Issues with Wet Steam on Single Stage turbine

[planck121]

Hello,
We have been running with errosion related issues on a single stage steam turbine running a pump. It is a 2002kW, 4500 rpm rated turbine. The material of consturtion on the pressure casing is CS (A216) and nozzles are S.S AISI 416 with the bladings being AISI 403.

The issue seems to steam from the wet steam during turbine start-up and one of the vendors are recommending centrifugal seperators upstream of the each turbine + steam traps on the down leg into the steam turbine. I do not have much experience with the centrifugal seperatores. Do these really work? My experience has shown that in spite we will observe issues with erorion due to the wet content in the steam.

Are there other practically implementable solutions out there.

Thanks

 

[ash9144]

I've never seen the separators or traps do much of anything for wet steam. The only solution is to eliminate the wet steam.

 

[racookpe1978]

One phrase jumped up at me ... "wet steam during startup" ....

If that is what is causing the erosion - according to this vender (who wants to sell his products obviously, but not necessarily incorrectly) ... do you know how long a "startup" is and when the wet steam is replaced by operating point dry steam into the turbine? Can you just blow off the "wet steam" around the turbine until all pipes and supply lines are hot? (That would require a non-turbine alternative be running longer ...)

 

[unclesyd]

I agree with the post byracookpe if the problem is only with wet steam during startup. If this is true and your are seeing erosion the turbine must see numerous start ups. If is wet steam long after start up you will have to ascertain if possible to leave some superheat in the steam or use a separators. If you have problems with wet steam at all time and there are bends in the supply steam lines I would suggest you measure the pipe wall thickness for at least two feet past the bend, this is especially true if the bend causes a change in elevation.

We use both types of separators linked below in our steam and process gas streams with very good results. We don't use the Leslie but use a type very similar to it. The steam pressures range from 25 psig to 300 psig.

Another thing we do, as mention above, in one area where we produce the 300 psig steam from 650 psig we leave around 75F superheat after the PRV. This was done as the 16 process steam lines off this 300 psig header are very complex and weren't properly trapped when built. Even with this the some portions of the process still require separators for quality steam.

http://www.pennseparator.com/inline_entrainment_separators.htm

http://www.lesliecontrols.com/catalogindex/StmSepProdPg.pdf

 

[rmw]

Separators are commonly used in front of steam jets for the very same reason. They are fairly intolerant of wet steam. A low point trap immediately in front of your turbine is a must, separator or not.

The key to proper operation of any turbine is supplying it with dry steam.

Here is another separator that has lots of years of success.

http://www.wrightaustinseparators.com/?gclid=CM2tkJe1oKoCFSE_gwodhhnVXw

rmw