Question 491Steam Plants - Assistant Engineer

The correct answer is D) in a storage tank. The flash point of a residual fuel oil is used to determine the maximum safe temperature for storing the oil in a storage tank. The flash point is the lowest temperature at which the oil gives off enough vapor to form an ignitable mixture with air. Heating the oil above this temperature could create a fire hazard. Therefore, the flash point sets the upper limit for the storage tank temperature to ensure safe handling and storage of the fuel oil. The other options (A, B, C) are incorrect because the flash point is not used to determine the temperature limits for recirculating lines, atomizing, or centrifuging the fuel oil. Those processes have their own temperature requirements based on the oil's viscosity and other physical properties.