R E DUCING Haz­ard

DEMM Engineering & Manufacturing - - FRONT PAGE -

WorkSafe NZ says a num­ber of en­quires have been re­ceived re­gard­ing the manda­tory na­ture of the “test and tag” pro­vi­sions of AS/ NZS 3760, par­tic­u­larly sit­u­a­tions where RCD pro­tec­tion is pro­vided in the sup­ply ar­range­ment es­pe­cially for lo­ca­tions such as of­fices and other in­doors en­vi­ron­ments sim­i­lar to res­i­den­tial premises and how an al­ter­na­tive might re­late to “all prac­ti­ca­ble steps”.

The use of AS/NZS 3760 is cited by the Reg­u­la­tions (Reg­u­la­tion 26) as be­ing deemed to be safe. AS/NZS 3760 fo­cusses on pro­tec­tion against elec­tric shock us­ing tests con­ducted us­ing gen­eral or pur­pose built test equip­ment used by trained and com­pe­tent per­sons. It is not as some peo­ple be­lieve a sys­tem of test­ing a sup­ply cord, but a sys­tem of test­ing the safety of an en­tire ap­pli­ance.

How­ever, it also con­tains ad­di­tional re­quire­ments to ver­ify the pres­ence and op­er­a­tion of guards and bar­ri­ers that pro­tect against me­chan­i­cal in­jury and con­tact with live parts, and in­cludes an in­spec­tion to iden­tify any dam­age to the equip­ment.

The ma­jor­ity of th­ese ad­di­tional re­quire­ments are vis­ual in­spec­tions.

It is not ac­cept­able to is­sue a com­pli­ance Tag on the ba­sis of test­ing alone.

Be­cause AS/NZS 3760’s test and tag regime is a recog­nised (deemed to be safe) method of achiev­ing the gen­eral safety re­quire­ments for the use of plug-in ap­pli­ances, in the reg­u­la­tion’s risk based ar­chi­tec­ture, it’s ap­pli­ca­tion is not manda­tory, nor does the Stan­dard rep­re­sent a min­i­mum bench­mark by which an al­ter­na­tive safety method­ol­ogy must be as­sessed. Nor are the re­quire­ments nec­es­sar­ily a mea­sure of all prac­ti­ca­ble steps.

The Reg­u­la­tions, through the ci­ta­tion of IEC 60479, also recog­nise that RCD pro­tec­tion is an ac­cept­able method­ol­ogy of pro­vid­ing pro­tec­tion against elec­tric shock.

There­fore, the use of an RCD pro­tected sup­ply, where the users of equip­ment per­form their own vis­ual safety checks for dam­age and the func­tion­ing of guards on a daily ba­sis is not nec­es­sar­ily in­ad­e­quate.

Like­wise, where the equip­ment does not rely on guards or bar­ri­ers to pre­vent me­chan­i­cal in­jury or ac­cess to live parts, and the use of the equip­ment is un­likely to re­sult in dam­age to the equip­ment, the use of RCD pro­tected sup­plies backed up by reg­u­lar vis­ual in­spec­tions for dam­age car­ried out by re­spon­si­ble and com­pe­tent per­sons would not be nec­es­sar­ily in­ad­e­quate.

How­ever, in sit­u­a­tions where a mi­nor elec­tric shock may re­sult in dan­ger­ous in­vol­un­tary re­ac­tions, such as con­struc­tion and de­mo­li­tion sites, the use of RCDs alone is un­likely to be ad­e­quate. In th­ese cases, the pro­vi­sions of AS/NZS 3012 (“Test and Tag” and RCD pro­tec­tion) should be em­ployed.

In any cir­cum­stances where “Test and Tag” is be­ing em­ployed it is crit­i­cal to ver­ify the com­pe­tency of the tester to as­sess the over­all safety of the equip­ment and not sim­ply tag on the ba­sis of test­ing us­ing a pur­pose built tester.

It is also im­por­tant to ver­ify that the ap­pli­ance be­ing tested is one that would have been de­signed to com­ply with the re­quire­ments of the rel­e­vant safety Stan­dard at the time of its in­tro­duc­tion into the NZ mar­ket. AS/NZS 3760 only ver­i­fies cer­tain pa­ram­e­ters of elec­tri­cal safety based on safety com­pli­ance when new..

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