Questions & Answers

Add conductive drag chains and casters to materials and carts to ground them to esd flooring.

The photo to the right shows a recently completed Conductive Vinyl tile installation. This client plans to use "wire shelf carts" to move electronics assemblies around the floor. Even though this floor is grounded and conductive, the cart will not be grounded as its wheels are insulators. Static cannont drain through an insulator even if that insulator is resting on an esd, anti static floor. The cart shown in the photo does not have a conductive drag chain or conductive casters. Adding conductive wheels or drag chains to the cart provides a path for charge in the cart to drain to ground, in this case the conductive floor.

A chain is only as good as its weakest link. In an electrical chain, a weak link creates a breach in conductivity. A loose or disconnected wire is the simplest example: If a wire is loose or a cord is unplugged, the chain ends; the electrical current does not reach its intended target. With static control, the idea is to discharge the built-up (static) electrical current to ground. A person can wear a wrist and/or heel strap and sit on an ESD chair, but if the floor cannot discharge the static generated by friction-walking across the floor, moving in the chair-the charge cannot flow to ground. It has no way to get there.

Remember: a static charge cannot discharge through plastic or other electrically insulative flooring materials.

Think of a person's body as an isolated conductive object (AKA a capacitor) capable of storing static electricity. Kind of like a two-legged Van-de-Graff generator. When the static-charged person approaches and then sits in the conductive chair, the static charge on the body immediately flows to the chair-until both the body and the chair share the same charge. We call this sharing potential.

An electrical charge can flow only between conductive objects. Since the floor is non-conductive, the charge remains static. In the scenario you have described, the chair and the person remain ungrounded because they are isolated from ground. There is no conductive path through the floor. If either the person or the chair make contact with electronic equipment - both will discharge to the equipment simultaneously. Without a conductive floor, a conductive chair is nothing more than another charged body looking for a place to discharge. Kind of like an accident waiting to happen.

What you're really asking is this: how do I ensure continued conductivity across the static control floor? The answer must involve your choice of static control flooring.

First, there are several different types of static control floor covering. All possess different properties and some of the floor coverings have limitations. For example, Armstrong manufactures a product called SDT. Armstrong SDT requires special waxes to make it perform. Some antistatic broadloom cannot be grounded at all because it is not conductive.

Staticworx® vinyl tile is a permanently conductive material that requires no special care to remain conductive. Waxes are not needed. Our vinyl tiles can be grounded using a simple 24 inch long, 2 inch wide, copper strip under one tile. We provide the strips as part of our package. The other end of the strip is attached to an electrical outlet using one of the screws in the outlet box.

Only one ground connection is needed per 1000 square feet. The other tiles are bonded via our conductive pressure sensitive adhesive-GroundTack-which contains conductive coated fibers.

Questions about the differences between what we commonly call “antistatic carpet” versus “permanent static control carpet” (also known as ESD carpet) usually get raised at some point in every project. The distinction is critical. Numerous flooring products are bought with the belief that they are antistatic when in fact - they often are, or become, static generators. When that misapplication involves the choice of flooring for common office space or a hotel lobby, it’s no big deal. But if the flooring is for the command center of a public utility or the server room for a stock exchange, not understanding the technical differences can be catastrophic.

In order to answer this question clearly there are a few pieces of information you’ll need to know.

Never rely on the AATCC-134 specification to judge a floors' static control protective properties. To protect electronic devices and equipment, static control floors must:

1. Be antistatic - the floor must prevent the generation of static electricity
2. Be capable of being grounded. A ground wire alone does NOT ground the floor. The ESD flooring material must be made with conductive elements such as carbon, carbon fibers or other conductive materials
3. Must have permanent static control properties - independent of environmental conditions such as temperature or humidity.
4. Be traffic-resistant — traffic and chair castors should not diminish the static control performance of the floor.
5. Perform without the need for special maintenance procedures such as waxing, spraying or buffing with antistats.

Conductive properties are easily measured with simple, inexpensive ohm-meter.

Random static discharge will wreak havoc inside your data or call center causing lost or corrupted data, dropped calls, pc lockup and blown headsets. Designers of 24/7/365 mission critical spaces such as data centers, 911 call centers, command centers, server rooms and flight control towers routinely design their spaces to withstand external threats such as weather, power outages, earthquakes and, in some cases, even biological threats. An invisible internal threat that is sometimes overlooked, electrostatic discharge (ESD) can wreak havoc inside any mission-critical space. Dropped calls, blown headsets, PC lockup and lost or corrupted data represent just a few of the problems.

Although we appreciate your interest in our epoxy ESD flooring, we need to caution you about the limitations of static dissipative or conductive epoxy coating in a data center/server room application.

All ESD coatings are formulated to eliminate static build-up by providing a ground path. The ability to be grounded is achieved by adding either conductive fibers or carbon and graphite particulate. The fibers and particulate enable us to create an electrical bridge through a material that otherwise, is an insulating static generator. However, conductivity is the only static control property provided by a coating. The coating is not antistatic. In other words, ESD coatings will only eliminate static if they are used in conjunction with special static control footwear. If people walk on them with standard footwear (dress shoes, sneakers, hiking boots etc.) the coating will neither prevent the generation of static nor remove the charge after it is generated. You would still need to bridge the electrical gap between your body and the floor by wearing special footwear special. Walking on any ESD coating in street shoes would be the same as walking across a sheet of plastic. The result would be the generation of thousands of volts and an increased likelihood of an ESD event!

In data centers we recommend the following conductive materials:

1. Conductive rubber that also has anti-static properties.
2. Conductive vinyl tile with anti-static properties.
3. Conductive carpet tile with anti-static properties.

We often supply floor finishes for use on soiled ESD vinyl sheet flooring. The application of a polish or finish usually becomes necessary a few months after installation; as you probably know, when vinyl ages and is exposed to foot traffic, it becomes porous and begins to collect dirt. A good ESD polish will re-seal the pores without hurting the static control properties of the floor.

Additionally, if the flooring in the MRI suite is only static dissipative and not a conductive product, it would not be unusual for people to generate static when they walk on that floor with ordinary footwear – as opposed to special static footwear. Keep in mind, a person would not even realize they were generating charges because it takes at least a 3500 volt zap before the human body can sense a static discharge. The electronics inside MRI equipment is sensitive to a lot less than 3500 volts – hence the reason for installing the ESD floor in the first place. The static control coating would deal with that problem as well.

If you encounter flooring applications for these types of areas in the future, we strongly recommend installing 2 layer Staticworx® EC Rubber. A recent study done by MIT demonstrated the near impossibility of generating appreciable amounts of static on 2 layer rubber – no matter what footwear was worn. As a comparison they measured fewer than 200 volts on rubber versus over 3000 volts on the dissipative vinyl. And because 2 layer Staticworx® EC Rubber flooring is plasticizer-free, it presents none of the maintenance issues associated with vinyl.

From a purely technical perspective, a floor’s ESD properties can be evaluated:

1. by measuring the floor’s resistance to ground;
2. by measuring the total resistance ground of the system including the person and the floor;
3. by using a walking test to measure voltage generation on a person;
4. or by testing some combination of the above.

According to the recommendations of ANSI/ESD S20.20, it is acceptable to install a floor with a resistance to ground (RTG) that is =1.0 X10E9. But, to comply with ESD standards, the floor must not allow body voltage generation over 100V.