Seaward B255 - Manual (Page 13)

Operating Manual Clare B255 Power Tool & Appliance Test Station
9
4.Introduction to Safety Testing
Under the requirements of the Health and Safety at Work Acts it is the
responsibility of the ‘supplier’ of electrical equipment to ensure that it is
electrically safe. The ‘supplier’ can be the Manufacturer, the Importer or the
Hirer and by inference the Repairer.
Manufacturers and Importers generally satisfy their obligations by ensuring
conformity to the relevant safety standards prior to placing the equipment on
the market and have little or no further interest in the continuing in-service
maintenance and routine testing of the product other than in responding to
customer feed-back and enquiry.
The Hire Industry however must ensure compliance with safety regulations
each and every time a power tool or appliance is hired out.
Repairers of power tools and appliances also have statutory obligations to
ensure that the repaired item complies fully with original manufacturer’s
specifications and the relevant standards.
As well as being aware of the legal requirements it also helps to appreciate the
reasons for testing if there is a clear understanding of how construction and
test requirements aim to provide ‘Electrical Safety’ –
Methods of Construction for Electrical Safety
To provide the user with protection against electric shock, general methods of
construction must ensure firstly that all ‘live’ parts are insulated and secondly
that should this basic insulation fail the ‘live’ parts are prevented form creating
a hazard to the user.
This second level of protection is achieved either by ‘earthing’ all accessible
conductive surfaces or by providing ‘double insulation’ in the form of a second
insulating layer or by reinforcing the primary insulating layer.
Earthed equipment is referred to as Class I. Earthing is achieved by
connecting all accessible conductive surfaces (the tool body or outer casing
and associated fixings etc) to the supply earth via a low impedance protective
conductor. Then if any ‘live’ part comes into contact with these surfaces the
hazardous current is drawn harmlessly to earth through the protective
conductor rather than the person holding the tool. The protective conductor
is the green/yellow ‘earth’ wire in standard 3 core mains supply leads.
Double Insulated equipment is referred to as Class II. All accessible
conductive surfaces are additionally insulated from internal ‘live’ parts and
components. No ‘earth’ wire is present in the supply lead. All such equipment
is clearly identified by a prominent square within a square symbol.