Two heavy fuel clean engines leakage collecting double bottom tanks (one per the fwd engines and one for the aft engines). One (1) pump is to be installed to transfer the clean leakage from the DB tanks to one (1) of the settling tanks. Normally one group of purifiers will take suction from the dedicated settling tanks in their respective engine room and after processing discharge to the dedicated service tanks in the same engine room. The purifiers are to operate continuously. Excess fuel from the service tanks will overflow to the settlings tanks.