Hello friends,

I have a query relating to the turbine allowables.

The allowables at steam inelt flanges are specified by supplier.(fx,fy,fz & mx,my,mz)

In displacement, there are 2 sets
1. Nominal operating point
2. No load point.

What do they exactly mean?

Also in my main steam piping, i have warm up vent line connected to silencer with its ends are butt welded.

Do we need to consider the loads on turbine steam inlet flange during warm up vent case(as per supplier allowable loads) & what displacement should i specify at steam inlet flange while considering warm up vent case.

Waiting for your guidance. Thanks in advance.

You could ask the turbine supplier to be sure of a correct answer.

Dear friend,

My seniors suggested me to match the steam inlet nozzle load for warm up vent case also, with zero displacement at inlet flange end.
Considering this case, i think it leads to over constraint of the piping system, and may affect the flexibility in operating case.
Kindly give your views and the way u all follow and understand.
Waiting for your useful suggestions....

nishit,

The turbine and steam piping have several cases for normal operation, startup, and shutdown. The best solution would have the piping be flexible enough for the worst combination, so that forces are within allowable loads for all conditions.

First, the turbine vendor provides two sets of displacements, since the turbine casing will have two very different outlet temperatures depending on load / no load. During no-load startup or shutdown conditions, the outlet temperature will be much higher, almost the inlet steam temperature. Startup casing thermal growth will be greater than the normal condition when outlet temperature would be maybe 200 deg C less. The outlet steam piping needs to also consider the higher temperature during no-load startup/shutdown, along with normal outlet temperature of turbine.

The inlet steam piping during start up venting could be modeled with zero displacement of turbine inlet connection, but it might have only small difference from full temperature condition with casing displacement and steam piping thermal growth.