With more than 50 years’ experience in the local and international flooring industry, Denver Coleman, Chairman of Polyflor SA, answers questions posed by installers, architects and readers on their flooring challenges.* In this issue, he discusses static dissipative and static conductive flooring.
“I often hear people talk about Static Dissipative and Static Conductive flooring. Please can you explain the difference between these two terms?” Michael Cooke, Cape Town.
In order to understand the difference between Static Dissipative and Static Conductive floorcoverings we need to understand what they are designed to do, and why.
The human body can generate up to 30 000 volts in static electricity depending on the type of clothing we wear, the type of upholstery we sit on or floorcoverings we walk on.
This electricity is discharged when we touch a grounding source, and many of us would have felt that discharge when climbing out of a car or touching someone’s hand. This energy discharge, however, is problematic when working with flammable gasses or sensitive electronic equipment and the static charge needs to be dissipated via the floorcovering in a controlled manner in order to avoid damage to equipment or people.
Most types of vinyl flooring claim to be anti-static. This means that they do not contribute towards the buildup of static electricity in the human body. They also do not drain the static charge already built up. High levels of static are generated in dry areas and conditions are much worse inland away from the coast.
The international norm for an electrically conductive floorcovering is that it should have a resistance-to-earth level of between 104-106 ? and an electrically dissipative floor should be between 106-109 ?.
It stands to reason that the electrically conductive floorcovering will drain the static charge more quickly than an electrically dissipative floorcovering as it has lower resistance to earth.
So what is the difference?
Static dissipative (SD) floorcoverings are chemically treated to discharge static electricity and must be used in a controlled environment with a relative humidity of above 40%. Typical areas of use would be operating theatres, computer areas and instrument control rooms.
Electrostatic conductive (EC) floorcoverings contain carbon and discharge static electricity more quickly and can be used in less controlled environs. In controlled environments they would be used in sensitive electrical and assembly areas as well as explosive manufacturing areas.
Electrostatic conductive and dissipative floorcoverings are usually laid on a cement subfloor. Concrete is a poor conductor of electricity, so this type of floorcovering needs to be laid using a conductive adhesive and earthed in order to drain the discharge.
Aluminium or copper tape is laid in the adhesive under the floorcovering and taken to an earth point. Use two earth points in case one fails. For larger areas allow one earth point for every 20m2.
The floorcoverings are available in both sheet and tile form. The tile sizes are 608mm x 608mm in order to accommodate raised access floors. Raised access floors are usually made of steel, so ensure that the legs are earthed.
As a rule, electrostatic dissipative floorcoverings are never sealed. Sealers create a barrier between the floorcovering and the human body and so prevent the discharge. Conductive sealers are available if required.
I recommend that for a problem-free ESD installation the services of a reputable static solutions control company be enlisted in order to do an audit of the premises prior to specification.
If you have any flooring question relating to design, installation, problems or commentary you wish to share with Denver, please e-mail him at firstname.lastname@example.org“>email@example.com with ASK DENVER in the subject line or phone Blythe at Polyflor on 011 609 3500.
*The views expressed in this article are not necessarily the views or opinions of FLOORS in Africa and may not be applicable to all resilient floorcoverings. This article has not been solicited or sponsored by FLOORS in Africa.