Steam turbine discharge

[planck121]

Hello
We are looking at possibly increasing the steam turbine speed by about a 150 rpm to bring down the discharge temp of the steam for downstream equipment. This is a small single stage turbine. And the plan is to increase the speed at no load condition to drop steam enthaply. The use of desuperheater downstream was addressed and discarded due to certain reasons.

Does this pose any issues I do not see this to have any major implications. Are there other ways to drop steam temp on the discharge without doing any major modifications.

Thank you

 

[racookpe1978]

What is the steam turbine "doing" now, and what will happen to that load/that service when you change its speed?

 

[JJPellin]

I would not expect increasing the speed on an unloaded turbine to have much benefit in terms of exhaust steam temperature. You are more likely to be successful by reducing the temperature of the steam supply to the turbine, increasing the load on the turbine or reducing the exhaust pressure. If the turbine has economizer valves, close them.

Johnny Pellin

 

[planck121]

Thank you gentlemen for your replies. I have decided to setup the model in hysys and simulate some conditions to see then temp profile on the outlet steam. The turbine will be started on a no load condition or load condition depending on the start up requirement and the vendor had just come back with the discharge temp in the no load case that would be quite high.

 

[rotw]

For example, with variable speed turbines API requests to have 5% margin between rated speed and maximum continuous speed and that is to cover the many things that can be deviate from design in real world which needs to be covered with a safety margin.
If you run over speed, means between rated and max continuous speed you will reduce this 5% margin available so this needs to be carefully evaluated from mechanical and rotor-dynamic point of view (check the critical speeds of the turbine for example) assuming the amount of over speed you intend to apply really provide the advantage in terms of temperature drop you are looking for. At no load it is normal that the temperature is high. You could also inject water condensate at no load to reduce the exhaust temperature.

Best advice is to contact manufacturer for feasibility.
You should have given more details on the application/machine type.