Marley Sigma Steel CoolingTower
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Engineering Data & Specifications
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Marley Sigma Steel CoolingTower Table of Contents
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Engineering Data
Schematic
6
7
Support
Concrete Basin
Piping
8
9
Environmental
Energy Management
10
11
Specifications / Base
Base
12
13
14
15
15
17
18
18
18
19
19
Thermal Performance
Construction
Fan Deck and Fan Cylinder
Mechanical Equipment
Fill, Louvers and Drift Eliminators
Hot Water Distribution System
Casing
Access
Cold Water Collection Basin
Scope of Work
Specifications / Options
Control Options
Control System
Basin Heater
Fan Motor Variable Speed Drive
Marley Premium VFD System
Vibration Limit Switch
20
21
21
22
23
Convenience and Safety Options
Stairway
24
24
24
24
25
Plenum Walkway
Ladder Extension
Ladder Safety Cage
Oil Level Sight Glass
Miscellaneous Options
Steel Cold Water Basin
Factory Mutual Approval
Hot Water Basin Covers
Air Inlet Screens
25
25
25
25
26
27
Low NoiseTower
Service Life-Relate Customization
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Marley Sigma Steel CoolingTower
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5
he Sigma Steel is a galvanized steel, field-erected,
Tgeneral purpose crossflow cooling tower, designed
to serve normal air conditioning and refrigeration sys-
tems as well as medium sized industrial loads. Evolv-
ing from the crossflow concept of towers pioneered
by Marley in 1938, and incorporating over 70 years of
design advancements, the Sigma Steel represents the
current state of the art in this cooling tower category.
only accomplish the specified thermal performance—
but which will include normal operation- and mainte-
nance-enhancing accessories and features. It will also
incorporate those standard materials which testing
and experience has proven to provide best results in
normal operating conditions.
Pages 20 thru 27 provide some paragraphs intended
to add those features, components, and materials that
will customize the tower to meet the user's require-
ments.
This booklet not only relates the language to use in
describing an appropriate Sigma Steel cooling tow-
er—but also defines why certain items and features
are important enough to specify with the intention of
insisting upon compliance by all bidders. The left-hand
column of pages 11 thru 25 provides appropriate text
for the various specification paragraphs, whereas the
right-hand column comments on the meaning of the
subject matter and explains its value.
Space does not permit definition and explanation of
all of the possible options that can be applied to the
Sigma Steel. SPX CoolingTechnologies realizes that
you, the purchaser, must be happy with the tower's
characteristics, and we are prepared to provide—or
provide for—any reasonable enhancement that you
are willing to define and purchase.
Pages 12 thru 19 indicate those paragraphs which will
result in the purchase of a cooling tower which will not
Your needs will become part of the continuing better-
ment of this Marley product line.
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Marley Sigma Steel CoolingTower Engineering Data : Schematic
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6
C
C
C
L COLUMN
L COLUMN A BAYS AT 4'-0" = LCOLUMNL
C
DIAMETER FAN
1
1
4 /
2"
4 /2"
TOP OF
FAN CYLINDER
FAN DECK
B
Use this data for preliminary layouts only.
Obtain current drawing from your Marley sales
representative.
H
The UPDATE web-based selection software
—available at spxcooling.com—provides
Sigma Steel model recommendations based
on customer's specific design requirements.
1
13'-1 /
8"
BASE OF
TOWER COLUMNS
Average
Pumping
Head
Dimensions
Tower
Model
GPM
per cell
Maximum
Motor hp
W
L
H
A
B
C
121-111
122-111
123-111
124-111
125-111
126-111
127-111
500-4500
650-6000
25'-4"
27'-4"
29'-4"
29'-4"
33'-4"
33'-4"
33'-4"
12'-0"
16'-0"
16'-0"
20'-0"
20'-0"
24'-0"
28'-0"
19'-11⁄8
19'-11⁄8
"
"
3
4
4
5
5
6
7
6'-0"
6'-0"
7'-0"
7'-0"
7'-0"
7'-0"
7'-0"
120"
144"
168"
168"
216"
216"
216"
60
60
17.3'
17.4'
17.4'
17.4'
17.5'
17.5'
17.6'
650-6000
20'-11⁄8
20'-11⁄8
20'-11⁄8
20'-11⁄8
20'-11⁄8
"
"
"
"
"
75
1000-7500
1000-7500
1000-9000
1500-10500
75
75
100
100
NOTE
1 Use this bulletin for preliminary layouts only. Obtain cur-
rent drawings from your Marley sales representative.
2 Last number of model indicates number of cells. Change as
appropriate for your selection. Primary engineering data is per
cell.
3 Height shown is from base of tower columns to top of fan
cylinder.
4 Pumping head shown is from base of tower columns.
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Marley Sigma Steel CoolingTower Engineering Data : Support
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7
6"
A
SPACES AT 4'-0" =
L
AIR INLET FACE
SUMP
OVERFLOW
RECOMMENDED
OPERATING WATER LEVEL
1'-6"
6"
Section
AIR INLET FACE
INTERMEDIATE
BEAM
PRIMARY SUPPORT
BEAM
Plan
Dimensions
W
Operating Weight lb
Single Fan Cell Each Cell Add
Tower
Model
A
L
121-111
122-111
123-111
124-111
125-111
126-111
127-111
3
4
4
5
5
6
7
23'-8"
25'-8"
27'-8"
27'-8"
31'-8"
31'-8"
31'-8"
12'-0"
16'-0"
16'-0"
20'-0"
20'-0"
24'-0"
28'-0"
37670
49875
50320
60290
67150
77960
88850
33150
45105
45230
55200
61220
72115
83590
NOTE
1 Use this bulletin for preliminary layouts only. Obtain cur-
rent drawings from your Marley sales representative.
2 Steel beams must include 7⁄8" dia. holes to accept anchor bolts
provided with tower. Other contractors or purchaser must
design and erect supporting steel.
3 Maintain at least 2'-0" of clear space at tower endwalls for
construction purposes. Air inlet faces must have unobstructed
air supply. If obstructions exist nearby, consult your Marley
sales representative.
4 Operating weight is wet weight of tower and steel basin,
including 6" of water in the cold water basin.
5 View shown is typical single cell beam arrangement.
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Marley Sigma Steel CoolingTower Engineering Data : Concrete Basin
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8
6" MIN.
6" MIN.
W
IN TO IN OF BASIN
6" MIN.
5"
CASED ENDWALL FACE
ANCHOR BOLTS
(SEE NOTE 5)
SUMP
CASED ENDWALL FACE
6" MIN. 5"
Plan
RECOMMENDED
OPERATING WATER LEVEL
1'-6"
1'-0
Section
Dimensions
Operating Weight lb
Single Fan Cell Each Cell Add
Tower
Model
A
3
4
4
5
5
6
7
W
L
121-111
122-111
123-111
124-111
125-111
126-111
127-111
23'-6"
25'-6"
27'-6"
27'-6"
31'-6"
31'-6"
31'-6"
12'-0"
16'-0"
16'-0"
20'-0"
20'-0"
24'-0"
28'-0"
25200
32280
33300
39230
42800
48780
54830
21525
28430
29080
35025
37715
43910
50550
NOTE
1 Use this bulletin for preliminary layouts only. Do not
use for construction. Obtain current drawings from your
Marley sales representative. Concrete basin design and
construction are by other contractors or purchaser.
2 Operating weight is total wet operating weight of tower
only, excluding water in concrete basin.
3 Maintain at least 2'-0" of clear space at tower endwalls
for construction purposes. Air inlet faces must have
unobstructed air supply. If obstructions exist nearby,
consult your Marley sales representative.
4 Minimum basin depth is 1'-6". Basin depth may vary to suit
your storage requirements.
5 All anchor bolts complete with nut and washer must be
furnished by others. Bolts must be 3⁄4" diameter with 11⁄2
all-thread projection.
6 Other contractors or purchaser must design, locate,
construct, and furnish sump(s) and overflow(s) to suit
"
requirements. The sump(s) should be designed according
to the pump manufacturer’s recommendations. Other
design sources: ANSI/HI specifications 1.1-1.5 for
centrifugal pumps, 2.1-2.5 for vertical pumps, and 9.8 for
pump intake design.
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Marley Sigma Steel CoolingTower Engineering Data : Inlet Piping
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9
C
D
C
C
C
L FAN
L FAN
TYP. SINGLE CELL
TYP. MULTICELL
C
C
C
C
L COLUMN AND
L COLUMN AND
L INLET
L INLET
ANCHOR BOLT
ANCHOR BOLT
B
DIA FLOW
FACE OF
A
DIA
E
C
L
CONTROL VALVE
FAN
INLET FLANGE
C
MARLEY PIPING
STOPS HERE
L TOWER
G C OF FLANGE TO
L
BASE OF TOWER
COLUMNS (USE FOR
STATIC LIFT)
Dimensions
Tower
Model
GPM
per cell
A
B
C
D
E
F
G
500-3800
10"
8"
8'-101⁄2
"
"
14'-63⁄4
14'-73⁄4
14'-73⁄4
14'-73⁄4
14'-73⁄4
14'-83⁄4
14'-83⁄4
14'-83⁄4
14'-93⁄4
"
"
"
"
"
"
"
"
"
121-111
6'-0"
12'0"
13'-11⁄4
"
3801-4500
650-6000
12"
14"
14"
14"
16"
16"
16"
18"
10"
10"
10"
10"
12"
12"
12"
14"
9'-01⁄2
"
122-111
123-111
8'-0"
8'-0"
16'-0"
16'-0"
10'-01⁄2
14'-11⁄4
15'-11⁄4
"
"
650-6000
11'-01⁄2
11'-01⁄2
11'-11⁄2
"
"
"
1000-6000
6001-7500
1000-7500
1000-9000
1500-10500
124-111
10'-0"
20'-0"
15'-11⁄4
"
125-111
126-111
127-111
10'-0"
12'-0"
14'-0"
20'-0"
24'-0"
28'-0"
13'-11⁄2
13'-11⁄2
13'-55⁄8
"
"
"
17'-11⁄4
17'-11⁄4
17'-11⁄4
"
"
"
NOTE
1 Use this bulletin for preliminary layouts only. Obtain
current drawings from your Marley sales representative.
2 Pumping head contributed by the tower is static lift
“G”. Actual pumping head will vary according to tower
circulating GPM. Total pumping head will be furnished at
time of proposal.
3 If your application requires a bypass system,
recommended location is through tower endwall into
plenum area. Review of the system by SPX engineering is
required.
4 Marley piping terminates at face of a cast iron flat face
flange. Bolt circle conforms to class 125 lb. ANSI B 16.1
specifications.
5 Supports on tower for crossover piping are part of the
tower design. Do not support the riser’s dead load or
operating load from the tower. Do not brace the riser’s
seismic or thrust loads against the tower.
6 Butterfly valves or piping expansion joints (if used) are
by others and must be located outside the limits of the
cooling tower “F”.
7 Motor must be located 180° from inlet.
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Marley Sigma Steel CoolingTower Engineering Data: Environmental
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10
Sound Control
Sound produced by a Sigma Steel tower operating in an un-
As suggested in the aforementionedTechnical Report, it
may also be advisable to specify a design wet-bulb tem-
perature 1°F higher than normal to compensate for potential
recirculation initiated by the enclosure. You’ll benefit from
discussing your project with your Marley sales representative.
obstructed environment will meet all but the most restrictive
noise limitations—and will react favorably to natural attenu-
ation. Where the tower has been sized to operate within an
enclosure, the enclosure itself will have a damping effect on
sound. Sound also declines with distance—by about 5 dBA
each time the distance doubles. Where noise at a critical point
is likely to exceed an acceptable limit, several options are
available—listed below in ascending order of cost impact:
Keeping It Clean
Cooling towers are very effective air washers. Atmo-
spheric dust able to pass through the relatively small louver
openings will enter the circulating water system. Increased
concentrations can intensify system maintenance by clogging
screens and strainers—and smaller particulates can coat
system heat transfer surfaces. In areas of low flow velocity—
such as the cold water basin—sedimentary deposits can
provide a breeding ground for bacteria.
•
In many cases, noise concerns are limited to nighttime,
when ambient noise levels are lower and neighbors are
trying to sleep. You can usually resolve these situa-
tions by using two-speed motors in either 1800/900 or
1800/1200 RPM configuration—operating the fans at
reduced speed without cycling “after hours”. The natural
nighttime 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.
In areas prone to dust and sedimentation, you should con-
sider installing some means for keeping the cold water basin
clean. Typical devices include side stream filters and a variety
of filtration media.
•
The Marley Variable Frequency Drive automatically mini-
mizes the tower’s noise level during periods of reduced
load and/or reduced ambient temperature without
sacrificing the system’s ability to maintain a constant
cold water temperature. This is a relatively inexpen-
sive solution, and can pay for itself quickly in reduced
energy costs.
WaterTreatment
Contaminants including Legionella, an effective consistent
water treatment program is required. Controlling blowdown
may be adequate in mitigating the potential of corrosion and
scale, but biological contamination can only be controlled with
biocides.
•
•
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 continuously at reduced (1200
or 900 RPM) motor speed. Typical sound reductions are
7 dBA at 2/3 fan speed or 10 dBA at half fan speed.
An acceptable water treatment program must be compat-
ible with the variety of materials incorporated in a cooling
tower—ideally the pH of the circulating water should fall
between 6.5 and 8.0. Batch feeding of chemicals directly into
the cooling tower is not a good practice since localized dam-
age to the tower is possible. Specific startup instructions and
additional water quality recommendations can be found in the
Sigma User Manual which accompanies the tower and also
is available from your local Marley sales representative. For
complete water treatment recommendations and services,
contact your local Marley sales representative.
Extreme cases may require inlet and discharge sound
attenuator sections—however, the static pressure loss
imposed by attenuators may necessitate an increase in
tower size. This is the least desirable approach because
of the significant cost impact—and because of the
obstruction to normal maintenance procedures.
Your Marley sales representative will help you meet your
sound requirements.
Enclosures
Occasionally, cooling towers are located inside architec-
tural enclosures for aesthetic reasons. Although Sigma tow-
ers adapt well to enclosures, the designer must realize the
potential impact of a poorly arranged enclosure on the tower’s
performance and operation. The designer must take care to
provide generous air inlet paths, and the tower’s fan cylinder
discharge height should not be lower than the elevation of the
top of the enclosure. Obtain a copy of MarleyTechnical Report
#H-004, “External Influences on CoolingTower Perfor-
mance” from your Marley sales representative or on the web
at spxcooling.com.
CAUTION
The cooling tower must be located at such distance
and direction to avoid the possibility of contaminated
discharge air being drawn into building fresh air intake
ducts.The purchaser should obtain the services of a
Licensed Professional Engineer or Registered Architect
to certify that the location of the cooling tower is in
compliance with applicable air pollution, fire and clean
air codes.
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Marley Sigma Steel CoolingTower Engineering Data: Energy Management
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11
Cooling towers are usually selected to produce a specific
cold water temperature at the higher summertime wet-bulb
temperatures. During the remainder of the year, the cooling
tower is capable of producing much colder water. Unless your
system will benefit from the coldest possible water tempera-
ture, you should consider controlling cold water tempera-
tures to higher levels. You’ll also save energy by using such
control. For greater insight on cold water temperature control,
please read “CoolingTower Energy and its Management”,
Technical Report #H-001A, available from your Marley sales
representative or on the web at spxcooling.com.
Normally, two-speed motors are provided in 1800/900
RPM, single winding configuration, which is the least expen-
sive two-speed option. They are also available in other combi-
nations including the more expensive double winding.
Variable Speed Fan Drive
Frequency modulation devices work well on induced draft,
propeller fan cooling towers such as the Sigma Steel cooling
tower. However, their design must include the capability to
lock out any critical fan speeds and the very low fan speed
ranges.
Always control leaving water temperature by manipulating
the quantity of air that the fan moves through the tower. Vary-
ing the quantity of water flow is not normally recommended
and can be harmful in freezing weather. You can alternately
start and stop single-speed motors to maintain water tem-
peratures within an acceptable range. However, exceeding a
total acceleration time of 30 seconds per hour can overheat
the motor, causing the insulation to fail. Limiting the number
of motor starts, on the other hand, can produce significant
variations in the temperature of the water delivered to the
process.
Marley VFD drive systems are designed to combine abso-
lute temperature control with ideal energy management. The
cooling tower user selects a cold water temperature and the
drive system will vary the fan speed to maintain that tem-
perature. Precise temperature control is accomplished with
far less stress to the mechanical equipment components. The
improved energy management provides fast payback. Indeed,
many utilities offer generous rebates for users having installed
VFD drives.
Increased flexibility can simplify your operating procedures
and save you money in the long run, both on operation and on
maintenance. Here are two of the more popular options.
Two-Speed Motors
Two-speed motors improve operating flexibility by increas-
ing the number of potential operating modes. Users in north-
ern climates will find that the tower can carry winter loads at
half-speed; reducing fan power requirements by 85+% during
that time. Two-speed motors also help to control icing during
wintertime operation. See MarleyTechnical Report #H-003,
“Operating CoolingTowers During FreezingWeather”,
available from your Marley sales representative or on the web
at spxcooling.com.
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Marley Sigma Steel CoolingTower Specifications: Base
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12
Specifications
Specification Value
1.0
1.1
Base:
■Your specification base establishes the type, configuration, base mate-
rial, and physical limitations of the cooling tower to be quoted. During
the planning and layout stages of your project, you will have focused
your attention on a cooling tower selection that fits your space allot-
ment, and whose power usage is acceptable. Limitations on physical
size and total operating horsepower avoid the introduction of unfore-
seen operational and site-related influences. Specifying the number of
cells, and the maximum fan hp/cell will work to your advantage.
Furnish and install an induced-draft,
crossflow-type, field-erected, steel-
framed, PVC-fill, industrial-duty cooling
tower of _____ cell(s), as shown on
Plans. The limiting overall dimensions
of the tower shall be _____ wide,
_____ long, and _____ high to the top
of the fan cylinder. Total operating
horsepower of all fans shall not exceed
____ hp, consisting of ___ @ _____ hp
motor(s). Tower shall be similar and
equal in all respects to Marley Model
_______.
Crossflow towers are noted for the accessibility and maintainability of
all operating components.The spacious interior provides easy access to
fill, drift eliminators, all basin accessories — and is one of two primary
access ways to the fan, Geareducer, and other mechanical components.
At the fan deck level, the hot water distribution basins are easily
inspected and cleaned — while the tower is operating, if you wish.The
mechanical equipment can also be readily accessed from this level.
Except for the cold water basin, no counterflow tower component
requiring routine maintenance is as easily accessed.The confined areas
that typify counterflow designs can make difficult work for maintenance
personnel!
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Marley Sigma Steel CoolingTower Specifications: Base
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13
Specifications
Specification Value
■ Your reason for purchasing a cooling tower is to obtain a continuing
flow of cooled water as defined in the first paragraph at left. If the
tower that you purchase is incapable of performing as specified, then
you will not have received full value for your money.
2.0
2.1
Thermal Performance:
The tower shall be capable of cooling
_____ GPM of water from ____ °F to
_____ °F at a design entering air wet-
bulb temperature of _____ °F. The cool-
ing tower manufacturer shall guarantee
that the tower supplied will meet
the specified performance conditions
when the tower is installed according
to plans.
Bear in mind that the size—and cost—of a cooling tower varies directly
with its true thermal capability.This paragraph is intended to protect
you against either intentional or inadvertent under sizing of the tower
by the manufacturer. Judging the level of performance of a cooling
tower on critical processes is never easy, and the potential risk of a
non-performing cooling tower usually causes the requirement for a
mandatory acceptance test to be very desirable.
2.2
The purchaser will arrange for an
Your contract with the successful bidder should establish the accept-
able remedies for missed performance, which might include:
on-site thermal performance test, to
be conducted in the presence of the
manufacturer and owner, and under
the supervision of a qualified, disinter-
ested third party in accordance with
CTI (Cooling Technology Institute) ATC-
105 standards during the first full year
of operation. If the tower fails to per-
form within the limits of test tolerance,
then the cooling tower manufacturer
will install additional cells and/or make
such corrections as are agreeable to
the owner and shall pay for the cost of
a retest. If the tower still fails to per-
form as specified, then the manufac-
turer shall make such reimbursements
as are appropriate and agreeable to the
owner to compensate for the perfor-
mance deficiency.
•The addition of one or more cells of tower, as necessary, to bring the
cooling tower to the specified level of performance.This is usually
limited to the scope of work as defined in the specs, which means that
you (the owner) will have to pay for the additional basin, wiring, start-
ers, piping, etc.
•The reimbursement of a portion of the total contract price equal to the
percentage deficiency in performance.
Under no circumstances should you allow the manufacturer to re-pitch
the fans to increase motor brake horsepower above that shown in the
proposal.That creates additional operating costs that will continue for
the life of the tower—and imposes no penalty on the manufacturer.
95°
90°
85°
80°
5°F RANGE
10°F RANGE
15°F RANGE
75°
70°
65°
60°
55°
50°
55°
60°
65°
70°
75°
80°
WET BULB TEMP. (°F)
Typical cooling tower performance curve.
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Marley Sigma Steel CoolingTower Specifications: Base
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14
Specifications
Construction:
Specification Value
■ The limiting water quality values indicated are those which are accept-
able for the normal materials of construction specified. If water of more
aggressive quality is anticipated, consider specifying a stainless steel
Sigma tower. See page 27.
3.0
3.1
The tower shall be capable of with-
standing water having a pH of 6.5 to
8.0; a chloride content (NaCl) up to 300
ppm; a sulfate content (SO ) up to
4
250 ppm; a calcium content (CaCO )
3
up to 500 ppm; silica (SiO ) up to
2
150 ppm; and design hot water tem-
peratures up to 120°F. The circulating
water shall contain no oil, grease, fatty
acids, or organic solvents.
■ Hot-dip galvanizing after fabrication assures that all steel surfaces will
be heavily coated with zinc. All shearing, bending, drilling, punching,
etc. will have been completed prior to galvanization.
3.2
3.3
The structural framework of the tower,
as well as all basins and decking, shall
be of heavy gauge cold-formed steel
and/or mill shapes, hot-dip galvanized
after fabrication to a deposition of at
least 2.25 ounces of zinc per square
foot.
■ Multicell towers must have plenum partitions between cells. Otherwise,
air will be induced downward through an inoperative fan, bypassing
the fill entirely. Without these partitions, part-load or off-season opera-
tion of the tower would be completely unsatisfactory.
Column lines shall be on no greater
than 4' longitudinal centers, and the
base of all columns shall be firmly
anchored. Basic design criteria shall
be 30 psf wind load and 5%g seismic
load. Framing joints shall be made
with 1⁄2" diameter and larger Series 300
stainless steel machine bolts, nuts and
washers.
3.4
Towers of more than one cell shall
include galvanized internal partitions
to separate the fan plenums, and a
hinged access door shall be provided
in each partition for freedom of access
throughout the tower.
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Marley Sigma Steel CoolingTower Specifications: Base
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15
Specifications
Specification Value
4.0
4.1
Fan Deck and Fan Cylinder:
■ The indicated design values for framing and decking not only give you
assurance that the tower can withstand long term operation in a hostile
environment — but that it will accept many years of inspection and
maintenance traffic by your operating personnel.
The fan deck shall act as a working
platform for maintenance personnel. It
shall be fabricated of no less than 12
gauge steel, and shall be designed for
a uniform live load of 60 psf.
■ Fiberglass-reinforced polyester fan cylinders provide the close tip clear-
ances and smooth airflow contour necessary for good fan performance.
The inert, noncorroding nature of FRP assures that these characteristics
will persist.Their 6' to 7' height also provides protection for operating
personnel.
4.2
Fan cylinders shall be molded FRP.
They shall be through-bolted to the fan
deck structure to provide a consistent-
ly stable operating shroud for the fan.
5.0
5.1
Mechanical Equipment:
■ Propeller-type fans require only half the operating HP of blower-type
fans.
Fan(s) shall be propeller-type, incorpo-
rating heavy duty blades of cast alumi-
num or high strength, inert composite
material. Blades shall be individually
adjustable and replaceable. Fan(s) shall
be driven through a rightangle, indus-
trial-duty, oil-lubricated, geared speed
reducer. Speed reducers employing
pulleys and belts will not be accepted.
They should be readily adjustable to permit compensation for job site
conditions that may tend to overload the motor.The fans of one manu-
facturer require the purchase of special positioners for each increment
of fan blade pitch.
Standard fan drives of other manufacturers may use V-belts.
Considering the size of fans involved — and the horsepower applied —
this is not good design practice. Geareducer® drive is far more reliable
and trouble free, and is currently offered as an option by at least two
other cooling tower manufacturers.
■ Unless otherwise specified, motor speed will be 1800 RPM in 60 Hertz
areas and 1500 RPM in 50 Hertz areas. If you prefer the operating flex-
ibility of two-speed operation, please specify the RPM to be 1800/900
(1500/750 in 50 Hertz regions).
5.2
Motor(s) shall be ____ hp maximum,
TEFC, 1.15 service factor, and specially
insulated for cooling tower duty. Speed
and electrical characteristics shall be
1800 (1800/900) RPM, single winding,
___ phase, ___ hertz, ___ volts.
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■ The driveshaft turns at the motor speed and is, therefore, most sensi-
tive to operational imbalance. Stainless steel manufacture assures that
the driveshaft will not become unbalanced as a result of corrosion.
5.3
Motor shall be located outside the fan
cylinder at the fan deck, and shall be
connected to the speed reducer by
a tubular stainless steel, dynamically
balanced driveshaft equipped with neo-
prene flexible coupling elements.
5.4
5.5
A galvanized oil gauge and drain line
shall extend from the gear reducer to
the vicinity of the motor, and shall be
equipped with a dip stick for oil level
measurement.
■ Fans of the size used on large cooling towers are applied at speeds and
horsepower that generate considerable torque—and structural tubular
steel resists this torque very effectively. Marley torque-tube assures that
all of the mechanical equipment remains aligned, and that the rotating
fan is properly positioned within the fan cylinder.
The complete mechanical equipment
assembly for each cell shall be sup-
ported by a rigid, unitized support that
resists misalignment between the
motor and the gear reducer. Support
shall be heavy-wall tubular steel, to
which heavy plate platforms for the
motor and gear reducer have been
welded and the assembly shall be hot-
dip galvanized after fabrication. The
support assembly shall also provide
an inlet connection for incoming hot
water, and shall serve as a crossover
pipe to deliver water to both sides of
the tower.
■ The value of a 5 year mechanical equipment warranty speaks for itself.
Except for the motor, all of the mechanical equipment on a Marley
tower is made by SPX CoolingTechnologies. Cooling tower vendors
who purchase commercial fans, gear boxes, driveshafts, etc. may
require that you deal directly with those commercial suppliers for war-
ranty satisfaction.
5.6
The mechanical equipment assembly
shall be warranted for no less than five
(5) years. This warranty shall cover the
fan(s), speed reducers, driveshafts and
couplings, and the unitized supports.
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6.0
6.1
Fill, Louvers and Drift Eliminators:
Fill shall be film-type, 15 mil thick,
thermoformed PVC, with louvers
formed as part of each fill sheet. Fill
shall be suspended from stainless
steel structural tubing supported from
the upper tower structure, and shall
be elevated above the floor of the cold
water basin to facilitate cleaning. Air
inlet faces of the tower shall be free of
water splash-out.
■ Louvers integral with the fill keep the flowing water within the confines
of the fill.The separate external louvers used by others permit water to
escape the fill and form ice or produce an unsightly situation adjacent
to the tower. If you plan to use your tower in the wintertime, particu-
larly for free cooling, integral louvers will put your operating concerns
to rest.
6.2
Drift eliminators shall be PVC, triple-
pass, and shall limit drift losses to
0.005% or less of the design water
flow rate.
■ Vertical blade-type eliminators, as well
as misdirected cellular types, cause
much of the fan power to be wasted
in turning the horizontal flow of air
vertical for its exit through the fan
cylinder.This power is, of course, not
available for contribution to thermal
performance.
Drift rate varies with design water
loading and air rate, as well as drift
eliminator depth and number of direc-
tional changes. A drift rate of 0.001%
is readily available in standard configuration without premium cost. If a
lower rate is required, please discuss with your Marley sales represen-
tative.
Drift Eliminator
Section
Louver
Section
Fill Section
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7.0
7.1
Hot Water Distribution System:
The mechanical equipment support/
crossover pipe shall deliver water to
two open hot water basins per cell
at the fan deck elevation. Water shall
exit these basins to the fill by gravity
through metering orifice-type polypro-
pylene nozzles situated in the basin
floor. Nozzles shall be easily removable
and replaceable.
■ Gravity-flow distribution basins are a feature
of crossflow type towers.These basins are
out where they can be easily inspected—even
maintained—while the tower is in operation.
Spray systems of counterflow towers, sand-
wiched between the top of the fill and the drift
eliminators, are extremely awkward to access
and maintain.
7.2
Heavy-duty, industrial grade flow-
control valves shall be provided at
the inlet to each basin. These valves
shall permit both flow balancing and
maintenance shut-off to selected cells,
or portions of cells. Valves shall have
machined cast iron bodies, with stain-
less steel operating stems, and heavy-
duty locking handles.
■ Marley flow-control valves remain serviceable for the life of the tower,
and provide a continuing means of flow-regulation between hot water
basins—and between cells of multicell towers as well.Towers without
valves do not provide this valuable operating flexibility.
8.0
8.1
Casing:
Tower endwalls shall be cased with
corrugated FRP panels, attached with
corrugations running vertically and
overlapped one corrugation at joints.
Tower corners shall be finished with
FRP corner rolls over the ends of the
casing sheets.
■ Steel inner casings provide lateral sup-
port for the fill that FRP panels cannot.
They also support the FRP casing pan-
els against the high wind loads that
will act on the tower during its lifetime.
8.2
In the water-washed fill areas, inner
casings of 16 gauge galvanized steel
shall also be provided.
9.0
9.1
Access:
There shall be a 33" wide by 61" high
access door in each endwall casing to
provide access to the interior of the
tower. Access doors shall be hinged
and equipped with a latch operable
from both inside and outside the
tower. Internal partitions between cells
shall include hinged doors to give free
access through the tower.
■
The access doors on other towers may be unreasonably small.
Specifying the size of the door will cause those bidders to take excep-
➠
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tion, alerting you to a potential maintenance head-
ache.
9.2
The top of the tower shall be equipped
with a sturdy 42" high guardrail sys-
tem, complete with top rails, interme-
diate rails and toeboards, conforming
to OSHA standards. Guardrails and
posts shall consist of 1.66" O.D. x 15
gauge galvanized structural tubing.
Posts shall be spaced on centers of 8'-
0" or less.
■ Good maintenance practice requires period-
ic access to the top of the tower to inspect
the distribution basins, as well as the struc-
tural integrity of the fan deck, fan cylinder,
and fan — especially the fan blade secur-
ing hardware. There are no induced-draft
cooling tower designs that are immune to
this need!
9.3
One endwall of the tower shall be
equipped with a 20" wide aluminum
vertical ladder, through-bolted to the
endwall structure. Ladder shall rise
from the cold water basin level to the
top of the fan deck guardrail, and shall
be designed and installed in confor-
mance with OSHA standards.
■ For the comfort and safety of your operating personnel, the Sigma
Steel tower includes a ladder and guardrail of the quality and design
indicated — and we strongly recommend that you require it of all bid-
ders! Portable ladders and other "make-do" access means are inappro-
priate for equipment of this size and complexity.
10.0 Cold Water Collection Basin:
10.1 The collection basin shall be heavy-
gauge galvanized steel and shall
■
This basic specification assumes that the tower will be erected over
a concrete basin at grade level. If the tower is to be installed on an
elevated supporting platform, the steel cold water collection basin indi-
cated on page 24 should be included in the specifications.
include the number and type of suction
connections required to accommodate
the out-flow piping system shown on
the plans. Suction connections shall be
equipped with debris screens. A fac-
tory installed, float operated, mechani-
cal make-up valve shall be included. An
overflow and drain connection shall be
provided in each cell of the tower. The
basin floor shall slope toward the drain
to allow complete flush out of debris
and silt which may accumulate.
11.0 Scope of Work:
11.1 The cooling tower manufacturer shall
be responsible for the design, fabrica-
tion, and delivery of materials to the
project site, and for the erection of
the tower over supports provided by
others. Unless otherwise specified, all
external piping, pumps, controls, and
electrical wiring will be outside the
cooling tower manufacturer's scope of
work.
■ Please be clear in your specifications and inquiry
documents regarding the full scope of work
expected.That will help assure that your
bid comparisons will be made on as equal
a basis as possible—and will help to
avoid any misunderstandings during
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the execution and implementation of the contract.
Control Options
Control System:
5.7: Add the following paragraph in
the Mechanical Equipment section:
Each cell of the cooling tower shall
be equipped with a UL listed control
system in a NEMA 3R or 4X outdoor
enclosure capable of controlling
■ If it is your opinion that the control system for the cooling tower should
be part of the tower manufacturer’s responsibility, we are in whole-
hearted agreement with you. Who better to determine the most efficient
mode and manner of a tower’s operation—and to apply a system most
compatible with it—than the designer and manufacturer of the cooling
tower?
single-speed or two-speed motors
as required, and designed specifi-
cally for cooling tower applications.
The panel shall include a main fused
disconnect with an external operating
handle, lockable in the off position for
safety. Across-the-line magnetic start-
ers or solid state soft-start starters
as required shall be controlled with a
thermostatic or solid state tempera-
ture controller. Door mounted selector
switches shall be provided to enable
automatic or manual control and wired
for 120VAC control. Control circuit to
be wired out to terminal blocks for
field connection to a remote vibration
switch and for access to extra 120VAC
50VA control power, overload trip
alarms and remote temperature control
devices. The temperature controller
shall be adjustable for the required cold
water temperature. If a thermostatic
controller is used it shall be mounted
on the side of the tower with the tem-
perature sensing bulb installed in the
cold water basin using a suspension
mounting bracket. If a solid state tem-
perature controller is used the control-
ler will be door mounted on the control
panel. The temperature controller will
display two temperatures, one for
outgoing water and the other for set
point. Water temperature input shall be
obtained using a three-wire RTD with
dry well in the outlet water piping and
wired back to the solid state tempera-
ture controller in the control panel.
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Specifications
Basin Heaters:
Specification Value
10.2 Add the following paragraph in the
Cold Water Basin section: Provide a
system of electric immersion heaters
and controls for each cell of the tower
to prevent freezing of water in the
collection basin during periods of shut-
down. The system shall consist of one
or more stainless steel electric immer-
sion heaters installed in the basin. A
NEMA 4 enclosure shall house a mag-
netic contactor to energize heaters; a
transformer to provide 24 volt control
circuit power; and a solid state circuit
board for temperature and low water
cutoff. A control probe shall be located
in the basin to monitor water level
and temperature. The system shall be
capable of maintaining 40°F water tem-
perature at an ambient air temperature
of __ °F.
■ The basin heater components described at left represent our recom-
mendation for a reliable automatic system for the prevention of basin
freezing.They are shipped separately for installation at the job site.
The ambient air temperature that you fill in should be the lowest 1%
level of winter temperature prevalent at site.
Fan Motor Variable Speed Drive:
■ Marley VFD drive systems are designed to combine absolute tempera-
ture control with ideal energy management.The cooling tower user
selects a cold water temperature and the drive system will vary the
fan speed to maintain that temperature. Precise temperature control is
accomplished with far less stress to the mechanical equipment com-
ponents.The improved energy management provides fast payback.
Indeed, many utilities offer generous rebates for users having installed
VFD drives.
Marley All Weather ACH550 System
6.4
Add the following paragraph in the
Mechanical Equipment section when
VFD is used with customers Building
Management System: A complete
UL listed Variable Speed Drive system
in a NEMA 1 indoor, NEMA 12 indoor
or NEMA 3R outdoor enclosure shall
be provided. The VFD shall use PWM
technology with IGBT switching and
integrated bypass design. VFD out put
switching shall not cause mechanical
issues with gearbox teeth or drive shafts.
The VFD shall catch a fan spinning in
the reverse direction without tripping.
The panel shall include a main discon-
nect with short circuit protection and
external operating handle, lockable in the
off position for safety. The VFD system
shall receive a speed reference signal
from the Building Management System
monitoring the tower fluid temperature.
As an option to receiving the speed
reference signal from a building manage-
ment system, the drive must have the
capability to receive a 4-20 ma tempera-
ture signal from an RTD transmitter. The
VFD shall have an internal PI regulator
to modulate fan speed maintaining set
point temperature. The drive's panel dis-
play shall be able to display the set-point
➠
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temperature and cold-fluid temperature
on two separate lines. The bypass shall
include a complete magnetic bypass
circuit and with capability to isolate the
VFD when in the bypass mode. Transfer
to the bypass mode shall be manual in
the event of VFD failure. Once the motor
is transferred to the by-pass circuit the
fan motor will run at constant full speed.
The bypass circuit will not modulate ON
and OFF based on fluid temperature. The
application must be able to handle very
cold fluid temperatures while the VFD
is in a by-pass mode. Operator controls
shall be mounted on the front of the
enclosure and shall consist of start and
stop control, bypass/VFD selection, Auto/
Manual selections, manual speed control.
To prevent heating problems in the fluid
cooloer fan motor and to assure proper
gear reducer lubrication the VFD system
shall de energize the motor once 25%
motor speed is reached and cooling is no
longer required. The fluid cooler manu-
facturer shall supply VFD start-up assis-
tance. Tower vibration testing throughout
the speed range is required to identify
and lockout any natural frequency vibra-
tion levels which may exceed CTI guide-
lines.
Marley Premium VFD System
6.4
Add the following paragraph in the
Mechanical Equipment section when
VFD is used as a stand alone system:
A complete UL listed Variable Speed
Drive system in a NEMA 12 indoor
or NEMA 3R outdoor enclosure shall
be provided. The VFD shall use PWM
technology with IGBT switching and
integrated bypass design. VFD output
switching shall not cause mechanical
issues with gearbox teeth or drive shafts.
The VFD shall catch a fan spinning in the
reverse direction without tripping. The
panel shall include a main disconnect
with short circuit protection and external
operating handle, lockable in the off posi-
tion for safety. The system shall include
a solid state, PI temperature controller
to adjust frequency output of the drive
in response to the tower fluid tempera-
ture. The temperature of the fluid and
set point shall be displayed on the door
of the control panel. The bypass shall
include a complete magnetic bypass
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circuit with capability to isolate the VFD
when in the bypass mode. Transfer to
the bypass mode shall be automatic in
the event of VFD failure or for specific
trip conditions allowing safe transfer of
utility voltage to the motor. Automatic
bypass with an earth ground condition
is not allowed. The bypass contactor
shall be cycled on and off while operat-
ing in bypass, to maintain the set-point
temperature of the cold water. The drive
design shall be operated as a stand-alone
system without the need for a BMS sys-
tem. Operator controls shall be mounted
on the front of the enclosure and shall
consist of start and stop control, bypass/
VFD selector switch, Auto/Manual selec-
tor switch, manual speed control, and
solid-state temperature controller. An
emergency bypass selector switch inter-
nal to the panel allowing the fluid cooler
fan motor to be run at full speed shall be
furnished. To prevent heating problems in
the fluid cooler fan motor and to assure
proper gear box lubrication the VFD sys-
tem shall de energize the motor once
25% motor speed is reached and cool-
ing is no longer required. The VFD shall
include de-icing logic with auto canceling
and adjustable time. Speed in De-Ice
mode shall not exceed 50% motor
speed. The fluid cooler manufacturer
shall supply VFD start-up assistance.
Tower vibration testing throughout the
speed range is required to identify and
lockout any natural frequency vibration
levels which may exceed CTI guidelines.
Vibration Limit Switch:
■ Unless specified otherwise, a Metrix switch
will be provided. A double-pole, double-throw
model is also available. If purchased in con-
junction with the Control System, it is also
factory-wired.The requirement for manual
reset assures that the tower will be visited to
determine the cause of excess vibration.
5.8
Add the following paragraph in the
Mechanical Equipment section: A
single-pole, double-throw vibration limit
switch in a NEMA 4 housing shall be
installed on the mechanical equipment
support for wiring into the owner’s
control panel. The purpose of this
switch will be to interrupt power to the
motor in the event of excessive vibra-
tion. It shall be adjustable for sensitiv-
ity, and shall require manual reset.
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Convenience and Safety Options
Stairway:
■ Although they are not necessary for routine operation and mainte-
nance, stairways do provide a safe and comfortable means of access to
the top of the tower that is often overlooked in the initial cooling tower
purchase.They are designed in straight-run or double-back configura-
tions to accommodate your site requirements.
9.3
Replace paragraph 9.3 with the fol-
lowing: A 30" wide, 45° steel stairway
with 8" rise and run, shall be provided
at the tower endwall rising from grade
(roof) to the fan deck elevation. Stair
treads shall be bar grating with checker
plate nosing, and shall be through
bolted to structural channel string-
ers. Stairway posts, guardrails and
toeboards shall be as specified per
Paragraph 9.2. Structural steel sup-
port columns for the stairway shall be
provided by the cooling tower manu-
facturer. Stairway foundation shall be
by others, designed in accordance with
drawings provided by the cooling tower
manufacturer. The entire stairway shall
be hot-dip galvanized after fabrication
and shall conform to OSHA standards.
PlenumWalkway:
■ This option permits freedom of movement for inspection or mainte-
nance within the tower without the need for wading boots or tower
drainage. It also helps prevent maintenance personnel from damag-
ing submerged accessories in the cold water basin (such as screens,
probes, basin heaters, etc.).
9.1
Add the following to the end of this
paragraph: Provide a 30" wide bar grat-
ing walkway extending from one endwall
access door to the other in each cell.This
walkway shall be supported by a galva-
nized steel framework, and the top of the
gratingshallbeabovethecoldwaterbasin
overflow level. If the cold water basin is
deeper than 4'-0", the walkway shall be
equipped with guardrails.
Ladder Extension:
■ Many towers are installed such that the base of the tower is 2'-0" or
more above the roof or grade level.This makes it difficult to get up to
the base of the attached ladder.The ladder extension alleviates this
problem. Marley ladder extensions are available in standard 5'-0" and
11'-0" lengths, and will be field-cut to fit.
9.4
Add the following paragraph in the
Access and Safety section: Provide
a ladder extension for connection to
the base of the ladder attached to
the tower casing. This extension shall
be long enough to rise from the roof
(grade) level to the base of the tower.
Anchorage and lateral bracing of the
ladder extension shall be by others.
Ladder Safety Cage:
■
To meet OSHA guidelines, towers whose fan
decks are 20'-0" or more above roof or grade, and
which are equipped with ladders, are required to
have safety cages surrounding the ladders.
9.3
Add the following to the end of this
paragraph: A heavy gauge galvanized
steel safety cage shall surround the
ladder, extending from a point approxi-
mately 7'-0" above the base of the
ladder to the top of the guardrail sur-
rounding the fan deck.
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Specification Value
Oil Level Sight Glass:
■ The oil level sight glass is a convenience item that is preferred by many
users.The same purpose is, of course, served by either the dip stick or
the sight glass.
5.4
Replace paragraph 5.4 with the fol-
lowing: A galvanized oil gauge and
drain line shall extend from the gear
reducer to the vicinity of the motor,
and shall be equipped with a bronze-
bodied oil level sight glass.
Miscellaneous Options
Steel Cold Water Basin:
■ Marley basins are used to permit the installation of towers on elevated
platforms or foundations.
10.1 Replace paragraph 10.1 with the fol-
lowing: Include a cold water collection
basin constructed of 12 gauge hot-dip
galvanized formed steel sheets. These
sheets shall be bolted, gasketed and
caulked to form a watertight basin 18"
deep. A depressed, side outlet sump shall
be included, having a 1/4" thick faceplate
drilled for a standard 125# flange connec-
tion. An appropriately sized (3" diameter
or larger) galvanized standpipe overflow
shall be provided. The standpipe shall be
removable for flush-out cleaning of the
basin. A float-operated, mechanical make-
up valve shall also be included, installed
adjacent to the endwall access door.
This is the simplest of several cold water basin designs available for
the Sigma Steel towers. Because of its bolted construction, it has the
advantage of being hot-dip galvanized after fabrication. Marley can
also install a 10 gauge welded stainless steel basin for a Stainless Steel
Sigma. See 24.
Factory Mutual Approval:
■ This could have a very beneficial effect
upon your fire insurance premiums.
Towers not able to meet FM require-
ments may require the inclusion of a fire
protection sprinkler system to achieve a
comparable level of insurance premium
cost.
3.5
7.3
8.3
Add the following paragraph in the
Construction section: The tower shall
include all design and material modi-
fications necessary to meet the fire
rating requirements of Factory Mutual.
The product proposed shall be listed in
the FM Approval Guide, latest edition.
Hot Water Basin Covers:
■ These covers are designed to keep leaves and debris out of the circu-
lating water system.They also serve to suppress algae formation by
shielding the incoming hot water from direct sunlight.
Add the following paragraph to
the Hot Water Distribution System
Section: The distribution basins shall
include galvanized steel covers. These
covers shall be designed for a uniform
live load of 40 psf, and shall be easily
removable for maintenance.
Air Inlet Screens:
■ In wooded or windy areas, these screens help to keep leaves or blow-
ing debris out of the cooling tower and circulating water system.
Add the following paragraph to the
Casing Section: The air inlet faces of
the tower shall be covered by 1" mesh
hot-dip galvanized welded wire screens.
Screens shall be mounted in galvanized
steel U-edging and shall be removable.
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Specification Value
Low NoiseTower:
■ Sound produced by a Sigma Steel 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 enclosure itself will have
a damping effect on sound. Sound also declines with distance – by
about 5 or 6 dBA 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:
1.1
Add the following at the end of this
paragraph: The cooling tower shall be
quiet operating, and shall produce an
overall level of sound no higher than ____
dBA at the critical location indicated on
the Plans.
• 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 nighttime, 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
1800/900 or 1800/1200 RPM configuration; and operating the fans at
reduced speed without cycling “after hours”. (The natural nighttime
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 sacri-
ficing the system's ability to maintain a constant cold water tempera-
ture.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 (1200 or 900 RPM) motor speed even at the highest
design wet-bulb temperature.Typical sound reductions are 7 dBA at
2/3 fan speed or 10 dBA at 1/2 fan speed, but larger reductions are
often possible.
• Extreme cases may require inlet and discharge sound attenuator
sections; however, the static pressure loss imposed by attenuators
may necessitate an increase in tower size. This is the least desirable
approach because of the significant cost impact – and because of the
obstruction to normal maintenance procedures.
Y
our Marley representative can help you meet your sound require-
ments.
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Service Life-Related Customization:
■ Some adverse water conditions, unsatisfactory air quality, and/or pro-
cesses that produce corrosive contaminants, may dictate the use of
stainless steel for materials of construction in the tower.
Refer to our Stainless Steel Sigma Series, in which the use of stainless
steel has been maximized. Except for valve bodies and Geareducer,
every steel component of that product line is manufactured of stainless
steel.
If your project has a need for the extended service life that premium
materials will offer, please obtain a copy of "Marley Sigma Stainless
Steel CoolingTower Specifications" from your local Marley sales rep-
resentative, and extract from it those paragraphs that make sense for
you.
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In the interest of technological progress,
all products are subject to design and/or
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©2008 SPX Cooling Technologies, Inc.
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