gas-tight flap after steam turbine

[Pederator]

Hello friends,

The company which I work for is a contract engineer of waste incineration plant (with energy recovery). The 13 MW steam turbine is extraction-condensing type, with outlet diameter 1,8 m. The technical terms of reference states that after the turbine it must be installed gas-tight flap, opened in normal operation, and closed eg. when turbine breakdown will occur (then live steam will be directed by the bypass reducing-cooling station to the condenser). We are wonder if this solution makes sense, as the turbine and condenser supplier is of the opinion that this is not necessary - they want to inject water to the condenser at bypass operation. The prospective problems with that flap could be vibrations and noise during normal operation, as the velocity of the steam after the turbine is above 100 m/s. But these problems are only suppositions, we do not have any experience with this kind (and size) of flap between turbine and condenser. What do you recommend? Have you ever heard of such a solution?

 

[dougarthur42]

A gas tight flap would be a check valve non return on the extraction. This is because if there is a turbine or extraction trip(shutdown) then you don't want water or steam to enter the turbine in this way. Many turbines have a bypass which takes an amount of steam and bypasses it directly to the condenser. If an extraction is off or the turbine trips then this allows the boiler(steam supply) to continue to run with out the turbine. It condenses the steam and sends it back to the boiler. Maybe there is a way to quick start the turbine and reintroduce the steam, or divert the steam to another turbine unit. Yes this is a normal way to set up a unit, but not all are this way.
Doug

 

[Pederator]

Thanks for the answer, Doug. I know that on the bleeds and on controlled extraction there must be non return valves, obligatorily. In the meantime I figured out what to do with that issue, so the topic is for quit.