ESD and Static Control Questions

Q:

Are ESD shoes and Conductive shoes the same thing?

A: There are two types of ESD shoes, Static Dissipative and Static Conductive.
�
The Static Conductive shoe will guarantee a combined resistance of personnel and footwear of less than 1.0E6 Ohms.  I have a pair of Static Conductive shoes that when I’m standing on a static conductive flooring system (2.5E4 Ω to 1.0E6 Ω), my combined resistance from my body through the ESD footwear and through the ESD conductive flooring system to electrical ground or earth is less than 1.0E6 ohms per DoD 4145.26-M, C6.4.7.5.1: “The maximum resistance of a body, plus the resistance of conductive shoes, plus the resistance of the floor to the ground system shall not exceed 1,000,000 ohms total”… “The contractor can set the maximum resistance limits for the floor to the ground system and for the combined resistance of a person’s body plus the shoes, as long as the total resistance does not exceed 1,000,000 ohms.”
�
This Static Conductive shoe is typically used for electrical safety requirements for facilities that deal with explosive environments such as ordinance, munitions, explosive powders, flammable liquids, etc.  This is outside of the realm of ANSI/ESD S20.20-2007 and MIL-HDBK-263B.
�
If you’re goal is the protection of static sensitive devices, then Static dissipative shoes on a static conductive flooring system or a static dissipative flooring system will suffice so long as the combined resistance of personnel, footwear, and flooring to electrical or earth ground is less than 3.5E7 Ω as per ANSI/ESD STM97.1-2006.  In that case, a good static dissipative shoe will be more than 1.0E6 or a meg ohm, but the resistance will probably be less than 35 Meg ohms.  The best way to measure the footwear is to have personnel wear them for at least 10 minutes prior to going to the tester and checking for pass/fail low/fail high, as that’s the most practical way to test them.  You can measure the resistance of the shoe from insole to outsole, but they aren’t used that way on the ESD flooring system.  The ESD shoe relies on sweat from the personnel that wears them.
�
My combined resistance from my body, through my Static Conductive C4327 (men’s) or C437 (woman’s) shoes and through a static conductive floor to electrical/earth ground is about 7.0E5 Ω.  My combined resistance from my body through my Static Dissipative C4341 shoes and through a static conductive floor to electrical/earth ground is about 1.6E6 Ω.
�
I hope this answers your questions.  Please comment.

…

Thank you very much, Pat

Static Conductive shoe C4327 Resistance per ANSI/ESD STM97.1-2006

Static Dissipative shoe C4341

Q: Is it ok to wear ESD shoes or heel, toe, or sole grounders outside?

A: No.  MIL-HDBK-263B Appendix 1 page 101 40.1.2 states, “Conductive shoes, shoe covers, or heel grounders should be used to discharge personnel on conductive floors. These items should only be worn in the ESD protected areas and should be kept clean so that contaminants do not inhibit their conductive interface with the floor.”

So, to protect your investment, for good house keeping and maintenance, longevity of the ESD personal equipment, just don them before going into the EPA and take them off when you leave.

Do this and keep them clean (vacuum inside of shoes weekly and maybe clean outsoles and grounders with soapy water once a week) and you’ll get more wear out of them and they’ll be more effective.

Q. What is the importance of having the personnel within an EPA to wear ESD footwear on an ESD Flooring system?

A. Thanks for the inquiry. It was good speaking with you earlier. You had stated that you had concerns about the grounding of your flooring system and my first question to you was about the use of ESD footwear. I believe that you had stated that not everyone was using esd footwear.

You pose a situation here that needs to be addressed as a top priority at all levels of ESD Awareness for every client that we come into contact with. I don’t mean to over-simplify this but I am seeing a common trend in the ESD industry; your ESD system is only as strong as the weakest link in the chain. Another way to say this is; If you buy a Plasma TV, it needs to come with a power cord and you need to plug that in.
Continue reading…

Q: What does ASTM F2413-05 compliant mean?

A: I’ve got the document from the American Society for Testing and Material Standards (ASTM) in front of me now.

They sent me a copyrighted document on June 2^nd of 2005.

It’s significance and use section is pretty encompassing;

1. This specification contains requirements to evaluate the performance of footwear for the following:
   1. Impact resistance for the toe area of footwear.
   2. Compression resistance for the toe area of footwear.
   3. Metatarsal protection that reduces the chance of injury to the metatarsal bones at the top of the foot.
   4. Conductive properties which reduce hazards that may result from static electricity buildup, and reduce the possibility of ignition of explosives and volatile chemicals.
   5. Electric shock resistance.
   6. Static Dissipative (SD) properties to reduce hazards due to excessively low footwear resistance that may exist where SD footwear is required.
   7. Puncture resistance of footwear bottoms.
   8. Chain saw cut resistance, and
   9. Dielectric insulation.

There’s a section in there that describes Performance Requirements and Workmanship, Hazard Assessment, Labeling and Identification, Marking and Compliance Requirements, and Keywords.