TM 5-684/NAVFAC MO-200/AFJMAN 32-1082
4-37. Overhead conductor repairs.
(1) Abrasion. Abrasion damage is a chafing,
impact wear that accompanies relative movement
Installation of repair sleeves, preformed line splices,
between a loose tie, or other conductor hardware,
armor rods, or line guards; or replacing broken tie
and the conductor or armor rods. Abrasion is a sur-
wire, may be the appropriate methods of maintain-
face damage and can be identified by black deposits
ing conductivity and retarding additional damage.
on the conductor or tie wire.
Preformed spiral vibration dampers should prevent
(2) Fatigue. Prolonged periods of vibration will
conductor fatigue and scoring of insulators. Line
cause fatigue failure.
replacement is indicated where more than two re-
b. Line interference sources. Where radio or tele-
pair sleeves are required to cover the length of the
vision interference complaints occur, check for pos-
sible sources of trouble covered in chapter 16, sec-
Section X - OVERHEAD CABLE
4-38. Overhead cable construction.
weather shielding, taping, or spreading single con-
ductors. Permanent repairs should be as extensive
The conductors of a cable, in contrast to open wire,
as necessary, from patching to replacement of the
are individually insulated so that they may be
closely spaced or tightly bundled together. Except
for some self-supporting cables (which are seldom
c. Messenger. The supporting messenger is usu-
used), all overhead cables consist of a messenger,
ally of stranded galvanized steel or copper-clad
which provides support, and one or more conductors
steel. The initial design will provide adequate
attached to it by rings, wrappings, lashings, or in-
strength to support the cable under the maximum
sulating spacers. The cable messenger is attached
loading of ice and wind, and the temporary loads
to the pole. In the case of secondary circuits, the
involved in installation and maintenance. Wear or
messenger may also provide the neutral wire.
rusting can reduce the messenger's strength. When
it reaches the minimum safe value, then a messen-
4-39. Overhead cable repair requirements.
ger replacement should be made. Under these con-
Aerial cable installations should be inspected for
ditions, it is probable that other parts of the cable
mechanical damage due to vibration and deteriorat-
assembly will also require replacement.
ing supports, especially at suspension systems and
d. Lashing. Metal rings are used with metallic-
dead-end supports. Check to see that cable insula-
sheathed cables for field-assembled aerial cable.
tion is not abraded, pinched, or bent too sharply.
The disadvantage of this combination is the rela-
a. Insulation. Insulation repair is covered in
tively rapid wear of the sheath at point of contact
chapter 5, section VI.
with the ring. Moving the rings periodically will
b. Sheath. A sheath is sometimes applied to the
alleviate this. When excessive wear occurs, lashing
insulated conductors to provide extra protection
with a spiral wrap of metallic band or tape is rec-
from moisture, mechanical damage, or atmospheric
ommended. This is the method used for factory-
contaminants. The sheath may be metallic armor,
assembled cables, and it can also be used for field
lead, or another protective covering. Wear at points
assembly, with little or no relative movement be-
of support and cracks from vibration are the princi-
tween conductors, messenger, and band.
pal causes of sheath failure, although burns and
mechanical damage are often contributing factors.
e. Splices and taps. When making splices and
Sheath repairs should be made as soon as the dam-
taps on aerial cables, procedures specified else-
age is discovered. If failure has not yet occurred,
where in this manual for overhead open wires in
temporary repairs or protection may be desirable.
section XI or underground cables in chapter 5, sec-
Such temporary expedients may include providing
tion VI, as appropriate, should be followed.
Section Xl - CONDUCTOR CONNECTIONS
4-40. Overhead line conductor requirements.
should meet the requirements of ANSI C119.4 for
aluminum lines or for connecting copper to alumi-
Line conductors must be joined together with full-
num lines. Only compression connectors will be in-
tension splices, if the conductors are under tension.
stalled on aluminum line conductors. Do not use
Bolted connectors can be used to join electric con-
screw clamps, split bolt connectors, or bolted con-
ductors at locations where the conductors are slack,
such as between conductor dead-ends. Connectors