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6122
Appendix T3 Electrical
Shock and Physical Hazard Prevention |
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1.0 Welding
Equipment
An environment is considered electrically hazardous whenever the welder has to work in physical contact with the work piece, particularly in a cramped (kneeling, sitting or lying) position. The environment is not electrically hazardous if the welder is electrically insulated from the work piece, but in many cases this may be impossible or uneconomical.
An electrically hazardous environment is compounded in wet, damp or hot locations where moisture or perspiration considerably reduce the electrical resistance of the human body and the insulating properties of accessories. If there is difficulty in keeping dry, a voltage limiting device should be used to limit the open circuitry voltage (OCV) to a maximum of 25 volts, or the power should be controlled by a contactor switch.
Factors which affect the severity of the shock are:
· The no-load or OCV of the welding machine.
·
The presence of moisture from
rain, perspiration or other source.
·
How well the victim is
insulated from the electrode and the work piece.
·
Which parts of the body are
in contact with the work and the electrode?
Current flow between the left hand and the torso is the most dangerous.
2.0 Installation
Requirements
·
Welding equipment must be
installed by a qualified electrician
·
The secondary and case of all
portable welding transformers must be grounded initiating switches must be
guarded to prevent unintentional operator activation.
·
A disconnecting switch,
circuit breaker, or circuit interrupter must be located at or near each
permanently installed welding machine that can isolate the machine from the
supply circuit.
·
Controls for automatic or air
and hydraulic clamps must be guarded to prevent unintentional operator
activation
·
Point-of-operation shield
guards and fire-resistant curtains must be installed to protect or passers-by
from flying sparks.
·
Heavy portable welding
equipment on wheels must be secured in position to prevent accidental movement.
·
Only approved welding
equipment, such as torches, manifolds, regulators, electrode holders, and
welding machines are to be used.
·
Hot surfaces that are
in a location where they can come into contact with incidental workers must be
labeled with a hot surface warning.
3.0 Work
Precautions
·
First aid equipment for
welders must be immediately available at all times
·
All persons who work near or
assist in welding operations should be familiar with rescue procedures. The following precautions are required to
protect from electric shock:
o
When a workplace hazard
assessment is conducted, ensure the risk of such electric shock is considered
and appropriate measures are taken to minimize the risk.
o
The use of dry, hole free
welding gloves on both hands while welding, particularly when changing
electrodes
o
Remove stub ends immediately
after welding; do not leave an electrode holder with a stub end in it.
o
Manual metal arc welding and
arc-air gouging are particularly risky because the electrode is changed
frequently while the electrode holder is electrically live. There is a high risk that the welder can
receive a shock by simultaneously touching the electrode and work piece. Fuses or earth leakage contact breakers do
not protect the welder from such a hazard. To avoid the hazard DO NOT allow bare skin to
come into contact with the electrode.
o
Turn off the power at end of
each shift or when taking a break. Do
not drag live leads to the work.
o
If possible make the
environment electrically safe by using dry, fire resisting insulation, leather
aprons, leather jackets, heat resisting blankets should be used to cover those
parts of the work piece which the welder may contact. If it is not possible to provide such
insulation or to keep it dry, the environment must be considered electrically
hazardous and equipment should be safe for such environments.
o
In hot conditions the risk of
electrocution is increased because of clothing and equipment being soaked in
perspiration. The risk is far worse in
closed environments, such as tanks or vessels, particularly when these are
exposed to the sun's heat. Take frequent
rest periods, during which time dry off equipment and clothing. Frequently change or alternate gloves and
protective clothing to avoid perspiration accumulating. Ventilate or if possible air-condition the
work air. Ventilation will help dry
perspiration and cool the body. Cool the
face with an air mask. If clothing
(including gloves) becomes soaked with perspiration, it must be changed.
o
If it is not possible to keep
it dry, the environment must be considered extremely dangerous. Either a voltage limited welding power source
should be used, or the power should be controlled by a switch on the torch.
·
Good housekeeping of welding
areas is required
·
Welding cables and hoses must
be kept clear of passageways, ladders, and stairways
·
Welding equipment used
outdoors must be protected from wetness and weather conditions. Care must be taken to cover the machine to
protect from wetness without overheating the unit.
o
Machines which have
become wet must be taken out of service and inspected when dry and before being
put back into service.
4.0 Maintenance
Requirements
·
Annual inspections of welding
equipment must be performed by qualified maintenance personnel.
·
A certification record
of periodically inspected welding equipment must be kept by the equipment
owner.
o Certification record of periodically inspected welding equipment must include the date of inspection, signature of the inspector, and equipment serial number or other identifier.
·
Welding machine operators
must report any equipment defect to line management.
·
Grounding of Welding
Equipment: Proper grounding of
electrical equipment is essential for safe work. A complete discussion of proper grounding of
welding equipment is presented in ES&H Manual Chapter
6122 Appendix T2 Fire Protection: Hot
Work Permit.
5.0 Welding
or Cutting on Containers
Before welding or cutting containers such
as barrels or tanks:
·
Thoroughly clean to
remove materials that, when heated, may cause fire, explosion, or release of
toxic materials.
NOTE: barrels or tanks may be filled with water as an alternative to cleaning.
·
All hollow spaces and
cavities must be vented to release trapped air or gases?
NOTE: Purging with inert gas is recommended.
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ISSUING
AUTHORITY |
APPENDIX
AUTHOR |
APPROVAL
DATE |
EFFECTIVE
DATE |
EXPIRATION
DATE |
REV. |
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ESH&Q Division |
04/12/05 |
04/12/05 |
04/12/08 |
0 |
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