Because of legal and process engineering reasons, crude - oil - tanks have to be tested in regular intervals, if they are in good condition. In the past the tanks had to be opened and cleaned, in order to attain a reliable inspection - result. By using modern testing methods inspection - stations, e.g. TÜVs, are able to receive inspection - results, without opening the tanks. Nowadays the opening and cleaning of tanks is often only necessary, if tanks have to be repaired from inside, or if sludge - sediments have to be removed from the tanks. A service from inside interrupts the operation, therefore the number of interruptions should be reduced to a minimum. So the tanks should only be opened and cleaned in necessary situations (maintenance is regarded at the actual condition of the tank). This work concerns with cleaning and maintenance of fixed - roof - tanks for crude - oil - production. The necessary maintenance measures (examination, cleaning and repairing) for a specific 1.000 m^3 crude - oil production - tank are planned in the practical part and a concept therefore will be presented.