(1) Soil treatment for good ground. The amount
shall be accomplished by soldering a copper strap or
wire across the joint as shown in figure 2-1-E.
of reduction in radiation which a good ground will
(2) Grounding the welding circuit and welder
produce will depend upon the ground resistance. The
case. The location of the welder should be chosen
lower the resistance between the ground rod and
the surrounding earth the lower will be the radiated
with respect to nearness to a suitable ground connec-
signal. It has been found that if the earth around the
tion. It is very important that not more than one
ground rod is treated with a conducting solution
ground be used in the welding circuit. The welder
known as an electrolyte, the signal will be lowered
case, firmly bonded to the power conduit, should be
by an appreciable amount.
grounded to the work terminal of the welder with a
(2) Outside ground. Dig a circular trench around
copper cable or braid with rated current carrying
the ground rod. Place in this trench 20 to 30 pounds
capacity equal to or greater than that of the power
of rock salt (copper sulphate or magnesium sulphate
service wires. The work output terminal should then
may also be used). Then flood the trench several
be connected to a good electrical ground with a No. 6
times with water, allowing the solution to soak into
AWG flexible, stranded copper wire (or larger) which
the ground. The trench can then be filled with earth.
shall not exceed 8 feet in length. (fig. 2-1-B). An
indoor ground rod installation may be necessary to
Normal rainfall will generally keep the ground moist
enough to continually dissolve more salt renewing
comply with the 8 feet maximum ground lead length.
The work or work table should not be grounded since
the electrolyte, thus maintaining a low ground re-
sistance.
the addition of a ground at this point will generally
(3) Inside ground. Fill the 6 inch diameter hole
increase the amount of radiation. If, for any reason,
around the ground rod with rock salt (copper sul-
it is impossible to avoid a ground at the work or work
table, then put the ground rod near the work table,
phate or magnesium sulphate is equally as effective)
and flood this a number of times with water until at
making this the only ground in the system. (fig. 2-1-
least 8 or 10 pounds have dissolved and soaked into
C). The ground connection to the enclosure of the
welder can still be connected to the work terminal of
the earth. Then fill the hole with salt and let it re-
main in this condition. It will be necessary to flood
the welder. However, the welder case will secure its
ground through the ground lead of the welding cir-
the hole periodically in order to keep enough elec-
cuit, to the work table, and thence to the ground rod.
trolyte in the ground circuit; therefore, provide a
removal cover instead of pouring concrete around the
The welder case should not be grounded by means of
ground rod.
a third conductor in the primary cable. The welder
d. Special Pocedures for High Frequency Sup-
should not be operated unless the case is grounded
in accordance with the foregoing. The metal enclosure
described in this manual, should be made in accord-
of the welder, if properly, grounded as outlined above,
will practically eliminate any radiation from inside
ance with the following instructions. The importance
the machine. However, all service and access doors
of a correct installation cannot be over emphasized
since case histories of radio interference due to high
must be closed and fastened during operation. Any
frequency stabilized arc welders have shown that,
opening in the metal case of the welder will allow
invariably, inadequate installation was at fault.
some radiation to escape.
(3) Shielding electrical conductors in close proxi-
(1) Shielding power service lines. The primary
mity to welding area. The most serious source of
power service leads serving the welder shall be com-
interference is reradiation from wires that are lo-
pletely enclosed, for a distance of at least fifty (50)
cated near the welding area. Any ungrounded elec-
feet in any direction from the welder, in solid metallic
trical conductor in the strong "directly radiated"
conduit or in equivalent shielding (copper braid sleev-
field, produced by the welding leads, serves as a pick-
ing or lead covered cable is satisfactory). This shield-
up device and may conduct the interference for some
ing shall be grounded at the farthest point from the
distance and reradiate strongly at another location.
equipment and should make good electrical contact
For purposes of simplification and standardization,
with the casing of the equipment. The ground should
the space all around the weld zone, at a distance of
be in accordance with the specifications outlined in
50 feet in all directions, is referred to as the high
field intensity (H.F.I.) Zone (fig. 2-1-F). To minimize
should be taken that paint or corrosion at the junc-
radiation of this type, all wiring in the H.F.I. Zone
tion of conduit and of the welder case do not interfere
shall be in rigid metallic conduit, lead covered cable,
with good electrical contact. There shall be no gap in
c o p p e r braid or material of equivalent shielding
this shielding run. If the electrical efficiency of the
e f f i c i e n c y . Ordinary flexible helically wrapped
joints between individual conduit sections, outlet
metallic conduit, commonly referred to as "B.X." is
boxes and the welder case are questionable, bonding
