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Fans
Marley designed and manufactured fans are used on
all Marley crossflow towers. The fan selection and fan
speed for a given tower are based on tower cell size,
system losses, and horsepower requirements. Depending
on fan size, blade material is FRP (fiber reinforced
polyester), GRE (glass reinforced epoxy), or cast
aluminum alloy. Above 20′-0″ diameter, Marley’s HP7000
hollow core fan with erosion-resistant leading edge is
standard. Large fan hubs are heavy-duty steel plate and
ductile cast iron components, hot dip galvanized after
fabrication. Smaller fan hubs are either epoxy-coated cast
iron or heat-treated aircraft aluminum alloy plate. All fans
are assembled with series 300 stainless steel hardware,
and all materials have been selected for the harsh cooling
tower environment.
Marley fans are applied in accordance with data
from model tests conducted in the wind tunnel at the
SPX Cooling Technologies’ Research and Development
Center. Model fan designs are tested in simulated cooling
towers, and are fine-tuned to maximize efficiencies
at actual conditions. The commercially available fans
used by other cooling tower suppliers lack this design
advantage. Consequently, they are often applied at flow
and pressure conditions for which they are ill suited.
Unpredictable lower efficiencies result, with proportional
reduction in tower capacity.
Fan Cylinders
Venturi-shaped FRP cylinders combine minimal
entrance losses with close blade tip clearances to
produce optimum fan performance. As cylinder heights
increase, cylinders are progressively flared to promote
recovery of velocity pressure—allowing fans to move
the required amount of air at significantly reduced
horsepower.
Unlike those used on other towers, Marley fan
cylinders have exceptionally large entrance diameters
which contribute to the “eased inlet” effect so necessary
to good fan performance. Smaller entrances do not
provide sufficient transition to deter turbulent flow at the
fan. Marley fan cylinders are through-bolted to the fan
deck and supporting framework. The combination of
a large foundation “footprint” and through-bolting has
enabled Marley fan cylinders to withstand wind velocities
in which other fan cylinders have failed.
/ Mechanical Equipment /