Published in September 2009 Australian Longwall Magazine
Micro Fresh Filters mining manager Stephen Gledhill said the filters, manufactured in China, looked similar to the existing exhaust filter that had been successfully operating in Australian coal mines for more than 15 years.
He said Micro Fresh had become aware of the imported filters following a complaint from a minesite that there was a fitment issue with their own filters. On inspection, the filters were found to be a Chinese import.
A diesel fitter at the site also told Micro Fresh the imported filters had been seen to blow out in operation, allowing the collected diesel particulate to pass through the filter and return to the mine environment.
The minesite immediately quarantined the offending filters.
“The decision to source an alternate unapproved filter had been made by the site procurement officer who had received misleading documentation from the local import agent that purported to claim that the filters were in some way approved by OEMs and the department,” Gledhill said.
“The Chinese-made filters in question have been sold to minesites for use underground despite not being listed on any of the relevant machine OEMs’ approval drawings, which is a New South Wales Department of Primary Industries requirement.
“Minesite personnel should check that any exhaust filter being used is listed on the relevant DES [diesel engine system] drawing. This is of vital importance given that unapproved exhaust filters have been responsible for fires in the past.”
Micro Fresh had the imported filters tested by Coal Services for efficiency and flammability. Hydraulic stall diesel particulate matter tests were conducted on Micro Fresh’s DA100 filter and the imported filters sourced from the minesite.
“The import filter was found to be well below the efficiency of the standard model,” Gledhill said.
“The standard model allowed an average of just 0.5mg per cubic metre of DPM to pass through the exhaust, whereas the import allowed a massive 16mg per cubic metre.
“This is clearly seen with no smoke being omitted from the exhaust of the test vehicle [an old PJB] when fitted with a standard model filter. However, on testing the imported filter, there was very considerable smoke emission from the exhaust.”
Inspection of the two filters after testing revealed the exterior of the approved filter to be white, whereas more than 75% of the external side of the imported filter media had turned black.
In addition, the imported filter media ignition temperature was 410C. Gledhill said this was about the temperature of raw exhaust and could cause a problem where a scrubber could lose water.
The imported filter test also showed part of the filter media was composed of paper.
The 100% polymer filter media used in the approved filter showed no ignition at 960C when tested to the Australian Standard AS/NZS 60695.2.11:2001.
“Adding to the main concerns of using unapproved exhaust filters [flammability and efficiency], the construction of the imported filters indicates a further potential to fit incorrectly and continue to blow out when in operation,” Gledhill said.
“We have seen containers of them come into the country previously, last time being 2004 where again we were alerted to their presence by similar failures.
“Previously imported Chinese filters only lasted around four hours in applications where Micro Fresh DA100 filters lasted between 10 and 18 hours,” Gledhill said.
He added that in more than 15 years there had been no reported failure or non-conformance of a Micro Fresh DPM filter in Australia or the United States.
