7.
As discussed, aerial installation will be used first. Before the line is brought to a point where it
will be secured, check the line at the telephone and make sure there is a 6-inch drip loop under the
telephone. This permits the water, when it rains, to run down the line and drip off the wire rather than
running to the telephone and causing trouble on the line.
a.
Because the installation is in a NODE, you want to consider secondary roads. A
minimum height clearance of 14 feet is necessary for secondary roads. Primary roads require a height
clearance of 18 feet. When the desired height is reached, an aerial loop-knot tie will be used. Refer to
graphic training aid (GTA) 11-1-13 for the aerial loop-knot tie.
b.
At this time, if equipment is available, practice the aerial loop-knot tie with a 12-foot
piece of WD-1( )TT. When you are confident you can make the tie, proceed with the lesson.
c.
Take the line up to the desired height and tie an aerial loop-knot tie. Go to the next pole
or post and continue the installation with an aerial loop-knot tie. When the end of the aerial installation
is reached you will have to bring the line back down to the surface mode of construction. At the surface,
and no higher than 3 to 6 inches off the ground, tie a ground loop-knot tie. Refer to GTA 11-1-4, ground
loop-knot tie. Leave enough slack for repair should the line be broken.
d.
If it is available, take that same 12-foot piece of WD-1( )/TT and practice tying a ground
loop-knot tie until you can do it correctly.
e.
If you are practicing ties, practice the clove hitch tie. Refer to GTA 11-1-2, clove hitch
tie. Practice that tie until you can do it correctly.
f.
Remember to tag the line when you change construction from aerial to surface. You
must remember that whenever you change construction-surface to aerial, aerial to surface, surface to
buried, and buried back to surface-you must tag the line and properly identify the circuit. When a line is
run beside another line and there is a possibility of confusion later on, you can tag at several points to
help you identify that circuit. Tagging is important. You will find that out when it is time to
troubleshoot the line turn the line over to another unit that is relieving your unit, or when it is time to
recover the line. On poles, tag the line 6 inches up from the knot.
g. Another important area to discuss at this time is sag. When wire lines are tied in an aerial
condition you must provide for the weather, heat, cold, and the wind to have an effect on the lines.
There must be some sag in the line so it does not break when it gets cold or when the wind blows
excessively. To allow for sag in the line, you must know the distance between the two aerial ties.
Provide 6 inches of sag for every 25 feet of line. If the line is stretched 100 feet between ties you would
have to provide for 24 inches of sag in the middle of the line. How did you get 24 inches? Divide the
length 100 by 25 inches equals 4 and then multiply that by the 6 inches and you get the 24 inches of sag
needed on that particular line. Check the line to be sure there is the right amount of sag in the line.
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