Drag chains vs Grounding cables

#1

Currently we are using grounding cables to ground units when we move them.

we wanted to get rid of the grounding cables and use drag chains.

we did testing with a couple of 1 megohm Drag chain attached to the framed custom fixture on an ESD floor and the test results are good.

Do you see any issues/concerns I’m not seeing why this isn’t a good idea?

Thanks!!

#2

Duncan,

Your methodolgy is sound. There will be opinions on the effectivness of drag chains and how bad they may be. Determine what works with your floor and continue to measure the resistance to ensure that they continue to work. You may find that they need to be cleaned on a peridic basis, you may find you need another type of chain, maybe heavier and longer.

As long as you continue to ensure that the carts can be measured to ground, then the idea is a good one.

#3

Duncan,

I have not had much success with drag chains, but as John mentioned if maintained properly and you have a robust compliance verication measurement plan, you may have good success.

For me, I have had good success with installing conductive casters (wheels) on my mobile carts. I have found they give better more consistent contact with my floors.

Just a thought

#4

Thanks for you expertise!

#5

Thanks for you expertise and suggestion!

1 Like
#6

Hello,
Greetings of the day from India.
I vouch the opinion of both the ESDA experts.

  1. The best is always with ESD safe wheels for a uniform consistent contact with a grounded ESD safe floor
  2. The drag chains have been a built-in feature by default with all movable ESD safe items viz; trollies / chair etc., But in most of the cases it would be MS plated which over a period of time due to higher moisture start rusting and also, many a times (My comments and observations are all from the Indian users’ sites during PQ-CV test audits) are too light or short in Length to develop perfect contact for sufficient friction between the chain and floor unlike with wheels. Of course, as Mr. JK has mentioned bit heavier-longer and SS chains would be good r to have better surface contact with the floor.
    However, as they both have mentioned you need to determine whether or not you are able to meet the Rg per ANSI /ESD S 20.20 or IEC 61340-5-1 guidelines. If you are meeting the requirements regularly upon your every CV test audit, then there should not be an issue at all.
    I do not think that either of the two standards speak about attaching 1 Mega ohm resistance to the chain or the grounding lead. However; it does not matter as long as the measured results fall well within the specified limits per either of the two standards.
    Thank you