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Marley
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NC Class Stainless Cooling Tower
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Specifications: Options
21
Ultra Low-Noise Fan
1.4 Replace paragraph 6.1 with the fol-
lowing: Fan(s) shall be propeller-type,
incorporating wide-chord forward-
swept FRP blades and galvanized
hubs. Blades shall be individually
adjustable. Maximum fan tip speed
shall be 51 m/s. Fan(s) shall be driven
through a right angle, industrial duty, oil
lubricated, geared speed reducer that
requires no oil changes for the first
five (5) years of operation. The gearbox
bearings shall be rated at an L
10A
ser-
vice life of 100,000 hours or greater.
Available on Models NC8302 through NC8312.
Single Hot Water Inlet Connection
per Cell:
8.2 Replace this paragraph with the
following: Each cell of the tower
shall include a single hot water inlet
connection located as shown on the
plans. An internal system of piping
shall deliver water equally to the dis-
tribution basins without the need for
balancing valves. This internal piping
system shall require no scheduled
maintenance, and shall be located such
that it does not interfere with normal
maintenance access. The internal pip-
ing must extend to the tower exterior.
Removable, interchangeable polypro-
pylene nozzles installed in the floor of
these basins shall provide full coverage
of the fill by gravity flow.
Air Inlet Screens:
9.1 Add the following paragraph to the
Casing, Fan Deck and Fan Guard sec-
tion: The air inlet faces of the tower
shall be covered by 1" mesh hot-dipped
galvanized welded wire screens.
Screens shall be secured to removable
galvanized U-edge frames.
High Wind Load/Seismic Designs:
4.1 Replace this paragraph with the fol-
lowing: The tower structure, anchor-
age and all its components shall
be designed by licensed structural
engineers per the international build-
ing code to withstand a wind load of
■ For more severe cases requiring the lowest possible fan sound levels
the Marley “Ultra Low-Noise” fan option is now available on all but the
NC8301 NC Class models. Tower height may increase slightly—obtain
current sales drawings from your Marley sales representative for accu-
rate dimensions. If your requirement calls for inlet and outlet attenu-
ation, you might consider the Ultra Low-Noise fan in lieu of attenua-
tion. Outlet attenuators are not available with the Ultra Low-Noise Fan
option.
■ This option reduces what might otherwise be a complex hot water
piping layout to a simple, single connection per cell. It also avoids an
unsightly (perhaps unsafe) maze of pipe exposed above the top deck of
the tower.
The single inlet connection can be located either in the tower's endwall
casing, or below the cold water basin. The endwall entry point is suit-
able for single-cell towers, and for those that might be installed in
groups of two cells each. Bottom inlet piping lends itself to close-
spaced, multicell installations and to those situations where it is appro-
priate to keep all pipework below the level of the tower.
Be sure to specify that the internal pipe extends to the tower exterior
panel, either the casing panel or collection basin floor. Some manufac-
turers require the contractor to complete the internal piping adding to
your cost.
■ In wooded or windy
areas, these screens help
to keep leaves or blowing
debris out of the cool-
ing tower and circulating
water system.
■ High wind load designs
greater than 30 psf are
available up to 100 psf.
It is important to consult
the local code official for actual requirements. Some manufacturers will
claim their tower is capable but have never had the design reviewed by
a licensed structural expert. Not requiring expert review for high wind
and seismic regions is dangerous to you and the public.
➠