At what temperatures does the fuel oil transfer heater operate to purify fuel?

The correct answer is the option indicating "Optimum temperatures" because fuel oil transfer heaters are specifically designed to operate at a range of temperatures that maximize the efficiency of purification processes. When fuel oil is heated to its optimum temperature, numerous beneficial effects occur.

At these temperatures, the viscosity of the fuel oil is reduced, allowing for better flow and improving the separation of impurities, such as water and particulates. This separation is crucial for ensuring that the fuel remains clean and performs optimally within the system. If the temperature is too low, the purification process becomes ineffective, as the impurities do not separate adequately from the fuel. Conversely, operating at excessively high temperatures can risk damaging both the hardware and the fuel, potentially leading to degradation.

Thus, maintaining the heater at optimum temperatures is critical for effective purification, making this the most accurate choice regarding the operational temperature range for fuel oil transfer heaters.