IS 12082-2: Control of Asbestos Emission - Recommendations, Part 2: Milling of Asbestos Ore

2006·1.3 MB·English

by  Bureau of Indian Standards

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IS 12082-2 (2006): Control of Asbestos Emission -
Recommendations, Part 2: Milling of Asbestos Ore [CED 53:
Cement Matrix Products]
“!ान $ एक न’ भारत का +नम-ण”
Satyanarayan Gangaram Pitroda
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“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता हहहहै””ै”
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“Knowledge is such a treasure which cannot be stolen”

IS 12082 (Part 2) :2006
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Indian Standard
CONTROL OF ASBESTOS
EMISSION — RECOMMENDATIONS
I
PART 2 MILLING OF ASBESTOS ORE
(First Revision)
lCS 13.040.40
i

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0 BIS 2006
BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002

February 2006 Price Group 3
I
.— ~--’, , “~.. -———.
Cement Matrix Products Sectional Committee, CED 53
FOREWORD
This Indian Standard (Part 2) (First Revision) was adopted by the Bureau of Indian Standards, after the draft
finalized by the Cement Matrix Products Sectional Committee had been approved by the Civil Engineering
Division Council.
Inrecent years there has been agrowing awareness that exposure to asbestos can have harmful effects onthehealth
of workers. In order to give guidance on how the risk of exposure to wsbestosdust can be prevented, controlled
or minimized, itwas felt necessary to laydown some standards regarding safe use of different products containing
asbestos, improving conditions in workplaces, preventive measures, protection and supervision of the health of
workers, packaging andtransport, disposal ofwaste, etc. This standard laysdown the recommendations forcontrol
of emission of airborne asbestos dust during miIIing operation of asbestos ore.
In the formulation of the standard, due weightage has been given to international co-ordination among the
standards and practices prevailing indifferent countries inaddition to relating itto the practices inthe field inthis
country. This has been met by deriving assistance from the following publications:
ILO Codes of practice: Safety in the use of asbestos, 1984, published by the International Labour OffIce,
Geneva
RAJHANS(GS) and BRAGG (GM) Engineering aspects of asbestos dust control. Ann Arbor Science
Publishers, USA
This revision has incorporated the experience gained inthe past and inputs from Mining Research Cell of Indian
Bureau of Mines. It has incorporated/elaborated provisions of conveyance of asbestos containing mineral rocks,
filtration through high efficiency filters, which can trap the dust up to 0.4 micron, and dust separation bycyclone
discharge into water precipitator tank. Acombination of approaches to control airborne asbestos dusts, including
that of thick green barrier trees have been recommended.
This standard is one of a series of Indian Standards on safety in handling and use of asbestos. Other standards

in the series are as follows:

IS No. Title
11450: 1986 Method for determination of airborne asbestos fibre concentration in work
environment by light microscopy (membrane filter method)
11451 : 1986 Recommendations for safety and health requirements relating to occupational
exposure to asbestos
11767:1986 Recommendations for cleaning of premises and plants using asbestos fibres
11768: 1986 Recommendations for disposal of asbestos waste material
\ 769 Guidelines for safe use of products containing asbestos:
(Part 1) : 986 Asbestos cement products
(Part 2) : 987 Friction materials
(Part 3) : 987 Non-cement asbestos products other than friction materials
1 770 Recommendations for control of emission of asbestos dust in premises
manufacturing products containing asbestos:
(Part 1) :1987 Asbestos cement products
(Part 2) :1987 Friction materials

(Part 3) :1987 Non-cement asbestos products other than friction materials
(Continued on third cover)
1S12082 (Part 2) :2006
Indian Standard
CONTROL OF ASBESTOS
EMISSION — RECOMMENDATIONS
PART 2 MILLING OF ASBESTOS ORE
(First Revision)
1 SCOPE stages of crushing to release the fibres, screening to
remove the rock particles and dust, suction to carry
This standard (Part 2) lays down the recommendations
away the fibres, cyclones to separate solids from air
for control of airborne asbestos dust emission during
solid mix, and subsequent de-dusting, de-gritting,
milling operation of asbestos ore.
classification, grading, etc, to produce a commercial
fibre. Conveying equipment like elevators, screw
2 REFERENCES
conveyors, belt conveyors form an essential part of
The standards listed below contain provisions, which
mechanized milling. Large volumes of air are used to
through reference in this text, constitute provisions of
convey fibre and fibre rock concentrates as well as for
the standard. At the time of publication, the editions
de-dusting operations for the purposes of classification
indicated werevalid. Allstandardsaresubject torevision
and other operations.
and parties to agreements based on this standard are
encouraged to investigate the possibility ofapplying the
The types ofequipment used vary widely, depending on
most recent editions of the standard indicated below:
trade and brand. But, generally speaking the crushers
used are, depending on stage of crushing and circuit
[S No. Title used, gyrocentric crushers, jaw crushers, cone crushers,
11450: 1986 Method for determination of airborne impactors hammer milIs, tibrezers, ball mills, edge
asbestos fibre concentration in work runner mills, pulverisers, etc. Screens are generally
environment by light microscopy gyrocentric but may also be of vibrating type. While
(membrane filter method) multi-deck sifters are used in de-dusting operations of
11451 : 1986 Recommendations forsafetyandhealth fibres, trommels are also used in de-dusting of fibre
requirements relating to occupational concentrators. Everystageofoperation includingmaterial
exposure to asbes t os transfer points and tailing disposal points, involves
generation of asbestos dust, and therefore, shall be
11767: 1986 Recommendations for cleaning of
handled properly to prevent the release ofasbestos dust
premises and plants using asbestos
into the working environment.
fibres
11768: 1986 Recommendations for disposal of 4.2 The processing operations should be carried out
asbestos waste material in closed encasing for reduction of release of dust in
12079: 1987 Recommendations for packaging, work environment. Provision shall be made at all dust
transport and storage of asbestos generating points of the mill to collect the dust laden
air, which shalIbe filtered through high et%ciency bag
3 OBJECT filters which cantrap the dust ofO.4microns andhaving
higher filter efficiency up to 99.9 percent.
The objectives of this standard are as follows:
a) Toprevent orminimize thepotential forexposure
4.3 The dust generating points are generally
toairborne asbestosdustduringmilling operations
associated with the following operations:
of asbestos ore; and
a) Material loading,
b) To reduce the probability of release of airborne
b) Conveying,
asbestos dust into the environment.
c) Crushing,
4 GENERAL d) Screening,
e) Size reduction, and
4.1 The asbestos fibre is usually found in the form,of

veins embedded in rock. It is released by successive o Material transfer, bagging and other operations.
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1S12082(Part 2) :2006
4.3.1 Design principles for material handling system conveyors to conveyors, from conveyors to crushers
layouts including transfer points enclosures are: and screens, conveyors to final discharge intobags, etc.
a) Exhaust hood to capture dust emission at the These particles remain air-borne and effect the quality
source, of the work environment. Dust control at the transfer
points canbeachieved byanyone orcombination ofthe
b) Duct work to provide a channel for flow of
following three approaches:
contaminated exhaust air to the dust collection,
a) Prevention of dust by minimizing the impact of
c) Aircleaner toremove dust from thecontaminated
bulk material, attrition and air entertainment,
air, and
d) A fan to provide necessary exhaust flow rates, b) Dry dust collection, and
c) Dust separation using liquid spray.
The exhaust hood isacritical part ofanydust collection
item. Properly designedhood ensuremaximumeftlciency
Transfer points shall also be ‘completely enclosed and
of the system, minimum exhaust volume, unrestricted
connected to dust extraction system. Figure 5 shows
movement of the operator and free flow of material
one typical example”of enclosing feeding point ofjaw
being processed. Conveyors, screens, sifters, trommels
crushers.
andelevators shallbecompletely enclosed andconnected
todustextraction system.The loading pointsofconveyor
A dust separation techniques using liquid can reduce
shall be provided with rock boxes, where ore enters
air-borne dust, elimina~eair-borne dust orseparate dust
along the line of conveyor with reduced velocity on to
at its source. The type of system can be classified as:
the conveyor and reduces the dust generation. Figures
a) Water sprays, and
1,2,’3 and 4 show typical examples of dust extraction
systems, includinglocationvfrock box,enclosedGont%yor b) Water sprays with additives.
and vibrating screens.
These wetdust separation techniques require arelatively
lowcapital expenditure, limited maintenance and offer
Exhaust fans shall be provided for pneumatically reasonable control.
conveying the final dust particles to water precipitators
forreduction ofdust from the crusher/pulverizers units. 4.3.3 Wheneverbucketelevatorsareusedfortransporting
For effective capture ofthe dust, it is important to have theoretofiberizer,thebucketelevatorshallbecompletely
an adequate but not exhaustive volume. Adequate dust enclosed and connected to a dust extractor.
collection system shall be provided for all operations.
4.3.4 The feeding point at the bucket elevator shall be
4.3.2 Dustparticles become air-borne duringthe transfer provided with proper suction hood sothat asbestos dust
of material, like points from bins to conveyors, from does not become air-borne.

m
SI
CRUSHER TRANSFER POINT
FIG. 1 DUSTGENERATINGPOINTSINHANDLINGASBESTOSOREFROMTHECRUSHER

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1S12082 (Part 2) :2006
FiG.2 CONVEYORBELTENCLOSUREINTHELOADINGREGION(THISARRANGEMENTISINTENDEDFORORE LOADING,ANDIF
FIBREWEREBEINGLOADED,THEROCKBox WOULDBEREMOVED)
Cl

TOTALLYENCLOSED
CONVEYOR
. ~SCRApER CONvEYOR
OR CLEANING BELT
RET: LJNBRHT SCRAPER

FIG. 3 CONVEYORENCLOSUREFORCONVEYORBELTDIJMPINGORTRANSFER
3
—-
1S 12082 (Part 2) :2006
FIG.4 GYRATORYFIBRESCREENANOROTARYASPJRATOR
PILLOW~LOCK
“’’’”’1 n-’””

ROTATING PIPEm \ll

4
SWIVEL BEARING
‘“0 SHAFT
TO BAG FILTER
FEE DER
JAW CRUSHER

FIG. 5 DUSTCONTROLFORTHEJAWCRUSHER
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1S12082 (Part 2) :2006
5 BAG HOUSE the asbestos bearing rock is fed directly to the runner
machines (edge-runner, crusher or fiberizer), dust
:i,, 5:1 Theexhaust airfrom various dust generation points generation is high as compared to the plants having
:’ shallbe passed to abag house, preferably preceded by bucketelevator arrangement. Theprocessing plantlayout
,,,
a cyclone separator with an air lock, where required. shouldhavecontinuous material flowarrangement inside
,,.
the plant to reduce the number of dust generations
,,
,,!!. 5.2 Theairused inaspiration andpneumatic conveying points in the plant and the manual feeding of asbestos
offibre, often passirrgthrough cyclone collectors, shall
~II !i bearing material in fast moving machines like edge-
,‘i1\ alsopassthrough the main bag house before itisletout runner,crusher orfiberizer etc,shouldbetotally avoided.
,,, into atmosphere.
Ill
7.1.2 Crushing and Screening
5.3 If dampers are used in ducts and pipe-lines, it is
$ preferable touserotary dampers (butterfly typedampers)
,1,,1,1 than slide dampers since they provide better sealing. 7.1.2.1 Control ofdustduring orecrushing andscreening
shall be by exhaust ventilation to a cyclone and bag
house.
5.4 Thefilterbagsoftheunitshallbecleanedperiodically
t by mechanical shaking to improve filtering efficiency.
7.1.2,2 Owingtotheirhigherpotentialfordustgeneration,
Other means of cleaning such as, reverse jet, pulsejet,
vibrating screens and grizzlies shall be in leak-proof
etc, also may be used, provided they do not blow fine
enclosures withsuitable flexible connections tothe feed
dust out due to more vigorous cleaning action,
and outlet chutes exhaust vents.
5.5 Fabric filters to be used in bag house as filtering
medium shall preferably be made of cotton satin cloth, 7.2 Chutes
Itisboth eflicient and durable. Other suitable synthetic Chutes which feed belts, either from other belts or from
materials may also be used. other equipment, shall always be closed.
While selecting the filter cloth, appropriate air to cloth
7.2.1 Chutes should feed axially, where practicable.
ratio shall be considered. Selection of improper filter
cloth may lead to ineftlcient running of dust collection
7.2.2 Long vertical drops which cause puffing of dust,
system or increase in emission of asbestos dust into
shall be avoided.
atmosphere. 4
7.2.3 Chute shall be run at angles exceeding the angle
6 GENERAL MAINTENANCE OF CONVEYORS,
of repose of the materials to reduce the velocity of the
PIPES AND DUCTS
materials fed to the conveyor.
The ducts and lines used for carrying dust laden air
have to be maintained properly to prevent dust leaks 7.2.4 Chutes shall have adequate cross-section and t
and withstand wear. The maintenan ce personnel shall shall run at appropriate slopes so that it shall carry
be issued his powered lights to locate dust leakage’s
required material withoutplugging. Surgefeedconditions
when repairs are required. A system of patch marking
shall be considered, wherever required.
shallbeusedfor locating the leakagepoint. The detected
leaksshallberepaired expeditiously. Itisrecommended
7.2.5 Chute enclosures shall be leak-proof and yet
to have the system under vacuum so that only
allow ready access.
in-leakage occur.
NOTE—The initiator of a work order shall mark the 7.2.6 Access doors to chutes shall be of leak-proof
leakage point with fluorescent patch or other suitable design.
identification mark and the maintenance man shall remove
the patch identification mark and attach itto the work order
7.2,7 Where ore containing rocks are being conveyed
whenrepairsarecompleted. Thepatchoridentification colour
shall be changed each week so that outstanding work can be and chutes of bolted construction are used, the joints
spotted ataglance shall be fitted with packing.
7 CONTROL OF ASBESTOS EXPOSURE IN 7.2.8 Where only fibre is conveyed, fully welded
SPECIFIC ACTIVITY chutes may be used but the same shall be leak-proof.
7.1 Loading, Crushing and Screening 7.3 Conveyors
7.1.1 Material Loading 7.3.1 All conveyors shall be totally enclosed.
The asbestos bearing rock feeding is one of the main
dust generation activity in a processing plant. Where 7.3.2 Belt width and speed shall beadequate enough to

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