Under an Australian Coal Association Research Program (ACARP) grant, Gillies Wu Mining Technology (GWMT) have trialled a cap lamp battery-mounted personal dust monitor (PDM) that gives real-time response to a miner’s current dust exposure.

GWMT mining engineering and ventilation consultant Stewart Gillies told International Longwall News that the coal mining industry, management, technical engineering staff and the workforce all give strong recognition to the challenge of dust as an increasing hazard, particularly as higher production levels are achieved.

Gillies said throughout the GWMT trials the PDM had successfully demonstrated its potential use as an engineering tool to locate and assess various sources of dust during normal mining operations.

GWMT began trialling the PDM in April last year, but since then further in-mine trials have been necessary to determine the long-term durability, stability and maintenance requirements of the monitor.

The underground coal mining environment, particularly near the longwall face, presents varying dust conditions due to aspects such as ventilation conditions and air velocity, shearer activity and design, chock movement, AFC movement, outbye conditions and measurement instrument behaviour.

Developed by the United States National Institute for Occupational Safety and Health (NIOSH), the PDM can be used to improve productivity by evaluation of engineering dust improvements such as sprays, scrubbers and miner position.

Gillies said the PDM is configured to provide accurate respirable dust personal exposure information in a form that is easy for a miner to use and wear and has two main objectives:

To provide the miner and mine operator with timely values to avoid overexposure to dust by making any necessary changes during the course of a work shift; and

To compute an accurate end-of-shift statistic for a miner’s average respirable dust exposure.

The PDM is believed to be the first personal dust monitor instrument that reliably delivers a near real-time reading and can quickly highlight high dust situations and allow the situation to be corrected.

“Being a personal dust monitor, the instrument measures the airborne dust from the breathing zone region and so has many advantages over instruments that measure from a fixed point location,” Gillies said.

“The major innovation of the PDM is the near real-time dust concentration display – the ability to associate dust make with an individual’s activities and position over time and so allow an objective means of applying corrections and remedial action.”

The technology that forms the heart of the PDM is the tapered element oscillating microbalance (TEOM) system, which is unique in its ability to collect suspended particles on a filter while also determining the accumulated mass.

“Using the device, miners and mine operators have the ability to view both the cumulative and projected end-of-shift mass concentration values as well as short-term 15 or 30-minute running average,” Gillies said.

Gillies is currently undertaking considerable field work in a number of operating underground coal mines.

“It was found that the best way to evaluate changing dust concentrations within mine sections was to download the monitors' data bank of dust reading against time and then add recorded activity information, location and other information,” he said.

“Some of this latter information is recorded manually during the survey and some can be downloaded from the mine communication computer face or belt activity log. This computer activity data stream can be put through [Microsoft Office] Excel into a graphical form that gives powerful objective information that can aid interpretation and evaluation of improvement strategies.

“The successful use of the instrument provides a significant advance on the current shift-length determinations taken by personal respirable monitors in use, or occasionally the optical instruments that give instantaneous readings but cannot distinguish different types of dust and exhibit sensitivity to water sprays.”

Gillies said the instrument is proving very reliable and performing to expectations, “I have no doubt that it will play a major role in mining occupational health and safety in the future,” he said.

Mine managers from several Australian mines have already shown interest in obtaining the units when they meet IS standards in Australia and are commercially available.

Gillies said he couldn’t say for sure when they would be available on the market, but suggested maybe in 12 months depending on the policies of the United States-based manufacturer, Thermo Electron in Albany, New York.