First Class Steam License Practice Test 2026 - Free Practice Questions and Study Guide

Turbine feedwater pumps are classified as positive-displacement pumps because they operate by trapping a fixed volume of fluid and forcing it into the discharge line with each cycle. This mechanism ensures a steady flow of water regardless of the pressure conditions downstream, which is crucial for the feeding of water into the boiler system in steam plants. The design allows these pumps to maintain high efficiency at varying pressures, making them well-suited for applications where precise flow control is necessary, such as in feedwater systems.

In contrast, other pump types mentioned operate on different principles. Centrifugal pumps increase fluid flow through rotational energy but do not provide the same pressure stability as positive-displacement pumps. Diaphragm pumps utilize a flexible diaphragm to create suction and pressure, while screw pumps operate using helical screws to move fluid, neither of which match the specific characteristics of turbine feedwater pumps. The classification as positive-displacement is therefore essential for understanding the functionality and application of turbine feedwater pumps in steam systems.