CLASSIFICAZIONE AREE EX
adatto il tipo di materale
di situazione pericolosa /anno
di protezione per assicurare il livello di sicurezza
e, Ex d, Ex p, Ex m, Ex o, Ex ib
> ore < 1000
nA, Ex nW, Ex nL, Ex nP, Ex nR
Direttiva 94/9/CE – ATEX 95
In such areas there
is a necessity to eliminate sources of ignition such as
sparks, hot surfaces or static electricity which may ignite
equipment has to be used in these areas it must be so
designed and constructed as to not create sources of ignition
capable of igniting these mixtures.
equipment can be used in a potentially explosive atmosphere
a representative sample has to be fully tested and certified
by an independent authority such as BASEEFA in the U.K.
or UL in the U.S.A.
is intended as a guide only and further expert guidance
should be sought before placing into service, maintaining
or repairing any item of equipment in a Potentially Explosive
are shown between, for example, European and North American
practice this may be an approximation and individual standards/codes
of practice should be consulted for precise details.
MEDC have spent 25 years
Process plants are
divided into Zones (European and IEC method) or Divisions
(North American method) according to the likelihood of
a potentially explosive atmosphere being present.
Groups (plus dusts and fibres)
There are two main
gas groups, Group I – Mining only and Group II –
are used in European and I.E.C. groupings.
is concerned only with underground mining where methane
and coal dust are present.
gases occurring in surface industries, are sub-grouped
according to their volatility. This enables electrical
equipment to be designed to less onerous tolerances if
it is to be used with the least volatile gases.
Note : North
e.g. Butane has an
ignition temperature of 365 degrees Centigrade, equipment
used in the vicinity of this gas would need a T rating
of T2 or higher.
are used to prevent electrical equipment from igniting
explosive atmospheres. There are restrictions on where
these different types of equipment can be used as follows
* This type of protection is only recognised
by National Authorities, not as a
European-wide type of protection.
International and national standards are
published giving details of requirements for the safe
use of Electrical Equipment in Potentially Explosive Atmospheres
as follows :
All Explosion-proof electrical
Any spare parts used
should be purchased from the original Manufacturer and
repairs should be carried out by the Manufacturer or under
his supervision, in order that the item remains in conformance
with the certification documents.
All Electrical Equipment,
intended for use in a Potentially Explosive Atmosphere,
should be certified as suitable for such use.
The methods of obtaining
certification differ in detail, see below, between each
certifying body or group of bodies (e.g. CENELEC). Basically
this process consists of supplying a representative sample
of the equipment along with a set of drawings to a recognised
test/certification body e.g. BASEEFA who in turn test
the equipment against a recognised Standard e.g. EN50018
and issue a Certificate. The user of the equipment can
then refer to this Certificate to enable him to safely
put the item into service in a zone appropriate to the
After the above date
the ATEX Directive comes into force throughout
the EEC. This becomes a mandatory requirement for all
equipment intended for use in a hazardous area. The fundamental
difference between current practice and ATEX certification
is that ATEX addresses the essential safety requirements
for hazardous area equipment and uses Standards as part
of the method of conforming to these. Amongst other documentation
required by certifying authorities will be Technical Manuals
in order that the user is informed of installation methods
BOTH ELECTRICAL AND MECHANICAL, INTENDED TO BE PUT INTO
SERVICE WITHIN THE EEC AFTER 1ST July 2003, WILL HAVE
TO HAVE BEEN CERTIFIED IN ACCORDANCE WITH THE ATEX DIRECTIVE.
In practice this
means re-certification of all currently certified electrical
started this process and all relevant equipment will be
covered by the implementation date of 1st July 2003.
It should be noted
also that MECHANICAL equipment is covered by the
ATEX Directive so for the first time items such as gearboxes
will have to carry ATEX certification.
The equipment coding
will be as the current practice plus an additional code
Ex – Explosion
proof in accordance with ATEX.
II – Group II
G – suitable
for atmospheres containing gas ( D is suitable for atmospheres
Equipment will be
The method is basically
When certified, an
E – European
Ex – Explosion-proof
d – flameproof
II – Group II
B – gas group
T4 – temperature
The equipment is
The product is marked
Most countries outside
Europe or North America use the IEC Standards as a basis
for their own national standards.
The Russian Federation certifies
There is a scheme
in place which will when fully adopted allow for internationally
recognised certification to become a reality, this is
the IEC EX SCHEME. This uses the IEC standards and IEC
recognised test and certification bodies to issue mutually
recognised test reports and certificates. The scheme is
in its infancy and its level of success cannot yet be
2 digits are used to
North American practice