This is an example of a severe malady that has hit our industry and the
general public of recent years: a lack of commonsense to the extent of
stupidity. Commonsense would dictate that the chain length should be
sufficient to ensure dissipation of any potential charge (which can be
verified with an instrument). Stupidity would dictate that the length
must be standardised, whether it is sufficient to dissipate the charge
or not.
For Goodness's sake, when are we going to wake up to the fact that a
surfeit of standards is a very costly alternative to practical
commonsense? If the final product does the job for which it is designed
for the length of time for which it is intended, then it is good enough,
whether or not it conforms to a thousand standards, causing it to be
thus grossly and expensively over-specified.
There is a corollary to this: it is bad engineering to over specify. If
an engineer says that if one unit in a standard is good, then two units
must be better, he should be given his pink slip on the spot. Why?
Because he is not applying scientific principles to his job. As a stupid
contextual example, let's imagine that Standard XYZ1234-5A states that a
trailing chain on a trolley should have 10 cm in contact with the ESD
flooring, then 100 cm must be 10 times better, even if it means that the
guy pushing the trolley trips up over the chain (in links 22.3 mm ±0.5
mm long and 14.1 mm ±0.2 mm wide, in 25 µm ± 2 µm copper-plated Swedish
Armco iron, diameter 4 mm ±0.1 mm, with each link electrically welded
and X-rayed for weld integrity) and breaks his front teeth on the handle.
Oh! How many times in my 51 years in the electronics industry have I
seen bad engineering because some inept engineer has followed a standard
or a specification that is not relevant to the work he is doing?
Thousands! And each time this happens, he is wasting his employer's
hard-earned cash. I am not saying that specs are bad: they are necessary
in some cases (a few?). But one ounce of common sense is frequently much
better than a tonne of documents specifying how an avionics device
should be built, when you are making I-Pods.
Can the IPC make an ANSI Standard stating that commonsense rules over
all other specs that are not absolutely relevant to the job in hand?
Brian
Joseph Sokalski 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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