Boiler desuperheating water
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Instruction manual from a boiler factory: At the rated evaporation rate, the total amount of superheater desuperheating water should be kept within 50–200% of the design value. Why not 0–200%?
The specified value must have been calculated; this indicates that the superheater may overheat if the value is below 50
It reflects the amount of heating surfaces available for overheating control; generally, tender specifications require that parameters be maintained at 50%, meaning that even when the evaporation rate is at 50%, the steam temperature parameters must still be met without the use of desuperheating water. This requires installing more superheated heating surfaces.
Thank you to Chuanyou for the answer. After communicating with the manufacturer, it was stated that, at the rated evaporation rate, the total amount of water used for superheater cooling should be kept within 50–200% of the design value; in other words, it ranges from 0 to 200%. A range of 0 to 50 doesn’t have much practical significance, as the steam temperature cannot reach the rated values at low load levels.
Let me put it this way: if the total amount of cooling water used at rated load is too low, it means that the furnace cannot maintain the parameters of superheated steam when operating at low loads