need not be so flexible as the cable that connects
incorrect current setting, incorrect electrode, or
the machine and the electrode holder.
incorrect polarity. Check the current output settings
and make any needed adjustment. If that does not
Two factors determine the size of the welding
solve the spatter problem, check the polarity. Either
cable that should be used: the amperage rating of
reverse the polarity of the generator or try an
the machine, and the distance between the work and
electrode of the opposite polarity. Excessive spatter
the machine. If either amperage or distance is
should not occur if you use the proper welding
increased, the cable size must also be increased. A
technique, the right polarity, and the correct current
cable that is too small for the amperage used will
output adjustment.
become overheated. A cable that is too small for
Most difficulties with generator welding units
the distance between the machine and the work will
can be avoided through routine maintenance and
not carry enough current to the arc without
periodic overhaul. Here again the Electrician's
becoming overheated. On the other hand, the
Mate has primary responsibility. However, you are
larger sizes of cable are more difficult to handle.
r e s p o n s i b l e for keeping the outside of the
The best size, therefore, is one large enough to
meet the manufacturer/NSTM requirements.
equipment clean. Once each month, blow the
outside and inside of the unit free of dust with
clean, dry, compressed air. At that time, oil the
As a rule, the cable between the machine and
wheel bearings on portable welding units. Operate
the work should be as short as possible, preferably
each of the machines for at least a few minutes once
one continuous length of cable. If it is necessary to
a week. In addition to routine maintenance,
use more than one length of cable, join the sections
inspection, and testing, each machine should be
with insulated, lock-type cable connectors. Joints in
completely dismantled, thoroughly cleaned, and
the cable should be at least 10 feet away from the
overhauled as necessary every 2 years. Again, this
operator.
i s a job performed by Electrician's Mates.
Instructions governing maintenance and overhaul of
GROUNDING ELECTRICAL
electrical equipment, including welding machines,
WELDING EQUIPMENT
are discussed in the NSTM, chapter 074.
Most shipboard welding is done by the shielded
Rectifier-Type Welding Machine
metal-arc welding process, and you will frequently
be responsible for seeing that the equipment is
properly set up and properly grounded. Incorrect
The rectifier-type welding machine operates
from an ac power source but delivers ac high
grounding permits the electric current to return to
the welding generator through the water, the ship's
frequency and dc welding current. There are several
types of rectifier welders, but they are basically the
hull, and the piping systems. This may result in
electrolytic corrosion and cause serious damage to
same. The majority of the units consist of three
the ship's underwater body, shafting, and propellers.
supply voltage (220 or 440 volts) to lower voltage
suitable for welding; (2) a movable core reactor, to
adjust the welding current; and (3) a rectifier cell
CAUTION
(copper oxide or selenium plates), to change the ac
to dc.
Grounding must comply with the
criteria of NSTM, chapter 074, volume 1.
WELDING CABLES
The welding cables conduct the welding current
Location of ground cables should be a major
from the power source to the weldment and then
concern when setting up welding machines. When
back to the source. They must be flexible, durable,
welding on systems, such as piping, pressure vessels,
well insulated, and large enough to carry the
or machinery, the ground-return cable connection
required current. Only cable that is designed for
should be located as close to the work as possible.
welding should be used for welding. A highly
This ensures that welding current does not flow
flexible cable must be used between the welding
through bearings, threaded joints, and other joints
machine and the electrode holder. The ground
where arcing could occur. If arcing is allowed to
cable, which connects the work and the machine,
happen across bearings in motors, lathes, and other
10-5