Solution for turbine nozzle load restrictions

[garfio]

Turbine nozzles per NEMA SM-23 have very low allowable loads. Although the preferred solution is to obtain enough flexibility with the piping, I believe that there are cases where this solution is not possible, and expansion joints have to be used.

I would like to here people's experience about this matter. Are there conditions under which it is know (or suspected) that expansion joints have to be used? Is this related with size of turbine? I've seen some small turbines with support that look like stanchions connected to their lines (both in and out)and some other larger ones seem to have an expansion joint.

How typical is the use of an expansion joint at the exhaust connection, which is larger and more difficult to satisfy with the piping arrangement?

 

[C2it]

An expansion joint on a steam turbine discharge is quite common, where space is limited by close location of a condenser for example. On the supply side you would need to consider the usual risks of using an expansion joint .... non-shock service, pressure and temperature limitations, proper restraint.

If you cannot meet NEMA allowables, discussions with the vendor are always worth a try.

 

[MJCronin]

C2it..

I believe that the nozzle allowables are set low in the NEMA standard in order to generate more money for the turbine manufacturers.

Getting acceptance for the loads that your particular piping system will generate is always a big moneymaker for these people....has been for decades

Turbine manufacturer's acceptance of your loads always trumps NEMA SM-23 requirements.

-MJC

 

[PaulDBerg]

As a vendor of expansion joints (Flexicraft), we run into this a lot. Normally when expansion joints are used on the turbine, they are a special "pressure balanced" type that minimize the nozzle loads. Otherwise, adding an expansion joint can actually bring the loads up, due to the "thrust load" generated with an expansion joint under pressure.

http://www.flexicraft.com.