Steam turbine 1

[hemnish]

Procedure and detailed methodology for wet steam washing of steam turbine may be forwarded

 

[JJPellin]

I am afraid I don't have the detailed procedure available, but I will still describe the general method that we use in order to get the discussion started. The main applicaion that is relevent in our plant is the 17,000 HP driver for our main air blower in the FCC. This turbine runs on 400# steam and exhausts at vacuum. We use an interstage pressure tap to determine when a water wash is needed. The efficiency of the turbine drops as deposits build up. As the efficiency drops, this interstage pressure builds. Our process engineers have determined (theoretically and from experience) when this is likely to start limiting our production at high charge rates. When we reach this point, they do the wash. We inject boiler feed water through an atomizing nozzle upstream of the turbine. An instrument is used to monitor the conductivity of the condensate coming off of the surface condensor. There is a temperature instrument immediately before the turbine steam inlet to monitor the steam temperature. They begin the water injection very gradually, monitoring the inlet temperature. They bring the temperature down at about 100 F per hour until they reach saturation. At that point, they begin to see changes in the conductivity of the condensate which indicates we are washing out mineral deposits. They hold the injection rate constant until the conductivity peaks and begins to drop. Once the conductivity drops below some predetermined level (I don't recall the value), they start reducing the water injection. They increase the steam temperature at the same rate of 100 F per hour until the water is completely removed. Following the water wash, they do a full performance evaluation to verify that the turbine efficiency returned to the original value. We used to have to do this once per year or more. I believe that our steam quality has improved such that we don't have to do this as often.

 

[electricpete]

what does FCC stand for?
thx

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[JJPellin]

Sorry. We uses so many TLA's (Three Letter Acronyms), that I sometime forget to spell them out. An FCC is a Fluidized Catalytic Cracking unit. This is one of the main units for making gasoline in an oil refinery.