When you are not running the steam turbine and dumping steam directly into the condenser you need to make sure that the steam conditions match those for steam exiting the turbine. So you use cold water spray to de-superheat the steam.
Too little spray and you will damage the condenser sue to high temp and thermal stresses, too much spray and the high velocity water droplets will cut right through most condenser tubes.
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P.E. Metallurgy, Plymouth Tube