11 Ways to Improve Gas Turbine Fogging System Performance

1. Upgrade to Seal-Flushed Pumps

Older high-pressure fog pumps can experience accelerated seal wear when operating with demineralized water. The low mineral content provides limited lubrication at the sealing surfaces, increasing maintenance requirements and the frequency of seal replacements. Worn seals can also cause leakage and affect pump reliability.

Upgrade: Replace conventional pump seals with a seal-flushed design that circulates re-mineralized water through the cavity between the high-pressure and low-pressure seals. This separate flushing circuit provides lubrication at the sealing surfaces while keeping the demineralized water used for inlet fogging separate.

Benefit: Upgrading to seal-flushed pumps can extend the seal life to 6,000 hours or more by circulating re-mineralized water through the cavity between the high- and low-pressure seals. Longer seal life can reduce maintenance frequency, replacement costs, and pump downtime.

2. Upgrade to Water-Lubricated Pumps

Older high-pressure pumps use oil-lubricated crankcases that require regular oil changes and periodic maintenance. These servicing requirements increase maintenance costs and can reduce pump availability, particularly in power plants where gas turbine inlet air cooling systems operate for extended periods.

Upgrade: Replace conventional oil-lubricated pumps with water-lubricated pumps designed for high-pressure fogging applications. These pumps use water instead of oil for lubrication, eliminating the need for routine crankcase oil changes. The upgrade reduces maintenance requirements while maintaining the pressure needed for consistent fog generation.

Benefit: Water-lubricated pumps can operate for up to 8,000 hours between rebuilds. Eliminating crankcase oil changes every few thousand hours reduces routine servicing, maintenance costs, and equipment downtime.

At a Wisconsin power plant, MeeFog replaced two older fogging systems with a new installation featuring a single water-lubricated pump, reducing maintenance requirements and improving operational reliability.

3.Install High-Pressure Filters

Pump seal wear can release small particles into the high-pressure piping of a fogging system. These particles may accumulate inside fog nozzles, restricting water flow and affecting atomization. Frequent nozzle plugging increases maintenance requirements and can reduce cooling performance.

Upgrade: Install high-pressure filters downstream of the pumps to capture particles before they reach the fog nozzles. When making this gas turbine efficiency upgrade, you should select filters based on system pressure, flow requirements, and nozzle specifications.

Benefit: High-pressure filtration can significantly reduce nozzle plugging and the frequency of nozzle cleaning. Cleaner nozzles maintain more consistent spray patterns and water distribution, helping the system deliver reliable cooling.

4. Improve Duct Drainage Systems

Poorly designed drainage systems allow unevaporated water to collect or flow along the inlet duct surfaces. Some older gas turbine fogging installations lack adequate drainage capacity, increasing the risk of liquid water being drawn into the compressor.

Upgrade: Install or improve duct drainage systems to remove flowing and pooling water before it reaches the compressor inlet. Drain locations and capacity should account for duct geometry, airflow conditions, and expected water accumulation. You can also install viewing windows to allow operators to inspect nozzle manifolds and conditions near the compressor inlet.

Benefit: Effective drainage reduces the risk of accumulated water entering the compressor and improves control over liquid-water management. Inspection windows make it easier to identify abnormal spray conditions, water accumulation, and maintenance requirements.

5.Recondition Fog Nozzles

Fog nozzles can become clogged, worn, or damaged during extended operation. Changes in nozzle condition can affect spray patterns, droplet formation, and water distribution across the inlet airflow. Poor atomization may reduce evaporative cooling performance and increase water accumulation inside the duct.

Upgrade: Visually inspect fog nozzles once a year to identify spray irregularities, blockages, or physical damage. At MeeFog, we offer a nozzle reconditioning service that restores serviceable nozzles and replaces those that cannot be reconditioned. You can also stock a spare nozzle set to replace affected nozzles during scheduled maintenance or short outages.

Benefit: Regular nozzle reconditioning helps maintain consistent atomization and cooling performance while reducing unexpected maintenance. Keeping spare nozzles lets you replace affected components immediately.

6. Correct Fog Nozzle Line Distribution

Some early fogging systems have nozzle manifolds that do not cover the full cross-section of the inlet duct. Uneven nozzle placement creates areas with excessive fog concentration while leaving other sections of the airflow with little or no fog. This can reduce evaporation efficiency, cause water accumulation on duct surfaces, and create temperature differences across the compressor inlet.

Upgrade: Evaluate the existing nozzle manifold layout and reposition or replace nozzle lines to distribute fog across the full airflow cross-section. You should consider duct dimensions, airflow distribution, nozzle spacing, and available evaporation distance.

MeeFog nozzle lines meet the ASME B31.1 Power Piping Code, making them suitable for high-pressure gas turbine fogging systems.

Benefit: Proper nozzle distribution improves contact between fog droplets and inlet air, supporting more uniform evaporation and cooling. It can also reduce localized water accumulation and temperature variation at the compressor inlet, improving overall system performance.

7. Replace Rubber Hoses with Stainless Steel Braided Hoses

Older gas turbine cooling water systems may use rubber hoses that deteriorate with age and prolonged exposure to operating pressure. Worn hoses can develop leaks or require frequent replacement. This increases maintenance demands and the risk of unplanned shutdowns, 24% of which stems from application or infrastructure failures.

Upgrade: Replace existing rubber hoses with high-quality stainless steel braided hoses designed for high-pressure water service. The braided construction provides mechanical reinforcement and improves resistance to operating pressure. Be sure to verify pressure ratings, fitting compatibility, and installation requirements before replacement.

Benefit: Stainless steel braided hoses can provide maintenance-free operation for many years. This upgrade reduces hose-related maintenance requirements, improves connection reliability, and helps maintain consistent water pressure throughout the fogging system.

8. Upgrade to TIG-Welded Nozzle Adapters

Early fogging installations frequently used soldered or brazed connections to attach nozzle adapters to stainless steel fog lines. These joints can weaken or fail over time, creating potential leakage points in the high-pressure distribution network.

Upgrade: Replace soldered or brazed nozzle adapter connections with Tungsten Inert Gas (TIG) welded joints. TIG welding creates a permanent connection between the stainless steel nozzle adapter and fog line. It provides a stronger joint without relying on the original soldered or brazed connection.

Benefit: Properly fabricated TIG-welded nozzle adapters provide long-lasting connections that can eliminate recurring failures associated with older joints. This upgrade reduces your maintenance requirements and improves the reliability of the high-pressure nozzle distribution network.

9. Upgrade Programmable Logic Controllers (PLCs)

Many early fogging systems operate with programmable logic controllers that manufacturers no longer support. Replacement components may be difficult to obtain, and outdated control software can restrict system modifications. These limitations become problematic when turbine operating requirements change, or additional control functions are needed.

Upgrade: Replace obsolete PLCs with modern controllers that support updated fogging control software. MeeFog offers field-installed PLC replacements that can be completed in a few days. You can then upgrade the control software.

Benefit: Modern PLCs improve serviceability and make future software modifications easier. Updated controls also simplify troubleshooting and reduce maintenance challenges associated with obsolete equipment.

At La Paloma Generating Station, MeeFog installed a system with 11 stages of fogging control, each providing approximately 2°F of cooling. The programmable controls allow operators to activate individual stages based on power demand and recover an extra 5 to 6 MW.

10. Enable Fogging Below Base Load

Some early fogging systems were programmed to operate only when the gas turbine reached base load. When the turbine ramps up to base load, the fogging system starts, potentially creating a sudden increase in turbine output. This behavior can complicate power output control, particularly at facilities that frequently operate at partial load.

Upgrade: Modify the fogging system’s control software to permit operation below base load where turbine operating requirements allow it. Review the turbine’s operating conditions, fogging stages, and control logic before implementing the change. Coordination with turbine operating limits is necessary when establishing the revised fogging sequence.

Benefit: Below-base-load fogging allows operators to use inlet air cooling across a wider range of operating conditions. It can reduce sudden output changes associated with fogging activation at base load and support smoother turbine load transitions.

11. Add Wet Compression for Increased Power Output

Conventional inlet fogging cools the incoming air through water evaporation before it enters the compressor. Once the air approaches saturation, additional evaporative cooling in the inlet duct becomes limited. This restricts the additional power output available through conventional inlet air cooling alone.

Upgrade: Incorporate wet compression by injecting more water into the inlet airflow than can evaporate before reaching the compressor. The remaining droplets travel into the compressor, where evaporation provides an intercooling effect that reduces compression work. The design requires careful evaluation of water flow, atomization, compressor compatibility, and turbine operating limits.

MeeFog has installed many wet compression systems on turbines ranging from aeroderivatives to modern F-Class turbines with fog flow rates of as much as 2.5% of the gas turbine air mass flow.

Benefit: Wet compression can provide an additional power boost beyond conventional inlet air fogging. Injecting water equivalent to 1% of the gas turbine air mass flow can increase power output by 5% or more, depending on the turbine.

For example, a Southwestern US power station installed MeeFog wet compression systems on two SW 501FD2 gas turbines. Each system provides wet compression (2% of air mass flow) and produces a 22 MW power boost.