Grounding and Arc Welding Safety

Grounding and Arc Welding Safety
By Frank Stupczy, Compliance Engineering Manager, The Lincoln Electric Company
What does grounding have to do with arc welding safety?
Grounding of electrical circuits is a safety practice

that is documented in various codes and
standards. A typical arc welding setup may
consist of several electrical circuits. Applying and
maintaining proper grounding methods within the
welding area is important to promote electrical
safety in the workplace. Associated processes
such as plasma cutting will also benefit from
proper grounding. The important grounding topics
in a typical welding environment are discussed.
Welding machine ground
Welding machines that utilize a flexible cord and plug arrangement or those that are permanently
wired into an electrical supply system contain a grounding conductor. The grounding conductor
connects the metal enclosure of the welding machine to ground. If we could trace the grounding
wire back through the electrical power distribution system we would find that it is connected to
earth, and usually through a metal rod driven into the earth.
The purpose of connecting the

equipment enclosure to ground is to
ensure that the metal enclosure of the
welding machine and ground is at the
same potential. When they are at the
same potential, a person will not
experience an electrical shock when
touching the two points. Grounding
the enclosure also limits the voltage
on the enclosure in the event that
insulation should fail within the equipment.
The current carrying capability of the grounding

conductor is coordinated with the overcurrent device
of the electrical supply system. The coordination of
ampacity allows the grounding conductor to remain
intact even if there is an electrical fault within the
welding machine.
Some welding machines may have a double insulated

design. In this case, a grounding conductor
connection is not required. This type of welding machine relies on extra insulation to protect the
user from shock. When double insulation is present it is identified by a "box within a box"
symbol on the rating plate.
For small welding machines that utilize a plug on the end of a power
cord, the grounding conductor connection is made automatically when
the welding machine is plugged into the receptacle. The grounding pin of
the plug makes a connection within the receptacle. The use of adapters
that effectively remove the grounding pin connection at the plug is not
recommended. Furthermore, do not cut off or remove the grounding pin
from the plug. All safety benefit of the grounding conductor is lost
without the connection.
Receptacle circuit testers will easily check the continuity

of the grounding conductor. Receptacle circuit testers for
120-volt circuits are available at electrical supply or
hardware stores; these inexpensive test devices plug into
an electrical outlet. Indicator lights show whether the
grounding circuit is available at the outlet, as well as other
circuit tests. If the test device shows the absence of a
ground connection or other circuit problem, call a qualified
electrician for assistance. This is a simple test and should
be done periodically. Consult with a qualified electrician to
test circuits greater than 120 volts.
Workpiece ground
The welding circuit consists of all conductive material through which the welding current is
intended to flow. Welding current flows through the welding machine terminals, welding cables,
workpiece connection, gun, torch, electrode holder and workpiece. The welding circuit is not
connected to ground within the welding machine, but is isolated from ground. How do we
ground the welding circuit?
According to ANSI Z49.1, "Safety in

Welding, Cutting and Allied Processes," the
workpiece or the metal table that the
workpiece rests upon must be grounded. We
must connect the workpiece or work table to a
suitable ground, such as a metal building
frame. The ground connection should be
independent or separate from the welding
circuit connection.
Grounding the workpiece has similar benefit

to grounding the welding machine enclosure.
When the workpiece is grounded, it is at the
same potential as other grounded objects in the area. In the event of insulation failure in the arc
welding machine or other equipment, the voltage between the workpiece and ground will be
limited. Note that it is possible to have an ungrounded workpiece, but this requires the approval
of a qualified person.
The workpiece connection is not a ground clamp
"Ground clamp" and "ground lead" are common terms used by many welders. The workpiece is
connected to a welding cable typically by means of a spring loaded clamp or screw clamp.
Unfortunately, a workpiece connection is often incorrectly called a "ground clamp" by many
welders and the workpiece lead is incorrectly called "ground lead." The welding cable does not
bring a ground connection to the workpiece. The ground connection is separate from the
workpiece connection.
High frequency ground
Some welding machines utilize starting and stabilizing circuits that contain a high frequency
voltage. This is common on Tungsten Inert Gas (TIG) welding machines. The high frequency
voltage may have frequency components that extend into the megahertz region. In contrast, the
welding voltage may be as low as 60 Hertz.
High frequency signals have a tendency to radiate away from the welding area. These signals
may cause interference with nearby radio and television reception or other electrical equipment.
One method to minimize the radiation of high frequency signals is to ground the welding circuit.
The welding machine instruction manual will have specific instructions on how to ground the
welding circuit and components in the surrounding area to minimize the radiation effect.
Portable and vehicle mounted welding generator grounding
Portable and vehicle mounted arc welding generators often have the capability to supply 120 and
240 volt auxiliary power. These generators are used in remote locations away from an electrical
power distribution system. A convenient earth ground is not usually available for connection.
Should the generator frame be grounded?
The rules for grounding depend on the specific use and design of the auxiliary power generator.
Most applications fall into one of the two categories summarized below:
1. If all of these requirements are met, then it is not required to ground the generator frame:
 The generator is mounted to truck or trailer;

 The auxiliary power is taken from receptacles on the generator using a cord and plug
arrangement;
 The receptacles have a grounding pin;
 The frame of the generator is bonded, or electrically connected, to the truck or trailer
frame.
2. If either of these conditions are met, then the generator frame must be grounded:
 The generator is connected to a premises wiring system. For example, to supply power to
a house during a blackout.
 The auxiliary power is hard wired into the generator without the use of cords and plugs.
The summary above does not go into details and the reader is urged to consult their local
electrical codes and ANSI/NFPA 70, "National Electrical Code" for the specifics.
Extension cord grounds
Extension cords should be periodically tested for ground continuity. Extension cords lead a
rough life while lying on the ground; they are under foot and prone to damage. The use of a
receptacle circuit tester will confirm that all of the connections are intact within the cord, plug
and receptacle.
Welding circuit shock hazards
Utilizing proper grounding in the welding environment is a good practice, but it does not remove
all possibility of electrical shock. The welding circuit is energized by welding voltage. A person
will receive a shock if they become the electrical path across the welding circuit. Precautions
must be taken to insulate the welder from the welding circuit. Use dry insulating gloves and
other insulating means. Also maintain insulation on weld cables, electrode holders, guns and
torches to provide protection.
Similarly, electric shock originating from the electrical supply system can be prevented. Proper
maintenance of electrical equipment and extension cords will insulate the welder from electrical
sources.

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Grounding and Arc Welding Safety

By Frank Stupczy, Compliance Engineering Manager, The Lincoln Electric Company

What does grounding have to do with arc welding safety?

Grounding of electrical circuits is a safety practice

Welding machine ground

The purpose of connecting the

The current carrying capability of the grounding

Some welding machines may have a double insulated

Receptacle circuit testers will easily check the continuity

According to ANSI Z49.1, "Safety in

Grounding the workpiece has similar benefit

The workpiece connection is not a ground clamp

High frequency ground

Portable and vehicle mounted welding generator grounding

 The generator is mounted to truck or trailer;

Extension cord grounds

Welding circuit shock hazards

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