What is NOT a requirement for the safe and effective use of a crude oil washing system?

Correct Answer: Option B — Use portable washing machines to reach areas obscured by structural members in the tanks.

Under 33 CFR 157.120, crude oil washing must be conducted exclusively using permanently installed, fixed tank washing machines. Portable washing machines cannot maintain inert gas integrity, pose severe electrostatic hazards, and introduce flammable vapor exposure risks; therefore, using portable equipment is explicitly prohibited during crude oil washing operations.