Transcript Atex presentation - Shapa Solids Handling & Processing

CERTIFICATION OF
EQUIPMENT FOR USE IN
POTENTIALLY EXPLOSIVE
ATMOSPHERES
What do I Really Have to Do ?
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UK’S IMPLEMENTATION OF
ATEX

1999/92/EC – ATEX 137 – Implemented as
The Dangerous Substances and Explosive
Atmospheres Regulations 2002 (DSEAR) –
Social Directive

94/9/EC – ATEX 100 – Implemented as the
Equipment and Protective Systems for Use in
Potentially Explosive Atmospheres
Regulations 1996 (EPS) – Trade Directive
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DUTIES UNDER DSEAR

Conduct Risk Assessment relating to
Explosive Atmospheres and their potential
threat to people – hazards from flammable
gases and vapours and combustible dusts

Conduct Area Classification – define locations
of Hazardous Areas in the workplace

Employ suitable Safety Management systems
to ensure that an adequate level of explosion
safety is maintained
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SUPPLIER RESPONSIBILITIES
UNDER EPS

Assess risks associated with equipment to
demonstrate it is safe for use

Ensure that equipment supplied for use in areas
defined as hazardous by the customer is
suitably certified for the type of hazardous area
in which it will be installed

Must consider all potential ignition sources – e.g.
flames, sparks, static, etc – not just electrical
ignition sources
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Supplier’s Responsibilities (cont)

Ensure equipment is suitably labelled

Maintain a technical file and quality
records re production

Provide instructions for Installation,
Maintenance, Inspection and Use
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Operator’s Responsibilities when
Ordering
– Tell the supplier what classification of hazardous
area the equipment will be installed in
– Tell the supplier if the equipment is to be
connected to other equipment which may contain
an explosive atmosphere
– Tell the supplier what material the equipment will
handle (if it is processing material) and provide
information on material properties
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Information on Material
Properties

As a minimum
–
–
–
–

Whether the material can support an explosion (gas or dust)
Physical characteristics
Gas – autoignition temperature
Dust - Layer Ignition Temperature & Minimum Cloud Ignition
Temperature
Other data which the supplier may need to request
(depending on how equipment is to be protected)
– Minimum Ignition Energy
– Explosion Indices
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CUSTOMER MUST PROVIDE
INFORMATION ON HAZARDOUS
AREAS
WHAT IS A HAZARDOUS AREA?

“A place in which an explosive atmosphere may occur in sufficient
quantities to require special precautions to protect the health and
safety of the workers concerned is deemed to be hazardous”

“A place in which an explosive atmosphere is not expected to occur
in such quantities to require special precautions is deemed to be
non-hazardous within the meaning of these Regulations”
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HAZARDOUS AREA
DEFINITIONS UNDER DSEAR

Zone 0 (20): A place in which an explosive atmosphere consisting of
a mixture with air of flammable substances in the form of gas,
vapour or mist (or dust) is present continuously or for long periods or
frequently.

Zone 1 (21): A place in which an explosive atmosphere consisting of
a mixture with air of flammable substances in the form of gas,
vapour or mist (or dust) is likely to occur in normal operation
occasionally.

Zone 2 (22): A place in which an explosive atmosphere consisting of
a mixture with air of flammable substances in the form of gas,
vapour or mist (or dust) is not likely to occur in normal operation but,
if it does occur, will persist for a short period only.
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Problems re Classification of
Hazardous Areas

Customers tend to be conservative and “over-classify”
hazardous areas

Customers may not have classified hazardous areas

Zone 0/20 & 1/21 require that explosive concentrations are
present in normal operation
(e.g. >20,000ppm or 50g/m3)

Majority of workplaces will be no worse than Zone 2/22 (and
may be safe)

Need to include the new equipment in the evaluation of
workplace hazardous areas – ideally operator would consult
with supplier

Be prepared to challenge the customer’s area classification
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Classification of Gas Hazardous
Areas

Tendency is to be too conservative (e.g.
extent of flammable atmosphere above
flammable liquids will generally be small)

Historical “Flameproof” areas might not be
zone 1

Take credit for ventilation
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TABLE 3.1 : INFLUENCE OF VENTILATION ON TYPE OF ZONE
Ventilation
Degree
Grade of
release
High
Medium
Low
Availability
Good
Continuous
Poor
Zone 2 1)
Zone 1 1)
Zone 2 1)
Zone 2 1)
2)
3)
Poor
Good, fair
or poor
Zone 0
+
Zone 2
Zone 0
+
Zone 1
Zone 0
Zone 1
+
Zone 2
Zone 1
+
Zone 2
Zone 1
or
Zone 0 3)
Zone 2
Zone 2
Zone 1
and even
Zone 0 3)
1)
2)
Secondary 2)
(Zone 2 NE) (Zone 2 NE) Zone 2
Nonhazardous
Fair
1)
(Zone 1 NE) (Zone 1 NE) (Zone 1 NE) Zone 1
Nonhazardous
1)
Good
(Zone 0 NE) (Zone 0 NE) (Zone 0 NE) Zone 0
Nonhazardous
Primary
Fair
1)
Nonhazardous
Zone 2
1)
Zone 0 NE, 1 NE or 2 NE indicates a theoretical zone which would be of negligible extent
under normal conditions.
The zone 2 area created by a secondary grade of release may exceed that attributable to a
primary or continuous grade of release; in which case, the greater distance should be taken.
Will be zone 0 if the ventilation is so weak and the release is such that in practice an
explosive atmosphere exists virtually continuously (i.e. approaching a “no ventilation”
condition).
NOTE - “+ ” signifies “surrounded by”.
EXPLOSIVE DUST
ATMOSPHERE
A cloud of 40 g/m3 of coal dust
in air is so dense that a glowing
25W light bulb can hardly be
seen through a dust cloud of
2m thickness
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CLASSIFICATION OF
EQUIPMENT
You have agreed with your customer what
the hazardous areas are – what do you
now have to do to classify your equipment
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Certification of Equipment for
Use in Hazardous Area
1.
Equipment which does not handle hazardous
material – only need to address the potential for the
equipment to ignite a surrounding explosive
atmosphere
2.
Equipment which handles hazardous material –
have to address control of explosion risks inherent
to the equipment, the potential to ignite a
surrounding explosive atmosphere, and the
potential to ignite an explosive atmosphere in
connected equipment
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Equipment Classification to EPS

Category 3 – equipment which does not represent
an ignition source in normal operation – suitable for
use in zone 2 (22) area

Category 2 – equipment which does not create an
ignition source in normal operation, or in the event of
a foreseeable malfunction – suitable for use in zone 1
(21) and 2 (22) areas

Category 1 – equipment which does not create an
ignition source even in the event of a rare malfunction
– suitable for use in zone 0 (20, 1 (21) and 2 (22)
areas
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Authority to Classify

Category 3 – self certification by supplier

Category 2, non-electrical ignition sources – self
certification by supplier (technical file to be sent to a
Notified Body)

Category 2, electrical ignition sources (or internal
combustion engines) – certification by Notified Body

Category 1 – certification by Notified Body

Have to be clear if the equipment is certified for
Gases (G) or Dusts (D) or both (G/D)
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Equipment from Outside the EC

For equipment manufactured in the EC the
supplier is responsible for the certification

When equipment is imported from outside the
EC it must still be certified, and either the EC
agent (if there is one), or the EC customer
has to take on the responsibilities of the
supplier
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Certification of Equipment

Have to consider the Machinery Directive as well as
EPS

Do risk assessment for Machinery Directive first, then
move on to EPS

Machinery Directive requires a demonstration that the
equipment is safe for intended use – requires
consideration of inherent explosion hazards – may
determine that equipment requires explosion
protection

Having completed the Machinery Directive risk
assessment conduct an Ignition Hazard Assessment
for EPS
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Explosion Protection Devices

Equipment Intended to provide protection against
explosion affects, or to prevent explosion propagation
from an item of equipment to another are “explosion
protection devices” and must be Certified under EPS
(by a notified body)

Examples are :
–
–
–
–
Relief panels
Suppression Systems
Explosion Barrier Valves
etc
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Let’s look at how to classify the
two types of equipment (that
which does not handle a
flammable material and that
which does)
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Equipment which does not
handle Hazardous Material

Machinery Directive assessment will
concentrate on basic health and safety
requirements (e.g. guarding) and will not
touch on EPS matters

Ignition Hazard Assessment required to
categorise equipment depending on its ability
to ignite a surrounding explosive atmosphere
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Ignition Hazard Assessment

Systematically review the operation of the equipment to identify
conditions when ignition sources could arise

Consider all potential sources of ignition (e.g. electrical &
mechanical sparks, friction / hot surfaces, static)

Consider normal (intended) operation first

Identify foreseeable malfunctions and decide whether these
could create ignition sources (considering ignition of a
surrounding explosive atmosphere)

Identify rare malfunctions (e.g. two simultaneous malfunctions)
and decide whether these could create ignition sources

BS EN 13463 provides a methodology
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Possible Outcomes of Ignition
Hazard Assessment
1.
2.
3.
4.
Equipment provides an ignition source in normal
operation – can’t certify under EPS (need to look at
measures to remove the ignition source)
Equipment provides an ignition source as a result
of a foreseeable malfunction – self certify as
Category 3
Equipment provides an ignition source as a result
of a rare malfunction – self certify as Category 2 (if
no electrical ignition sources). If machine has some
electrical components then invite Notified Body to
certify, or use pre-certified category 1 or 2 electrical
components in the assembly - lodge technical file
with Notified Body
Equipment does not provide an ignition source in
the event of a rare malfunction – invite Notified
Body to certify as category 1
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Further Considerations

Creation of sparks or hot surfaces inside
equipment may ignite a surrounding
explosive atmosphere if there is no isolation

Have to consider how the equipment might
be used (abused) by the customer – may
need some additional controls to prevent
inadvertent incorrect use – or some warnings
in instructions provided with the machine
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Equipment Handling a
Hazardous Material

Conduct Machinery Directive Risk Assessment
– Identify causes of explosive atmosphere within equipment
– Look for possible sources of ignition of any such
atmospheres
– Determine whether ignition sources can be adequately
controlled
– Decide whether explosion protection is needed (will depend
on overall risk – frequency and consequences)
– Define explosion protection controls

Complete Ignition Hazard Assessment in relation to
an explosive atmosphere surrounding the equipment,
and any explosive atmospheres in items which will be
connected to the equipment, taking into account
controls defined by the Machinery assessment
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Implications of Internal Ignitions

Ignition of an explosive atmosphere within an item of
equipment may create an ignition source to an
explosive atmosphere surrounding the equipment, if
there is no isolation

e.g. assessment of components on the outside of the
equipment might allow Category 2, but internal
ignition from a foreseeable malfunction would reduce
this to Category 3 if flame can propagate from inside
to outside

Isolation devices will be “explosion protection
devices” under EPS and will have to be certified by a
notified body
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Transfer of Ignition Sources to
Connected Equipment

“Internal” classification of machine (i.e.
likelihood of ignition sources to up- and downstream equipment) may be different to
external classification

If internal classification is not compatible with
hazardous area classification for connected
items will have to advise the customer that
the connected items require explosion
protection
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Key Problems with the
Regulations

Many suppliers are not confident enough to self
certify equipment

Operators tend to overstate the hazardous areas

Difficult to take into account the different ignition and
combustion properties of different materials

Assistance from Notified bodies can be expensive
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EXAMPLE – Hammer Mill





Zone 22 workplace, Category
3D mill required as a
minimum
But internal explosive
atmosphere in normal
operation identified by the
Machinery Risk Assessment,
and possible ignition source
in the event of a malfunction
Large volume grist hopper –
consequences of explosion
could be severe
Explosion protection required
EPS certified explosion
barriers required to prevent
explosion protection to
connected equipment (which
might also contain explosive
atmospheres)
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So if my risk assessment
determines that my equipment
requires explosion protection
what can I do ?
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Explosion Protection
 Explosion Containment
– design plant for maximum explosion pressure
 Explosion Suppression
– install extinguishing system
 Explosion Venting
– provide weak panel to relieve pressure
 Explosion Isolation
– prevent explosion propagation

In all cases would have to use Certified Devices
approved by a Notified Body
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MYTH
Existing equipment must be replaced
by ATEX approved equipment

Equipment on the market before 1st July 2003
exempt from EPS (ATEX 100)
– i.e. already installed, second hand or in stores

Equipment must be safe for use in hazardous
areas
– e.g. old “Ex” rated electrical equipment in
gas/liquid zones & suitable ‘IP’ rating for dust
zones – suitable surface temperatures in both
cases
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MYTH
Existing protective systems must be
replaced by ATEX certified systems

Protective systems on
the market before 1st
July 2003 are exempt
from EPS
– Aluminium panels
secured by nylon bolts
– Explosion Doors with
Brixon Latches

OK to retain so long as
they provide effective
protection
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OTHER AREAS OF
CONFUSION

Maintenance of Certified Equipment
– Under EPS Suppliers must provide essential information for
operation and maintenance – qualified technicians should be
able to perform all necessary maintenance

Refurbishing Old Equipment
– Can legitimately refurbish equipment back to its original state
without having to certify it – only have to certify if
functionality is changed

Use of Plastic in Hazardous areas
– No restriction in zone 2/22 areas
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SUMMARY





Operator is responsible for Area Classification and
must tell the Supplier what classification of hazardous
area equipment will be required to operate in, and
whether it will be connected to hazardous areas in
other equipment
Be prepared to challenge the Customer’s area
classification
Most equipment will be going into zone 2 (22) areas
at worst, so can self certify
Conduct Machinery Assessment first to define any
explosion controls, then conduct Ignition Hazard
Assessment
Suppliers should provide instructions for safe
operation which should cover maintenance as well
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