Pumps & Systems, October 2007

Q. Is it true that centrifugal pumps should be built with ball bearings that have greater than normal internal clearance?

Pumps & Systems, July 2007

The food processing industry is one of the largest manufacturing industries in the U.S., accounting for approximately 14 percent of the total U.S. manufacturing output. A typical food processing plant uses equipment of varying ages, constructed of a myriad of materials, including carbon steel, aluminum, stainless steel and plastics. Corrosion - an attack on a material due to a chemical or electrochemical reaction with a surrounding medium - can be an enemy of many of those materials.

Pumps & Systems, November 2007

Rotary positive displacement (PD) pumps are not well understood by many specifying engineers and users and are sometimes misapplied, incorrectly specified or simply not used where they could or should be. This article explores the areas of commonality between centrifugal and PD pumps and ten common PD pump misconceptions and the reality behind each.

Pumps & Systems, July 2007

Since the early 1970s, pressure sewer systems have been an effective method to move residential wastewater through small diameter pipes to collection facilities where other methods are less economical or less feasible.¹

The keys to understanding the differences between conventional gravity sewer systems and pressure sewer systems are the piping network and the reduction of solids size in the wastewater. Pressure sewer systems use grinder type pumps to reduce the solids present to particles, which can easily be moved through small diameter pipes.

Pumps & Systems, July 2007

When is a metering pump not just an ordinary metering pump? When it exceeds API 675 performance standards with "pulse-free" linear flow that is being accomplished through the latest technological improvements.

While many institutions and associations have developed performance criteria for metering pumps, the American Petroleum Institute (API) Standard 675 for controlled-volume, positive displacement pumps is perhaps the most widely cited. It specifies accuracy (performance at a set point) of ±1 percent, linearity (speed/flow rate relationship) of ±3 percent, and repeatability (return to set conditions) of ±3 percent.

Pumps & Systems, August 2007

When we start the pump selection process for a particular application, one of our major concerns is efficiency. If several different models of similar quality meet our conditions, we will usually select the one with the highest efficiency. After all, higher efficiency reduces the cost of electrical power. There are times, however, when efficiency can take a backseat to the true, overall cost of operation.

Pumps & Systems, July 2007

Hose pumps have been around for many years, with some designs dating back more than 75 years. They are excellent devices for pumping slurries, due to their ability to handle very abrasive slurries. Hose pumps are also very good at dosing chemicals, since they are a positive placement device that can very accurately control the flow rate desired.

Pumps & Systems, July 2007

Last month we took a close look at the flow of voltage and current in purely resistive and inductive circuits. We showed how inductive reactance can inhibit the flow of primary current in a circuit and how this lagging effect determines the value of power factor (PF).

Although the purely resistive and inductive examples we used helped us understand what was happening, they do not represent a typical electrical circuit. Almost all circuits are a combination of resistive and inductive loads and, in some cases, those that are capacitive as well. Motors, arc welders, transformers, heaters, incandescent lighting, ballast lighting, solid state power supplies, and many other electrical devices contribute to the overall load on the circuit.

Pumps & Systems, July 2007

Intuition is wonderful, but sometimes deceiving. For example, I have always intuitively felt that "the better the alignment, the longer the pump life." But intuitively preaching about the horrors of bad alignment from an air-conditioned office is one thing; actually chasing a 0.001-in alignment issue under a 100-deg summer sun is something else entirely.

In other words, intuition does not address the real question: how much longer? So let's talk facts: what we know, not what we think we know.

Pumps & Systems, July 2007

When I first discovered the affinity laws, I was impressed by their simplicity, versatility, and power. For me, they held a certain allure. I believed I could use these three simple relationships to solve any pump problem: