We have several metal shelving units on our production floor in various areas that are used to store pcba’s. I was trying to find the correct way to ground these shelving units. Our electrical outlets are in our ceiling with drop cords, and I was initially planning on making drop cords with only the electrical ground and attach that to the shelving with a ground lug. I’ve seen online mentioning using a 1 Megaohm resistor inline as well but wasn’t sure what to look for.
We cannot drill into the floor to make grounding points due to needing to move the shelving locations at times. We are using the electrical ground for our regular EPA locations.
Josh,
I think your idea of drop cords from the ground of the outlet will be fine. If the PCBA is charged and then discharged into the shelf, a Mohm resistor will not help you. If that is a concern, I suggest lining the racks with a dissipative covering like an ESD mat.
If you have ESD floors, you could consider putting the rack directly on the floor. If you need feet on the shelves, you could consider conductive feet if you can find them. You could also use drag chains or ground cords between racks with one rack bonded to ground. Hope this helps. Thanks
1 Like
Hello Josh,
At a previous company I too had drop cord power and we used a pig-tail (single wire connected to ground) that I connected to a common point ground bar and then ran a ground wire from my shelving to the common point ground.
A word of caution however, you need to make sure that each of your shelves have continuity from one shelf to another in order for all shelves to be grounded.
I would also recommend that you take a look at the ESDA Technical Report TR20.20 section 16.2 that talks about Storage Area Shelving.
Best to you