I agree with Phil's advice. I would just add weight; if the chain is too light,
it is more likely to get high readings.
Just this weekend, I was in an ESD Association working group meeting, and no one
knew of any mention or guidance on the use of drag chains. This includes ESD
6.1 and the 126 page ESD Handbook TR20.20 which the ESD Association sells at
www.esda.org.
Table 1 of ANSI/ESD S20.20 has the minimum recommended technical requirement
range for Mobile Equipment < 1 x 10^9 ohms. How one reliably accomplishes this
is up to the user.
Gene Felder
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phillip Bavaro
Sent: Friday, September 16, 2005 1:03 PM
To: [log in to unmask]
Subject: Re: [TN] ESD Drag Chain Length
Hi Joseph,
Internally I specified a 6 inch minimum contact length with the chain connected
at both ends to the cart, but I don't remember any ESD standards that concurred
with this.
If you have access, you might check ANSI/ESD S6.1-2005 Grounding.
ANSI/ESD S20.20 does not list a spec controlling grounding of mobile equipment
but does list the resistance requirement.
It cannot just be in contact with, or hanging down to the floor, instead it must
function constantly as the cart is moved. If you break the connection to the
grounded flooring, it will not work.
And don't forget the insulation problem that contamination such as dust will
have on the chains so you have to include these in your audit program for
equipment grounding verification.
Hope this helps,
Phil
Joseph Sokalski <[log in to unmask]> wrote:
Dear Technetters:
Has anyone seen a documented standard for the recommended drag chain length
attached to rolling carts? During a recent customer audit, I was cited for
insufficient chain contact with our ESD flooring. I looked in ANSI/ESD
S20.20-1999 and did not see any reference.
Any assistance would be appreciated.
Joseph Sokalski
Test Technology, Inc
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