Jim, The flame test very often is not stricly required by RBOCS. One reason is that does not prove anything , secondly EPA got into the act \ and test causes polution.
The safe way I took in the past first was to demostrate that product meets UL1950 and all materials have 94V0 rating. That includes all plastics etc. Based on that you will have to negotiate with Belcore that overall flambility of the product is 94V0 and go from there. Jan Purwin JIM WIESE wrote: > Experience is relative, but I would say we have been fighting the same > issue for over a year now. between in-house burn tests and tests at > various NRTL labs, we have burned over 40 shelves varying in height from > 1 RU to 6 RU. We have discussed this issue several times with Bellcore > and they concur there is a problem, but insist they are trying to > harmonize with the ANSI T1.319 1995 and therefore cannot justifiably > change the test method. Here is basically the history, the problem and > suggested solutions. > > 1.) Until 1995 the TR-NWT-000063 did not have a burn test designed for > shelves or small systems. The test was designed for cabinets and fully > loaded frames. As a result, Bellcore decided to incorporate a shelf > level burn test "loosely" based on ANSI T1.319 1995 into the new > GR-63-CORE. At this point they ignored a circuit pack level test which > is basically what ANSI T1.319 1995 is all about. > > 2.) The intention of ANSI T1.319 1995 was to obtain supplemental > information about the burning characteristics of an assembled circuit > pack that would not be evident based on a flame database, needle flame > tests, etc.. The idea was to place lots of the circuit packs in a > configuration independent of the host system and see what the affect was > of the placement and quantity of various components on the overall burn > characteristics of the cards. Placing lots of 94V-0 and 94V-1 polymeric > components together on a circuit board and applying a flame source is > totally different than doing a needle flame test on a single component. > > 3.) ANSI T1.319 1995 defines a flow rate and burner configuration for > applying the flame. It was based on statistical data obtained from > fully ignited 8"x12" circuit cards loaded with a variety of 94V-0 and > 94V-1 components supplied by major telco providers at the time. The > study was conducted in conjunction with Underwriters Labs and lasted > about 30 months. As a result the flow rate in Table 1 and the line > burner in Section 5.2.4 of the ANSI document were modeled to duplicate > the characteristics of a fully engulfed 8"x12" loaded circuit pack. The > only pass/fail criteria was a heat release rate. > > 4.) Bellcore then adopted this ANSI standard and applied it in > "complete" shelves and systems less than 36" in height, and created a > several new pass/fail criteria (R4-20). Unfortunately for vendors these > days, Bellcore assumed that they were the only ones that would actually > perform testing to GR-63-CORE where the results would be reviewed by > telco providers. Bellcore provided "Technical Audits" and if they felt > a failure mode of a system was not a substantial risk then they would > make that kind of statement in their Technical Audit and the RBOC's > would not be concerned because Bellcore said it was probably OK. > > 5.) What Bellcore did not realize was that independent labs would start > performing these tests due to the vast number of new products, long > turnaround times and very high test costs at Bellcore. As a result, > most/many burn tests are performed by labs other than Bellcore who do > not have the leeway to use good engineering judgment when evaluating the > burn tests. They can only state that a system complies with or does not > comply with the requirements or objectives. Due to attrition, layoffs > and shortages of manpower, the RBOC's, GTE and other independents do not > have the time or desire to interpret the flame data for products as > stated in the opening paragraph of section 4.2 of GR-63-CORE. As a > result, they typically want a report that simply states "complies with > ALL requirements". If they don't get that, our experience has been that > they typically will not buy! There are some exceptions such as Bell > Atlantic North and South who have very experienced people who are > willing to work with a vendor on this subject. They realize that > mitigating certain failure modes creates bigger problems. > > 6.) Vendors are building smaller systems (1-2 RU high) with circuit > boards that are substantially smaller than 8"x12" with far fewer > combustible components (due to surface mount technology) and the test > labs must still apply a flame that is ridiculous based on the intent of > the ANSI T1.319 1995. As a result, the only way to pass all criteria is > to enclose the shelf with solid metal or a fine mesh perforated > material. This however causes a much worse problem since the heat from > normal operation is trapped in the shelf, which will eventually result > in premature failure of the components. In addition, the burn > characteristics of horizontal circuit boards were not studied in the > ANSI T1.319 yet Bellcore GR-63-CORE does not address this "substantial" > difference between a horizontal board and a vertical board and you must > test both the same. As a side note, horizontal boards burn much less > than vertical. > > 7.) If I were Bellcore, I would address this issue five ways: > > a) Make the requirements in R4-20 objectives and add wording stating > that these criteria should be used carefully by the lab and customer to > analyze the overall flammability risk, and that shelf and circuit pack > size should be considered while making this assessment based on the > application of the EUT and the resultant affects of mitigating a > specific failure mode. > An example would be a 2 RU high shelf that is densely populated with > 2"x 8" circuit cards. If flames extend beyond the vertical confines for > more than 30 seconds after the 3.5 minute point, that is technically a > failure. However, the flame from the burner is still roughly 8 " tall. > The only way to meet this criteria is to place a solid top or mesh > screen over the shelf to smash the flame horizontally inside the shelf. > The problem is that this substantially reduces airflow and increases > internal system temperatures (reduces reliability). > The flame used is far too much since the methane flow rate in the > standard is based on a 8"x12" card (96 square inches) and the card under > test is 16 square inches which is roughly 18% of the flame mass. It > also increases the cost of the system to the end user as mesh materials > are fairly expensive. And lastly by spreading the flame horizontally, > the equipment becomes much hotter during the burn test, the system > basically self consumes due to the heat pocket and creates several > orders of magnitude more smoke which is more harmful in a C.O than the > fire itself. So by mitigating an unrealistic failure mode, reliability > during normal operation is reduced and if a fire did occur the damage > would be far worse due to smoke. > > b) I would provide an option that stated that if a system is Listed > to > UL 1459 or UL 1950 3rd Edition and it meets the criteria stated in the > material analysis section 4.2.3 of GR-63-CORE and ANSI T1.307 1997 then > requirement R4-20 is exempt. > > c) I would prorate the flow rate of the methane burner to the > proportion of the circuit board which is being simulated compared to a > 96 square inch circuit pack. > > d) I would incorporate the ANSI T1.319 1997 document as a way to show > compliance of circuit packs that are provided for existing systems. > > e) I would make provisions for different line burner lengths so that > circuit board/ system formats that have depths less than 6.5 inches > (such T400 or T200) do not have a flame burning in front of the > faceplate due to the line burner. > > Jim > > James Wiese > Regulatory Compliance Engineer > ADTRAN, Inc. > 205-963-8431 > 205-963-8250 FAX > [email protected] > > >---------- > >From: Dwight Hunnicutt[SMTP:[email protected]] > >Sent: Friday, March 13, 1998 6:35 PM > >To: [email protected] > >Subject: NEBS 5.2.3 Fire Test > > > > > > NEBS Group- > > > >I'm wondering if any of you have experience with > >the fire test of GR-63-CORE 5.2.3, and the grisly > >outcomes of misapplying the test to certain equipment. > > > >Specifically, I question the applicability of this > >test to a "pizza-box" type unit (1 RU height), that > >can be rack, wall, or desktop mounted. Assume the > >unit is CPE(customer premises equipment),and Listed > >to UL1950. It would not (normally) go in a C.O., but > >only an equipment closet at a business. > > > >My understanding is that the fire test of 5.2.3 was > >designed for large cabinet racks of cards, and tries > >to determine the relationship of one's equipment to > >the outcome of a severe fire in an equipment room or > >C.O., whether or not the fire started in one's own > >equipment. > > > >For a unit with top openings complying with UL1950, > >the flames from the 5.2.3 test burner would just shoot > >up through these top openings and burn the two test > >cards in the test setup, thus failing the fire test. > >Same or worse results should occur if the unit was > >wall-mounted vertically for the test, since the top > >openings would now be side openings, and the flames > >would just lick up the sides. > > > >Question: Is there a consensus that this 5.2.3 fire > >test does not apply to the "pizza-box" CPE type unit? > >Or can the "shelf-level" test be interpreted to apply > >to this type of unit? > > > >Any of you have any success convincing a customer of > >the "misapplicability" of this test to your equipment, > >even though the customer insists it does? > > > >If it does apply, do any of you have experience to say > >that you agree that TOP openings complying with UL1950 > >BOTTOM opening requirements would be small enough to > >contain the test burner flames (sufficient to pass the > >fire test)? > > > >Thanks in advance for your comments. > > > > > > RCIC - http://www.rcic.com > > Regulatory Compliance Information Center > > > > > > > >
