As per asib 11th and 12th edition rule 2035.
“pipes that carry lubricating oil or fuel shall be of flame resistant reinforced flexible hose or suitable material listed for this service.
Pipes shall not be made from plastic, rubber and pipe joints may not be soldered.
Piping for any fuel line shall not be copper, cast iron, aluminum or galvanized tubing.”
Recent experience has shown that copper fuel lines are not suitable for delivering diesel fuel to the engine. Condensation in the tank lines combines with the sulphur in the diesel fuel to produce sulphuric acid. The molecular structure of copper or galvanized lines or tanks reacts with acid and contaminates the fuel.
Materials that are not deemed to be suitable are copper, cast iron, aluminum or galvanized tubing. Copper and aluminum also tend to harden over time and become brittle. We therefore recommend that the fuel lines be replaced with an acceptable alternative such as braided hose.”