I received a complaint about a "shock hazard". Folks in a new store were receiving a shock when they touched the metal racks. Investigation indictaes its a startic charge, not actually power. I've seen this before with carpeted floor, but this floor is tile. They wish to eleiminate the problem. Any suggestions.
static electricity
- Thread starter augie47
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bdarnell
Senior Member
- Location
- Indianapolis, IN
- Occupation
- Retired Engineer
This is not uncommon. VCT (tile) floors do not dissipate static charges due to their high surface resistance. We had a similar problem in an alarm central station and had to install static mats for all of the operators' chairs. When they would roll across the floor and scoot their feet, they were taking out circuit boards in alarm receivers with static hits.
Try a Google search on "VCT floors and static electricity" You'll get hits from compaines that sell anti-static flooring materials and high pressure laminates (HPL)
Hope that helps some.
Try a Google search on "VCT floors and static electricity" You'll get hits from compaines that sell anti-static flooring materials and high pressure laminates (HPL)
Hope that helps some.
bphgravity
Senior Member
- Location
- Florida
I receive pretty severe shocks when pushing a grocery cart through the store and touch the metal racks or cooler doors. You would think I would get use to it after a while, but I don't. 
The law of Conservation of Electric Charge requires that every time you create a region of negative charge, you must also create a region of positive charge. In other words you must create a separation of opposite charges. The correct term for static electrification is CHARGE SEPARATION. As negative particles are pulled away from the positive particles, equal and opposite areas of imbalance are created. In one place you'll have more protons than electrons, and this spot will have an overall positive charge. Elsewhere you'll have more electrons than protons, for an overall negative charge.
Try adding a humidifier in the store. Adding moisture to the air will reduce / subdue the static discharge.
The law of Conservation of Electric Charge requires that every time you create a region of negative charge, you must also create a region of positive charge. In other words you must create a separation of opposite charges. The correct term for static electrification is CHARGE SEPARATION. As negative particles are pulled away from the positive particles, equal and opposite areas of imbalance are created. In one place you'll have more protons than electrons, and this spot will have an overall positive charge. Elsewhere you'll have more electrons than protons, for an overall negative charge.
Try adding a humidifier in the store. Adding moisture to the air will reduce / subdue the static discharge.
eric stromberg
Senior Member
- Location
- Texas
Or, you could move the store to the Gulf coast. There is so much humidity down here that all we know about static is what we read in books. :wink:
Of course, we have other problems. "You never solve problems, you only trade problems." :roll:
Eric
Of course, we have other problems. "You never solve problems, you only trade problems." :roll:
Eric
peteo
Senior Member
- Location
- Los Angeles
What will generate static is either lack of an equipotential plane or moving air. If the racks are sitting on tile they'll generate a charge from having HVAC blow over them, and there won't be a way to dissipate this charge without equipotential bonding. What's more, sometimes (normally only with energized equipment) an added bonding mechanism or even local supplemental earthing is necessary.
When customers are moving on an isolated surface they'll generate a charge. Relative humidity and to a greater extent moving air will influence the generation of that charge, as has been pointed out. Get that venting moved off my end cap! Very few customers will have shoes which dissipate charge, otherwise I'd suggest changing the floor wax to a more ESD friendly type; realistically not hard to try out once but also not likely to provide much benefit when wearing sneakers.
So IMO you'll need to try a couple things to see what works, step one look at where the air vents are pointing, next look at the displays, then try a different floor wax. In any case, establish whether the racks are bonded to the building structure. May be just sanding will fix this; most every metal coating I've seen needs to be cut through in order to conduct well. For customers who are generating charge, humidity and air movement will affect how well they generate, while ESD mats and/or a different floor treatment will affect how well they dissipate. Note that ESD bonding is always connected using a large resistor, which can and does affect one's perception of charge dissipation.
When customers are moving on an isolated surface they'll generate a charge. Relative humidity and to a greater extent moving air will influence the generation of that charge, as has been pointed out. Get that venting moved off my end cap! Very few customers will have shoes which dissipate charge, otherwise I'd suggest changing the floor wax to a more ESD friendly type; realistically not hard to try out once but also not likely to provide much benefit when wearing sneakers.
So IMO you'll need to try a couple things to see what works, step one look at where the air vents are pointing, next look at the displays, then try a different floor wax. In any case, establish whether the racks are bonded to the building structure. May be just sanding will fix this; most every metal coating I've seen needs to be cut through in order to conduct well. For customers who are generating charge, humidity and air movement will affect how well they generate, while ESD mats and/or a different floor treatment will affect how well they dissipate. Note that ESD bonding is always connected using a large resistor, which can and does affect one's perception of charge dissipation.
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