Self-Fusing Silicone Rubber
Electrical Tape 70 HDT with
Tapered Edge
Data Sheet
1.0 Product Description
Scotch
®
Silicone Rubber Electrical Tape 70
HDT is a high-temperature arc-and track-
resistant tape composed of self-fusing,
inorganic silicone rubber and easy-tear
and easy-strip liner. The 70 HDT product
also has a triangular (tapered edge) profile
and blue guidelines to make half-lapping
application easier.
Tape Features
- PVC
- Low and high-density polyethylene
cross-linked
•
As primary insulation where Class
"H" (80˚C/356˚F) temperatures are
encountered i.e., silicone rubber cables.
As splice overwrap on spacer cable
operating at 5 kV and above.
•
3.0 Data
Scotch 70 Tape has a peak thickness of 20
mils, an edge thickness of 8 mils, and a blue
center guideline. It is available in roll size
in. wide x 30 ft. long. The core is in. I.D.
•
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Excellent track resistance
Excellent arc resistance
Excellent ozone resistance
High dielectric strength
Class “H” material
(80°C continuous operation)
Workable at extremely low temperatures
Excellent conformability
Excellent instantaneous fusion; does not
need to be held down
Matches Sky Blue Gray Munsell
5BG7.0/0.4
Excellent weathering characteristics
AA-5963 Class-I Type-II
As an overwrap for protection of
terminating high-voltage cables against
arcing and tracking. High-voltage
cables with these insulations should be
overwrapped:
- Butyl rubber
- Oil-base rubber
- Ethylene propylene rubber
4.0 Specification
s
Product
The insulating tape must be composed
of self-fusing, inorganic silicone rubber
with an easy-tearing and easy-stripping
polyester liner. The product must be Sky
Blue Gray and conform to Munsell Color
No.5BG7.0/0.4. The tape must be capable
of operating continuously at Class H
temperatures (80°C/356°F). The tape
must be compatible with all synthetic
cable insulations as well as cable splicing
compounds.
E
ngineering/Architectural Specifications
All tape or tape-like terminations which
will be operated either outdoors or in areas
subjected to contamination or moisture shall
be overwrapped with at least one layer of
Scotch Silicone Rubber Electrical Tape 70
HDT.
2.0 Applications
Page of 4
The exposed cable insulation on the lug
side of assembled stress cone kits, which
will be operated either outdoors or in areas
subjected to contamination or moisture,
shall be overwrapped with at least one layer
of Scotch
®
Silicone Rubber Electrical Tape
70 HDT.
All splices on spacer cable operating at 5
kV and above shall be overwrapped with
Scotch 70 HDT Tape.
All splices on silicone rubber cables or
other cables which can operate at room
temperatures in excess of 30˚C/266˚F,
but not exceeding 80˚C/66˚F, shall
use Scotch 70 HDT Tape as the primary
insulating material.
Dielectric Constant
Table 2 shows the dielectric constant versus
temperature of 70 HDT Tape. This test was
run according to ASTM-D-50-8 at a stress
of 50 V/mil and a frequency of 60 cycles
per second.
Dielectric Constant vs. Temperature
Scotch 70 HDT Tape
Temperature
(˚C/˚F)
23/73
90/194
130/266
150/302
Table 2
Dielectric
Constant
3.0
2.9
2.6
2.5
6.0 Performance Tests
Termination Tracking Test
Reduced-dimension terminations are
prepared according to 3M print 2047-B-6
(Se Figure ). Each specimen consists of 8
feet of 5 kV cable and two terminations.
5.0 Characteristics and Test Data
Color
Thickness - Peak
ASTM-D-2148
Thickness - Edge
ASTM-D-2148
Tensile Strength
ASTM-D-412
Elongation at Break
ASTM-D-412
Typical Electrical and Physical Properties
Physical Properties
Munsell 5BG7.0/0.4 Sky Blue Gray
.020 in.
.008 in.
1000 psi
300%
The contaminant employed in this test is the
formula called out in ASTM Dust and Fog
Test D-232, as shown below:
Flint (SiO
2
floated) 240 mesh
Clay 325 mesh
Salt (Na Cl) technical grade
Paper, filter pulp
85 parts
9 parts
3 parts
3 parts
all by weight
Electrical Properties
Dielectrical Strength
ASTM-D-2148
Arc Resistance
ASTM-D-495
Fusion (Self Adhesion)
ASTM-D-2148
Volume Resistivity
ASTM-D-1458
600 V/mil
1 min. (minimum)
0.125 in.
7 x 10
14
ohm•cm
This mixture is then ball milled using 3/4
inch diameter ceramic cylinder. The milled
dust is then mixed with equal parts by
weight of water to make a slurry of paint
consistency.
Next, each termination is carefully coated in
such a manner as to deposit a uniform and
reproducible amount of contamination. The
following procedure is used:
. Mix the slurry thoroughly.
2. Submerge the inverted termination into
the slurry.
3. Withdraw the termination from the
slurry, taking care not to throw off
too much excess slurry in rotating the
termination from the inverted to an
upright position. The majority of the
excess slurry should drain off when the
termination is upright.
Dissipation Factor
Table shows the dissipation factor versus
temperature of 70 HDT Tape. This test was run
according to ASTM-D-50 at a stress of 50 V/mil
and a frequency of 60 cycles per second.
Dissipation Factor vs. Temperature
Scotch 70 Tape
Temperature
(˚C/˚F)
23/73
90/194
130/266
150/302
Table 1
Dissipation
Factor
1.3%
1.1%
0.5%
0.7%
Page 2 of 4
4. Allow the termination to air-dry in the
upright position before applying the
voltage.
This method, when tested on various
surfaces including silicone rubber and glazed
porcelain, has repeatedly produced a coating
thickness of from 0.2 to 0.5 grams per
square inch of surface.
The terminations are then tested in a
contamination building. All terminations are
mounted vertically. The uniform fog rate
called out in ASTM-D-232 is obtained by
the use of special atomizing, wide-angle
nozzles.
An on/off cycle is controlled to give a fog
rate of 7 to 9 milligrams per square inch per
minute.
Each sample is energized at 8.7 kV. The
system is set up such that approximately
500 milliamps trip the circuit breaker. All
samples are recontaminated every seven
days. The new contaminant is applied over
whatever contaminant remains.
The sample is considered to have failed
when:
. 500 milliamps over the surface
continuously cause the circuit break to
trip.
2. Cable failure occurs.
3. The surface of the termination is
severely burned.
The time in hours for each failure is
recorded the results are as follows:
Tape Termination
Protection
No protection
Scotch
®
Silicone Rubber
Electrical Tape 70 HDT
self-fusing
Time to
Failure
15 hrs.
100 hrs. MIN
Page 3 of 4
7.0 Installation Techniques
Scotch
®
Silicone Rubber Electrical Tape 70
HDT should be applied in half-lap layers
using moderate tension.
70 HDT Tape should be applied on all tape-
like terminations which will be operated
either outdoors or in areas subjected to
contamination or moisture. The following
procedure should be used:
If possible, connect the termination to its
final position. Otherwise, take care not to
damage the final overwrap of silicone tape
during installation. Overwrap the end seal
with several half-lapped layers. Overwrap
the entire termination with one additional
half-lapped layer. For upright termination,
begin from one inch on cable jacket and
end at the lug. For inverted termination,
end taping on the cable jacket.
Wrap with
moderate tension (10 to 100% elongation).
Apply last lap with zero stretch. Press down
to avoid endlifting before fusion takes place.
70 HDT Tape can also be applied over the
exposed cable insulation and/or end seal
used in conjunction with molded (slip-on)
stress cones.
Techniques for the proper use of 70 HDT
Tape are contained in standard and special
prints available through the 3M Systems
for Splicing and Terminating Program.
This material may be obtained through
your local 3M Electrical Markets Division
representative.
NOTE REGARDING LINER REMOVAL:
To separate the liner from the tape when
starting a new roll, simply stretch the liner
and tape until the silicone tape breaks. The
liner will then separate at the point.
8.0 Shelf Life
Scotch 70 HDT Tape has a 5-year shelf
life (from the date of manufacture) when
stored under the following
recommended
conditions. Store behind present stock in
a clean dry place at a temperature of 70°F
and 40 to 50% relative humidity. Prolonged
exposure to temperatures in excess of 49°C
(20°F) can cause a loss of fusion in the
tape. Proper stock rotation is recommended.
9.0 Availability
Scotch 70 HDT Tape is available from your
electrical distributor in -inch by 30-foot
rolls.
3M and Scotch is a trademark of 3M Company.
Other trademarks used herein are properties of their respective owners.
Important Notice
All statements, technical information, and recommendations related to 3M’s products are based on information believed to be reliable, but the
accuracy or completeness is not guaranteed. Before using this product, you must evaluate it and determine if it is suitable for your intended
application. You assume all risks and liability associated with such use. Any statements related to the product which are not contained in
3M’s current publications, or any contrary statements contained on your purchase order shall have no force or effect unless expressly agreed
upon, in writing, by an authorized officer of 3M.
Warranty; Limited Remedy; Limited Liability.
This product will be free from defects in material and manufacture for a period of one (1) year from the time of purchase.
3M MAKES NO
OTHER WARRANTIES INCLUDING, BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR
A PARTICULAR PURPOSE.
If this product is defective within the warranty period stated above, your exclusive remedy shall be, at 3M’s
option, to replace or repair the 3M product or refund the purchase price of the 3M product.
Except where prohibited by law, 3M will not
be liable for any indirect, special, incidental or consequential loss or damage arising from this 3M product, regardless of the legal
theory asserted.
Electrical Markets Division
680 River Place Blvd.
Austin, TX 78726-9000
800-626-838
Fax 800-828-9329
www.3M.com/electrical
Page 4 of 4
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