Tweco 250 Weldskill MIG - Manual (Page 22)

3-2 Manual No 0-5072
weldskIll 250, 350 INstallatIoN
December , 2008
detected then it shall be the responsibility of the user
of the welding equipment to resolve the situation with
the technical assistance of the manufacturer. In some
cases this remedial action may be as simple as earth-
ing the welding circuit, see NOTE. In other cases it
could involve constructing an electromagnetic screen
enclosing the Welding Power Source and the work,
complete with associated input filters. In all cases,
electromagnetic disturbances shall be reduced to the
point where they are no longer troublesome.
NOTE
The welding circuit may or may not be
earthed for safety reasons. Changing the
earthing arrangements should only be au-
thorised by a person who is competent to
assess whether the changes will increase
the risk of injury, e.g. by allowing parallel
welding current return paths which may
damage the earth circuits of other equip-
ment. Further guidance is given in IEC
974-3 Arc Welding Equipment - Instal-
lation and use (under preparation).
3.06 Assessment of Area
Before installing welding equipment, the user shall
make an assessment of potential electromagnetic
problems in the surrounding area. The following shall
be taken into account:
. Other supply cables, control cables, signalling
and telephone cables; above, below and adjacent
to the welding equipment.
2. Radio and television transmitters and receiv-
ers.
3. Computer and other control equipment.
4. Safety critical equipment, e.g. guarding of in-
dustrial equipment.
5. The health of people around, e.g. the use of
pacemakers and hearing aids.
6. Equipment used for calibration and measure-
ment.
7. The time of day that welding or other activities
are to be carried out.
8. The immunity of other equipment in the en-
vironment: the user shall ensure that other
equipment being used in the environment is
compatible: this may require additional protec-
tion measures.
The size of the surrounding area to be considered
will depend on the structure of the building and other
activities that are taking place. The surrounding area
may extend beyond the boundaries of the premises.
3.07 Methods of Reducing
Electromagnetic Emissions
A. Mains Supply
Welding equipment should be connected to the mains
supply according to the manufacturer’s recommen-
dations. If interference occurs, it may be necessary
to take additional precautions such as filtering of
the mains supply. Consideration should be given to
shielding the supply cable of permanently installed
welding equipment in metallic conduit or equivalent.
Shielding should be electrically continuous through-
out it’s length. The shielding should be connected
to the Welding Power Source so that good electrical
contact is maintained between the conduit and the
Welding Power Source enclosure.
B. Maintenance of Welding Equipment
The welding equipment should be routinely maintained
according to the manufacturer’s recommendations. All
access and service doors and covers should be closed
and properly fastened when the welding equipment
is in operation. The welding equipment should not
be modified in any way except for those changes and
adjustments covered in the manufacturer’s instruc-
tions. In particular, the spark gaps of arc striking and
stabilizing devices should be adjusted and maintained
according to the manufacturer’s recommendations.
C. Welding Cables
The welding cables should be kept as short as possible
and should be positioned close together, running at
or close to the floor level.
D. Equipotential Bonding
Bonding of all metallic components in the welding
installation and adjacent to it should be considered.
However. Metallic components bonded to the work
piece will increase the risk that the operator could
receive a shock by touching the metallic components
and the electrode at the same time. The operator
should be insulated from all such bonded metallic
components.
E. Earthing of the Workpiece
Where the workpiece is not bonded to earth for electri-
cal safety, nor connected to earth because of it’s size
and position, e.g. ship’s hull or building steelwork,
a connection bonding the workpiece to earth may
reduce emissions in some, but not all instances. Care
should be taken to prevent the earthing of the work-
piece increasing the risk of injury to users, or damage
to other electrical equipment. Where necessary, the
connection of the workpiece to earth should be made
by direct connection to the workpiece, but in some
countries where direct connection is not permitted, the