Horizontal vs Vertical: Choosing the Right Centrifugal
When choosing the right centrifugal or booster pump for a new system, there are factors that should be considered. Flow rates, piping configurations and dimensions are commonly considered. But what about the pump configuration? Should a horizontal or vertical pump be selected?
When selecting a pump, the footprint should be examined. A horizontal pump will occupy floor space which could be critical in a water treatment system. A vertical pump takes up less floor space but requires vertical headroom as well.
Typically, end suction centrifugal pumps need to be mounted horizontally. While the Webtrol EZ Series is a multistage horizontal pump, it can be mounted vertically on a wall or rack to suit a specific application. The Webtrol NV Series is a vertical pump which uses very little floor space.
Priming and start up should also be investigated when selecting the pump. Horizontal pumps are easily primed. Vertical pumps, however, may be harder to prime initially since air can get trapped in the upper portion of the impeller stack. Additional bleeding the air and cycling are sometimes needed. Once the system is operational, priming should not be an issue unless air is drawn into the system by lack of water.
Net Positive Suction Head (NPSH) should also be weighed when choosing the pump configuration. If the NPSHa (Net Positive Suction Head available) is sufficient to avoid cavitation, both configurations will work. If NPSHa is marginal due to a negative elevation of the fluid in relation to the pump, a foot valve to hold the pump full of water will be needed or additional priming equipment may be necessary. In some cases, a self-priming centrifugal might be an option to ensure that the prime is not lost.
Finally, performance near best efficiency is always a consideration. In selecting a pump that runs nearest to the best efficiency point, you are choosing the manufacturer’s selected performance in both operation and energy savings. This adds up to life cycle cost of the pump being held to a minimum.