Which of the following is NOT one of the main categories of pump types?

The classification of pump types typically includes designs based on their operational principles or mechanisms. Piston pumps, diaphragm pumps, and centrifugal pumps are widely recognized categories.

Piston pumps operate by using a piston to create pressure and move fluid, making them efficient for high-pressure applications. Diaphragm pumps utilize a flexible diaphragm to alternate between filling and expelling fluid, which is effective for handling corrosive or abrasive liquids. Centrifugal pumps function by converting rotational energy, usually from a motor, into hydrodynamic energy, efficiently moving fluids at relatively low viscosity.

In contrast, "Turbo" is not categorized as a main type of pump. While turbo pumps exist, they are generally specific to applications such as gas or vapor pumping rather than being classified alongside the more commonly utilized pump types mentioned. Therefore, in the context of main categories, turbo does not align with the conventional classifications of pumps.