On a turbine driven feedwater pump, which piping is typically larger?

In a turbine-driven feedwater pump system, the turbine steam exhaust piping is typically larger because it has to accommodate the large volume of steam that exits the turbine after it has performed work. This steam must be efficiently directed to either a condenser or to another part of the system for further processing. The larger diameter of the steam exhaust line allows for reduced pressure loss and ensures that the steam can flow freely without creating bottlenecks that could affect system performance.

Additionally, the steam exhaust is subject to high temperatures and pressures, requiring a robust design, which often translates to a larger pipe size for strength and thermal efficiency. In comparison, the other piping options, such as the return water line, boiler blowdown line, and condensate line, involve different functions that do not require the same volumetric capacity or robust thermal considerations as the steam exhaust from the turbine. These lines are generally smaller in diameter as they handle fluid at lower pressures and volumes compared to the turbine steam exhaust.