Engineering Notes

This page once carried a manufacturer's press releases — product launches, trade-show schedules, the news cycle of an industrial sales office. We have kept the address and repurposed it for something with a longer shelf life: in-depth articles on the engineering problems that pumps pose to the people who run them. New notes are added as they are written; each is meant to stand alone and stay useful for years.

The Notes

NPSH and Cavitation: The Suction-Side Story — Every pump has a price of admission: enough absolute pressure at the suction nozzle to keep the liquid from boiling inside the impeller eye. This note explains net positive suction head from first principles — what NPSHa and NPSHr actually mean, why the 3% head-drop test understates the onset of damage, how to recognize cavitation by ear and by impeller autopsy, and the practical levers (elevation, temperature, line losses) that fix it.

Pump Selection and Sizing: Reading the Curve — The most expensive pump mistakes are made on paper, before anything is bought. This note walks through the selection workflow: establishing the duty point honestly, constructing a system curve, reading manufacturer performance curves, understanding the best efficiency point and the cost of operating far from it, and deciding between rotodynamic and positive displacement designs in the borderline cases.

Maintenance and Reliability: Why Good Pumps Fail — Industry studies consistently find that most pump failures trace to a handful of preventable causes — and the pump itself is rarely the original culprit. This note covers the dominant failure modes (seals and bearings), the operating habits that drive them, condition monitoring that actually pays for itself, and the difference between fixing failures and engineering them out.

A Short History of American Pumping — From the steam-driven waterworks engines of the nineteenth century to canned motor pumps and cryogenic submerged-motor machines, the story of pumping in America is the story of its industries. This note traces the technology's arc and explains how the demands of chemicals, refining, water, and energy shaped the machines described elsewhere on this site.

One Idea Worth Keeping

A reader of the original site's archives will find, buried in a 2001 press release, a genuinely durable engineering point: reciprocating positive displacement pumps demand constant torque across their entire speed range, while centrifugal pump power falls away steeply as speed drops. Pair that with the fact that standard motors produce less cooling and less usable torque at low speed, and you have the reason variable-speed metering installations need drives and motors selected for the duty — not just whatever inverter is on the shelf. Twenty-five years later, with variable frequency drives everywhere, that lesson still catches people out. We explore it further in the metering pump note.

Suggest a Topic

The queue of future notes is shaped by reader requests — mechanical seal flush plans, vibration analysis, viscosity corrections, and self-priming designs are all candidates. If there is a topic you want treated properly, tell us.