Hello experts
When the standard ESD20.20 in 8.2 calls for “The personnel grounding method(s) shall be selected from table 2”. Can I select just Wrist strap system (table 2) and have footwear and flooring separately (from table 3)?
Or what is the difference between selecting footwear/flooring system vs footwear and flooring separately? Isn’t it the same since both would be qualified? (If its the same, what is the benefit of selectin one way or the other?).
Thank you very much in advance.
Santiago,
Sounds like you need both wrist straps (for seated operations at a work bench) and footwear/flooring (for handling ESDS items while not at the workbench). If this is correct, then you would select both wrist straps as well as footwear/flooring as your personnel grounding from table 2.
The difference between the requirements in table 2 vs table 3 for wrist straps and footwear/flooring is in product qualification (compliance verification is the same). Table 2 gives system requirements while table 3 gives requirements for the individual ESD control item. For example, table 2 for footwear/flooring states that all combinations of footwear and flooring used together must meet the resistance and voltage requirements as measured by ANSI/ESD STM97.1 and 97.2. Table 3 gives requirements for the footwear and flooring by themselves (ANSI/ESD STM9.1 for footwear and ANSI/ESD STM7.1 for flooring). Hope this helps. Thanks
The standard states that one (or more) of the grounding systems in table 2 needs to be slected for grounding of personnel. If you decide on wrist straps as the only way to ground people, then yes you can qualify floors and footwear sparately.
If there is a combination of grounding people through wrist straps and a footwear/flooring system, then the requirements on a footwear/flooring system must also be measured. This includes the body voltage measurements and the resistance measurements of the person-footwear-floor.
Qualifying just the floor and footwear would not be enough for qualification of a footwear/flooring system for personal. The indivigual qualifications are for a user to discuss requirements with a flooring or footwear supplier. The flooring supplier does not know what kind of footwear that will be used and the footwear supplier does not know what floor will be used.
Thank you very much for the clarity!