Technical article
March 2014
192
An elongation percentage was measured
15 minutes later. After that, the load was
removed. After the temperature of the
oven was restored, the test pieces were
removed and cooled down to room
temperature. An elongation percentage
was measured again. Test results are
judged as acceptable if an elongation
percentage under load is lower than 100
per cent and if an elongation percentage
after the removal of load is 25 per cent.
3.2 Heat Deterioration Properties
An insulating tube-shaped piece and a
sheath tube-shaped piece were cut out
from a cable. The time when an elongation
residue percentage had reached 50 per
cent at each deterioration temperature
of 180ºC, 158ºC and 136ºC was verified.
Judging from the Arrhenius curves of
these three standards, the temperature at
which an elongation residue percentage
after 20,000 hours of deterioration had
reached 50 per cent was verified. Test
results are judged as acceptable if the
above-mentioned temperature is higher
than 120ºC.
3.3 Single Vertical Combustion Test
A single vertical combustion test was
performed in conformance to the
IEC60332-1-2 standards. A 60mm sample
was burned with a specified burner so
that the lower part of the sample was
ignited for 60 seconds. After the flame was
detached, the sample was left unattended
until the flame was extinguished by itself.
After the extinguishing was completed,
the upper edge of a carbonised length
was measured from the upper part of
the sample, and the lower edge of a
carbonised length was measured from the
upper part of the sample.
Each carbonised length is judged as
acceptable if it is longer than 50mm or
shorter than 540mm, respectively.
4 Test Results
4.1 Hot-set Test
The results of the hot-set test are shown
in
Table 1
. Judging from the table, it was
verified that this cable has excellent high
temperature heat resistance without the
use of electron beam irradiation.
4.2 Heat Deterioration Properties
Table 2
shows a temperature at which
an
elongation
residue
percentage
reaches 50 per cent after 20,000 hours of
deterioration as determined by Arrhenius
curves. Judging from the table, it was
verified that this cable has excellent heat
deterioration properties.
4.3 Single Vertical Combustion Test
The results of the single vertical
combustion test are shown in
Table 3
.
Judging from the table, it was verified that
this cable has excellent incombustibility
because the spread of fire did not occur in
the upward and downward directions.
4.4 Other Characteristics
Other characteristics of the newly
developed cable are introduced below.
Figure 1
shows the results of evaluating
the end-strip workability of this cable.
These results represent the observations
of processed portions after stripping
insulators by using a general insulation
stripper.
This
newly
developed
product
is
structured of two layers: insulation and
sheath. Any moustache-shaped burrs were
almost not observed even after the two
layers were processed at the same time.
It was verified that these two layers had
been stripped without problems.
In addition, the results of evaluating the
bleed characteristics of this cable are
shown in
Figure 2
.
Developed wire
Test
Required
Developed wire
INSULATION
Hot-set test at 200º for 15 min
Under load of 20N/cm
2
(%)
100>
30
After unloading (%)
25>
3
JACKET
Hot-set test at 200º for 15 min
Under load of 20N/cm
2
(%)
<100
29
After unloading (%)
<25
4
Test
Required
Developed wire
INSULATION
>120
121.2
JACKET
>120
121.9
Test
Required
Developed wire
CABLE
Vertical flame spread resistance
Length from top of cable to point of
ending carbonisation (mm)
Length from top of cable to point of
starting carbonisation (mm)
>50
<540
370
510
▲
▲
Table 1
:
Hot-set test
▲
▲
Table 2
:
Thermal endurance properties
▲
▲
Table 3
:
Single vertical combustion test
▼
▼
Figure 1
:
End strip workability
