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

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

33 CFR 157.120 mandates that crude oil washing (COW) systems utilize permanently installed, fixed washing machines. Portable washing machines are strictly prohibited for crude oil washing operations due to safety hazards, such as static electricity generation, vapor exposure, and the loss of inert gas containment required in petroleum tanks during COW.