Theory of centrifugal pumps and key equations typically used for designing of such pump systems -
Net Positive Suction Head - Net Positive Suction Head or NPSH for pumps can be defined as the difference between liquid pressure at pump suction and liquid vapor pressure, expressed in terms of height of liquid column. Definition of available net positive suction head or 'NPSHA' can be found here along with a brief explanation.
Pump Performance curves - Pump performance curves are important drawings produced by the pump manufacturer. Pump performance curves are primarily used to predict the variation of the differential head across the pump, as the flow is changed. A sample pump performance curve included in this post helps to understand pump performance curves and the information that they usually provide such as variation of differential head, power requirement, NPSH requirement and pump efficiency, along with variation of operating flow.
Pump Specific Speed and Pump Suction Specific Speed - Pump specific speed and pump specific speed are two quite different entities but can be confused with each other at times. This post defines both the terms with an equation for each - pump specific speed and pump suction specific speed. Difference between the two is clearly outlined.