ATEX - in bulk material handling by kfq20208

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Exclusive contribution for CITplus, issue 03/2004




Subject:             ATEX – in bulk material handling


Author:              Gerhard Nied
                     Technical Manager



Company:             AZO GmbH + Co. KG
                     Industriegebiet Ost
                     D- 74706 Osterburken

                     Tel. 06291/92-0
                     Fax 06291/929 500
                     e-mail: info@azo.de
                     Internet: http://www.azo.de




Osterburken, 08.12.2004 nd-ns
(CIT03_04.doc)
                                                                                   Page 2 of 7


ATEX – in bulk material handling
On 1st July 2003, an essentially changed legal situation became effective for
all operations in which an explosive atmosphere can be caused by gases or
dusts. A new, Europe-wide legal foundation for explosion protection was
provided by two directives: (RL) ATEX 100a and ATEX 137.
The European Directive 94/9/EG - also known as "ATEX 100a Product
Directive" - governs those who produce or market products (devices etc)
to be used in hazardous surroundings.
Like the EC Machine Directive, ATEX 100a is directed at those who produce or
market devices, components, protective, safety or control systems used in
hazardous locations. For the first time, non-electrical equipment and protective
systems are also included in ATEX 100a.                                            Diagram 1
                                                                                     Photo 1
The European Directive 1999/92/EG - also known as ATEX 137 Operator
Directive - governs the working safety to be ensured by operators of
technical facilities. ATEX 137 is directed at operators of technical facilities;
transferred into German law by working safety regulation (BetrSichV), it has
been effective since 3rd October 2002.


Many types of industry are affected by ATEX, e.g. food production, feed
production, pharmaceutical and plastics processing. All combustible (and
therefore organic) substances finely distributed in the air as a dust cloud are
capable of reacting explosively with an ignition source. This applies to flour,
coffee and cocoa as well as for wood, plastic and feed. Metal dusts such as
aluminium and magnesium are also flammable – therefore the regulations of
dust explosion protection also apply to sections of the metal-working industry.
Consequently, in hazardous areas only equipment which possesses a
certification of CE conformity according to ATEX 100a is acceptable and is
identified belonging to one of the defined categories.
                                                                                           Page 3 of 7

The equipment categories may only be used in zones which are defined
accordingly (see Table 1):


TABLE 1: ZONES AND CATEGORIES

Zone                     An explosive            Category according to Safe operation of
                         atmosphere…             ATEX 100a             equipment must be
                                                                       ensured…
20/0                     …is to be expected                1           …even with infrequent
                         constantly, frequently                        occurrences of
                         and over longer periods                       equipment trouble
                         of time
21/1                     …is to be expected                2           …with equipment
                         occasionally                                  trouble to be expected
22/2                     …is not to be expected            3           …during normal
                         or only over short                            operation
                         periods of time



Products subject to the ATEX 100a directive
   1. Equipment
       Machines, equipment, devices, control and equipment parts, warning
       and preventive systems
       (e.g. mixers, mills, centrifuges, agitators, elevators, hoists, conveying
       screws, lamps etc)
   2. Protective systems
       Devices that immediately stop incipient explosions and/or limit affected
       areas;
       are put separately on the market, generally with design inspection
       certificate (e.g. explosion-suppression systems, pressure relief devices,
       quick-lock valves etc)
   3. Components
       Components required for safe operation;
       without autonomous function
       (e.g. pressure-proof housings, sensors, bearings, etc.)
   4. Safety, monitoring and control systems
       Used outside explosion-protection areas, but important for safe
       operation of equipment and protective systems in explosion-protection
       areas
       (e.g. control centre for explosion-suppression system)


How does the ATEX directive affect the machine directive?
The machine directive loses its validity as a basic regulation for the
subject matter covered by the 94/9/EG.
                                                                                        Page 4 of 7



For machines not subject to RL 94/9/EG (ATEX 100a), however, point 1.57
of the machinery directive does apply, which stipulates:
The machine must be designed and constructed in order to avoid any risk of
explosion posed by itself or by gases, liquids, dusts, vapours and other
substances released or used by the machine.


Therefore, the manufacturer must take appropriate measures to
    •   avoid hazardous concentration of the substances in question;
    •   avoid ignition of hazardous atmosphere;
    •   limit, if an explosion does occur in spite of this, the effects on the
        locality to a harmless degree.


The same measures have to be taken if the machine is intended by the
manufacturer to be used in an explosive atmosphere. Electric equipment
belonging to such machines must be conform to specific directives concerning
the danger of explosion.


In production plants with bulk material handling, two areas constitute a typical
connection between the applications of RL 94/9/EG and RL 1999/92/EG (in
Germany BetrSichV).


Pickup of product in bags
In this area, feed hoppers are frequently used for manual product intake from
bags.
Case 1:
A feeding hopper without ventilation (advisable only for bulk material with a
slight tendency to develop dust). In this case, Zone 20 must be defined in the
interior of the feed hopper. All around the intake opening, Zone 21 must be
defined (usually 1 m radius around the opening, see EN 50281-3).
Case 2:                                                                            Photo 2
Much more frequently, feeding hoppers with dedusting filters and dust
collectors are used. In this case, too, Zone 20 must be defined in the hopper
interior and in the filter. Round about the feed opening, no dust will escape in
normal operation, meaning that here Zone 22 is to be defined (usually 1 m
radius around the opening, EN 50281-3). These definitions necessitate the use
of equipment in the zones of corresponding categories according to RL
94/9/EG.
In case 1, category 1D inside, category 2D within a 1-m radius outside around
the opening.
In above case 2, category 1D inside, but only category 3D within a 1-m radius
around the opening outside.
                                                                                  Page 5 of 7



Safety screening is often done in the product intake area, using cyclone
screeners. Due to the high circumferential speed, a potential ignition source
exists in the screener interior and in Zone 20. Therefore a design inspection
must be carried out by a "specified authority" before the machine will receive
an identification in accordance with the directive.                                Photo 3



Identification according to ATEX 100a

Identification is an important part telling whether ATEX 100a was applied. The
directive outlines that the identification must consist of the CE sign and - in
cases additionally requiring an EC design inspection - the ID number from the
specified authority that has checked the QA system. In addition, the ID
contains the characteristic hexagonal explosion-protection sign required by
equipment for use in explosive atmospheres, in conjunction with information as
to Group (e.g. II = above ground) and Category plus specification “gas (G)
and/or dusts (D).This identification is also required for components, with the
exception that the CE sign must not be affixed.


Example:
An AZO screener for use in the vicinity of zone 22, i.e. category 3 (D = dust),
which may have a maximum surface temperature of 135 °C, is identified as
follows (as described before, the interior of the screener is zone 20.).
                                                                                         Page 6 of 7

Discharge systems for BIG BAGs
With the continuing trend to supply products in medium-sized packing units,
systems for BIG BAG discharge are becoming increasingly popular. In this
area, systems which operate with the BIG BAG connecting system have
established themselves. With a double-ring locking element, this involves fitting
the outlet spigot of the BIG BAG over a pipe, producing a dust-tight connection
with a clamping lid. Only then will the BIG BAG be opened by untying the cord
at the outlet. Normally by emptying BIG BAGs this way, dust will not usually
escape, belongs in Zone 22. Dust leaks can occur particularly when the BIG
BAG is emptied of product residue and compressed. There are measures to
prevent this, such as evacuating the BIG BAG, ensuring it is totally empty and
the air is completely removed. When BIG BAGs are used in bulk material
handling, an occasional, brief escape of dust cannot be avoided. Therefore this
is one of the critical points of operation within an automatic material handling
system.                                                                             Photo 4




Effects on manufacturer and system operator
The two EU directives 94/9/EG and 1999/92/EG (ATEX 95 and 137) have been
implemented nationally. The conversion process has caused manufacturers a
great deal of cost and effort, especially in approved documentation and in
certification of components and machines. Now the onus is on the system
operators to establish zones for their existing and new machinery and to
produce the required explosion protection documents in relation to safety
regulations.


Especially in dust areas, zones (Zone 21, Zone 22) organisational procedures
should be dispensed by the system operator.
Suitable measures are as follows:
    -   Instruction of personnel
    -   written instructions, work authorization and naming of persons
        responsible
    -   Avoidance of ignition sources (smoking)
    -   Cleaning measures to avoid hazardous dust deposits
    -   Immediate removal of dust deposits caused by operational trouble
In pharmaceutical production, for example, even Zone 22 can be avoided
totally by the systematic cleaning after every batch or every shift (required
anyway).                                                                                  Photo 5


In addition, it is necessary to identify a zone area at its entrances with the
triangular W21 sign "Warning of explosive atmosphere".
                                                                              Page 7 of 7

Correct zone definition can save costs and work in connection with CE
conformity. Operators of automated material handling systems are challenged
with many new requirements but competent manufacturers will be able to
operate comfortably within the guidelines.




Osterburken, 30 January 2004 nd-ns-bn
(CIT03_04.doc)
Photos for CITplus, issue 03/2004




Photo 1 (AZ029712.tif)                       Photo 2 (AZ032010.tif)
Product intake area for bags and BIG BAGs    Feeding hopper without aspiration for low-
                                             dusting bulk materials




Photo 3 (W440010.tif)                        Photo 4(AZ031411.tif)
Cyclone screener for safety screening        BIG BAG discharge system
below feeding hopper




                                        Page 1 of 2
Photos for CITplus, issue 03/2004




Foto 5 (AZ036607.tif)
Reconfiguration of external BIG BAGs
into internal containers (pharmaceutical)




Grafik 1(B003-03.bmp)
Typical example of product process with
bags and BIG BAGs




                                            Page 2 of 2

								
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