Paul, thanks for the reply. Now, the real stickler for me is that we are trying to leverage an existing non-I-safe design - the entire enclosure is plastic. There are materials available with the correct properties but they are prohibitively expensive, and because the shrink factor is different, would require re-tooling, making the development cost prohibitive.
Clause 7.3.2 (b)allows an expansion of the size to 100cmsquared "if the plastics parts are additionally protected against the occurance of dangerous electrostatic charges". Also, 7.3.2 (c) gives a very ambiguous statement about other methods being acceptable - it's basically an out allowing engineering judgement. I'm interested in learning what some of the other methods are. I believe that the use of a leather case may meet the requirements of sub-clause (b) as long as the size of the openings are constrained to <100cmsquared, and may meet sub-clause (c) with larger openings based on engineering judgement. By the way, the standard still allows warning text. I shy away from that because while it may help in litigation, the bottom line with this type product is someone's life is definitely at stake. Also, I'm not sure what safety measures there may be that can reliably prevent ESD from occuring. Doug -----Original Message----- From: Finn, Paul [mailto:[email protected]] Sent: Friday, November 17, 2000 6:56 AM To: Massey, Doug C. Subject: RE: Intrinsically safe equipment This requirement addresses the likelihood of ignition to the release of a static electricity which is capable of building up on a non-metallic surface. Prior to ATEX you were able to address this issue by means of a warning label. Know you must either select a suitably rated material, i.e. tested in accordance with 23.4.7.8 which verifies it has a resistance less than 1Gohm at 23C, 50%RH. Or to reduce the total area of the non-metallic surface to 100cmsquared for gas groups IIA, IIB and 20cmsquared for IIC. This can be accomplished by segregating a lager area into smaller sections which meet the requirements. The sections need to be separated by grounded partition. I do not know the requirements for the grounding of the partitions. Paul Finn Panametrics Inc > -----Original Message----- > From: Massey, Doug C. [SMTP:[email protected]] > Sent: Thursday, November 16, 2000 2:59 PM > To: 'IEEE Forum' > Subject: Intrinsically safe equipment > > > Hello group - > > I'm looking for help regarding the safety of equipment for use in > hazardous > locations, especially intrisically safe systems. > Specifically, I have questions regarding clause 7.3.2 of standard EN > 50014:1997, concerning electrostatic charges of enclosures of plastic > materials. > > If anyone has experience with the ATEX Directive standards (IEC-79 based), > I > would greatly appreciate hearing from you. Please e-mail me directly or > call > at (770) 447-4224 x3607. > > I'm afraid this discussion may get a little large for this forum, so I am > hesitant to post detailed questions here to a group that may likely be > uninterested in the topic. > > Thanks in advance. > > Doug Massey > Safety Approvals Engineer > LXE, Inc. > Norcross, GA., USA > Ph. (770) 447-4224 x3607 > FAX (770) 447-6928 > e-mail: [email protected] > > Cruise our website at: http:\\www.lxe.com > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
