Hi Kazimier and Terry:
Kazimier suggests asking the question:
"what's the safety concern"
Unfortunately, safety certification houses
do not have the option of accepting products
based on the answer to this question.
A safety certification house certifies a
product to a standard. Supposedly, the
requirements contained in the standard make
the product safe.
In this case, IEC 60950, Sub-clause 4.4.3.2
requires all materials and components be
rated V-2 or better. So, the certification
house is requiring that the construction
comply with the standard. You can't fault
the certification house for imposing a
requirement explicitly stated in the standard.
The small-part exemption cited by Terry only
applies to small parts separated from electrical
parts by at least 13 mm (1/2-inch) of air. I
would guess, from Terry's description and the
action of the certification house, that this is
not the case. (If it is the case, then you can
invoke this sub-clause and the matter is closed.)
Fortunately, the standard provides an option of
testing.
If you test the stand-off for flammability and
it is flame-retardant, then your construction
is acceptable. Now, instead of proving to the
inspector that the material is V-2, you need
only prove to the inspector that the stand-off
is the manufacturer and "model" number that was
tested.
If you can't do this, then there is still
another test option. You can test a non-flame-
retardant standoff. If the resulting fire does
not spread within the equipment, then you have
proved that the standoff is indeed inconsequential
to any fire. If you prove this, then there is
no need to control the material.
Best regards,
Rich
ps: Being a long-time certification house
basher, I can't believe I've written a
message defending a certification house!
> Hi Terry,
>
> Sounds like a discussion with your agency safety engineer might be in order.
> It's certain there's a line of reasoning behind the "new" approach taken by
> the agency, that you've described below. Question is, since the standard
> clauses you've called out make certain allowances, the real issue might
> easily be addressed by asking "what's the safety concern"? If the agency
> rep. understands your product, your reasoning and it all falls into an area
> of interpretation without any blatant standard violations, a certain amount
> of engineering judgment might help resolve the situation.
>
>
> My opinion only and not that of my employer.
>
> Good Luck.
> Regards,
> Kaz Gawrzyjal
> kazimier_gawrzy...@dell.com
>
>
> -----Original Message-----
> From: Terry Meck [mailto:tjm...@accusort.com]
> Sent: Tuesday, February 20, 2001 9:44 AM
> To: emc-p...@ieee.org
> Subject: FLAME RATING OF STANDOFFS
>
>
>
> Hi group!
>
> I need a sanity check on a `new approach' our safety agency has recently
> taken.
>
> We have an open frame power supply ( has all the certs through the CB report
> etc. for EN 60950 UL 1950 )
>
> On of the conditions of acceptability is one mounting standoff shall be
> insulated. We have this supply in no less then 4 listed products without
> any reference to the flame rating of the standoff having to be checked when
> the inspector comes in.
> I consider that to be reasonable. section 4.4.3.3 UL 1950 has exception:
> "gears, cams, belts, bearings and other small parts which would contribute
> negligible fuel to a fire;"
>
> Recently new products have been reviewed and the new procedures require
> `traceable 94V-2' standoffs!?!? Which manufacturing engineering says is
> difficult to procure a traceable recognized plastic standoff.
>
> Questions:
> Has my fever and pneumonia the past weeks clouded my reasoning? What am I
> missing? You place a .5 inch #6 standoff between a V-0 board and a medal
> chassis what requires a recognized part except maybe `straining out the
> gnats so we can swallow the camel' somewhere else.
>
> Sick and Tired
> Terry J. Meck
> Senior Compliance / Test Engineer
> Accu-Sort Systems
>
>
> -------------------------------------------
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
>
> To cancel your subscription, send mail to:
> majord...@ieee.org
> with the single line:
> unsubscribe emc-pstc
>
> For help, send mail to the list administrators:
> Jim Bacher: jim_bac...@mail.monarch.com
> Michael Garretson: pstc_ad...@garretson.org
>
> For policy questions, send mail to:
> Richard Nute: ri...@ieee.org
>
>
>
> -------------------------------------------
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
>
> To cancel your subscription, send mail to:
> majord...@ieee.org
> with the single line:
> unsubscribe emc-pstc
>
> For help, send mail to the list administrators:
> Jim Bacher: jim_bac...@mail.monarch.com
> Michael Garretson: pstc_ad...@garretson.org
>
> For policy questions, send mail to:
> Richard Nute: ri...@ieee.org
>
>
>
-------------------------------------------
This message is from the IEEE EMC Society Product Safety
Technical Committee emc-pstc discussion list.
To cancel your subscription, send mail to:
majord...@ieee.org
with the single line:
unsubscribe emc-pstc
For help, send mail to the list administrators:
Jim Bacher: jim_bac...@mail.monarch.com
Michael Garretson: pstc_ad...@garretson.org
For policy questions, send mail to:
Richard Nute: ri...@ieee.org
