I think I know the reason for the different approach to at least the two above environments.
Equipment for use in explosive atmospheres must be Type Approved by bodies such as H&SE or BASSEFA against Euro standards or (in the case of exceptional circumstances) national specs specifically for this type of environment. This is a different regime and the specs are looking at other hazards in addition to the normal definition of User safety. It also assumes that in the most dangerous environments (off shore oil rigs, coal mines etc.) the user of such equipment is not a general member of the public and is therefore aware of certain types of danger. I remember that when I migrated over from explosive approvals to ITE approvals 10 years ago, I found the approach of the different requirements for electrical safety a surprise but we are now delving back into the inner most reaches of my mind where things become a blur (along with wedding anniversaries, birthdays etc.). JohnP Polycom Inc. >---------- >From: [email protected][SMTP:[email protected]] >Sent: Tuesday, February 11, 1997 5:20 PM >To: [email protected] >Cc: [email protected] >Subject: Re: BS EN 41003: 1997 now available > > >>The LVD specifically states in Article 1 >>"For purposes of this Directive 'electrical equipment' means >> any equipment designed for use with a voltage rating of >> between 50 and 1000V for alternating current and between >> 75 and 1500V for direct current, other htan the equipment >> and phenomena listed in Annex II." >> >>Annex II goes on to list >>"EQUIPMENT AND PHENOMENA OUTSIDE THE SCOPE OF THE DIRECTIVE >> Electrical equipment for use in an explosive atmosphere >> Electrical equipment for radiology and medical purposes >> Electrical parts for goods and passenger lifts >> Electricity meters >> Plugs and socket outlets for domestic use >> Electric fence controllers >> Radio-electrical interference" > >Coming from a software background, I must say that I find this wording >bizarre. From an outsider's perspective, I would expect everything >on this list to have to be protected to _stricter_ standards than >the basic LVD. Ordinarily, I would expect to see this expressed by >words to the effect that such equipment must conform to product- and >application-specific rules _in_addition_to_ compliance with the LVD. > >>Now, even when TTEs operating at 48vdc allow for a >>Bellcore lower/nom/upper limit of 42.4/48/56.5 tolerance, >>those dc TTEs are not covered by the lower >>75vdc limit of the LVD. > >Terminal equipment (and switches) using analog telephone signaling >get included becaused they "are used with" the 90V AC ringing voltage. > >For other terminal equipment, I'd agree that the LVD does not apply, >and if it was meant to, they would have defined the DC voltage limit >to start at 45 V DC. > >On the other hand, as a responsible person, you want to keep your >customers safe, and you would do well to design _as_if_ you had to >comply with the directive. > >/ Lars Poulsen [email protected] +1-805-562-3158 > OSICOM Technologies (Internet Business Unit) (formerly RNS) > 7402 Hollister Avenue Manager of Remote Access Engineering > Goleta, CA 93117 Internets designed while you wait > >
