Boart Longyear engineer manager, Ross Stutchbury pinpointed the management of filter change out as an area where running costs could be significantly reduced if handled correctly.

“The end user needs to make sure they get the allocated hours out of their filters, otherwise it is really going to cost them a lot of money,” Stutchbury said.

“A lot of the guys go down to start a shift and they grab a couple of filters and throw them in, but they may have only done four hours when they should be doing 10. This makes a dramatic difference in your running costs.”

Stutchbury presented figures where the total machine owning and operating costs per hour for an unmanaged exhaust filter method was $151.55/hr whilst a managed exhaust filter system was substantially lower at $136.55/hr.

VA Eimco Australia engineer, Phil Nelthorpe spoke on a combined approach of utilising catalysts, filters and electronic engines to decrease diesel particulate exposure.

Research undertaken at TestSafe Londonderry revealed catalysts took 20% to 50% of diesel smoke out of VA Eimco's latest engine package. Previous tests by BHP found water bath scrubbers took approximately 25% of the particulate emissions.

Tests completed at mine sites for machines doing normal duties, not chock transport, on wet system Micro Fresh filters found the operating time on wet systems varied with an average life of 10 hours per filter. One filter was required per 50kW of engine power to obtain a reasonable life.

VA EImco's experience found filters were very sensitive to water vapour in exhaust gas, which reduced the life of the filter. Consequently, filter housing design was developed with vapour elimination in mind.

The tests also looked at the sensitivity of the filters to amounts of water vapour in the gas and the processes undertaken to reduce the damaging water vapour.

Nelthorpe also addressed the possible introduction of electronic engines into the Australian underground mining industry.

"One of the ways to meet proposed regulations being introduced by the EPA and the US is through the use of electric engines," Nelthorpe said.

"The implementation of electronic engines in an explosion protected environment is not easy and that is something we are working on at present."

New Proposed EPA and (US) regulations will see the drop from 0.5g/kWhr down to .02g/kWhr, between the existing T1 regulations and proposed T4 regulations proposed for 2008.

DBT Diesel had carried out extensive testing on a number of wet and dry filters and catalysts which managing director, Greg Venticinque presented at the seminar.

The results of these tests will be available on the Coal Services website.

The testing found a multitude of factors that affected filter performance and longevity, including raw exhaust gas temperature increases which may be caused by increased backpressure resulting from a fouled heat exchanger, a blocked outlet flame trap or exhaust filter or a failure of the exhaust filter bypass valve.

Other factors affecting exhaust temperature at the filter included incorrectly sized exhaust piping, high fuel temperature, blocked air intake filter, poor fuel quality, incorrectly calibrated sensors, blocked radiator, failure of the cooling fluid system or failure of the low water shutdown float.

Venticinque envisaged a number of future developments to improve the reliability and operability of particulate filters including a water injection systems to cool the exhaust after high loads, the use of other filter media such as stainless steel or sintered metal filters or new low temperature ceramics and a larger freer flowing exhaust systems to reduce cleaning intervals and reduce back pressure.

He also saw benefits in developing new exhaust heat exchangers with less fouling and improved access for cleaning as well as new engine developments including exhaust gas recirculation, electronic control and fuel additives.