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STEAM TURBINE VANE MODIFICATION

STEAM TURBINE VANE MODIFICATION

STEAM TURBINE VANE MODIFICATION

(OP)
DEARS,

DUE TO LACK OF ENOUGH WATER, I DECIDED TO GO WITH DRY COOLING INSTEAD OF WET COOLING

FOR OUR COMBINED CYCLE CONDENSING STEAM TURBINE, FOR A SURPRISE I HAVE BEEN TOLD THAT I NEED
TO MODIFY THE ROTOR VANES IN THE REAR SIDE OF THE TURBINE.

IS THIS TRUE? IF YES THEN WHY?

RE: STEAM TURBINE VANE MODIFICATION

The existing steam turbine was designed for an exhaust pressure range consistent with water cooling in the condenser. If cooling is switched from water to dry (air) cooling, the exhaust pressure will be higher, especially in extreme hot weather. Higher exhaust pressure means higher temperature of the exhaust steam. I can see two possible effects of the higher temperatures:
- Reduced tip clearances of the low pressure (LP) end rotating blades (last two or three stages)
- Change in natural frequencies of the LP end rotating blades (potential for resonances at operating speed)

Operating the existing blades with dry cooling may result in damage to the LP end rotating blades and/or damage to stationary parts of the turbine.

Best of luck!

RE: STEAM TURBINE VANE MODIFICATION

And, of course you will make a little less power.
Part of the change may be in order to try and get some of that power back.
When using air cooled condensers they also don't have to be as worried about wet steam in last stages.

Have you looked at hybrid systems?
Where the bulk of the heat removal is done with air cooling but there is a small final condenser that is water cooled.
This system can use much less water and still reach higher performance levels.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: STEAM TURBINE VANE MODIFICATION

1. "You" have decided to make a major change to your plant's turbine cooling system.

2. Have "you" told your turbine vendor about this change? Have "you" voided your warranty and repair schedules?

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