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Need help about steam turbine

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I am working at a 1223 MW CCPP installed with 2 x GE H class gas turbines and 1 x Alstom triple pressure steam turbine. We are having a shutdown these days and got a chance to go inside the condenser or LP turbine exhaust section. There, we saw an open flange at either side of the LP turbine after its final stage and before de-superheating nozzles manifold. That open flange is associated to a line that is going vertically in the upward direction but it cant be traced because of space issue.

I have checked the cross sectional diagram of the steam turbine and according to my knowledge both of the above mentioned flanges are shown there ( attached please find the drawing) .

Can anyone please help me and my follows in understanding the purpose of these two lines ending on open flanges? any help in this regard will be very beneficial


thanks in advance 




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I have worked with the equipment you describe and have also looked inside these machines many times over the past 40 years. Your description is not accurate. There are no de-superheating nozzles anywhere near the final stage of this or any other LP steam turbine. The steam would only be superheated at the inlet. Besides, you would only desuperheat steam at the HRSG, not at the turbine, where you want it to be superheated. I have attached an actual expansion line from a similar 3-pressure system, also using an Alstom STG. I have many detailed steam cycle models for this type of system. The steam at the exit will be moist (about 3% to 7%) at the exit of such a turbine, as shown where the red line crosses and extends below the blue one in the figure.


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