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Dräger Safety and Schubert Head
Protection Technology rely on head protection
systems made of thermosetting
materials.
The subject of helmets and their heat resistance
is one that is frequently discussed in
practical applications and in the press. In its
risk assessment for firefighters, the CEN
TC162 Joint Working Group / Firefighters'
Personal Protective Equipment defined
three areas of work:
- routine work
- hazardous environments and
- emergency situations.
The data is based on studies that have been
verified many times worldwide. One of
the best known results of relevance and
practical use is N. Hoeschke's table from
the “Fires” project. These tests, in which
NASA was involved, were initiated and
conducted in the USA in the early 1970s
with a view to improving protective clothing
designed to be worn by firefighters.
Such tests clearly illustrate the range of
temperatures which a firefighter is confronted
with in their daily work. What is more,
they make clear the need for fire helmets
to provide effective protection to the wearer
not only during routine work, but also in
all hazardous environments and for short
periods at the sort of temperatures which
occur in emergency situations.
The helmet test of the German Federal
Association of Accident Insurers (BUK),
conducted in cooperation with the German Association of Fire Brigades, also revealed
shortcomings as regards heat resistance
and response to fire exposure in many of
the fire helmets available on the market at
the time. This served to trigger another
long overdue discussion of what the right
material for fire helmets is.
Joint helmet development
In cooperation with the company Schuberth
Head Protection Technology Braunschweig,
Dräger Safety started work in 2002 on
developing two new helmets for use by fire
services.
The declared objective was to design a
new head protection system offering full
all-round safety for fire and ermergency
services. The outcome is impressive:
the Head Protection System – known as
the HPS – meets not only all the relevant
requirements for safety, but also offers
additional protection and a high degree
of comfort. Strategic partners Schuberth
Head Protection Systems and Dräger
Safety have launched a series featuring the
Dräger HPS 6100 and Dräger HPS 4100
models – two premium class head protection
systems.
Half-shell helmet
The Dräger HPS 4100 is a classic half-shell
helmet, the kind which has been popular
in Germany for many years and other countries,
e.g. Sweden. The helmet shell of the
HPS 4100 is made of HighTemp fibre, a
glass-fibre-reinforced, thermosetting synthetic
resin. This material, featuring a specially
developed resin system, offers among
other things outstanding resistance to low
and high temperatures. The helmet's design
is based on the PASGT shape (Personnel
Armor System for Ground Troops), the
proven military helmet shape in broad international
use. The basic concept proved a
success, the helmet's excellent functionality
being combined harmoniously with practical
comfort. The maximum weight of the helmet
is 950 grams (in size 53-61).
The helmet features a four-point strap
system with a neck strap made of flameresistant
Aramid and a Nomex inner lining
which can be removed and washed in the
interests of hygiene and straightforward
decontamination.
Two adapter slots make for easy fitting of
the visor, which is made of a special polycarbonate
material for better vision and can
be locked in three different positions. An
extensive range of accessories completes
the Head Protection System. The Dräger
HPS 4100 is available in the sizes H2 (53–
61 cm) and H3 (59–64 cm).
The photo-luminescent helmet conforms to
DIN EN 443: 1997 inclusive of all options –
40 °C, 14 kW/m2, and E2 and E3 (other
colours are available upon request).
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The Dräger HPS 6100 follows the proven
concept of a full-shell helmet with the familiar
Supra system, which is fully backwards
compatible. It is also based on the high-performance helmet shell technology featuring
the thermosetting material.
The helmet shell is designed to allow the
use of a radio or telephone, so the wearer
does not have to make the impossible
choice between communication and safety.
The integrated, scratch-resistant visor
(DIN EN 166) can be stowed in the helmet
shell in one quick movement when it is not
needed. The front section of the HPS 6100
offers plenty of space for national emblems,
station identification, rank badges, and
frontshields.
The flame-resistant and washable Nomex
inner lining comes as standard and is likewise
easy to replace and decontaminate.
Special additional options are available to
increase wearing comfort, and the full range
of accessories offers just about everything
one could possibly need.
The development of both helmets drew on
the expertise and latest research of two
technology leaders in the field of “head
protection and respiratory protection”:
Schuberth Head Protection Technology
from Braunschweig and Dräger Safety from
Lübeck.Safety, heat resistance and comfort
are combined in the new design of the
HPS 6100. For the first time, Dräger chose
not to use thermoplastic materials in either
helmet, opting instead for the much higherperformance
thermosetting material – a
decision which clearly improves safety
levels for the firefighter.
Thermoplastic materials
Thermoplastic materials such as polyethylene
can, as the name implies, be repeatedly
shaped by applying heat. Even at temperatures
of 100 °C, components made of
this material may in some cases lose their
rigidity of form, while properties the material
possesses when cold change very
significantly upon exposure to higher temperatures.
At temperatures of between
200 and 250 °C, the material's impact and
penetration resistance is greatly reduced,
and at 250 to 300 °C thermoplastic materials
start to become liquid.
If a thermoplastic helmet is used for firefighting
purposes – where temperatures of
250 ° Celsius are by no means uncommon
– the helmet will not be able to withstand
the sort of stress applied in impact and
penetration tests. In the summer of 2000,
studies conducted by the TNO Institute in
Eindhoven in the Netherlands arrived at
precisely these conclusions. Given such
unambiguous findings, therefore, it is surprising
that fire helmets made of thermoplastic
materials continue to be supported,
sold and indeed worn.
Thermosetting materials
Thermosetting materials like glass-fibrereinforced
plastics are composite materials.
They are created by using heat and pressure
to join together two different components
which can only be shaped at an intermediate
stage of their processing. In their
final state, they are changed irreversibly to
a hard rigid form and will not soften even
when exposed to high temperatures.
Consequently, at very high temperatures,
no thermoplastic helmet (even if fibrereinforced)
can offer anything like the
mechanical resistance of a helmet made
of a thermosetting material.
Taking account of all facts relating to the
properties of the helmet materials currently
available on the market, the obvious choice
must be to use a thermosetting material.
Does in fact any realistic test exists that
reflects the actual conditions faced during
firefighting applications?
Besides other test the so-called “Nordtest”
has been conducted in Scandinavia since
the beginning of the 1990s (Personal Protective
Equipment for Firefighters Complete Suit Test in Hazardous Conditions).
During the Nordtest, the test subject – a
fully trained firefighter – has to undergo a
test course under controlled yet realistic
firefighting conditions in a container specially
designed for the purpose.
Inside the container the average temperature
at 1.20 m is 250 °C, with temperatures
reaching as high as 320 °C at a height of
2.20 m. Under these conditions, the test
subject, who is also fitted with numerous
temperature sensors on his skin, has to
perform various tasks within the space of
five minutes. The temperature measured
by the sensors must not exceed 47 °C at
any point during the exercise. This limit
corresponds to values ascertained during
the course of clinical trials and has been
found to be the temperature above which
the body's core temperature rises to a dangerous
level, causing probable harm to the
health of the test subject.
Under these test conditions, the insulation
values for every part of the firefighter's protective
clothing can be ascertained and
proven by scientific means.
Both models – the Dräger HPS 4100 and
the Dräger HPS 6100—have been subjected
to this test and obtained excellent
results:
- Dräger HPS 6100
very good temperature measured by the
head sensor: 39.1 °C after 5 minutes.
- Dräger HPS 4100
very good temperature measured by the
head sensor: 38.7 °C after 5 minutes.
If these findings are applied to the “tried
and tested” aluminium helmet, which still
continues to be used today, its protective the temperature on the dummy test head
had reached in excess of 55 °C after just
five minutes, despite the head being fitted
with a flame protection hood conforming
to prEN 13911. By the end of the required
20 minute exposure period, the temperature
had reached nearly 100 °C – a result
that speaks for itself. However, as if this
wasn't enough, the aluminium helmet also
failed to perform well in the following areas.
The shell of the aluminium helmet
- conducts an electric current
- has high thermal conductivity
- offers a low penetration resistance
- offers no protection against dripping liquid metal (see photograph above) and
- has poorer impact absorption properties.
Bearing in mind all the currently available
knowledge and tests conducted on the
various helmets of different manufacturers,
the only possible conclusion is that neither
aluminium nor any thermoplastic material
can be regarded as the material of the
future.
In the new draft of the EN 443 standard,
forward-looking aspects of safety are discussed:
- General requirement for radiant heat flux
to meet the higher option of 14 kW/m2
- Extension of radiation exposure from
three to eight minutes.
- Additional tests for impact absorption
and penetration using a sharp-edged
falling object within 60 seconds
following exposure to heat for a period
of eight minutes (14 kW/m2).
- Testing of the helmet response to flame
exposure based on the flame engulfment
test specified in DIN EN 137
The only way to ensure completely reliable
personal protective equipment is to use
the mask-helmet combination. When purchasing
such products, it is essential to
ensure that they are approved in accordance
with the vfdb [Association for the
Promotion of German Fire Safety] guideline
08/02:2002-11. Appendix A of guideline
08/02 contains binding requirements for
the design and testing of mask-helmet
combinations for use by fire brigades and
stipulates practical performance testing to
be conducted by the Professional Fire
Brigade of the City of Essen – the authority
responsible as agreed by Germany's federal
states.
In Germany, testing of the mask-helmet
combination in accordance with EN 136 –
the so-called leakage requirement – is not
sufficient.
At the present time, no European Standard
exists for mask-helmet combinations due
to the fact that the member states have as
yet been unable to agree on a standard.
In Germany, the vfdb guideline is and remains
the standard most relevant to safety
and, in conjunction with a helmet shell
made of thermosetting material, represents
the non plus ultra in helmet safety.
Christian Jährling
Dräger Safety AG & Co. KGaA
Stephan Rode
Schuberth Head Protection Technology
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Dräger Safety AG & Co. KGaA |
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Revalstrasse 1 |
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23560 Luebeck, Germany |
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Tel +49 451 882 0
Fax +49 451 882 2080
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