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March 2010

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Subject:
From:
Gene Felder <[log in to unmask]>
Reply To:
Date:
Mon, 22 Mar 2010 07:54:00 -0700
Content-Type:
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I agree with Rex.  He is consistent with the UL warning "It will not reduce
or increase your risk of receiving electric shock when using or working on
electrical equipment. Follow the same precautions you would use without
wrist straps,"

"Note: This product is not recommended for use on equipment with operating
voltage exceeding 250 VAC.
CAUTION: The ESD Series is for electrostatic control. It will not reduce or
increase your risk of receiving electric shock when using or working on
electrical equipment. Follow the same precautions you would use without
wrist straps, including:
. Make certain that equipment having a grounding type plug is properly
grounded.
. Make certain that you are not in contact with grounded objects other than
through the ESD Series."

Regarding the ESD Handbook ESD TR20.20, it was updated in 2008  The Shoe
section 5.3.3.3.3 now reads:
"If static control shoes are chosen, special care should be taken to ensure
proper fit.
Shoe construction is important. Shoes designed specifically for ESD control
purposes should be used.
Because many static control shoes look like ordinary shoes, a visible tag or
marking on the shoe will assist in the monitoring and auditing process.
Occasionally, there are people with special shoe requirements such as
orthotics. It should be assured that special requirements do not adversely
affect the ESD protective function of the shoes."

So this sentence was removed "NOTE: Ordinary leather shoes should not be
used in ESD controlled areas."

The statement was probably removed because it is not true.  Certainly, a
person grounded via a wrist strap can wear ordinary leather shoes.

Gene Felder
[log in to unmask]

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: 2010 - 03 - 22 4:24 AM
To: [log in to unmask]
Subject: Re: [TN] ESD protection / high voltage safety question

ESD TR20.20 - ESD association technical report for the Development of an
Electrostatic Discharge Control Program for the Protection of Electronic
Parts, Assemblies, and Equipment Section 5.3.3.3.3 Shoes

If static control shoes are chosen, special care should be taken to ensure
proper fit.
Shoe construction is important. Shoes designed specifically for ESD control
purposes should be used. 
Because many static control shoes look like ordinary shoes, a visible tag or
marking on the shoe will assist in monitoring and auditing process. NOTE:
Ordinary leather shoes should not be used in ESD controlled areas. 
Occasionally, there are people with special shoe requirements such as
orthotics. It should be assured that special requirements do not adversely
affect the ESD protective function of the shoes.

My copy of the Handbook is ten years old. Was this recommendation removed? 

Guy

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rex Waygood
Sent: Monday, March 22, 2010 3:32 AM
To: [log in to unmask]
Subject: Re: [TN] ESD protection / high voltage safety question

I disagree with the approach taken by the feedback you have received.
The ESD requirements are nothing to do with your problem.
To me your problem is that you are admitting there is a risk of
electrocution in your work place and that is the problem you must address.
At 20kV it seems to me that this carries the risk of death (with or without
wrist straps) and therefore your risk analysis and work procedures should
reduce this risk to zero. If not you are effectively planning to kill
someone.
Once you have done that risk analysis and altered your work procedures to
make it safe then wearing heel straps or wrist straps should be neither here
or there. 
The only reason that I can think that it might not be OK to wear heel
grounders or wrist straps is if you decide that contact with live parts is
likely and therefore the operators must wear rubber gloves, rubber boots of
a suitable rating etc.
I have operators in my ESD area who wear leather shoes and pass the ESD
footware tests every day. Your approach would mean having to replace those
shoes. The benches in my ESD area are earthed, so a risk of touching
something live and the bench is there with or without wrist straps.
We do Hi-Pot tests in our ESD area, the operators wear their standard ESD
heel grounders and wrist straps. The whole process has been risk assessed
and is considered safe.
If your work procedures are correct then the work environment should be
safe, with or without ESD precautions.

Regards
Rex






-----Original Message-----
From: TechNet on behalf of Graham Collins
Sent: Fri 3/19/2010 1:33 PM
To: [log in to unmask]
Subject: [TN] ESD protection / high voltage safety question
 
Hello TechNet
A question for you guys concerning ESD protection and it's interaction
(conflict) with safety.

We use the standard wrist strap and cord with the built in resistor, and
practice that any time an ESD sensitive assembly is being worked on we
have to wear the wrist strap.  This is fine in the production
environment, but in test we can be dealing with some scary voltages, and
being nicely grounded is not necessarily a good thing.  Say for example,
when working with something that has up to 20,000 v DC running through
it.

What are other folks doing in cases like this?

My first instinct is that our rule should be modified to say that the
wrist strap is not to be used if voltages in excess of 250v are present.

regards, 
  
Graham Collins 
Halifax Production Engineering 
L-3 communications Electronic Systems 
(902) 873-2000 ext. 6215 


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