Effect Of Minimum Exhaust Flow In Steam Turbines

The effect of minimum flow in the low pressure section/s is an increase in temperature caused by windage. The alarm and trips are usually set in the area of 185 F. and 210 F. respectively.

Some of the older units were not fitted with trips or alarms and the blistered paint gave a visual indication of the effect. The long term effect is to warp the hoods and casings. A more immediate effect can be light to heavy rubbing in the affected hood.

ok sir, Is it a similar conditon during rolling time & during, minimun load condition?

If you are asking if increasing the roll speeds and holds by a factor of 3, then you have a lot of consequences to consider most of them not related to the hood temperature.

Before you start modifying your controls or startup procedure check out your present operating conditions. Modern units have hood sprays, this is usually supplied from condensate or other points in the feedwater cycle. Make sure the nozzles are intact and clear. Establish that flow in fact exists.

Vacuum must be maintained at the level specified by the manufacturer, This should have been calculated using the proper station elevation. If you are running on low vacuum you will only increase the problem.

Your reasoning is correct the way to put a band aid on the problem is to get flow in the LP sections. My guess is the design parameters need to be restored to cure the problem.