CONDENSER – AIR EXTRACTION EQUIPMENT ( 1 Of 3 )
 

[LEFT][B][F**T=&quot]C**DENSER – AIR EXTRACTI** EQUIPMENT[/F**T][/B]

[B]- Turbines are designed for a particular operating c**diti**s like steam inlet pressure, steam inlet temperature and turbine exhaust pressure/ exhaust vacuum, which affects the performance of the turbines in a significant way. Variati**s in these parameters affect the steam c**sumpti** in the turbines and also the turbine efficiency. Theoretical turbine efficiency is calculated as work d**e by the turbine to the heat supplied to generate the steam.[/B]
[B]- Higher exhaust pressure/ lower vacuum, increases the steam c**sumpti** in the turbine, keeping all other operating parameters c**stant. Exhaust pressure lower than the specified will reduce the steam c**sumpti** and improves the turbine efficiency. Similarly exhaust vacuum lower than the specified, will lower the turbine efficiency and reduces the steam c**sumpti**.[/B]
[B]- The air extracti** equipment must be capable of meeting two c**diti**s; **e met during normal operati**, the other when raising vacuum ** the turbo-generator unit.[/B]
[B]- When raising vacuum the air extracti** equipment must deal rapidly with a large quantity of air and sufficient capacity must be installed to reduce pressure quickly in the c**denser to a level which allows the turbine to be started. The last row blades of a 500 MW turbine will overheat if they run at speed and at low load in a poor vacuum. Thus, a vacuum of 20 in.Hg must be obtained before steam is admitted to the turbine and a vacuum of 26 in.Hg for full speed. It is important that the time taken to bring a turbo-generator ** load shall not be increased by sufficient air extracti** capacity.[/B]
[B]- Under normal operating c**diti**s the quantity of air to be exhausted is lower. It c**sists of air leakage into the c**denser via flanges and glands and also of inc**densable gases that are present in the steam exhausting from the turbine. Air and inc**densable must be removed from the c**denser as their presence in any quantity impairs the heat transfer capability of the c**denser and hence its performance. C**versely, excessive air extracti** capacity should not be run, as this involves unnecessary running costs and also results in the extracti** of an unwanted quantity of water vapor from the c**denser steam space.[/B]


[B][I][U][F**T=&quot]“We will talk about the equipment for the extracti** in the 2 upcoming articles”[/F**T][/U][/I][/B][/LEFT]

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