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In light of the recent record-setting floods in Texas, government entities, companies and individuals have stepped forward to ease the pain of residents and businesses across the ravaged state. Employees of Xylem, with offices in Houston, Dallas, San Antonio and Corpus Christi, acted quickly to support the dewatering needs of local businesses.

Editor's Note: While running a pump at its best efficiency point saves money, reduces downtime and improves performance, many plant managers are unaware of how their equipment is actually performing. The following real-world scenario is intended to illustrate the importance of monitoring pump efficiency.

The Jordan, Knauff & Company (JKC) Valve Stock Index was down 16.3 percent during the last 12 months, while the broader S&P 500 Index was up 10.7 percent. The JKC Pump Stock Index also decreased 15.4 percent for the same time period.1

Sealless centrifugal pumps with a magnetic coupling have become more popular among end users in the chemical industry.

Q. What are the best materials to use in pump construction to minimize part corrosion?

There's an old adage—usually credited to Otto Von Bismarck, the first chancellor of Germany—that says, "Laws are like sausages. It is better not to see them being made."

The implication is that reaching the consensus required to create a new law can be unpleasant, and it may be best not to know what the "ingredients" are and how that consensus was reached.

The Hydraulic Institute (HI) recently announced the publication of a new document, ANSI/HI 9.6.8 Dynamics of Pumping Machinery, that addresses the need for guidance on dynamic analysis of different pump applications.

Letter from a Reader

The following comments relate to scenarios described in Parts 1 and 2 of “Can Deaerators Create Pump Trips?” (Pumps & Systems, March and April 2015), which discuss handling power plant transients.

Rotary positive displacement (RPD) pumps theoretically displace a fixed amount of fluid per revolution. However, some loss in output is typically caused by the fluid slipping past the rotors. The difference between the quantity displaced (Qd) and the actual output quantity (Q) is slip (Sq).

Q. What principles drive the pumping action in a controlled-volume metering pump?

A. The pumping action is developed by a reciprocating piston. This reciprocating motion develops a flow profile represented by a sine wave. Actual rate of flow is determined by the following formula:


A reciprocating power pump, as depicted in Figure 1, is a displacement machine. It has characteristics that are different than a centrifugal pump.


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