IET logo
 
IET
Decrease font size
Increase font size
Topic Title: Conductive floors.
Topic Summary:
Created On: 20 June 2013 02:58 PM
Status: Post and Reply
Linear : Threading : Single : Branch
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 20 June 2013 02:58 PM
User is offline View Users Profile Print this message



BRIANINBLACK

Posts: 30
Joined: 19 August 2009

What is the difference between them and anti static floors and how do they work??
 20 June 2013 03:20 PM
User is online View Users Profile Print this message



AJJewsbury

Posts: 11285
Joined: 13 August 2003

Not sure what you mean by a 'conductive floor' - to my mind that's just a floor made of steel or similar (industrial mezzanine kind of thing). Anti-static stuff usually has a fairly high deliberate resistance included in it (a Meg Ohm or two) so static will still drain away, but it doesn't significantly increase the shock risk.
- Andy.
 20 June 2013 03:28 PM
User is offline View Users Profile Print this message



BRIANINBLACK

Posts: 30
Joined: 19 August 2009

A conductive floor is a floor made up of a resin that when tested to earth has a value of around 20k ohms, tested at 100v. I think it's function is to drain away any voltages that we may not be able to feel, but can damage certain electronic equipment.
 20 June 2013 04:00 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19465
Joined: 23 March 2004

Conductive flooring and anti static flooring are esentially different ways of achieving the same static disapative effect.

It depends on what you are protecting but generally an antistatic regime would be where you want to control the energy in a static discharge to a given level.

Conductive regimes would be used where you want much lower values of discharge energy.

So for explosives as an example, you would use anti static where you could tolerate ignition energies above 1mJ - you would use conductive regimes for ignition energies of a much lower magnitude.

In both cases you would have direct earthing to a grid below the flooring system - and because of the increased hand to foot shock risk, RCD's are present on every circuit.

To determine which system to use in a particular application, you need knowledge of the charging current and the dissipation current - so to keep potentials low (less than 100V) then you would be looking at say 2.5microjoules for a typical 500 picofarad person. Ohms law says that the floor needs to be around 1 megohm.

So conductive flooring regimes (coupled with appropriate clothing and heel grounders in footwear) would tend to a floor resistance below 100kilohms

For antistatic, the flooring restance needs to be about 50 kilohms or above, and result in a slow but fairly continuous static discharge from persons etc walking on it.

For each type of system control of the environment RH is critical - never below about 40% RH for antistatic and about 70% for conductive systems - and you need to be very careful about what "insulators" you allow in the space - a good knowledge of the materials surface resistance at a particular humidity is critical - electrostatic charging occurs at material surfaces. Basically it's why we see far more static problems in winter when cold outside air is warmed up, the RH drops and the surface charge on materials increases

So as Andy mentioned, conductive systems are more conductive than antistatic systems, to allow dissipation to occur at lower charging energies whilst not being truly conductive.

Determining which type of system to deploy can be a real issue - and the relevant analysis and calculations can get very complex very quickly - so rule based approach is more usual.

Regards

OMS

-------------------------
Failure is always an option
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.