Attemperation is the process of controlling the amount of superheat in a boiler or a Heat Recovery Steam Generator (HRSG). Spray water is injected into the superheated steam, reducing its temperature. Spray water flow is controlled by an external water control valve and injected perpendicular to the steam flow using a series of spring-loaded spray water atomizing nozzles. The steam pipe is protected from thermal stresses by a floating liner which also acts as a flow profiler, increasing the relative steam velocity near the nozzles and improving evaporation.
The floating liner is installed without any welding, allowing it to move with the expansion of the material, making it more resistant to cycling.