Conclusion: As a result of the research conducted the following outcomes have been achieved:
- It is possible to use a small diesel generator to produce an exhaust stream that provides varying levels of elemental carbon (EC) at different engine loads with a reasonably even distribution across the exhaust pipe. This then provides a valuable means for the calibration of instrumentation directly to NIOSH method 5040 which is an internationally recognised standard for health assessment.
- The use of laser light scattering (LLS) instruments with generic factors to convert the measured total particulate matter (TPM) to EC is only valid for the types of engines that they were originally derived. On this basis every new type of engine that enters underground diesel fleets in coal mines should be evaluated to establish if the current factor remains appropriate. If this occurs, direct reading instrumentation (eg LLS) should provide a useful means for the quick measurement of raw exhaust EC. If the industry does not wish to undertake this work then TPM may be a possible metric for the estimation of raw exhaust DP however clarification of the variation in correlation issues raised by Vouitsis, Ntziachristos & Samara (2003) and the NSW Department of Primary Industries report (NSW 2004) will be required before this alternate metric could be used on all engines in current diesel fleets. In either case, checks at appropriate intervals by other potentially slower means would add significantly to the confidence of results obtained by LLS.
- The sampling of raw exhaust DP using quartz filters for subsequent EC analysis is a viable alternative to current technologies however the process does not lend itself to sampling post a water-filled scrubber tank or for the provision of instant results. It does however provide an excellent audit or checking method for direct reading instrumentation.
- The Freudenberg sampling system appears to be suitable for the collection of raw exhaust for subsequent EC analysis as a check method for LLS devices provided a number of modifications to the tested prototype recommended to the manufacturer are implemented.
- The depth that a probe is inserted into the raw exhaust of an engine can have an effect on the concentration of EC measured. This may be a factor in the high level of variability of results experienced by mines when using different testing organisations. For the engine used in this project a probe of 21 cm appears appropriate.
- No effect on raw exhaust EC concentration caused by temperature was observed when sampling the raw exhaust at approximately 115oC compared to that at 45oC. This is a significant finding as it allows the gas sampling point on the manifold of underground diesel engines used in the coal industry to be the place of choice to collect samples. This should have a major effect on minimising sampling errors provided the exhaust is appropriately cooled and mixed.
The device developed by Emission Reduction Products Engineering Pty Ltd (ERP) to collect a suitable sample from the gas sampling point appears to work, but further evaluation is required over a range of in-service vehicles.