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Fire Protection Options
The PVC fill, louvers and drift eliminators used on Sigma
towers are fire-retardant, having flame spread ratings less
than 25 per ASTM E-84. Standard fan decking material
is pressure-treated fir plywood which ignites poorly and
burns slowly. For these reasons, governing agencies (such
as Factory Mutual) may not require fire protection sprinkler
systems on Sigma towers.
On specific jobs you may want to weigh the cost of
various modifications against the cost (and maintenance)
of a sprinkler system – or the cost of higher insurance
premiums. One or more of the following tower modifications
may negate the need for a sprinkler system:
• Fire-retardantfancylindersandoptionalcasingoffer
flame spread less than 25 per ASTM E-84.
• A1/4"thickber-reinforcedcementboard(FRC)overlay
on the fan deck acts as a fire stop and provides a
nonskid walking surface.
• A1/4"FRCoverlayonthedistributionbasincoversacts
as a fire stop.
• Barrierwallskeeprefromspreadingbetweencells
in multicell towers. Specify barrier wall design by
containment period, such as a “20-minute fire wall”.
Barrier walls are full-width, full-height of the tower
interior (except cold water basin), and consist of
pressure-treated fir plywood both sides of the column
line between cells. Plywood thickness (and cost) vary
according to the specified containment time.
• Steelconstruction.RememberthattheSigmaseries
is available in steel construction – either galvanized or
stainless – as are a number of other Marley series, all of
which meet all established fire code requirements.
If your insurance carrier insists on a sprinkler system for
your tower, consult your Marley sales representative. We can
provide a sprinkler system to fit your needs, or work with
your people to be sure that the sprinkler system and tower
will meet your specification.
Non-Standard Motors
Although you can buy your Sigma tower “less motor” at
a cost reduction, it is not normally recommended. Motors
supplied on Marley towers meet rigorous specifications
developed from environmental chamber tests at our
Development Center. These specifications represent prudent
minimum design requirements.
Unless otherwise specified, motors provided on
Marley cooling towers are TEFC, 1.0 or 1.15 service
factor (appropriate to the applied load), 1800 RPM. Other
enclosures (such as Explosion Proof) and motors specially
wound for non-standard voltages are available at extra cost.
Two-speed motors are also available, and their
advantages are discussed on page 22.
/ Special Component Options /