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Marley
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MCW Cooling Tower
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Specifications: Options
32
Miscellaneous Options
Sound Control
1.2 Add the following paragraph under
Base: The cooling tower shall be quiet
operation, and shall produce an overall
level of sound not higher than _______
dB(A)measuredatthecriticallocation
indicated on the plans.
■ Sound produced by a standard MCW Series tower operating in an
unobstructed environment will meet all but the most restrictive noise
limitations—and will react favorably to natural attenuation. Where
the tower has been sized to operate within an enclosure, the enclo-
sure itself will have a damping effect on sound. Sound also declines
with distance—by about 5 or 6 dB(A) each time the distance doubles.
Where noise at a critical point is likely to exceed an acceptable limit,
you have several options—listed below in ascending order of cost
impact:
• Where only a slight reduction in noise will satisfy—and the source of
concern is in a particular direction—merely turning the tower may be
the answer. Less sound emanates from the cased face of the tower
than does from the air intake face.
• In many cases, noise concerns are limited to night time, when ambi-
ent noise levels are lower and neighbors are trying to sleep. You
can usually resolve these situations by using two speed motors in
either full / half speed or full /
2
⁄3 speed configuration, and operating
the fans at reduced speed without cycling “after hours”. (The natu-
ral night time reduction in wet-bulb temperature makes this a very
feasible solution in most areas of the world, but the need to avoid
cycling may cause the cold water temperature to vary significantly.)
• Variable speed drives automatically minimize the tower's noise level
during periods of reduced load and/or reduced ambient without
sacrificing the system's ability to maintain a constant cold water
temperature. This is a relatively inexpensive solution, and can pay for
itself quickly in reduced energy costs.
• Where noise is a concern at all times (for example, near a hospital),
the best solution is to oversize the tower so it can operate continu-
ously at reduced (
2
⁄3 or ½) motor speed even at the highest design
wet-bulb temperature. Typical sound reductions are 7 dB(A) at
2
⁄3 fan
speed or 10 dB(A) at ½ fan speed, but larger reductions are often
possible.
• The most extreme cases may require inlet and discharge sound
attenuator sections—however, the static pressure loss imposed by
discharge attenuators may necessitate an increase in tower size. Two
stages of inlet or discharge attentuators supported by the tower and
designed and tested for the most stringent requirements are avail-
able as an option. See page 18.
The advantage is yours. You now have the choices you need to bal-
ance your project’s performance, space and cost requirements with
your sound level needs for a win-win solution to your cooling system
design. Your Marley sales representative will be able to help you
meet you sound requirements.