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To achieve the electrical specifications for the static control
(esd) flooring materials you have selected
your floor must be properly grounded. Proper grounding runs the full
gamut from simple to technically challenging. Static control floor
grounding techniques are important in even the
most basic of environments and
critical in
protected electronic manufacturing environments, explosive,
ordinance and munitions environments.
At United SCP, we are specialist in grounding your
static control floor to a multitude of requirements from basic
to advanced to critical. When contracting requirements dictate
(as in the case of FAA and Ordinance installations) we work exclusively
with Ahrens Construction of Nevada to provide full building grounding,
full perimeter grounding and equiplane full copper sheeting
underlayments beneath our esd floors. Although grounding your esd floor is imperative, most
installations now dictate a relatively basic grounding method due to
recent advancements inherent in the new higher conductivity adhesives.
This basic method is now generally adequate in achieving an installed
electrical RTG (resistance to ground) close to the center of the
flooring systems electrical conductivity range. We generally
supply (at no charge with your flooring order) a quantity of grounding
hardware appropriate for basic grounding in non-critical standard
environments. The quantity of grounding hardware we provide is for
use with installations utilizing one of our conductive adhesive to concrete substrates. All of our
ESD flooring materials are designed to work in conjunction
with our permanent one part, water based acrylic liquid conductive
adhesive (US C 2000), our
unique releasable adhesive "Tape" (URAS),
or our NEW US C2004 R
Liquid
conductive releasable adhesive. All adhesives provide
reliable anchoring of the flooring, as well as a equiplane of fairly
high, permanent conductivity (typical between 1.0E02 and 1.0E04) allowing equalization of electrostatic potential for subsequent
elimination via ground straps placed into the adhesive and
beneath the esd floors.
Your goal when grounding any esd floor is to provide a reliable,
long lasting mechanical
connection from your ESD flooring and adhesive to a dependable earthed electrical ground
in your building and to come as close as possible to the lower middle of the
materials specified resistance to electrical ground.
A variety of substrates may be covered
with esd flooring. Non conductive (insulative) substrates will somewhat
alter the
conductivity of certain flooring, more so with static dissipative
materials like ElectraFloor
Static Dissipative (that rely mostly on the ambient
humidity in your environment for conductivity) than
conductive flooring like our
UltraStatic ESD control Tiles
(that are non humidity dependant). When covering wood, standard VCT
or epoxy substrates additional grounding straps may be required. It's always
best to "check RTG as you go" when encountering highly insulative
surfaces and adjust the number of flooring grounds accordingly.
Conversely, concrete surfaces, devoid of sealers and finishes are inherently
conductive. Although concrete's conductivity will fluctuate dramatically
(depending on the ambient humidity of your environment and the moisture
content of the concrete) it will always have areas of conductivity, helping to make grounding of your esd floor relatively easy. Our experience has shown that with the static conductive
or dissipative non-humidity dependant
esd vinyl's and carpeting, covering a cement substrate, only one ground per
2,500 SF is
normally required. When covering insulative substrates or
when working with humidity dependant esd floor covering materials 1 ground per
1,000 SF
will provide the best results. Always use a minimum of 2 ground
points, even in small installations
Method 1A) Copper foil tape method. One of the most popular methods of grounding is
to locate an AC electrical outlet, turn off the power to the outlet.
Place 12" of our 2" heavy duty foil into the wet adhesive
(directly beneath the outlet), place conductive adhesive over the
pre-placed strip (for subsequent covering with the esd flooring). Extend the
remaining 12" up the wall (double sided tape or a dab of adhesive
placed on the back of the strip can help hold the strip
securely to the wall). Carefully remove the face plate cover of the
outlet and loosen the bottom of the electrical plug from its wall
retainer. Most electrical outlets have 2 small "ears" at the
bottom of the outlet that facilitate as a flush mounting stop. Carefully
remove the center screw (between the ears) and run a section of the
copper strap behind the ears (trim as required). Replace the screw, going through the copper foil and pulling the outlet back flush with the
wall. Replace the face plate cover and test strap for electrical
resistance to ground. For esd floor grounding purposes a reading
below 1 ohm resistance to electrical ground is sufficient.
Method 1B) Aluminum foil grounding tape is now
highly recommended for use by United SCP.
1) Locate
AC power outlet. Remove electrical face plate cover (typically
plastic). Starting at a location about ½” beneath the outlet cutout (on
the drywall) run a piece of our 2" wide
aluminum foil ground tape down wall and onto floor about 2 or 3
inches. Note: for a great looking attachment cut any wall base, peel
back base and run strip behind re-glued base.
2) Run
another aluminum foil strip (about 36” long piece) over this 2" or 3"
piece that you've placed on the floor. Run this strip parallel to the
wall and stick to the concrete.
3) Cover
this strip with conductive adhesive and install flooring as recommended
4) Replace
plastic AC electrical face plate cover with a metal face plate cover
making sure metal face plate cover contacts the aluminum strip.
5) Your
floor is now grounded.
Method 2) Another popular method of grounding an esd
floor utilizes the same quantity and type of esd copper or aluminum foil. In
method 2 the foil may be terminated where convenient. With
approximately 8" of the copper foil placed into the wet adhesive and 8" running up the wall
to a heavy gauge copper grounding bus terminated to the building AC
electrical ground via electrician installed cabling.
Method 3) Useful on large
floors or floors where an ac outlet or grounding bus is not available
relies on the use of steel columns, water pipes and other permanently
grounded structural items for grounding terminations. First, check
the electrical resistance of the item, clean connection point as needed
to achieve <1ohm between item and AC electrical ground.
Permanently attach copper or aluminum strip (see drawing 2).
Figure 1
1:
conductive adhesive, prior to covering with esd flooring
2: copper or aluminum strip 1 to 3 feet
3: copper or aluminum strip "pig tail" (going up wall)
4: Pig tail terminated at electrical outlet, grounding bus or multi
point.
Figure 2
In this sketch a
steel column (1) is used as (2) an attachment point for the copper or
aluminum strap
subsequently placed in (3) wet conductive adhesive prior to covering
with (4) esd flooring.
- In all methods listed above the
copper strip is placed into the wet adhesive. A second coat of esd
conductive adhesive is typically applied over the strap prior to
installing flooring overlayment. Make sure to roll vinyl securely
in place over strap using 100# flooring roller. If using aluminum
foil ground tape simply place the aluminum foil onto substrate and cover
with conductive adhesive. See
http://ultrastat2000.com/esd_ground_tape.html for details.
 INSTALLATION AND USAGE OF COPPER OR SILVER GROUND GRID
In some situations a conductive foil ground grid is installed
on the substrate prior to application of the conductive adhesive.
Our 2' wide by .002 thick, adhesive backed (liner covered) esd
grounding foil works great for this application (if required by your
internal specifications). This is a common procedure for FAA
control towers and the Military. Attach grid per internal
specifications. Note:
with the use of the new higher conductivity adhesives and advancements
in the manufacturing of esd flooring this method generally will neither
increase nor decrease the electrical consistency or conductivity of your
flooring's resistance to ground.
Our conductive
adhesive backed
grounding foil is supplied in roll form and is convenient for
pre-placing any required grounding grid beneath your ESD flooring
material. The foil is subsequently attached to
multiple permanently grounded objects (such as those listed above).
To apply, sweep or vacuum substrate to remove loose dust and debris. Remove
the adhesive liner (backing) from the Foil and press firmly in place on
substrate. Gently pull tape as you unroll (to keep from puckering),
smooth the tape in place with foot or towel. The tape may be attached to
ground by simply (with liner removed), running the tape up (or on) the
permanently grounded object, however this will typically not meet our
<1ohm RTG as the tapes adhesive is not conductive. Better results
may be obtained by placing a 2" wide foil strap over convenient
sections of the adhesive covered grid and attaching as shown in methods
1,2 or 3. To achieve ultimate contact between the
grid overlayment center punch as shown. Test the grid for
electrical resistance to ground making sure to achieve
< 1
W
AC Impedance from any
given point.
Large floor, <
2 W AC Impedance
Center punch
GROUNDING FAA AND CANADIAN FORCES AIR TRAFFIC
CONTROL TOWERS
Air Traffic
control towers present many variables in grounding and covering.
This photo shows a plywood substrate primed with latex and "floated" with a
sanded, cementious underlayment and subsequent placement of
grounded foil
grid.
Air traffic control towers generally have
a combination of flooring substrates that must carefully be taken into
consideration when grounding and covering with esd flooring. The
majority of the substrate will typically be plywood with smaller access
panels made from steel. In most cases (especially older towers)
height differences, protruding and loose nails and excessively worn wood
substrates will necessitate the use of a latex primer and subsequent
application of a cementious underlayment prior to
grounding. The use of these underlayments and the fact that the
majority of the substrate is highly insulative and highly
conductive can present unusual variances in final resistance to ground
measurements of the applied flooring. To help alleviate potential
"hot and cold" electrical resistance readings in your finished floor we recommend the placement
of a copper foil grid (center punched at intersecting grid points) and
tested after attachment to approved grounding terminations, (typically
the multipoint equipment ground). This grid
should post < 1 W
AC Impedance to said grounding terminal at
any point tested.
In the Works EQUIPLANE GROUNDING
equiplane grounding INSTALLATION AND USAGE
OF FLOOR GROUNDING PLATES:
These plates are generally indicated if
flooring installers have NOT installed your floor grounding system
properly; The termination wires present an employee tripping hazard and
the addition of the plates present a long term nuisance when polishing
and cleaning. US ESD Floor Grounding Plates
(PN: US G109B) are manufactured in a 6" wide X 4.00 heavy gage stainless
steel. These devices are supplied complete with a conductive adhesive
backing and heavy gage test lead wiring terminated with a #10 ring
terminal. The
plates are designed to be placed on top of ESD flooring materials
and attached to flooring by removing the adhesive liner (on the
underside of the plates) and pressing firmly in place. The attachment of
ground terminal wire (#10 ring terminal eyelet) to center screw of AC
electrical face plate cover is compliant with most state and local codes
and provides a good mechanical connection of flooring to the electrical
grounding system of your building .
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