Question 35

The Correct Answer is A. **Explanation for Option A (the hand-operated or auxiliary lube oil pump):** When starting a large rotating machine like a turbogenerator, it is essential to establish proper lubrication oil pressure *before* the main shaft begins to turn. The main lube oil pump (Option B) is typically driven directly off the main shaft of the turbine or by a motor whose control logic requires the turbine to be running. Therefore, during the initial phases of starting (when the unit is at zero or very low speed), an independent, usually motor-driven, auxiliary or "jacking" oil pump must be used. This auxiliary pump provides the necessary high-pressure lube oil flow to lift the shaft (in the case of jacking oil) or provide hydrostatic lubrication (in the case of bearing lube oil) until the main pump can take over once the turbine reaches sufficient speed. **Explanation for Incorrect Options:** * **B) the main lube oil pump:** The main lube oil pump is typically driven by the turbine's main shaft, meaning it cannot provide pressure when the unit is stationary or just beginning to turn. It only provides adequate pressure once the turbine reaches operational speed. * **C) a line from the other generator:** While redundancy and interconnection exist in power plants, routing lubrication oil (which operates at specific temperatures, pressures, and flow rates required for a single machine) from a completely separate, potentially running generator is not standard practice for initial startup. Each unit is designed with its own dedicated auxiliary lubrication system. * **D) a line from the gravity tank:** Gravity tanks (often called overhead or emergency rundown tanks) are used as a *backup* or *emergency* measure to provide a limited, temporary supply of oil to the bearings during unit coast-down (after the pumps fail or power is lost). They do not provide the necessary pressure or volume required to start the unit.