etc., usually make excellent protective grounds for
emergency, an ordinary steel or brass pipe can be
electrical systems, but, in general, they should not
used, but, in general, it will be found that rust and
electrolytic corrosion will rapidly destroy the pipe,
particularly because of the ground treating elec-
(d) If a water pipe enters the ground not
trolyte which will be in contact with the pipe if
more than 8 or 10 feet from the welder, it may
recommended procedure is followed.
make a satisfactory ground. However, if the water
pipe runs above the ground level for some distance
(f) It is recommended that a rod having a
before it enters the ground, it will not be satisfac-
length of 8 feet and a diameter of either or 5/8
tory. The steel frame of a building or the walls of
inch be used. The connection from the ground rod
a corrugated-iron building are not satisfactory
to the work terminal of the welder or high fre-
and should not be used for grounding.
quency unit should be made by means of heavy
copper braid, using standard copper-weld clamps.
(e) It has been found that the best ground
Refer to figure 23. The copper braid should con-
is a copper-weld ground rod driven into the
sist of at least 240 strands of No. 30 wire, or its
ground as close as possible to the machine. Cop-
equivalent, and should in no case be smaller than
per-weld ground rods are standard devices which
the work lead of the welder. (A heavier braid can
are used by electric power and telephone compa-
be used.)
nies for ground purposes, and they can be ob-
tained from any large electrical supply house.
(g) When the welder is located near an out-
They consist of a pointed steel rod with a heavy
side wall and the earth beyond this wall is ex-
copper coating welded to the steel core. They are
posed, the ground rod can be placed outside the
easy to drive into the ground and will last much
building where a ground lead more than 8 feet in
longer than steel pipe or other substitutes. In an
length is required to reach an outside ground rod,
2-4
