TECHNICAL NOTES
CONSTRUCTION PRACTICES • Aerial
Trilogy
COMMUNICATIONS, INC
MC2 Trunk and Feeder Cable
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CONSTRUCTION PRACTICES • Aerial
INTRODUCTION
Sound installation practices should be followed during construction of an aerial plant. The purpose of this section is to highlight
the unique mechanical design of MC2 cable and to outline certain
practices for successful installations.
During the process of building an aerial plant, many different
construction techniques will be required. This section will describe
construction methods for proper installation of coaxial cables lashed
onto strand and installation of messengered cable.
Before going into the field, make sure that all tools and equipment are in proper working order. A preventative maintenance
program is a good idea for all mechanical items in order to save
time and expense for the contractor and/or system operator, regardless of the installation method.
BACK PULL METHOD
The back pull method of coaxial cable installation is the most
widely used and the recommended method for aerial installation.
This method can be used successfully with any size or number of
cables, even in locations where poles are not easily accessible.
First insure that all equipment is in good working order. Check
the maps for the day’s installation of trunk and feeder cable to determine the proper footages. After the reels are selected, make sure
that the cable has been tested for fault and proper length as
described in the testing section.
The cable ends on the reel must always be capped. If reels
have been stored outside and the cable ends have not been
capped, the cable must be retested. Installing improperly stored
cable can be costly and should be avoided.
When loading reels onto the trailer, make sure that the cable
pay off is from the top of the reel. This will provide a smooth incline
from the reel trailer to the cable chute. Always install reel brakes and
the appropriate spacers along with the reels (figure 6-1). Check to
see that cable ends are fastened to prevent loosening during transportation to the installation site.
When starting an unfamiliar cable route, walk or drive along
the cable run beforehand to check for trees, bad poles or make
ready. Also check for 90° or 45° turns along the cable route.
When encountering a 10° to 45° turn, use a 45° corner block
(figure 6-2) and with turns greater than 45°, use a 90° corner block
(figure 6-3). These blocks are necessary to prevent any mechanical
damage when pulling corners. No more than two 90° turns should
be pulled on any run.
After the cable route has been walked or driven out, it is time
to proceed with the installation. Position the trailer in line with
the strand at a distance of twice the strand height from the pole
1
Figure 6-1. Reel Brakes
Figure 6-2. 45 degree Corner Block
Figure 6-3. 90 degree Corner Block
(figure 6-4) and chock the trailer wheels to prevent movements when
the cable is pulled. Next, check reel flanges for nails or staples that
could damage the cable during pay off. As the cable is pulled off
of the reel, adjust reel brakes so that the reel will not continue to turn
if pulling is ceased. Attach a cable chute or 45° block at the first
pole location to support the cable through the transition angle from
the reel to the pole. At this point, mount a cable puller onto the
strand, pull the cable over the chute, and attach the puller with a
pulling grip. Swivels and/or thrust bearings should be used to
relieve twisting.
6-1
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MC2 coaxial cables can be pulled by hand, truck or winch. The
maximum pulling tensions and minimum bending radii for MC2
cables are listed below.
Size
.440
.500
.650
.750 “
1.00”
Minimum
Bending Radius
5“
6”
7”
8“
13”
Maximum
Pulling Tension
220 lbs.
270 lbs.
360 lbs.
500 lbs.
830 lbs.
As the cable is pulled over the cable chute towards the next
pole, position rollers at 25 to 50 foot intervals to provide support.
This will prevent the cable from bouncing while the pulling starts and
stops and eliminates mid-span damage. Also, a roller must always
be attached at each pole location after the puller is repositioned
from one side of the pole to the other to prevent the cable from coming in contact with the pole (figure 6-5). These practices should be
carried out through the entire cable pull.
When the cable route has been completed, the lasher should be
filled with lashing wire and ready for the crew member at the last
pole. If multiple cables are being installed, use a cable positioner to
provide uniform positioning and lashing of the cable. Also, a cable
block pusher should always be used between the lasher and the
positioner, and ahead of the positioner to uniformly guide the cable
from the rollers to the lasher. In the case of single cable installation,
when the positioner is not used, only one block pusher is needed
(figure 6-7).
As the lasher is pulled across a span, the block pusher will move
all rollers ahead of the lasher. Remove the collection of rollers and
lasher accessories at each pole. Cut the lashing wire and tem-
cable chute
Figure 6-5. Roller
porarily clamp it to the strand. Then reposition the lasher and accessories to the other side of the pole in order to continue the lashing
operation. Once this is done, securely fasten the temporarily
clamped lashing wire with a lashing wire clamp and position a
band and spacer on the strand to prevent the lashing wire clamp
from rubbing the cable. When forming the expansion loop, use a
loop forming tool, leaving the tool in place while the lasher is prepared for the next span. At this point the lashing operation begins
while the cable and expansion loop tool are held in place to prevent any pull out of cable from the loop. After pulling the lasher to
the next pole, remove the tool and proceed with the installation of
bands and spacers to prevent the cable from rubbing against lashing wire clamps and pole hardware and to hold expansion loops
in place (figure 6-6).
roller spacing
cable puller
25 - 50 feet
Trailer placement at twice strand height
Figure 6-4. Aerial back pull
6-2
1
TECHNICAL NOTES
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MC2 Trunk and Feeder Cable
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Figure 6-6. Band and spacer placement
Breakaway swivel
rated at maximum
pulling tension
Figure 6-7. Drive off
Pull off approximately 3 feet of cable to provide slack for
equipment splicing. All exposed cable ends are to be capped at all
times and should be pointing downward. Before leaving the location, check the cable for any damage that may have occurred during the pulling operation.
Continue these procedures from pole to pole until the final span
is reached, at which point the excess cable on the reel should be
taken up as the final span is lashed. Always cap the ends of any
cable that is left on the reel.
1
DRIVE OFF METHOD
When using the drive off method to install cable, follow the
same procedures for selecting reels and loading the trailer as previously described for the back pull technique.
To begin the drive off method, first mount the lashing equipment
on the strand. This equipment will consist of a cable chute or guide,
a pusher, a multiple cable positioner, a second pusher and the lasher, in that order. This sequence of accessories will provide uniform
lashing and will lessen the chances of mechanical deterioration. If
only a single cable is to be lashed, the multiple cable positioner and
one of the pushers will not be necessary (figure 6-7).
Once the lashing equipment is in position, move the truck and
cable trailer to about 50 feet from the starting pole or approximately
two times the strand height. Pull the cable from the reel back to the
6-3
TECHNICAL NOTES
CONSTRUCTION PRACTICES • Aerial
COMMUNICATIONS, INC
MC2 Trunk and Feeder Cable
first pole, feed it through the lashing equipment and secure. Then
fasten the lashing wire to the strand so that the drive off procedure
can begin. The pulling vehicle and trailer should always remain
approximately 50 feet from the lashed cable to assure a smooth
incline from the trailer to the cable guide.
When the lashing equipment reaches the next pole, cut the lashing wire and temporarily clamp it to the strand. The lashing equipment can now be transferred to the other side of the pole but be
careful not to damage the cable.
After the lashing equipment has been mounted on the opposite
side of the pole, form an expansion loop if necessary. As with the
back pull method, the loop forming tool should remain in place until
lashing resumes and the lasher is pulled to the next pole. At this
point the tool can be removed and the lashing wire clamps, cable
straps and spacers can be attached in the same fashion as previously described for the back pull method. Continue the drive off procedure in this manner until the last pole in the run is reached. If an
extra length of cable is required for equipment splicing, the tail
should extend beyond the pole approximately 3 feet.
All exposed cable ends must be capped and should be pointed
downward. Caps are available upon request. Before leaving the
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location, inspect the cable for any physical damage. Note: With this
method, pulling tension and axial or rotational tension cannot
be monitored on the cable. This method has a tendency to
allow the expansion loops to twist after lashing.
LASHER SET-UP AND OPERATION
As with any construction equipment, the lasher must be checked
before each day’s use to insure that it is in good working order.
Since smooth operation of the lasher is vital for successful construction, it must be well maintained. This may require tightening of loose
parts, replacement of broken or worn ones and periodic oiling as
recommended by the manufacturer.
There are a variety of lashers on the market that can be used for
2
MC installation. Since each type of lasher offers different features,
choice must be based on specific needs. However, one feature that
is recommended is a braking mechanism which prevents the lasher
from slipping back when pulling is stopped. Most lashers are
equipped with this feature.
The lasher must first be loaded with the appropriate lashing wire
according to the manufacturer’s specifications. Check the lashing
wire to ensure that it pulls easily from the lasher. Open the lasher
pulling rope
Figure 6-8. Lasher set-up
6-4
1
TECHNICAL NOTES
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MC2 Trunk and Feeder Cable
gates and strand locking mechanism and place the lasher over the
strand and cable. With the lasher in position, close the strand locking mechanism to prevent the lasher from falling, then close and
adjust the lasher gates so that the gate rollers ride snugly against the
cable. Tie the lashing wire to the lashing wire clamp and tie the
pulling rope to the lasher (figure 6-8).
The lashing machine can be pulled either by hand or by truck.
If using a truck, maintain a slow and even speed for best results.
With either method the lasher should be pulled down and to the side
in order to maintain uniform tension and lashing. When a pole is
reached at the end of each pull, check the amount of lashing wire
to ensure an adequate supply for the next span. Since a lashing
wire splice may rub the cable, all lashing wire ends must be
terminated using a lashing wire clamp.
Although some different equipment is required, multiple cables
can be installed in the same manner as previously described for
back pull and drive off techniques. For the pulling of multiple cables,
a multiple reel trailer, multiple cable puller and multiple rollers should
be used to maintain proper orientation between the cables. For the
lashing operation, it is necessary to use a lashing machine that can
accommodate the size and number of cables being installed. A multiple cable positioner should also be used to facilitate uniformity of
lashing. Multiple cables should always be double lashed.
In addition to multiple cable installations, double lashing is highly
recommended for highway crossings and spans greater than 200
feet.
Following these procedures will provide for the establishment of
a mechanically sound and uniformly lashed plant.
GROUNDING & BONDING - Aerial
The primary purpose of grounding is to provide a path for any
fault currents to be neutralized, thus to safeguard employees and the
public from injury. The following definitions come from the NEC1
“Grounded Effectively” or“Effectively Grounded”- Intentionally
connected to earth through a ground connection or connections of
sufficiently low impedance and having sufficient current carrying
capacity to prevent the build up of voltages that may result in undue
hazards to connected equipment or to persons.
“Bonding” - The permanent joining of metallic parts to form an
electrically conductive path that will insure electrical continuity and
the capacity to conduct safely any current likely to be imposed.
Grounding and bonding hardware will vary with different methods. Some of the following practices are taken from the NESC.2
Local codes or ordinances should also be followed.
Multi-current carrying conductors (such as high voltage power)
within close proximity of each other can induce unwanted fault
currents on other non-current carrying conductors. The cable carrying strand (CATV Plant) is constantly subjected to these unwanted
1
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fault currents. High power surges and lightning can also cause
induced voltages and currents to be present. Maintaining proper
clearances and using good grounding and bonding techniques will
provide a means of reducing and dissipating these fault currents to
a zero ground potential.
For a CATV plant to be ‘Effectively Grounded’ the National
Electrical Safety Code requires there to be no less than eight
bonding and or grounding connections per mile. If a vertical
utility ground does not exist, a ground rod must be driven.
Bonding Clamps
There are two categories of bonding clamps, one for similar
metals and one for dissimilar metals.
A bronze split bolt is usually used when a copper to copper
bond is made. For dissimilar metals, a bi-metal clamp is used with
one side for galvanized steel or aluminum and the other side for
copper. Multi-purpose clamps are also available which allow bonding of similar and dissimilar metals (figure 6-9).
Figure 6-9. Bonding clamps
A regular strand bonding clamp may be used to bond galvanized steel strand to itself. When strand and guys are not continuous, a continuity bond should be used. Splicing of the bonding wire
should be avoided.
Ground Rods
Ground rods or grounding electrodes should be a minimum of
eight feet in length and 5/8 inches in diameter, and have a conductive and non-corrosive outer surface. Driven ground rods should
be buried to a depth of eight feet at or below ground level. When
driving ground rods, always maintain a minimum of ten feet from
pipelines carrying any flammable liquids or gases. For the purpose
of grounding coaxial cable, “existing electrodes” may be used
1
National Electrical Code
2
National Electrical Safety Code
6-5
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under the proper circumstances, otherwise “made electrodes” must
be driven to ground the cable.
CATV
Strand
Existing Electrodes - Consist of conducting items installed for purposes other than grounding. Some examples of existing electrodes
include metallic water piping systems or steel reinforcing bars in
concrete foundations and footings.1
Made Electrodes - Should penetrate permanent moisture levels
below the frostline. The surface will be conductive and must be
made of metal or combinations of metals that do not corrode excessively under the existing conditions for the expected service life. One
example of a made electrode is a driven rod, usually made of copper or copper clad.1
Ground Wire
The “pole ground“-The ground wire or grounding conductor
provides a path for any fault current from the CATV Plant
(strand/cable) to the grounding electrode or ground rod. Use a minimum of No. 6 AWG copper wire to connect the galvanized steel
strand to the existing utility vertical ground wire. When bonding to an
existing ground wire, the two copper wires may be connected with
a single bonding clamp or split bolt, but a bi-metal clamp should be
used to connect the strand to the bonding jumper (figure 6-10).
When an existing utility vertical ground is not available it may
be necessary to install one. Ground wire should always be run as
straight as possible and any bends should be made gradual. Use
copper coated or copper clad staples to secure the ground wire to
the wooden pole, thus preventing any corrosive reaction between
the grounding conductor and the staple (figure 6-11).
Install a covering or molding over the first eight feet of the
ground wire to provide protection to the public and prevent any
mechanical damage.
A ground rod clamp is used to attach the copper ground wire
to the copper clad grounding electrode, usually made of bronze. In
any case, the clamp must be corrosion resistant.
EXPANSION LOOPS
Expansion loops are a common means for absorbing the effects
of thermal expansion and contraction in the cable plant.
It is recommended that expansion loops in MC2 coaxial cables
be formed into 12 inch flat bottom loop design for cables up to
and including .750 and 15 inch for 1 inch cables. This loop has
been extensively tested in the research lab and in field applications
with complete success. This design distributes strains across the flat
section rather than concentrating them at any single point.
It is recommended that expansion loops be placed at every pole
throughout the plant. For trunk cables we suggest that a loop be
placed on each side of amplifiers, passive devices and splices. It is
also recommend that expansion loops not be formed at the pole but
6-6
Trilogy
Existing Utility
vertical ground wire
Bonding Clamp
Bonding Jumper
#6 AWG Copper Wire
Split Bolt
Existing 8 ft.
Ground Rod,
5/8" diameter
Figure 6-10. Bonding to existing ground rod
CATV
Strand
Bonding Clamp
#6 AWG Copper Wire
8 ft. Ground Rod,
5/8" diameter
Figure 6-11. Bonding to new ground rod
rather on each side of a pole. Expansion loops that are placed
directly at the pole can be damaged from excessive contact with the
pole or pole hardware. When forming expansion loops in multiple
cables, straps should not be used in the bottom of the loops.
Additional loops may be needed in certain climates.
__________________________________________________________
1
National Electrical Safety Code
1
TECHNICAL NOTES
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MC2 Trunk and Feeder Cable
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When coaxial cable is installed on the strand, pay attention to
tensioning and sag limitations (See Sag and Tension Section). In most
instances the construction should match the amount of sag given to
telephone and power cables. The proper amount of sag can provide more cable in the span and create more room for expansion
and contraction. This practice will supplement the use of expansion
loops for reducing maintenance problems caused by cable expansion and contraction.
Expansion loop forming tools come in an array of designs ranging from simple contoured boards to mechanical bending
machines. Many of these tools can be used to form a flat bottom
loop on MC2 cables. Note: Expansion loop forming tools are
recommended for consistent formation of the expansion loop.
Procedures for their use are available from the manufacturer.
Since these are available in a variety of different sizes and features,
a choice must be made based on the particular need of a system.
Two of these tools will be described in this section.
Jackson Cable Bender
The Jackson cable bender is available in two sizes. The smaller
tool can be used to form loops in MC2 coaxial cable up to and
including the .750” size. The larger tool is used for the 1.00” size.
To form a loop, open the action of the bender completely and
mount the tool on the strand. Then place the cable onto the shoes
and crank the ratchet down until it reaches the stop. The action of
this device is such that the loop is formed by the application of
Figure 6-12. Lemco expansion loop tool
downward pressure of the shoes at each end of the flat 12 inch section, while the cable is supported by two other shoes at each outside end. Leave the tool in place if lashing is to resume. After the
lasher is pulled to the next pole, open and remove the tool.
Lemco Expansion Loop Tool
The Lemco expansion loop tool (figure 6-12) is available in two
sizes. The smaller tool is used for MC2 coaxial cable up to and
including the .750” size. The larger tool forms a 15 inch flat bottom
loop for the 1.00” size. This tool operates in a similar manner as
previously described, but the action is different in that pressure
applied to the inside radius of the loop is constantly moving.
See figure 6-6 for the recommended band and spacer placement for expansion loop geometry.
Pole spans Less than 200’ should incorporate one expansion
loop per pole (figure 6-13).
Pole spans greater than 200’ should incorporate two
expansion loops per pole (figure 6-14).
Less
than 200
feet
Less
than
200
feet
Figure 6-13. Less than 200 feet - one expansion loop per pole
Greater than
than 200
200 feet
feet
Greater
Figure 6-14. Greater than 200 feet - two expansion loops per pole
1
6-7
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SAG & TENSION
Proper sag and tension during cable installation maximizes
cable plant life.
Referring to Figure 6-18, sag is defined as the mid-span deviation (d) from a straight line, divided by the span distance (L),
expressed as a percent. For example, for d = 36” (or 3 feet) over
a span of 150 feet, the sag is (3/150) x 100%, or 2%.
Tension refers to the tension in the strand which is required to
produce a given sag condition.
The recommended sag for combined cable and strand is 2% at
a temperature equal to the mean climate temperature. The three
equations below are used to calculate sag and tension as a function of span length, and combined weight of cable(s) and strand.
The recommended procedure for achieving desired sag is as
follows:
1. Set initial strand sag slightly less than the target value, since
adding the weight of the cable (later) will increase the sag.
2. Place strand in the pole clamps, free to adjust tensions for final
recommended sag of 2%.
3. Adjust strand tension to achieve final sag value after cable is
lashed to strand. Adjust tension for each span of cable.
4. A dynamometer or equivalent device can be used to check
strand tension at any point in the procedure.
Because of the effects of thermal expansion and contraction,
sag will vary with temperature. Sag will increase slightly on hot
days and decrease slightly on cold days. This means that temperature at the time of the sagging operation must be taken into
account.
The first example of how temperature is accounted for during
the sagging operation is provided in figure 6-19a, where a single
.500” Bare MC2 cable is double lashed on 1/4” EHS steel
strand. Assume the span is 100 feet and the mean annual temperature is 70°F. The objective is to achieve the recommended sag
of 2% when the outside temperature is 70°F. But suppose the
sagging operation is being done on a very cold day when the
outside temperature is only 30°F. Referring to the upper table in
figure 6-19a, the proper sag to “install” under these conditions
would be only 21inches. Then, as the temperature warms to 70°,
thermal expansion will automatically result in a sag equal to the
desired 24 inches.
The lower table in figure 6-19a shows the strand tension values
for the corresponding sag conditions. Note that the effects of 0.5
inch of ice (@ 32°F) are shown in the far right columns of figure
6-19a.
Figures 6-19b through 6-19h provide additional examples of
various cable and strand combinations, intended for a 70°F mean
climate temperature, with sag of 2%, and showing what sag to
use if the sagging operation occurs at a different temperature.
Other factors which should be taken into account for proper
sagging include:
■ Normal daily temperature extremes (10 to 30°F).
■ Normal annual temperature changes (20 to 60°F).
■ Extreme annual temperature changes (60 to 140°).
■ Solar heating on bare aluminum can be as high as 20°F.
■ Jacketed cable can be as high as 40°F above ambient air temperature.
2% SAG @ 70°F
L=150 feet
d=36 inches
Figure 6-18 Sag example
6-8
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The examples provided in figures 6-19a through 6-19h are
for mean annual temperatures of 70°F. Sag and tension tables
for other cable and strand combinations, and for other mean
annual temperatures can be generated by computer program
(“SAG”) available on computer disc (IBM compatible). Contact
Trilogy Applications Engineering Department for information on
obtaining the SAG program disc, or if there are other questions
related to recommended sag procedures.
SAG AND TENSION TABLE
CABLE AND STRAND SAG (inches) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
18
27
37
47
19
29
39
49
21
31
42
53
22
34
45
56
24
36
48
60
25
38
51
63
28
41
55
68
.5’’ of ice
@ 32°F
31
48
68
89
STRAND TENSION (pounds) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0°F
10°F
30°F
50°F
70°F
90°F
120°F
175
259
342
422
167
247
327
405
152
227
302
376
141
211
281
351
132
198
264
330
124
186
249
312
115
172
231
289
.5’’ of ice
@ 32°F
913
1,343
1,680
1,994
Figure 6-19a.
Recommended sag and tension vs. installation temperature for 2% sag with an annual mean temperature of 70°F.
Cable installed with 1/4” ESH strand-all cable double lashed.
1@-MC2 .500 Bare
1
6-9
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SAG AND TENSION TABLE
CABLE AND STRAND SAG (inches) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
19
28
39
49
19
30
40
51
21
32
43
54
23
34
45
57
24
36
48
60
25
38
51
63
27
41
54
68
.5’’ of ice
@ 32°F
32
52
74
98
STRAND TENSION (pounds) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
359
528
691
852
344
508
668
825
318
473
625
776
296
443
588
733
278
417
556
695
263
395
528
661
243
367
491
617
.5’’ of ice
@ 32°F
1,386
1,902
2,372
2,811
Figure 6-19b.
Recommended sag and tension vs. installation temperature for 2% sag with an annual mean temperature of 70°F.
Cable installed with 1/4” ESH strand-all cable double lashed.
2@ MC2 .500 Bare
1@ MC2 .750 Bare
6-10
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SAG AND TENSION TABLE
CABLE AND STRAND SAG (inches) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
19
29
39
49
20
30
40
51
21
32
43
54
23
34
45
57
24
36
48
60
25
38
51
63
27
41
54
67
.5’’ of ice
@ 32°F
32
52
75
98
STRAND TENSION (pounds) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
413
605
793
976
396
584
767
947
367
545
721
894
342
512
680
847
322
483
644
805
304
458
612
767
282
426
571
717
.5’’ of ice
@ 32°F
1,477
2,026
2,527
2,995
Figure 6-19c.
Recommended sag and tension vs. installation temperature for 2% sag with an annual mean temperature of 70°F.
Cable installed with 1/4” ESH strand-all cable double lashed.
2@ MC2 .650 Bare
1@ MC2 .750 Bare
1
6-11
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SAG AND TENSION TABLE
CABLE AND STRAND SAG (inches) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
19
29
39
49
19
30
40
51
21
32
43
54
23
34
45
57
24
36
48
60
25
38
51
63
27
41
54
67
.5’’ of ice
@ 32°F
32
52
74
98
STRAND TENSION (pounds) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
386
567
742
914
370
546
717
886
342
509
673
835
319
477
634
790
300
450
600
750
283
426
570
714
263
396
531
667
.5’’ of ice
@ 32°F
1,431
1,964
2,450
2,903
Figure 6-19d.
Recommended sag and tension vs. installation temperature for 2% sag with an annual mean temperature of 70°F.
Cable installed with 1/4” ESH strand-all cable double lashed.
1@ MC2 .500 Bare
1@ MC2 .650 Bare
1@ MC2 .750 Bare
6-12
1
TECHNICAL NOTES
CONSTRUCTION PRACTICES • Aerial
Trilogy
COMMUNICATIONS, INC
MC2 Trunk and Feeder Cable
800-874-5649
601-932-4461
SAG AND TENSION TABLE
CABLE AND STRAND SAG (inches) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
18
28
37
47
19
29
39
49
21
31
42
53
22
34
45
57
24
36
48
60
25
38
51
63
28
41
55
68
.5’’ of ice
@ 32°F
29
48
68
90
STRAND TENSION (pounds) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
198
293
385
476
189
280
369
458
173
258
342
425
160
240
319
398
150
224
299
374
141
212
283
354
130
196
262
329
.5’’ of ice
@ 32°F
1,008
1,391
1,740
2,064
Figure 6-19e.
Recommended sag and tension vs. installation temperature for 2% sag with an annual mean temperature of 70°F.
Cable installed with 1/4” ESH strand-all cable double lashed.
1@ MC2 .500 JAU
1
6-13
TECHNICAL NOTES
MC2
CONSTRUCTION PRACTICES • Aerial
Trilogy
COMMUNICATIONS, INC
Trunk and Feeder Cable
800-874-5649
601-932-4461
SAG AND TENSION TABLE
CABLE AND STRAND SAG (inches) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
19
29
39
50
20
30
40
51
21
32
43
54
23
34
46
57
24
36
48
60
25
38
51
63
27
41
54
67
.5’’ of ice
@ 32°F
32
52
74
98
STRAND TENSION (pounds) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
434
637
833
1,026
417
614
807
996
387
574
759
942
361
539
717
893
340
509
679
849
321
483
646
809
298
449
603
757
.5’’ of ice
@ 32°F
1,487
2,042
2,548
3,020
Figure 6-19f.
Recommended sag and tension vs. installation temperature for 2% sag with an annual mean temperature of 70°F.
Cable installed with 1/4” ESH strand-all cable double lashed.
2@-MC2 .500 JAU
1@-MC2 .750 JAU
6-14
1
TECHNICAL NOTES
CONSTRUCTION PRACTICES • Aerial
Trilogy
COMMUNICATIONS, INC
MC2 Trunk and Feeder Cable
800-874-5649
601-932-4461
SAG AND TENSION TABLE
CABLE AND STRAND SAG (inches) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
19
29
40
50
20
30
41
52
21
32
43
54
23
34
46
57
24
36
48
60
25
38
50
63
27
41
54
67
.5’’ of ice
@ 32°F
32
53
75
99
STRAND TENSION (pounds) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
497
728
952
1,172
478
704
924
1,140
445
660
872
1,081
416
621
825
1,028
392
588
783
979
371
558
746
935
344
520
698
877
.5’’ of ice
@ 32°F
1,584
2,174
2,713
3,217
Figure 6-19g.
Recommended sag and tension vs. installation temperature for 2% sag with an annual mean temperature of 70°F.
Cable installed with 1/4” ESH strand-all cable double lashed.
2@-MC2 .650 JAU
1@-MC2 .750 JAU
1
6-15
TECHNICAL NOTES
MC2
CONSTRUCTION PRACTICES • Aerial
Trilogy
COMMUNICATIONS, INC
Trunk and Feeder Cable
800-874-5649
601-932-4461
SAG AND TENSION TABLE
CABLE AND STRAND SAG (inches) - no wind
Span Length
in feet
100
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
19
29
39
50
20
30
41
51
21
32
43
54
23
34
45
57
24
36
48
60
25
38
50
63
27
41
54
67
.5’’ of ice
@ 32°F
32
53
75
99
STRAND TENSION (pounds) - no wind
Span Length
in feet
100
466
150
200
250
Installation Temperature
0° F
10°F
30°F
50°F
70°F
90° F
120°F
.5’’ of ice
@ 32°F
448
682
893
1,099
416
659
866
1,069
389
617
815
1,012
366
580
771
960
346
548
731
914
321
520
696
872
1,536
485
650
817
2,108
2,631
3,119
Figure 6-19h.
Recommended sag and tension vs. installation temperature for 2% sag with an annual mean temperature of 70°F.
Cable installed with 1/4” ESH strand-all cable double lashed.
1@-MC2 .500 JAU
1@-MC2 .650 JAU
1@-MC2 .750 JAU
6-16
1
TECHNICAL NOTES
MC2
MESSENGERED CABLE INSTALLATION
Figure 8 Cables
Messengered (or ”figure 8”) cable is installed in a manner quite
different from lashed type construction. As messengered cable (cable
Trilogy
COMMUNICATIONS, INC
Trunk and Feeder Cable
OVERLASHING
Overlashing is a method of hanging cable on a strand with
existing cable already lashed to it. It is primarily used to replace old
or damaged cable in a system that has already been activated.
Overlashing may also be used in instances where it would be
impractical to remove other cables from the strand in order to add
new cable, such as rebuilds or upgrades.
Due to the binding effect that the existing lashing wire creates,
it is necessary to use a roller that does not lock to the strand. This
devise will hang on the strand and or cable. It supports the cable
and reduces the pulling tension during the cable installation.
The best rollers for overlashing are the type that lock around the
cable and strand without locking to the strand itself. It is advisable
to increase the roller spacing from the normal 50 foot spacing in
order to reduce the chance of rollers binding as the lasher pushes
them. Also, pay attention to supporting the cable when selecting the
roller placement.
The method for pulling cable for an overlash is similar to a normal pull, except there is no room for a cable puller to ride on the
strand. In this case, the best method for pulling is to attach a long
rope to the cable with a pulling grip and then pull the rope through
the rollers. In order to give ample support to the cable as it is being
pulled, the rope should always be laid over any roller immediately
preceding the cable before it is pulled, with proper back tension
maintained.
Once the cable is in place, set up the lashing machine. The lashing procedure for an overlash is the same as a normal back pull lash
except that it will be impossible to use a cable block pusher or a multiple cable guide due to the existing cable on the strand. Use caution when opening and closing the lasher gates since the gates
are the only mechanisms preventing the lasher from falling.
Once the gates have been closed, they should be adjusted to the
proper tension and the lashing wire should be attached to the strand.
Make sure to maintain proper tension should lashing be
stopped in order to free or remove a cable block. During the lashing operation, the cable should remain as tight as possible. This can
be achieved by turning the reel in order to take up slack as the lasher is pulled. This will straighten the cable, which in turn will provide
straight entry into the lasher and help insure tight wrapping of the
lashing wire. When constructed in this manner, an overlashed cable
can look and perform just as well as the cables that were originally
lashed to the strand.
1
CONSTRUCTION PRACTICES • Aerial
800-874-5649
601-932-4461
with built-in strand) is attached to the poles, tension and sag limitations must be observed. Creating expansion loops and slack for
splicing will also demand a different approach. Messengered cable
should only be installed in areas requiring a single cable.
BACK PULL METHOD
Figure 8 Cables
The back pull method for messengered cable begins by setting
up the reel in the same manner as previously described in back pull
techniques for lashed construction. Install a pole chute bracket and
a 45° corner block on the first pole to allow for the angle of cable
inclination, then attach pole hardware to all poles on the cable run
and messenger cable blocks at all required poles by using a 16 inch
length of 1/4- inch steel rod attached to the suspension clamps. The
type of cable block designed for this purpose will straddle the suspension clamp and hang from the rod on each side in order to stay
in place (figure 6-15). Cable blocks are only required at points of
stress when “J” hook hardware is being used.
Length of 1/4” steel rod
Figure 6-15. Messenger block
Once all rollers and hardware are in place, attach a pulling grip
to the messenger on the reel of cable and a pull line to the grip. Then
pull the cable span by span over the rollers. It will be necessary to
release tension at pole locations in order to lay the pull line over the
J hooks or rollers. 90° and 45° cable blocks should be used on all
turns in the pull and no more than one 90° turn should be pulled at
a time. Use caution so that the low hanging cable is not hit by passing traffic. Use additional rollers as necessary. After reaching the
end of the run, attach the strand to the hardware of the last pole
(figure 6-16).
Attach a pulling line to the messenger with a strand grip about
20 feet from the first pole. Then pull the line across the rollers of the
45° block in order to tension the cable and take up slack on the reel.
After the cable has been partially tensioned with the rope, use a
chain hoist to complete the tensioning and raise the cable to a safe
working height.
6-17
TECHNICAL NOTES
CONSTRUCTION PRACTICES • Aerial
COMMUNICATIONS, INC
MC2 Trunk and Feeder Cable
Using a chain hoist with two strand grips, provide the necessary
slack for the equipment to be spliced. Place the grips on each side
of the section where slack is needed and tighten the hoist until slackening begins. Then cut the cable away from the messenger between
the two grips, and remove the necessary section of strand with bolt
cutters. When slack for splicing is being created, the amount of
strand cut away should equal the amount of excess cable desired.
When making slack for expansion loops, remove the amount of
strand equal to 75% of the loop’s depth. After the length of messenger is removed, install a strand splice and release tension on the
messenger. It may be necessary to relieve tension at the first pole
during this process due to the increase in tension created by removing strand.
After all slack and expansion loops have been created, the messenger tension can be adjusted for proper sag and then permanently attached at the first pole. Once this is done, remove all rods
and cable blocks and secure the messenger to the suspension
clamps.
Trilogy
800-874-5649
601-932-4461
NOTES
DRIVE OFF METHOD
Figure 8 Cables
The drive off method for messengered cable begins by placing
pole hardware on all poles in the run. Attach cable blocks wherever necessary in the same manner as described for the back pull
method. Then drive the vehicle and trailer 50 feet ahead of the first
pole. After attaching the messenger from the reel to the hardware of
the first pole, pull the vehicle forward down the run so that the tension causes the cable to unreel. When the vehicle is about 50 feet
past the next pole, stop pulling and release the tension by backing
up. Raise the cable with a cable lifting tool, and place it on the cable
block. Use caution to insure that the low-hanging cables are not hit
by passing traffic (figure 6-17).
When the vehicle passes the end of the run, use a chain hoist
at the last pole to tension the cable to a safe working height. Once
this is done, create the expansion loops and finish the job in the
same manner as previously described for the back pull method.
Note: When using the drive off method, pulling tension and the
speed of the vehicle must be monitored closely.
GROUNDING AND BONDING
Figure 8 Cables
All guy wires and messengers of the self-support cable must be
bonded together using a No. 6 AWG copper wire. (Refer to section
on Aerial Grounding and Bonding for more details.) There must be
a minimum of eight grounded and or bonded connections per mile
to the existing verticals.
6-18
1
TECHNICAL NOTES
CONSTRUCTION PRACTICES • Aerial
Trilogy
COMMUNICATIONS, INC
MC2 Trunk and Feeder Cable
800-874-5649
601-932-4461
messenger
block
pull line/winch
pulling
grip
pull
line
twice strand height at pole
Truck moves 50ft past pole then backs up
to allow cable to be lifted to messenger block
wheel chocks
Figure 6-16. Messenger Back Pull
Figure 6-17. Messenger Drive-off
1
6-19
TECHNICAL NOTES
CONSTRUCTION PRACTICES • Aerial
MC2 Trunk and Feeder Cable
Trilogy
COMMUNICATIONS, INC
800-874-5649
601-932-4461
Vertical Clearances of Communications Cables from Supply Conductors and Equipment*
SUPPLY CONDUCTOR OR EQUIPMENT
REQUIRED CLEARANCES
1. Conductor, 0 to 8700 volts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 inches
2. Conductor, > 8700 volts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 inches plus 0.4 inches per KV above 8700 volts
3. Conductor Case (non-grounded), 0 to 8700 volts . . . . . . . . . . . . . . . . . . . . . .40 inches
4. Conductor Case (effectively grounded), 0 to 8700 volts . . . . . . . . . . . . . . . . .30 inches
5. Conductor Case (non-grounded), > 8700 volts . . . . . . . . . . . . . . . . . . . . . . .40 inches plus 0.4 inches per KV above 8700 volts
6. Conductor Case (effectively grounded), > 8700 volts . . . . . . . . . . . . . . . . . . .30 inches
7. Transformer Case (non-grounded), 0 to 8700 volts . . . . . . . . . . . . . . . . . . . . .40 inches
8. Transformer Case (effectively grounded), 0 to 8700 volts . . . . . . . . . . . . . . . . .30 inches
9. Transformer Case (non-grounded), > 8700 volts . . . . . . . . . . . . . . . . . . . . . . .40 inches plus 0.4 inches per KV above 8700 volts
10. Transformer Case (effectively grounded), > 8700 volts . . . . . . . . . . . . . . . . .30 inches
11. Street Light Bracket (non-grounded) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 inches
12. Street Light Bracket (effectively grounded) . . . . . . . . . . . . . . . . . . . . . . . . . .4 inches
*Supply conductors and equipment are located above the communications cables. (Source: National Electrical Safety Code)
Vertical Clearances of Wires, Conductors and Cables above Ground, Roadway, Rail or Water Surfaces**
(Non-insulated communication conductors, supply cables or 0 to 750V, meeting rules 230C2 or 230C3)
SURFACE
Where wires, conductors or cables cross over or overhang:
REQUIRED CLEARANCES
1. Track rails of railroads (except electrified railroads using overhead trolley conductors) . . . . . . . . . .24 feet
2. Roads, streets and other areas subject to truck traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 feet
3. Driveways, parking lots and alleys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 feet
4. Other land traversed by vehicles, such as cultivated, grazing, forest, orchard, etc. . . . . . . . . . . . . .16 feet
5. Spaces and ways subject to pedestrians or restricted traffic only . . . . . . . . . . . . . . . . . . . . . . . . .12 feet
6. Water areas not suitable for sailboating or where sailboating is prohibited . . . . . . . . . . . . . . . . . .14.5 feet
7. Water areas suitable for sailboating including lakes, ponds, reservoirs,
tidal waters, rivers, streams, and canals with unobstructed surface area of:
a. Less than 20 acres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 feet
b. Over 20 to 200 acres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 feet
c. Over 200 to 2000 acres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 feet
d. Over 2000 acres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 feet
8. Public or private land and water areas posted for rigging or launching sailboats . . . . . . . . . . . . . .Clearance above ground should
be 5 feet or greater than in 7
above, for the type of water areas
served by the launching site.
Where wires, conductors or cables run along and within the limits of highways or other road right-of-ways but do
not overhang the roadway:
9. Roads, streets or alleys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 feet
10. Roads in rural districts where it is unlikely that vehicles will be crossing under the line . . . . . . . . . .14 feet
**Source: National Electrical Safety Code: Rule 232
6-20
1