ment. As appreciable coupling between the cir-
Arc-Welding Equipment Installation.
cuits of welding leads and the unshielded wires
can take place when the unshielded wires are in
(1) Insure that the power leads to the high
the vicinity of the welding leads, all of the wiring
frequency stabilized equipment are in rigid me-
in the welding area as well as the wiring to the
tallic conduit.
welding equipment itself should be placed in con-
(2) If rigid metallic conduit is not used, use
duit or shielded in the manner described herein.
equivalent copper braid sleeving or lead covered
cable, etc.
m e t a l enclosure of the welder, if properly
Note. Spirally wound flexible metallic conduit is not
grounded, will practically eliminate any radiation
suitable for this purpose unless very well bonded.
from inside the machine. However, if the doors
(3) Insure that there is a good electrical con-
are left open, the shielding benefit of the enclosure
nection between the conduit and welding equip-
is lost and interference trouble might result,
ment cases and between conduit and service box or
switch.
(4) Shielding of plant wiring. If the plant
wiring is not in conduit, shield or change the loca-
(4) Insure that the service conduit system is
tion of all unshielded wiring for a distance of 50
grounded at a point at least 50 feet away from the
feet from the welding leads. This includes tele-
welding equipment case.
phone, lighting, control and signal wiring, as well
(5) If the conduit is coupled, insure that the
as power wiring (fig. 21 and 22).
joints are bonded within a distance of a 50-foot
radius from the equipment.
(5) Power lines.
(a) Usually installations having open
(6) All unshielded power, light, telephone,
and communication system wires originally in this
power wiring cause the most radiation. As pre-
50-foot radius zone must be placed in grounded
viously noted, radio frequency energy in the
shields as specified or relocated outside of this
welding leads will couple to any unshielded wires
zone. This applies to wires in and outside the
in the vicinity of the welder and these, in turn,
b u i l d i n g , guy and support wires, and large
will reradiate the signal, Therefore, it is necessary
metallic objects.
to avoid coupling to any unshielded wires such as
electric power wires, electric lighting wires, tele-
(7) Insure that the case is connected to the
phone wires, buzzer wires, or any other wires in
work terminal of the equipment with a copper
the vicinity,
braid.
(b) If the building wires are in a conduit
(8) Insure that the work terminal is con-
which is properly grounded in accordance with
netted to a good electrical ground with copper
these instructions there are no other exposed
braid required size. (Should be equivalent to or
wires near the welding machine, there usually will
greater than welding lead size.)
be no coupling into the wiring system of the
(9) Insure this ground cable is as short as
building, and practically all of the radiation will
possible. (8 feet or less.)
be from the welding leads alone. However, even a
(10) If driven ground rods are used for
few feet of exposed wire near the welding leads
grounds, they must be in moist or treated soil.
will pick up enough energy to cause considerable
(11) If a cold water pipe is used for ground,
it must enter the ground within 8 feet of the con-
(c) Therefore, the wires connecting the
nection.
welding transformer to the building wiring which
(12) All ground connections must be clean
is in conduit should be covered with a shield from
and tight.
end to end with no gap and with a good connection
from the shield to the welding transformer case
(13) If unit is operated in a metal building,
and to the conduit box. If there are any unshielded
the building must be properly grounded.
telephone, lighting or power wires in the vicinity
(14) The welding leads must be as short as
of the welding transformer, all such wires should
possible. (Not over 25 feet long.)
be enclosed in a shield for a distance of at least 50
(15) The welding leads should be on the floor
feet in all directions from the welder and welding
and as close together as possible.
leads, This shield should be connected to a ground
(16) All doors and panels of equipment
at some point near the welder and to another
should be closed and bolted,
ground at the extreme end of the shields.
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