Turbine bleed pressure
Turbine bleed pressure
(OP)
Hi,
I was wondering how high of a pressure the turbine bleeds, extraction piping and pre-heater can experience in case of blocked passage after the pre-heater (assuming no safety valves on the pre-heater shell sides).
To formulate the question in another way, what would be a good design basis for selection of design pressure of the bleed/piping/preheater.
I mean the worst possible situation would be all blocked bleeds and open turbine valves in which case the pressure would leak through and pressurize the whole system with the turbine inlet pressure. This situation is however not reasonable - what would be a reasonable worst case?
Drex
I was wondering how high of a pressure the turbine bleeds, extraction piping and pre-heater can experience in case of blocked passage after the pre-heater (assuming no safety valves on the pre-heater shell sides).
To formulate the question in another way, what would be a good design basis for selection of design pressure of the bleed/piping/preheater.
I mean the worst possible situation would be all blocked bleeds and open turbine valves in which case the pressure would leak through and pressurize the whole system with the turbine inlet pressure. This situation is however not reasonable - what would be a reasonable worst case?
Drex





RE: Turbine bleed pressure
The only thing that is going to see turbine inlet pressure is the first stage nozzle block. Anything downstream of that sees a continuously declining pressure which follows your turbine expansion line on a Mollier diagram.
rmw
RE: Turbine bleed pressure
Lets say during normal operation the pressure in the inlet/bleed/outlet is 20/4/0,1 bar and i block the bleed. This means the steam that escaped through the bleed will have to continue through the rest of the turbine. Intuitively I would assume the pressure in the bleed would go up, how much - I don't know. Say it would be 6 bar. So then the question is, would this pressure be a reasonable design pressure for the extraction piping and pre-heater?
I'm thinking about what scenarios I would have to consider in order to select a suitable design pressure/temperature for the extraction piping/preheaters.
RE: Turbine bleed pressure
If the flow through the turbine is restricted the throttle will close or pressure relief will open long before you reach high pressures in the extraction lines.
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Plymouth Tube
RE: Turbine bleed pressure
If extraction are shut off the pressure in that extraction zone will rise. The pressure in the extraction zone is essentially linear with the flow to the following blade group.
Best of luck!
RE: Turbine bleed pressure