Gas Turbine Efficiency has approached us for installing their high pressure wash skid. As per GTE, compressor efficiency will be maintained through regular online wash for 3 minutes.

I want Frame 9E users feed back who has installed this kind of skids.

 

As I could observe, the better word would be to elongate the degradation of GT efficiency due to compressor fouling. Don't expect the cleanliness of the compressor could be maintained with the high or even the low pressure skid as it is practically impossible. The best combination is to have the low pressure skid for offline washing and the high pressure skid for daily online washing.

I have worked with F9E installed with GTE high pressure washing previously and although in some way the washing did elongate the washing frequency, the period is not so much of a difference. Most importantly I could not imagine a thorough cleaning with a high pressure system which basically creates water mist to the compressor as compared to the "strong water" using the low pressure skid

 

The ambient conditions at any site will always determine how often a water wash (online or offline) should be done, and will also have a large impact on the efficiency of any on-line washing.

On-line washing is really only effective for the initial stages of the axial compressor, because the water eventually vaporizes as the air is compressed (heated) and so the effectiveness on later stages of the compressor is reduced.

I'm told that the theory behind high-pressure washing is that it is supposed to be more effective at cleaning the first stages, including the bellmouth and Inlet Guide Vanes, than a "low pressure" washing system.

As with any washing system, the angle of the nozzles and the cleanliness of the nozzles is very, very important. The spray is difficult to observe when the unit is running without additional lighting and viewing apertures (windows). The cleanliness of the water and detergent is also very important, as small particles can clog nozzles orifices.

Most of the sites I've been never perform any maintenance activities on their on-line washing systems. They just run them and presume they are working as designed and at the highest possible effectiveness. I can say that a lot of piping systems I observed at many new unit installations over decades were never properly flushed, if they were even flushed at all.

I've only been at a handful of sites (less than five, probably) where they actually had installed additional lighting and viewing windows in the inlet ductwork to be able to observe the washing sprays and even observe the effects of the online washing on the bellmouth and IGVs after the washing was complete. They stationed operators and technicians at the viewing windows during on-line washing and actively performed maintenance on the system during outages. These sites reported excellent availability and decreased need for off-line washing. They had studied their existing configuration, made changes to improve it, and then continually monitored the system to determine if it was performing as it should, including maintenance and replacement of defective components.

And, again, ambient conditions (volume of pollutants; type of pollutants); amount of leaks in inlet air ducts (and there are usually many in systems which were only stitch-welded together after a few years of service); ambient humidity; filter efficiency; the care with which filters are installed (some come loose over time if not properly installed); whether or not evaporative cooling or some other kind of inlet air cooling is used--all of these things are going to affect compressor efficiency over time. Even with a brand new and "more" effective system.

Every installation needs to be carefully evaluated for the ambient conditions and then some decisions made about whether to "upgrade" or replace an existing on-line washing system. Claims have to be closely examined.

I would venture to say that a lot of the effectiveness of an existing on-line washing system can be restored or even improved by a careful analysis of its current condition, by observing the spray pattern, examining the spray nozzles for blockage or even wear, making adjustments to nozzle angle or even changing nozzles for better angles and spray pattern, would all have a benificial effect on the performance of the system for that particular site and turbine. Most of the sites I've been to just presume the system is working at its best, and rarely, if ever, do any testing or analysis or maintenance to any component (including cleaning the detergent tank).

Maybe even as much or more than just abandoning the existing system and replacing it with another system which, if not maintained and monitored properly, will likely degrade over time for the same reasons.