-Overheated Level of Vapors In general, vapors are transported in a high-temperature and high-pressure state adjusted according to process requirements. To resolve problems, such as occurrence of condensate water caused by reduction in transportation efficiency from the boiler to the point of use and external heat loss in vapor pipelines, vapors need to be at an overheated level. In accordance with process requirements, high-temperature and high-pressure vapors are supplied to processing facilities after lowering the pressure with pressure- reducing valves. Compared with saturated vapors, the pressure-reduced vapors are overheated with higher temperature as shown in the red region of Figure 1. For example, if the 40 barA pressure saturated vapor (saturation temperature 250.3 ℃ ) is reduced to 5 barA (saturation temperature 158.8 ℃ ), it becomes 178.1 ℃ in an overheated vapor state, 19.3℃ higher than the saturation temperature