I'm not an expert in the subject. This is offered from the viewpoint of a Quality Engineer responsible for auditing suppliers. I believe you need to answer a couple of related questions to resolve the issue.
1) If you're interested in the function of the heel strap, why is it tested while it is being worn? (As a person with dry skin in the morning - especially during winter - I've had to use IC lotion on my feet to pass the heel strap test. IMO, verifying conductivity from the heel strap to the person's hands is probably as important a reason for testing as evaluating the function of the heel strap.)
2) If evaluating contact as well as function is important, how can you justify not testing after the heel strap is removed and reinstalled?
3) How many ungrounded operators are acceptable in an assembly area?
Answer questions one and two for an auditor - provide data to support your position and the issue should be resolved. By data, I mean evidence to support a statement that there was never a grounding failure due to operator error. No data, no justification, unhappy auditor, and we revert to the third question about how many ungrounded operators are acceptable. Sorry if I[m a bit terse. I've been typing up trip reports after a week on the road.
From your email address, I know that your company builds EECs and FADECs. As an auditor, how sympathetic would you be if there was a chance that ESD could produce a latent defect resulting in an in-flight shudown on your company's engine?
Don Vischulis
-----Original Message-----
>From: "Kane, Joseph E (US SSA)" <[log in to unmask]>
>Sent: Mar 7, 2006 5:05 PM
>To: [log in to unmask]
>Subject: [TN] ESD Heel Strap Testing
>
>I'm trying to get an idea about industry practice, how often
>heel strap testing is performed.
>
>An outside auditor has questioned our practice of testing
>heel straps just once a day. Operators wear a strap on each
>foot, and test each individually. We require operators to remove
>the straps if they leave the building, but we don't require
>them to retest when they put them back on, and there lies
>the objection.
>
>Our position is that the primary purpose of testing is to verify the
>integrity of the equipment, to make sure that the straps
>haven't worn out. It does matter how the straps are put on,
>but in our experience, operators usually get it right, and we don't
>see a lot of failures when footwear is tested. Of course, most of our
>people wear conductive shoes, not heel straps.
>
>We operate to MIL-STD-1686 and ESD S20.20, which do
>not speak to this issue, so what we have is a difference of opinion.
>I've seen shops that require testing every time a heel strap
>or wrist strap is put on, and this is certainly defensible. But
>I think there should also be some tolerance for considerations of
>practicality and general effectiveness of the ESD program.
>
>Any comments?
>
>Joe Kane
>BAE Systems
>Johnson City, NY
>
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