This article related ATEX standard mandatory for suction and filtering systems.

1. 26 XYLON INTERNATIONAL July-August 2006
TECHNOLOGY
Starting from July 1, 2006, in fact, the Atex
standard will become fully effective: it deals
with all the risks related with explosions, any
type, that may occur within a working envi-
ronment. It might not sound very interesting
for our industry, wood is not very explosive
after all... but reality is much different. In the
past three years, when it came to the pur-
chase of a new plant or machine, every
woodworking sector, from the production of
particleboard panels, furniture and plywood
to window manufacturers, small or large
handicrafts companies processing wood
and its derivates had to face the Atex stan-
dards. As a matter of fact, we cannot deny
that, whatever process must be carried out,
hazardous materials are produced or used,
for instance wood dust, or some products
used during the finishing stage, which in a
closed environment may create a potential-
ly explosive mix with air. By July of this year,
the compliance will have to be completed
also on old production plants and lines.
Except particular cases, the working envi-
ronment in woodworking companies is not
ATEX-classified because the dust concen-
tration in the air - even reaching 5 mg/m3,
which is considered as the maximum
accepted, or better tolerated limit for
hygienic reasons - would be well below the
value of explosion risk.
Standard cleaning procedures combined
with chip and dust suction plants - which
are currently compulsory on each machine -
allow to consider these risks as inexistent.
It is useful to point out that nowhere around
ARE YOU REALLY READY
FOR THE ATEX STANDARD?
Some tips, explanations and comments to employers and safety managers
about the compliance of the existing plants in the woodworking industry to
prevent the unpleasant consequences, also penal, listed in the standard.
ATEX directive
and test laboratories
Given the several applications
received, UNI decided to repeat the
course "ATEX - 1999/92/EC Directive -
Plants in environments with explosion
risks”, which was held on March 30 in
Milan, and the course “General require-
ments for the compliance of test and
calibration laboratories. UNI CEI EN
ISO/IEC 17025:2005 standard” was
held in Milan on April 27 and 28, 2006.
Effects of the explosion of non-ATEX sleeve filters.
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2. the world an explosion has ever occurred
inside a woodworking company in the
machining area, even though in the past (and
also today in certain geographical areas)
hygienic conditions were extremely different,
with the presence of dust accumulation and
the frequent absence of suction plants.
For processing machines and lines, the
Atex issue is not considered as significant
and, in fact, in more than thirty European
standards (most of them harmonized
according to the Machinery Directive) refer-
ring to an equal number of machine types,
the risk of explosion has always been
excluded, unlike the fire risk.
The situation is utterly different for suction
plants and in particular closed sleeve fil-
ters, storage bins, dust collection bins,
cyclones, suction units, etc., where the risk
of explosion in a potentially explosive
atmosphere not only exists, but the number
of accidents recorded, even serious,
requires utmost attention by manufacturers
as well as by users in the purchase phase.
Though in general, the environment is not
classified and machines and plants must
not be marked ATEX, to obtain the EC mark-
ing manufacturers must evaluate all existing
July-August 2006 XYLON INTERNATIONAL 27
risks, and in particular the RES 1.5.7 of
Annex I to the Machinery Directive and, as
relates to suction systems, they also have to
consider that the requirements of the spe-
cific directive 94/9/EC are applicable and
prevailing.
The 94/9/EC directive develops the men-
tioned concepts by giving a detailed defini-
tion of “explosive atmosphere” (see table
on page 30) and setting the limits of appli-
cation possibilities to ensure maximum
safety for the machine itself.
The same goes even when the working envi-
Protection systems
These are devices whose function is to block explosions and/or restrict the
affected area, which are separately marketed as systems with independent
operation (not a component). Safety and control systems installed outside
the classified zones are included only when they contribute or are request-
ed for the correct operation according to the risk of explosion. They do not
have to bear the EC marking as long as they can be considered as an inte-
gral part of the device.
Examples:
• Spark detection and extinguishing systems;
• explosion relief systems (explosion-proof devices); extinguishing curtains.
Effects of the explosion on an ATEX-compliant filter.
ronment is not at risk of explosion, but inside
the machine users process materials that
create a potentially explosive atmosphere.
Summing up, users must comply with two
Directives: one is addressed to employers
and deals with safety in working environ-
ments (99/92/EC) where they have to identi-
fy and declare the potentially hazardous
environments for explosions and the corre-
sponding level of hazard; the other (94/9/EC)
requires the construction of machines with
no ignition sources in case they are located
in explosive atmospheres or where potential-
ly explosive materials are processed.
It is therefore up to machine and plant users
to classify the different zones of the working
environments according to the related risks in
application of the corresponding directive.
Such information, which in case must
include precise indications about the exact
place where the machine will be installed,
must be handed over during the purchase of
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3. 28 XYLON INTERNATIONAL July-August 2006
TECHNOLOGY
machines to technology suppliers, who will
then provide the EC marking accordingly.
If the area is classified at risk of explosion,
machines (but also all equipment, electric
or not, located in that environment) will have
to be provided with ATEX marking, in addi-
tion to the usual EC marking.
If, like in most cases, the area is not classi-
fied, yet there is a risk of an explosive atmos-
phere in closed containers, such as in the
components of air intake systems, it is up to
the plant manufacturer to evaluate the risks
of potential explosion generated by the sys-
tem and the necessary corrective actions to
reduce or eliminate them. In case such
actions are not enough and there is still a
‘residual’ risk, it is necessary to adopt pas-
sive or active safety systems according to
the evaluated residual risk of explosion.
The manufacturer, or the person providing
the market with complete plants or
machines used in potentially explosive
atmospheres, will consider that:
- the air-wood dust mix is potentially explo-
sive in a closed environment;
- the explosion features of the mix depend
on multiple physical variables of the
processed product and, after sample analy-
sis, they are evident through Kst values
(pressure increase in the explosion time unit)
and Pmax values (maximum pressure value
that can be achieved by the explosion);
- the obligation to specify in the manuals the
suitability and application limits of their
machines, which may contain potentially
explosive atmospheres;
- the obligation to provide machines with all
active or passive safety and protection sys-
tems - following to risk analysis - which must
be certified by an authorized organization
on behalf of the manufacturer;
- the obligation to specify in manuals the
residual risks of the machine whenever it is
used in complex systems and/or plants;
- for complex systems or plants, the design-
ers or distributors must execute a new
analysis of the system’s risks, carefully eval-
uating the residual risks of each machine
of the system-plant, and applying or sug-
gesting the application of further safety and
protection devices which are certified or
from certified divisions.
- they must be able to prove the existence of
all the documents related to the analysis of
risks and calculations that have deter-
mined the choice of the different protection
and safety systems and their number (for
instance: number of certified passive pro-
tection diaphragms and calculation of the
relief areas).
Effects of the explosion inside
a non-ATEX centrifugal fan.
Centrifugal fans designed
to withstand 0.5 bar overpressure.
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4. July-August 2006 XYLON INTERNATIONAL 29
The manufacturers’ obligations are there-
fore rather heavy and they do not depend
only on the classification of the areas where
the machine or plant will be placed.
Once the compliant plant or machine is
installed, the supplier will hand over an EC
certification where also explosion risks are
considered. But this is not enough for the
purchaser to feel 'at ease' and with no
responsibility, most of all if the non-compli-
ant elements are evident.
Unfortunately, there are suppliers who mar-
ket non-compliant products and have no
scruples in certifying them with an EC-mark.
Whether they are panel, furniture manufac-
turers, joiners or other, final customers are
reassured, yet they are not aware they have
installed a non-compliant plant and they are
also responsible for it.
In some cases we also see an illegal atti-
tude where users of such plants are per-
fectly aware that a highly profitable price
hides a false EC marking by the supplier
and, despite that, they knowingly prefer to
save money and neglect the law obliga-
tions, pretending that...
They do not consider that, if a non-compli-
ant plant, yet EC marked by the supplier,
should occasionally cause an accident or
explosion damaging people or objects, the
responsibility is not only of those who have
Classification of zones
Categories Protection level Zone gas, mist, vapor Zone dust
Category 1 (certification) Very high 0 20
Category 2 (certification) high 1 21
Category 3 (certification) normal 2 22
Values for equipment not used in mines.
ATEX-compliant dust
and sawdust storage bin.
ATEX marking
Table with diagram (see drawing):
ATEX marking (additional to EC) when the machine operates in potentially
explosive environments.
EC: EC marking
xxxx: identification code of the Notified Institute (when necessary)
Ex: Additional Ex marking
II 3: Equipment group and protection category
G/D: Gas/Dust
IP55 T125°C: IP and maximum surface temperature developed
CE xxxx Ex II 3 D IP55 T125°C
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5. 30 XYLON INTERNATIONAL July-August 2006
TECHNOLOGY
light-heartedly, in good or bad faith, sup-
plied the plant certification, but also, if an
injudicious purchase should be proved, of
the owner and user. In fact, it not enough to
have a compliance certificate before evi-
dent law violations or faulty supplies. The
responsibility is also penal and in this case
it also affects the legal representative of the
user company or the safety manager.
So, on one hand, more attention is required
by purchasers during the acquisition of new
plants, on the other hand, it is important that
plant suppliers are able to fully comply with
standards. Purchasers must always make
sure that their supplier has carried out the
necessary calculations, tests and evalua-
tions. With the introduction of the Atex stan-
dards in 2003, in fact, technology manufac-
turers had to revise and adapt their prod-
ucts through studies and research to evalu-
ate the resistance of structures, closed con-
tainers, risks of explosion and propagation
by simulating the explosion inside the
machines they manufacture, to see their
elastic and plastic deformation, resistance
limits till destruction; accordingly, they have
adopted and installed a series of active and
passive safety devices (see box on page 27)
which, in case of accidents, minimize the
damages to people and objects and prevent
the explosion propagation to nearby
machines and environments. As you can see,
the compliance of woodworking plants with
the Atex directives is neither easy nor imme-
diate, and it requires a correct evaluation of
the operations to carry out, quality of actions
and persons in charge. In fact, it is funda-
mental to apply to skilled suppliers who have
already carried out a careful analysis of their
production, checking and comparing it with
the requirements of the standard, and who
are able to guide furniture, panel, window and
product companies by protecting them
against possible future risks.
With this article we hope we can increase
the awareness of the parties involved, users
and suppliers of machines and plants, con-
sidering that three years after the introduc-
tion of the standard on a European scale,
this standard is often totally unapplied! We
Atex compliant dust
and sawdust storage bin.
Atex compliant
passive safety screen.
Definition of Explosive
Atmosphere
• presence of gas, vapor, mist, dust
• mixture with air
• between 0.8 and 1.1 bar
• between -20 and +60° C
• risk of potential propagation
hope to make things clearer, so that many
false beliefs and commonplaces are ques-
tioned, such as the widely spread belief
that: “you only need certified passive pro-
tection diaphragms in a closed sleeve filter
or in a storage bin to comply with Atex”.
Well, that’s wrong!
The pictures and tables in this article are a
courtesy of the Research and Study office of
TVM termoventilmec SpA (www.tvm-ter-
moventilmec.com) based in Spresiano
(Italy), a company that designs, manufac-
tures and installs industrial suction, filtering
and purification plants, pneumatic transport
plants, storage bins, fans, sleeve filters,
safety devices, etc. During the latest
Xylexpo in Milan, in May, TVM presented an
operating air suction plant in compliance
with the current safety standards.
by Danilo Morigi
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