Forklift Operators Get Static Shock at Elevator Pendant

PW, I give you this GA because it is the only answer here that make sense.

To measure electrostatic charges there are special very expensive electrometers.

Victoreen and Keithley made these. Electrostatic charges occur when materials with high specific isolation resistance are used. To pick up some out of the OP's comment:

Dry air, Epoxy floor, Paint on the forklift, dry skin of the driver, cushion of the forklift, your forkflift tires, that for epoxy are also probably of a special material, otherwise they ruin the floor with black tire marks.

You can make a cheap electrometer yourself with a flat glass bottle, a cork, a metal pin as sensor and 2 strips of aluminum foil. the two strips and the sensor go in the botlle and when electrostatic charges occur the 2 alu strips come apart from each other on the free end. Use your imagination or try to find maybe a U tube presentation?

As long as the driver and that handle are not on the same electrostatic charge level there will be a equalisation of the charges, or a discharge.

Note that these charges occurs only on isolators and in dry air. Conductors almost have no electrostatic charges. They can only distribute them.

Other than bringing the charges, or the discharge together through the innocent hand of the dry driver, can be a metalized plastic guirlande, like used on the Christmas three around the neck of the driver, towards his hand.

That way he will not feel it anymore.

Discharging everything to your epoxy floor is also difficult.

You can try to "earth the handle" replace with something non plastic and also the rope.

If it still the same then your floor and air are the culprits.

A synthetic hair poppy is also a good electrometer or the hair on your chest.

Have fun.

Put a plastic bag over the control.......or hand

It'll jump through that like it isn't even there.

What about rubber gloves ?

How thick?

What would you estimate the electrostatic field strength at ?

Because the fork lift is grounded with straps / chains, most likely the static is in the elevator controls pendant, not the fork lift then. The static charge on the control pendant might be getting created when the elevator control cable rubs on something in the elevator shaft, then is discharging through the operator, to the fork lift, to the ground straps.

I think there are devices, old and new, that can show which way the charge is going. Maybe the fork lifts aren't properly discharging through the epoxy. If a person walks up and touches the pendant and gets zapped, there's your culprit.

Epoxies are excellent insulators. The triboelectric effect between them and rubber is also excellent. To accentuate your problem, that is.

You may have to upregulate humidity, that may be difficult. Or install ion generators, the type downregulates all kind of static electricity for static sensitive electronic assembly stations. It is standard for them.

My car zaps me when I get out of it. How about changing the trigger for the lift, maybe a rubber hose on the floor, like the bell ringer from the old gas stations, for old tech, or a high tech proximity switch or an optical switch the operator waves his hand through. Take the static problem out of the picture.

My sister tells me to put a safety pin on the cuff of my pants to ground me to keep the car from zapping me. I'll have to try that!

Just guessing , I have no idea about your plant layout.

Locate a mobile grounded metal brush on a flexible lever, near the elevator door, as the car goes near it , it will discharge.

Maybe to touch it by the car, bottom or both side .

Or a grounded metal strip at the floor , and a conductive rubber in the car.

You can locate the strip , under a thin epoxi cover , so the car´s braking will not move it , and make a good foundation to the concrete floor.

Is corrosion is a fact , use Stain less steel. AISI 416 or any suited to your invorement.

The same rubber conducting strip used on family cars.

Rub a dryer sheet on the seat of the car. Fabric softener is a great anti static material and a dryer sheet is very available. I have used them in the office to help keep from zapping the computers. Modern fabric chairs and clothing create big voltages and fabric softener keeps them from doing so.

The operators say they only get zapped at the elevator (pendants and wall panel controls)
Surely it's easy enought to ground the wall panel control (or check it is grounded).
Everyone seems to be missing that it could be the operators who are building up the static charge rather than the equipment?
Or am I too far out of the box?

Del

As already noted, epoxies are generally very good insulators. This means that your dragging chain has no ground to discharge into. Static-dissipating floor coverings are available; any supplier of industrial floor coatings should be aware of them, and able to supply them. Even if you only repaint the area where the forklifts are when the operator reaches for the pendant - and provide a ground that makes contact with the paint patch - the problem should go away. I worked in a facility building medical electronics, and every floor covering in our building was made to dissipate static charges.

Just for grins: could you spray the pendant cord with anti-static fabric spray, all the way up to where grounded metal is part of its support? You might even run a bare copper wire down alongside the pendant cord, grounded up top, and making contact with the fabric spray for most of the length. End the bare wire above the operator's reach, and sheath it with, say, electrical tape for a foot or two above that point.

Even if you only repaint the area where the forklifts are when the operator reaches for the pendant

GA

To try out this solution tape a piece of grounded aluminium foil to the floor under the point where the grounding straps touch.

When you get the answer, I'd like to know so that I can tell my local supermarket. Whenever I use a trolley, rather than a hand-basket, I seem to get zapped if I touch one of the cabinets. Maybe I shouldn't rush thru the place too fast. I did try dragging a length of chain from my tail, but stopped because I was getting funny looks from people.

Are you sure it's static? Have you opened the pendant to be sure there are no bare wires inside? the control box as well?

Is the pendant grounded to the control box into which it is connected? Is the control box properly grounded?

Sounds familiar; packaging powdered products into poly or plastic lined drums in the winter is another scale killer. We just punched in a ground rod and hooked up the scale bases- that way it tends to miss the load cells etc., as long as the connections are kept clean. This can be a big problem in an EX rated location!

"This can be a big problem in an EX rated location!"

Neither one one of my "EX's" wasn't very well grounded, one little spark from me and they would explode

At the toll booth for our bridge were metal springy rods that contacted every car and truck passing through. That way the toll collector didn't get zapped when he collected the toll. These could be retro-fitted into the factory floor, with a nice ground rod to insure a good discharge, all in the same installation hole.

Install a flat metal bar stock ground plate in front of the elevator that is bonded to the elevator structure and is common attached/bonded to the pendat.

Attach a braided, trailing ground to the forklift body that will contact the ground plate before the lift reaches the stopping location.

Install a metal ground that contacts the forklift operator while they are sitting on the seat.

This will help decrease if not eliminate the buildup.

I realize that, true to form, the person asking for help neglected to give a location, but, I think that the first response #1, is the simplest, cheapest, easiest thing to try.

If that doesn't work, there's a short somewhere and it will have to be lengthened.

Yup, pissing on the floor is cheap...
Del

And saves operators the bother of walking to the bathroom.

The original post contains an indication that this is NOT the answer: "The operators say they only get zapped at the elevator (pendants and wall panel controls) and not at other pendants like roll up doors." It seem highly improbable that the relative humidity differs so drastically from point-to-point in the plant that some pendants are always OK, and specific other ones are not . . .Even if some weather conditions or other factors influenced the RH values, it's hard to see how one area would CONSISTENTLY be so low as to provoke discharges,and all of the other areas would always have higher RH, so much different that static discharges never occur.

To me, that suggests that there's a difference in the conductivity of the floor in those areas just in front of the elevator on both floors.

Our plant is in southeastern Ohio.

There is only one climate controlled room with low humidity and it is not near the elevator, nor does this room have a problem with static electricity.

We do try to keep the plant between 70 and 74 deg F. year round.

It is possible that difference in floor conductivity may be what is causing the static shock problem.. But to correct that by installing Conductive flooring materials onto the immediate area of the elevator, as a static discharge path is going to be a very cost prohibitive. Beside the initial installation costs, there is also the added costs for the continued monitoring and maintenance requirements, just to ensure effectiveness of such solution..

"Instal" (conductive flooring) = "paint, and run a wire in a very shallow groove off to a decent ground." Think: one man, half a day, 1 gallon of paint. "Maintain, monitor" = the operators will tell you if it starts happening again. Someone suggested taping down a sheet of aluminum foil, grounded, to test; that ought to be even quicker - and the plant could leave one level as-is, for direct comparison testing, maybe get fancy and reverse which is grounded and which not, for higher confidence factor. We're talking what, $10 in materials? And the ground wire could be used again elsewhere. or left in place for the floor painting. For permanent installation, run a Skilsaw (r) across the space, with a carbide blade set 1/16th inch deep for grooving. Or wait & do it next time that the floor needs re-coating, and use a ribbon conductor.

I'd give you static about projecting your idea of what is cost-prohibitive onto troyalec, but I'm feeling mellow, so, no charge.

You could outfit your drivers with these snazzy static eliminator watches...

Until you find the source can you install a call chain from the pendant to a location where it would drag on the tow motors charge and equalize any charge? I don't know if sparks are allowed in the area but if everything is at the same voltage at least the operators will stop that funny twitch they developed.

On the other hand if the tow-motors are insulated from the floor you may be building a motorized version of a Kelvin Water Drop generator and charging the tow-motors up to a very high voltage. That in its self would be pretty interesting to try, if the operators hair starts to stick straight out you maybe on track to reducing your electric bill. Let me know if that works.

I tried some "static" testing with my cat and a balloon. I can get the balloon to stick to the wall but the cat keeps falling off. Hey Del do I need a long hair cat for this test?

Not necessarily....

Will some member of ASPCA please sharpen this cat's claws?

If it is the insulating floor, then there are "dissipative" cleaning materials that can be used without modification of the floor. They are used in electronics manufacturing facilities and the like since they don't want insulating wax layers on the floors.

Look up ESD protective surfaces and you will find the cleaning products necessary. They are not expensive and they do work.

If you want to get scientific about it there are ways to test the dissipative properties of the floor to confirm your diagnosis.

By the way, the earlier picture of the cat with styrene attachments would have made a good "caption this" with answers like "preparing for climate change, this cat has increased insulation properties" and so on.