24 Safety and compliance
Earthing of the workpiece
Where the workpiece is not bonded to earth for electrical safety, nor
connected to earth because of its size and position, for example, ship’s
hull or building steel work, 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 workpiece 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 a direct
connection to the workpiece, but in some countries where direct
connection is not permitted, the bonding should be achieved by suitable
capacitances selected according to national regulations.
Note: The cutting circuit may or may not be earthed for safety reasons.
Changing the earthing arrangements should only be authorized by a
person who is competent to assess whether the changes will increase
the risk of injury, for example, by allowing parallel cutting current return
paths which may damage the earth circuits of other equipment.
Further guidance is provided in IEC 60974-9, Arc Welding Equipment,
Part 9: Installation and Use.
Screening and shielding
Selective screening and shielding of other cables and equipment in the
surrounding area may alleviate problems of interference. Screening of the
entire plasma cutting installation may be considered for special
applications.
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