Table 1. Vertical Pumps: Not all they’re cracked up to be?
They have advantages…
Installation ; Eliminate inertia bases and springs since pump is
integral to piping
; Eliminate flexible connections
; Eliminate field grouting of base
Floor Space ; Offer potential to save space over horizontal
split-case pumps that have suction and discharge
connections at the 3 and 9 o’clock positions due to
long radius elbows
Maintenance ; Need pump seals replaced about every two years
for clean water applications
; Have split spacer coupling to access pump seals
without removing motor
; Have no bearings to service, thus save maintenance
but…
; Piping alone might not be a good method of supporting
a large pump, especially for seismic conditions.
; Floor savings is mostly achieved by using suction diffusers
and triple- duty valves that also act as elbows.
; Split couplings are a great idea, but truly a necessity due
to the weight of larger motors.
; Once the coupling is disassembled to access seals, the
impellor is unsupported and will slip to bottom of volute.
On large pumps it will take several strong adults to
reattach the split coupling by hand, thus increasing
maintenance costs and offsetting any potential
first cost savings.
; Some horizontal pumps have maintenance-free bearings.
Figure 4. Pump Room Layout Using Three
Vertical Pumps.
(figs. 3 and 4). While the vertical pumps
did appear to fit better, we were able to
add horizontal pumps in a similar floor
space using Bell & Gossett’s VSC pump
that has two vertical connections.
What ultimately won us over on the
horizontal pump were the following facts:
1. The project was located in a California
seismic zone, and a 400 HP motor
weighs more than 3,000 lb (if you
can, envision more than the weight
of a VW Beetle above the impellor).
While there are structural bracing
solutions, during a seismic event I
would be crushed like a beetle if I
were standing next to the pump, and
it decided to let loose after moving
from its center of gravity and picking
up some oscillating momentum!
Courtesy Syska Hennessy Group.
2. Any entrained air within the chilled-water system could naturally migrate
to the top of the impellor casing,
creating an air pocket and keeping
the pump seals dry, which would
accelerate their wear.
One last note – not related to our
project and more specific to a heating
water pump installation – is that the heat
rising from the pump casing will detract
from the cooling of the electric motor
above the pump casing, thus affecting its
life and effectiveness. While this sounds all
gloom and doom for the vertical pump, I
think it still has its place in the toolbox,
since in retrofit applications it may be the
only solution that will fit especially in
smaller pumps. I would also like to hear
from readers and IDEA members who
think otherwise or have different experiences or viewpoints from my own.
With my current research complete, it
must be time to settle back into my Lazy
Boy recliner and assume my favorite angle
for watching a weekend of football on
TV – horizontal. Maybe I will enjoy some
brownies – without nuts! – and catch a
wink or two of shuteye at half time. Oh,
and the answers to the other questions:
heavy ales, tastes great, apple pie and the
Vikings (even if I do live in Wisconsin), of
course! I will leave the chicken-and-egg
dilemma for another day.
Based in Madison, Wis.,
Steve Tredinnick, PE, is
vice president of energy
services for Syska Hennessy
Group, which has more than
16 locations across the U.S.
He has more than 26 years’
experience related to building heating, ventilation and air-conditioning
systems. The past 15 years of his work have
been focused on district energy systems.
Tredinnick is a graduate of Pennsylvania State
University with a degree in architectural engineering. He is a member of IDEA and
ASHRAE and is currently immediate past chair
of ASHRAE TC 6. 2 District Energy. Tredinnick
currently serves on IDEA’s board of directors.
He may be reached at stredinnick@syska.com.
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Become a member today. Contact Len Phillips, (508)
366-9339, len.idea@districtenergy.org.
