54 District Energy / Fourth Quarter 2009 2009 International District Energy Association. ALL RIGHTS RESERVED.

Horizontal orVertical:Whats your angle?Steve Tredinnick, PE, Vice President of Energy Services, Syska Hennessy Group

InsideInsights

Editors Note: Inside Insights is acolumn designed to address ongoingissues of interest to building owners,managers and operating engineers whouse district energy services.

Recently I came across what I think tobe one of the engineering worldsperennial dilemmas. You know, thetype of quandaries along the lines of,What came first, the chicken or the egg?Dark ale or light beer? Tastes great or lessfilling? Apple pie or pumpkin pie? Vikingsor Packers? Or the perpetual argument inour household, Do nuts really belong inbrownies?

My engineering dilemma reference is,What angle do you prefer horizontal orvertical? And no, Im not playing an anglehere. I am specifically referring to pumps.

Just like brownies and pies, pumpscome in several flavors and colors, as wellas different orientations with respect to ahorizontal or vertical axis. Horizontally ori-ented pumps are parallel to the horizontalaxis and usually are supported on an isola-tion base; vertically oriented pumps areparallel to the vertical axis and typicallysupported by piping, or the pump casingmay extend to the floor, depending on themanufacturer.

In recent years, I have seen both con-figurations installed at central plants that Ihave had the opportunity to visit either

for project-related reasons or as part of thegreat tours provided by IDEA during con-ferences. From these visits, I get theimpression that there is a clandestinemovement by engineers or contractors touse the vertical configuration for distribu-tion pumps.

Since I have never used the verticalin-line for large distribution pumps, I haveoften wondered, What am I missing onthis issue? Hence, I decided it was time todo some research and get smarter on thesubject. If you need a refresher course oran illustration for these pumps, pleaserefer to figure 1 for a typical double-suc-tion horizontal pump and figure 2 for adouble-suction vertical pump.

In general, the published literature forthe vertical pumps claims many advantagesover traditional horizontal split case-typepumps, including savings in the areas of

installation costs, floor space and mainte-nance. Those advantages sound great, butdo they apply everywhere? As you maysurmise, I am pessimistic about that. Forsome reason, vertical pump configurationsjust seem to bug me they seem likesomebody wimped out when fighting forspace. Its a bit like putting ketchup on achili dog: It just doesnt seem right. However,the pumping industry obviously felt therewas a need for vertical configurations,since it seems to be filling that gap. Sowhat is the big deal? Lets look at the prosand cons of a large vertical distributionpump, outlined in table 1.

To further illustrate my viewpoint: Werecently had a project to replace four exist-ing chilled-water distribution pumps withthree larger ones. The new pumps are10,000 gpm and 400 HP each. We selectedboth horizontal and vertical pumps andthen laid them out in the available space

Figure 1. Bell & Gossett Horizontal Pump (VSC).

CourtesyBell&Gossett.

Figure 2. Armstrong Vertical Pump (Series 4300).

CourtesyArmstrongPumps.

Figure 3. Pump Room Layout Using ThreeHorizontal Pumps.

CourtesySyskaHennessyGroup.

2009 International District Energy Association. ALL RIGHTS RESERVED. District Energy / Fourth Quarter 2009 55

Based in Madison,Wis.,Steve Tredinnick, PE, isvice president of energyservices for Syska HennessyGroup, which has more than16 locations across the U.S.He has more than 26 yearsexperience related to build-ing heating, ventilation and air-conditioningsystems. The past 15 years of his work havebeen focused on district energy systems.Tredinnick is a graduate of Pennsylvania StateUniversity with a degree in architectural engi-neering. He is a member of IDEA andASHRAE and is currently immediate past chairof ASHRAE TC 6.2 District Energy. Tredinnickcurrently serves on IDEAs board of directors.He may be reached at stredinnick@syska.com.

Table 1. Vertical Pumps: Not all theyre cracked up to be?

(figs. 3 and 4). While the vertical pumpsdid appear to fit better, we were able toadd horizontal pumps in a similar floorspace using Bell & Gossetts VSC pumpthat has two vertical connections.

What ultimately won us over on thehorizontal pump were the following facts:1. The project was located in a Californiaseismic zone, and a 400 HP motorweighs more than 3,000 lb (if youcan, envision more than the weightof a VW Beetle above the impellor).While there are structural bracingsolutions, during a seismic event I

would be crushed like a beetle if Iwere standing next to the pump, andit decided to let loose after movingfrom its center of gravity and pickingup some oscillating momentum!

2. Any entrained air within the chilled-water system could naturally migrateto the top of the impellor casing,creating an air pocket and keepingthe pump seals dry, which wouldaccelerate their wear.One last note not related to our

project and more specific to a heatingwater pump installation is that the heatrising from the pump casing will detractfrom the cooling of the electric motorabove the pump casing, thus affecting itslife and effectiveness. While this sounds allgloom and doom for the vertical pump, Ithink it still has its place in the toolbox,since in retrofit applications it may be theonly solution that will fit especially insmaller pumps. I would also like to hearfrom readers and IDEA members whothink otherwise or have different experi-ences or viewpoints from my own.

With my current research complete, itmust be time to settle back into my LazyBoy recliner and assume my favorite angle

for watching a weekend of football onTV horizontal. Maybe I will enjoy somebrownies without nuts! and catch awink or two of shuteye at half time. Oh,and the answers to the other questions:heavy ales, tastes great, apple pie and theVikings (even if I do live in Wisconsin), ofcourse! I will leave the chicken-and-eggdilemma for another day.

They have advantages but

Installation Eliminate inertia bases and springs since pump is Piping alone might not be a good method of supportingintegral to piping a large pump, especially for seismic conditions.

Eliminate flexible connections Eliminate field grouting of base

Floor Space Offer potential to save space over horizontal Floor savings is mostly achieved by using suction diffuserssplit-case pumps that have suction and discharge and triple- duty valves that also act as elbows.connections at the 3 and 9 oclock positions due tolong radius elbows

Maintenance Need pump seals replaced about every two years Split couplings are a great idea, but truly a necessity duefor clean water applications to the weight of larger motors.

Have split spacer coupling to access pump seals Once the coupling is disassembled to access seals, thewithout removing motor impellor is unsupported and will slip to bottom of volute.

Have no bearings to service, thus save maintenance On large pumps it will take several strong adults toreattach the split coupling by hand, thus increasingmaintenance costs and offsetting any potentialfirst cost savings.

Some horizontal pumps have maintenance-free bearings.

Figure 4. Pump Room Layout Using ThreeVertical Pumps.

CourtesySyskaHennessyGroup.

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