to bring inlet system tracking to your turbines, or book a demo to see it configured for your fleet.
