# Columns and Blogs

Specific speed is a concept developed for water turbines1 in 1915, which was later applied to centrifugal pumps (Stepanoff, 1948). Specific speed is a way to “normalize” the performance of these hydraulic machines.
Temperature changes can push pipe force beyond safe limits
Keeping a close eye on pump efficiency can lead to energy savings.

It's a New Year, time to make those New Year's resolutions.

This is a follow-up to my column on predicting centrifugal pump performance (Pump & Systems, May 2011), and offers equations that will enable the engineer to perform a partial analysis of the impeller eye.

Energy efficiency and reduced consumption are important issues in the pump and motor marketplace.

The radial forces that form about the periphery of a single volute pump's impeller are proportional to total pump head, impeller diameter and vane width. They are seldom balanced, but they reach their lowest intensity between 80 and 100 percent of BEP flow.

About 900 years before Newton formulated his universal gravitational theory, the Greek philosopher Aristotle espoused something different.

A number of choices are available when connecting pumps, fans and other rotating equipment to an electric motor. There are numerous mechanical and fluid coupling designs and, in some cases, a belt drive option is available.

In Pumps & Systems January 2007, I wrote an article about cavitation and how a collapsing water vapor bubble can damage an impeller. Since then, I have received a number of requests to address Net Positive Suction Head (NPSH) and its relationship to cavitation. Here it is in a very simple, Pump Ed 101 perspective.

The frame sizes (physical dimensions) of AC motors have changed substantially through the years. Originally, they were considerably larger than those in use today. This increased size was the result of inefficiency and the need to dissipate heat.

The frame sizes (physical dimensions) of AC motors have changed substantially through the years. Originally, they were considerably larger than those in use today. This increased size was the result of inefficiency and the need to dissipate heat.

Dr. Lev Nelik answers pump user questions.

Based on several of my previous Pumps & Systems articles, you probably know that I have major concerns about the off best efficiency point (BEP) operation of wastewater pumps.

Efficiency degradation in pumps can be related to three areas.

One of the major impacts on motor life is common sense—or maybe the lack thereof!

When the motor amps are kicking a unit offline, the first question is whether the motor or the pump is the problem.

There are several ways to control two identical, parallel pumps operating under variable frequency control in pumping applications.

While scheduled downtime is different from unscheduled, both can take away from a company.

This month we will quickly look at the load types that comprise a typical AC circuit.