Air movement specialist, Axair Fans, explains the steps needed when specifying and sourcing fans for use in potentially explosive environments.
Outside of major users such
as chemical, petrochemical
and process industries,
enquiries for flameproof
fans tend to come from specifiers,
resellers and end-users, many of
whom may not be aware of the ATEX
Directives.
ATEX is an acronym derived from
the French expression ATmosphères
EXplosibles and exists in the form
of two European directives for
controlling explosive atmospheres.
The first ‘equipment directive’ 94/9/
EC (ATEX 100) covers manufacturing
standards. The second ‘workplace
directive’ ATEX 99/92/EC (ATEX
137) seeks to ensure that people are
protected against the risk of blast
injuries or asphyxiation by dangerous
substances. The 2016 updated
legislation is Directive 2014/34/
EU and assists with establishing a
uniformity to the approach taken when
supplying and distributing equipment
such as industrial fans for explosive
atmospheres.
Everyone involved in the
specification, manufacture, installation,
and use of equipment in flameproof
zones has some responsibility in
ensuring that the law concerning
flameproof equipment is upheld.
Unfortunately, a lack of practice
with the subject tends to give
rise to enquiries that begin with
statements like “there is a slight risk
of explosion, but we don’t think we
need a flameproof fan”, which places
manufacturers and suppliers in an
awkward position because they are
not ATEX consultants and are not
qualified to know what the client can
lawfully install.
What can the fan supplier do with
casual enquiries that must at some
point turn into tightly specified orders?
The first option is a blunt “come
back when you know exactly what is required” and the second is to issue a
questionnaire, usually with tick boxes
and a bit of guidance appended, which
may then be returned with conflicting
selections
What is needed in
every case however is an
ATEX code that provides
a well-defined minimum
standard for the product that
is required. For example,
the code Ex II 2G IIC
T4 essentially means
European flameproof,
surface industry (not
mining), Category 2
(Zone 1), gas group II,
type C (hydrogen or
acetylene gas), maximum
surface temperature 135ºC.
It is strictly the responsibility of
the end-user to perform a DESEAR
(Dangerous Substances and Explosive
Atmospheres Regulations 2002) risk
assessment to ensure that flameproof
zones are properly defined in terms
recognised by ATEX 99/92/EC. It
is recommended in 99/92/EC that
an Explosion Protection Document
be produced,
which will help
to define the
ATEX code for
any equipment
to be installed in
the flameproof
zone.
There are
many other
coding permutations, including
slightly different formats for dusty
atmospheres (Zones 21 & 22). If codes
cannot be provided there is lingering
uncertainty over what is required.
Once an ATEX code has been
established by the end-user, the
process of selecting a fan model
and its essential features demands a
degree of application knowledge. For example, the type
of electrical supply is
important. Often the
response to “what
electrical supply do
you have”, is “can
be single- or three-phase”. Single-phase
is an expensive
option and not widely
available from ATEX
motor manufacturers.
It may be cheaper to run
a 3~ line than to buy a ~
fan on a long manufacturing
lead-time.
Any fan motor that is to be speed
controlled with a VSD must also
have thermistors fitted to protect
against motor shell temperature at
low speeds causing spontaneous
gas combustion. By not mentioning
the VSD aspect at the enquiry or
order stage the purchaser is likely
to ultimately face time and product
replacement costs.
Other matters include motors
that vary from the most secure
specification EEx d (explosion proof)
through EEx e
(increased safety),
down to EEx nA
(non-sparking)
which has many
similarities to a
standard non-flameproof motor.
ATEX must
be understood
as being an ever-evolving subject
requiring competence and
training. Anyone requiring a better
understanding of flameproof
requirements would be advised to
source training which is available
from a wide range of industry bodies
and organisations.
www.axair-fans.co.uk