Steam Turbine Fouling

[imans]

Dear Eng-Tips'er,

We have problems with our turbine in RCC unit. The steam flow to the turbine is decreasing everyday eventhough the governor has been kept in manual at maximum opening. The turbine is driven by steam produced in RCC catalyst cooler and RCC CO Boiler. Base on the lab result, the quality of steam is pretty good most of the time only one or two occasion when the steam quality is off (usually silica. the spec is < 0.02 ppm but sometime the silica in steam could reach 0.05 ppm). Last month , we cleaned the turbine and checked the deposit on the turbine blade. The deposit predominantly Phosphate, Silicate, Fe, and Al. Now, we already run the turbine but the performance is drop again. The steam quality seems pretty good. My question is
1. Does anyone know, where the Al in steam come from?
2. Does anyone have some clue where I can find literature on how deposit can be built up in steam turbine?
3. Is it true that once the deposit is built up in the turbine blade, we cannot preven the deposition eventhough the steam quality has already recovered?
4. Does anyone has experience with inline cleaning of steam turbine?

Thank you for your help

 

[sshep]

I know that our ethylene plant has descaled turbines on-line using atomized condensate in the supply steam, but this is something that you need to work out first with the turbine representative. If they agree it is possible then you will want to have their technical support onsite the first few times to help develop a procedure and monitor.

If you try to do on line cleaning without technical support from the representative then you risk wrecking your turbine, causing a accident, or worse.

best wishes,
sshep