Faculty of Engineering and the Built Environment,
School of Mining / Inhaling excessive amounts of respirable coal dust will lead to work-related lung disease
commonly known as Coal Worker’s Pneumoconiosis (CWP) or black lung. Prevention and
control of CWP requires accurate knowledge of the dose-response relationship to set-up and
review occupational exposure limits (OELs), which do not exist in SA. Due to historical
reasons, poor emphasis of occupational health on the mines resulted in inadequate exposure
data in SA. The new Mine Health and Safety Act (1996) overcame the deficiencies of the
past and require quantifying the dust exposure and efficiency of dust control measures, and
continuous risk assessments for dust exposure.
The current method of exposure assessment is expressed using an Air Quality Index (AQI)
which is the ratio of the measured dust level and OEL of coal dust. The difficulties with the
usage of AQI are poor descriptions of dust problem areas and its magnitude, poor quality of
the data leading to “no dust problem situation” and failure to extract information on ‘dose in
milligram’ to relate them to the disease rate. Gravimetric size-selective dust sampling was
introduced for the first time in 1990 in SA. Due to the lack of critically important coal dust
exposure data available, this thesis has set out to examine several critical exposure related
parameters and determine dust levels underground.
This research study had the objective of the development of a pragmatic diagnostic tool
(method) called the Dust Exposure Level Index (DELI) to evaluate the exposure of workers.
The DELI incorporates a set of controllable parameters and influential areas and prioritises
them to manage and reduce the worker exposure. The DELI model was to provide critical
information as an index, i.e., to show whether the environment is dusty, border line or
relatively free of dust and effectiveness of administrative and engineering dust control
measures. The research work in this thesis has led to very explicit conclusions, which were
based on extensive dust measurements in various coal mines over a five year period.
Conclusions obtained for the various sets of controllable parameters used in the DELI model
are as follows:
1. A previous analysis of the dust data during 1990 indicated that the dust levels have
increased with mechanisation. The contamination of coal dust samples due to stone
dusting can result in high dust levels giving a “false” indication of the efficiencies of
the dust-control systems.
2. The dust exposure levels during coal cutting indicated that a worker positioned inside
the cabin of a CM during the cutting of a 24 m coal block is at a higher dust exposure
risk than the worker when cutting a 12 m coal block. Also, the miner who is operating
in a heading is exposed to higher dust exposure risk than in a split.
3. The analyses of measured real-time dust data showed a clear relationship between the
average dust levels and the frequency of occurrence of “peak” dust levels. The study
demonstrated a clear method of using real-time dust data for assessing exposure.
4. The average measured section intake dust level was 0.80 mg/m3 and 60 % of the
collected data exceeded the 0.5 mg/m3 limit indicating that this is a base dust level to
which the worker is exposed without carrying out any additional work in the section.
5. The average measured section return dust level was greater than 2.0 mg/m3 indicating
the high exposure levels of workers, and ineffectiveness of the ventilation and dustcontrol
systems.
6. The results of this research study indicated that there is no conclusive relationship
between the rate of coal production and respirable dust levels. Also, the type of dust
control system used has pronounced effect on dust levels in the sections. The capture
efficiency of any dust control system is not one hundred percent at any given time.
During any cutting process for a given time and dust control type, part of the escaped
respirable dust is added to the coal face atmosphere through air re-circulation.
Therefore, respirable dust levels can be expected to increase with time during the
shift, even at constant production levels.
7. A limited number of particle size analyses have indicated that there is no clear
relationship between the dust concentration in mg/m3 and total surface area (m2) of the
respirable dust sample.
8. For the first time, a clear delineation of coal types (semi-bituminous and semianthracite)
that possess the most inherent respirable dust generation potential
(IRDGP) was possible (p = 0.000). Also, there was no conclusive relationship
(p = 0.373) between different semi-bituminous coal seams (1, 2, 4 and 5) and IRDGP.
9. The laboratory roll-crusher test results of South African coal types indicated that
average inherent silica for the test coals was 3.54 %.
The DELI model took into account, the merits of personal exposure data in exposure
assessment, but the limitations and quality of data one obtains in the South African situation
overweighed use of the fixed-point sampling. The “limits of acceptability” used in DELI are
based upon acceptable guidelines prescribed by the authorities such as National Institute of
Occupational Safety and Health (NIOSH), Mine Safety and Health Administration (MSHA),
South African Department of Minerals and Energy Affairs (DME) and latest information on
epidemiological studies. The DELI model gives the visual “colour” coding and descriptive
categories for easy interpretation and understanding of exposed dust level to uneducated
workforce. This type of DELI index representation gives a clear and concise picture of the
mine or various section dust conditions. The DELI model exposure assessment technique
gives accurate feedback because it was based on latest recommended size-selective
sampling methods and instrument and vast amount of measured data, which was not
previously available. The application of the developed DELI model for exposure assessment
and its comparison with AQI were evaluated for coal mine dust data. The study
demonstrated that the DELI model is a practical diagnostic tool that gives a fair reflection
and information on dust levels and is an exposure assessment tool for the coal mining
industry that will assist in reduction of CWP in South Africa.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/1859 |
| Date | 17 November 2006 |
| Creators | Belle, Bharath Kumar |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 5177241 bytes, 69171 bytes, 2437691 bytes, 713216 bytes, 712192 bytes, 696320 bytes, 1047552 bytes, 20193 bytes, application/pdf, application/pdf, application/pdf, application/vnd.ms-excel, application/vnd.ms-excel, application/vnd.ms-excel, application/vnd.ms-excel, application/pdf, application/pdf, application/vnd.ms-excel, application/vnd.ms-excel, application/vnd.ms-excel, application/vnd.ms-excel, application/pdf, application/pdf, application/pdf |
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