Which statement is true regarding cleaning tanks after carrying a cargo of crude oil?

The correct statement regarding the cleaning of tanks after carrying a cargo of crude oil is that steam cleaning and water washing generate electrostatic charges within a tank. This is a critical safety consideration in tanker operations. When vessels have carried cargoes like crude oil, cleaning the tanks using steam or water can create conditions where static electricity builds up. The movement of liquids, especially in the presence of impurities or the nature of the liquids being used, can lead to the generation of static electricity, which poses a significant hazard if it discharges in the presence of flammable vapors.

Understanding the electrostatic charge generation is vital for preventing ignition and explosion risks within the tanks. Operators must take precautions to mitigate these risks by properly grounding equipment and following safety protocols during the cleaning process.

In this context, while there's merit to the other statements, they do not accurately reflect the primary concern when conducting tank cleaning operations. For instance, while raising ambient temperatures can be a concern, it's not the principal hazard associated specifically with washing tanks after crude oil cargoes. Likewise, the handling of washing water in relation to electric potential and the protocols surrounding the use of hoses are important operational aspects, but they do not address the critical issue of electrostatics as directly as the correct statement does