8413.91 - Of pumps:

This HTS category, 8413.91, encompasses parts specifically designed for pumps that handle liquids. It covers a broad range of components, excluding those pertaining to liquid elevators. The primary function of these parts is to contribute to the operation of various types of liquid pumps, facilitating the movement or pressurization of fluids in diverse industrial, commercial, and domestic applications.

Distinguishing this category from its sibling, 8413.92.00.00, is crucial. While 8413.91 focuses exclusively on parts of liquid pumps, 8413.92.00.00 is reserved for parts of liquid elevators, which are devices used to raise liquids by mechanical means rather than through direct pumping action. Therefore, the classification here hinges on whether the part is integral to a pump's mechanism for drawing in and expelling liquid, or part of a separate lifting apparatus.

The subcategories within 8413.91 further refine the classification based on the specific type of pump the parts are intended for. For instance, 8413.91.10.00 isolates parts for fuel-injection pumps used in compression-ignition engines, a specialized application. Similarly, 8413.91.20.00 addresses parts for stock pumps designated for use with machinery in the pulp, paper, and paperboard industry. The residual category, 8413.91.90, serves as a catch-all for parts of other liquid pumps not otherwise specified, ensuring comprehensive coverage.