Russia has announced a DPM-2 programme to modernize old power plant equipment. One of the main areas of modernization is the replacement of some of the equipment while maintaining the foundations, building structures, most of the equipment and piping of the turbine unit. It is common practice to introduce additional equipment, such as control and protection units for electro-hydraulic control systems, as well as new pipework, which leads to problems in the layout of the steam turbine unit.The oil system is an integral part of the turbine unit. It accounts for a significant proportion of the cell volume of the steam turbine unit layout. This property of the system can be used to solve problems associated with the layout of a steam turbine unit in modernizations. A solution is proposed for redesigned layout of the oil system in the cell by introducing an oil supply module (station) into the structure of the steam turbine unit. As of now, there are no commercially available offers of an oil station with the required oil tank capacity. The oil station module is arranged at places free from equipment of the cell, for example, at the 0.000 elevation or under the upper operating mark near the generator and below the level of turbine unit bearings to enable oil drainage by gravity. The main differences are outlined between the proposed oil station and the existing oil system.The oil system determines the reliable and trouble-free operation of the steam turbine unit. In order to be able to introduce an oil supply module into operation it is necessary to design the system based on the requirement of maximum reliability. Reliability analysis of oil supply unit has been carried out. The regularities between the designer's decisions and the reliability of the resulting system are revealed. The influence is considered of the oil station components on individual reliability constituents: survivability, durability, fail-safety, maintainability, fire safety.