A B777-200 equipped with Rolls Royce engines developed a fuel leak in a line between the tank and the engine after a foam liner between a bracket and fuel line wore away.

Narrative

The Captain; the First Officer and myself suspected a fuel leak because of a fuel imbalance and fuel quantity below the planned numbers. The Captain declared an emergency and then diverted directly to ZZZZ where he made an uneventful landing. Later; our maintenance personnel identified and repaired a crack in a fuel line on the left engine. After the proper documents were completed we departed for ZZZ later that day. Solutions: The fuel line and the faulty bracket needs to be inspected on every Rolls Royce engine world wide. The foam liner between the bracket and the fuel line had worn away and the metal against metal contact created the crack. Our maintenance personnel stated they were on the problem; but there needs to be some follow-up from the very top!Supplemental info from ACN 825155: Maintenance found a fuel leak in a line between the tank and the engine. The part and maintenance crew were flown into ZZZZ to fix the line. After they did an engine run we flew the aircraft back to ZZZ.