This existing Lube Oil System was provided by a major US supplier and was less than ten years old. It had a number of weak points, the most serious of which was that the DC powered Emergency Lube Oil Pump almost always failed to start pumping oil when it was turned on.
In this case, the focus was on the DC powered emergency lube oil pump that was a vertical centrifugal pump mounted on top of the oil reservoir with the pump suction bell in the oil. The suction bell filled with vapor from bubbles in the oil that gathered and coalesced, displacing the oil. When the centrifugal pump started, it could not pump oil until the vapor had been removed, which took many seconds. In that time period, a serious "Loss of Lube Oil" Event had occurred, with considerable damage to the bearings of the turbine-generator, requiring full disassembly, rotor machining for seals and journals, and repaired bearings.
This sequence of events was not fully understood until it occurred multiple times. A contributing factor was that the entire oil skid was built on top of a small reservoir and it was installed so that it was almost impossible for an operator to get to any of the major components. Maintenance on critical components had to wait for a major outage.
TRI designed and supplied a Complete Replacement Lube Oil System. This system was built like many other TRI oil systems, with duplex AC powered pumps, duplex filters and duplex coolers that were located separately so that most maintenance could be performed without a major outage. Almost always TRI designs use DC powered pumps that are mounted horizontally, are positive displacement, and are fully flooded, with considerable attention paid to isolation valves, pressure regulator valves, and pressure relief valves. Where possible, a separate battery is used for the DC Motor of the emergency lube oil pump. TRI uses a combination of hard-wired and DCS or PLC programmable controls.
While this case involved a 30 MW Turbine-Generator, the same design features apply to any size machine, whether new or in-service.