you'll gain extra few MW during online water wash during unit at BASELOAD. it just like power argumentation in Alstom machine.
First off, depending on what type/brand of GT you have. With GE's, especially LM6000's and other smaller turbines, the coating on their compressor blades cant handle the impingement/erosion effects of regularly performing an online water wash at base load. Second, the stability of the combustion dynamics basically go out the window, making you susceptible to a large number of trip points (high vibs, high temps, etc.)
The third thing, which is applicable to almost all GT's, is an online water wash does act as a "mini" power augmentation for the time it is performed. Depending on you air permitting, it could cause an exceedance/high emissions. Also depending on what type of generator protection you have, the increased load can cause some AVR and reactive power issues.
Overall, it would be prudent to reduce the load rating in order maximize compressor hardware lifespan => minimizing long term maintenance costs, while also maintaining maximum GT reliability and avoiding any contact with the EPA.
Hope this helps!!!
We Operate 7FA's and have begun Online Water Washing recently. SOP is to have Unit at Base load when Online Wash is done. Is recommended to watch your firing temp for deviation as it can take the Unit out of Base Load.
So far we have had no issues with Firing temp deviations or being taken out of Base Load. We only wash for 5 min a day on each unit, and have seen no significant increase in MW during wash.
Remains to be seen when we scope our blades to see the effects of washes on cleanliness and erosions. GE recommends water temps to be between 150 deg.(F)and 180 deg.(F).