108 / 120
Wire & Cable ASIA – September/October 2007
106
11
The acid gas emission test of
IEC60754-1 and/or the indirect
corrosivity test of IEC60754-2 may
be used.
Products meeting the requirement
of less than 0.5% acid gas emission
when tested to IEC60754-1 are
often referred to as “halogen free”.
In some product standards, an
additional test for fluorine content
(IEC60684-2) is required.
Cables having low emission of
toxic gases are generally restricted
to specific applications where
end users have imposed such
a requirement. Such cables are
particularly found in the rail sector.
Users have their own “toxic
emission” standards ranging from
a simple restriction on certain
elemental groups to indices derived
from an analysis of the gases
evolved and weighted according
to the known mammalian toxicity
factors of the gases present.
The lack of general use of toxicity
testing for cables may be explained
by early work carried out in the UK
which concluded that “From this
brief excursion into consequences
it appears that the acidic gas
concentrations likely to cause
harm to people and plant are
similar”
(11,12)
.
Current work
(13)
continues to
demonstrate the large contribution
of HCl to the fire hazard. Some
interesting new work studying the
effect of important irritant gases
on animal lungs
(14)
has also found
that HCl and PVC smoke inhalation
caused an acute effect with a rapid
decline in the lung physiology
parameters.
This work would appear to support
a cable industry position to offer for
particular applications products not
releasing important irritant gases
(ie HCl from PVC compounds) due to the ability of such
gases to hinder escape and damage lungs and reinforce
the position of “acidity” as an “indicator” for important
irritant toxic effects.
The generic description Low Fire Hazard has recently been
adopted by European cable manufacturers to describe
cables incorporating the performance characteristics of
reduced flame propagation and low emission of smoke
and harmful gases.
Although the existing suite of IEC TC20 standards allows
a basic overall approach to fire safety when combining
the various elements (it is common for product standards
to call up IEC60332-3, IEC61034, IEC60754-1 and/or
IEC60754-2), recent developments have been towards a
more integrated approach with test standards that have
the potential to measure flame spread, heat release, smoke
obscuration and combustion gas release.
European Reaction to Fire Classification
for Cables Under the CPD
Of particular importance to the European market is the
development of prEN50399
(15,16)
which is a test standard
based upon the apparatus of IEC60332-3-10 with the
addition of an exhaust duct equipped to measure heat
release rate and smoke production rate. prEN50399 has
been developed to support the classification “Classes of
reaction-to-fire for electric cables” given in Commission
Class Test method(s)
Classification criteria
Additional classification
A
ca
EN ISO 1716
PCS ≤ 2,0 MJ/kg (1)
B1
ca
FIPEC
20
Scen 2 (5)
and
FS ≤ 1.75 m
and
THR
1200
s
≤ 10 MJ;
and
Peak HRR
≤ 20 kW;
and
FIGRA ≤ 120 Ws
-1
Smoke production (2, 6) and
Flaming droplets/particles (3)
and Acidity (4, 8)
EN 60332-1-2
H ≤ 425mm
B2
ca
FIPEC
20
Scen 1 (5)
and
FS ≤ 1.5 m;
and
THR
1200s
≤ 15 MJ;
and
Peak HRR
≤ 30 k W;
and
FIGRA ≤ 150m Ws
-1
Smoke production (2, 7) and
Flaming droplets/particles (3)
and Acidity (4, 8)
EN 60332-1-2
H ≤ 425mm
C
ca
FIPEC
20
Scen 1 (5)
and
FS ≤ 2.0 m; and THR
12oos
≤ 30 MJ;
and
Peak HRR ≤ 60 k W;
and
FIGRA ≤ 300 Ws
-1
Smoke production (2, 7) and
Flaming droplets/particles (3)
and Acidity (4, 8)
EN 60332-1-2
H ≤ 425mm
D
ca
FIPEC
20
Scen 1 (5)
and
THR
1200s
≤ 70MJ;
and
Peak HHR ≤ 400 k W;
and
FIGRA ≤ 1300 Ws
-1
Smoke production (2, 7) and
Flaming droplets/particles (3)
and Acidity (4, 8)
EN60332-1-2
H ≤ 425mm
E
ca
EN 60332-1-2
H ≤ 425mm
F
ca
No performance
(1) For the product as a whole, excluding metallic materials, and for any external
component (ie sheath) of the product
(2) s1 = TSP1200 ≤ 50 m
2
and Peak SPR ≤ 0.25 m
2
/s
s1a = s1 and transmittance in accordance with EN 61034-2 ≥ 80%
s1b = s1 and transmittance in accordance with EN 61034-2 ≥ 60% < 80%
s2 = TSP1200 ≤ 400 m
2
and Peak SPR ≤ 1.5 m
2
/s
s3 = not s1 or s2
(3) For FIPEC
20
Scenarios 1 and 2: d0 = No flaming droplets/particles within 1200 s;
d1 = No flaming droplets/ particles persisting longer than 10 s within 1200 s;
d2 = not d0 or d1
(4) EN 50267-2-3: a1 = conductivity < 2.5 μS/mm and pH > 4.3; a2 = conductivity
< 10 μSmm and pH>4.3; a3 = not a1 or a2. No declaration = No Performance
Determined.
(5) Air flow into chamber shall be set to 8000 ± 800 l/min
FIPEC
20
Scenario 1 = prEN 50399-2-1 with mounting and fixing as below
FIPEC
20
Scenario 2 = prEN 50399-2-2 with mounting and fixing as below
(6) The smoke class declared for class B1ca cables must originate from the
FIPEC
20
Scen 2 test
(7) The smoke class declared for class B2ca, Cca, Dca cables must originate from
the FIPEC
20
Scen 1 test
(8) Measuring the hazardous properties of gases developed in the event of fire,
which compromise the ability of the persons exposed to them to take effective
action to accomplish escape, and not describing the toxicity of these gases
❍
❍
Figure 4
: Classes or reaction-to-fire performance of electric cables