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removing its rotating element or bothering theelectric motor or piping.

Only one person is needed to repair an HSCpump for most HVAC sizes.

An HSC pump has a longer useful life than other

pumps. An HSC pumps efficiency is

equal to, or better than, that of otherpumps.

footprint

An HSC pump requires less total space than otherpumps.If space is critical, an HSC pump can bereversed to reduce the total room required for severalpumps. Just because suction and discharge nozzlesstick out of the sides of an HSC pump does not meanthe total room needed is greater. Most HVAC pumpmanufacturers can provide suction diffusers for theirpumps so that the five suction diameters normallyrecommended are not needed.

inspection

A common complaint is, My pump is noisy ornot producing.

An HSC pump can be opened for inspection overthe lower casing without disturbing the motor orpiping (Figure 1). Flip the lid on an HSC pump, andthe entire rotating element is exposed. The element

can be turned in place to see if dirt or damage hasaffected the pump. This way, a problem can be foundbefore the element is disassembled.

one-person repair

Usually, only one person is required to repair anHSC pump.

The horizontal split-case centrifugal (HSC)pump is more than 100 years old, yet stillis the workhorse of the HVAC pump

industry. If a lot of water has to be moved efficientlywi th a mi nimum of fus s, no other pump can

outperform it. This article describes five reasons whyan HSC pump is useful.

An HSC pump takes up lessspace than other pumps whentaking into consideration the roomneeded for repairs.

An HSC pump can be checked without

ByJaMes B. (BUrt) risHeL, pePumping Solutions LLC

Cincinnati, Ohio

Horizontal Split-Case

Centrifugal PumpsFive advantages help achieve efficiency, quality, and low first costs

July 2007 HPAC Engineering

FIGURE 1. HSC pump with open top.

James B. (Burt) Rishel, PE, is owner and manager of Pumping Solutions LLC, a firm devoted to the evaluation ofwater systems and the development of variable-speed pumping stations to achieve efficient pumping with reduced

wear on centrifugal pumps. He also is the director of mechanical operations for tekWorx of Cincinnati. Former chair-man and chief executive officer of Systecon Inc., he holds two U.S. patents related to the determination of pump headand the programming of centrifugal pumps. He is the author of three books, 11 papers, and more than 40 articles.

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Circle 000

normally used in the HVAC field.

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These advantages should be consid-ered carefully before a pump is speci-fied. It is possible to achieve the ulti-mate in pump quality and first cost ona project with an HSC pump.

FIGURE 2. Cutaway of an HSC pump.

Longer Life

Radial and axial thrusts wear outpumps. One manufacturer has a uniquedesign for extending the useful lifeof an HSC pump. The manufacturerhas shortened the distance between

the inboard and outboard bearingsto reduce the cantilever effect on thepump shaft and cut deflection at theseal faces (Figure 2). The results are alonger seal life and fewer problems withcase rings.

An HSC pumps double-suctionimpeller can reduce the axial thrust

on its rotating element comparedwith the greater axial thrusts of otherend-suction pumps. Many HSCpumps have been in operation for morethan 75 years and still are performingefficiently.

efficiency

A double-suction impeller and halfas much flow through each suctionarea are the foundation for high pumpefficiency. A survey of sales catalogsshows HSC pumps have efficienciesas high or higher than other pumps

HPAC Engineering July 2007

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