Ventilation in the 21st century

LONGWALL ventilation expert and Dallas Mining Services managing director John Rowland reveals tips for ventilation officers to streamline their monthly collection processes, helping deliver better reports that can increase management understanding of minesite ventilation.
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Camgas: Courtesy of Simtars

Blair Price

In his paper Moving the ventilation report into the 21st Century, delivered in February at the ninth Australia Coal Operators’ Conference in Wollongong, Rowland took a swipe at regulations that did not demand much more from ventilation officers than what was required in the 1970s.

“Fortunately most ventilation officers have moved with the times and have a far greater level of understanding and control over their ventilation circuits than in the old days when it was basically an add-on job, and the standard of the average modern ventilation report reflects that,” Rowland said.

“There are still, however, a number of sites without operating or active ventilation models with which to carry out predictive analysis of circuit changes and the law makes no mandatory prescription in this regard.”

He said the regular maintenance of a ventilation model was relatively simple if there was careful planning around the monthly data collected.

He stated the maintenance of a validated model should be encouraged as a high priority.

By using efficient processes, the data could provide handy ventilation reports for frontline supervisors. Rowland did not discount supervisors’ capacity to absorb the information.

“They are like sponges and at all costs should be afforded access to the information to make both the ventilation officer’s job an easier one and, more importantly, the minesite a much safer place.”

He said a ventilation report in the 21st century should contain:

Where the total underground flow distributions can be determined;

Where the efficiency of individual splits can be determined and tracked;

Where the condition of groups of appliances can be assessed and remedial works prioritised;

Where the total distribution of particular contaminants, such as gas, heat or dust, can be identified and managed;

Where the mine resistance/equivalent orifice can be determined and trended;

Where the operating point on the fan is recorded and used to substantiate the accuracy of existing curves or even build an operational curve if there is not one available;

Where the power and efficiency of fans can be validated against claimed performance;

Where the base data enables the maintenance of a ventilation model that can accurately predict ventilation change results; and

Where the model accuracy is such that intricate and complex ventilation changes can be done using pressures alone, with the only flow recordings being validation readings on completion.

The benefits of the report itself, once assembled, included:

Management sees the benefit of distributing the report to the underground workforce and, in particular, the supervisors that can learn greatly from the contents;

The report itself becomes a communication vehicle for any ventilation matters of interest, such as “how to take a bag sample” or “how to build a stopping” and so on;

The report becomes entrenched as a long-term training tool for front line supervisors, deputies and undermanagers; and

People are heard to remark “How come I didn’t get a copy of the vent report last month?”

In contrast, Rowland said assembling a ventilation report last century involved burying it under a pile of books until the next survey, carrying out ventilation changes using the “gut feel” method and still hearing people ask ventilation officers “What are you doing with that wand thingy?”

“Ventilation changes in the absence of an accurate ventilation model are ad hoc, risky and almost always subject to some rework, causing them to drag out over a substantially longer timeframe, impacting negatively on both safety and production.”

He said collecting the minimum data to satisfy regulations, then hiding the report under a pile of books, would make it likely the intricacies of the ventilation circuit would not be understood by either the management or the workforce.

Using a simple generic longwall layout, Rowland outlined eight measuring station locations to determine flow and contamination.

They should cover main return flow, outbye longwall flow, tailgate flow, outbye maingate flow, mains last line flow, maingate entry, intake and return flow, maingate lastline flow, and longwall blind road flow.

He said routine pressure stations should cover the main fan and pit bottom, in mains across doors near flow stations, across longwall and development panel entry, across all regulators and across any unusual resistances.

On the amount of raw data to be collected, Rowland said his own analysis of monthly routine surveys he had carried out at 10 operating mines showed that nine out of 10 mines could be surveyed in one day by one person and the other took two full days.

He said the average number of flow/gas determinations per mine was 31 and the average pressure determinations was 16.

The data could be seen as slightly skewed as Rowland said one of the mines had arguably the most complex circuit in the country, but the important point of note was that most mines could be comprehensively surveyed in just one work day.

With the ventilation model validation and accuracy, Rowland said the model would never exactly replicate the underground data but was adjusted on a monthly basis to be as close to the measured data set as practically possible.

Rowland noted the increasing importance of keeping on top of flow distribution and leakage reduction.

“If face flows are satisfactory then the improved efficiency brought about by the leakage improvements may afford a reduction in the main fan operating point, which will save power and money.

“This factor is being looked at more closely due to the world economic downturn and, more importantly, the onset of the Rudd government’s emissions trading scheme in 2010, which will see main fan power reduction become a far higher priority.

“The biggest drivers affecting main fan power usage are both leakage and resistance reduction. As such the ventilation officer will play an increasingly critical role in such initiatives.”

Rowland also championed the use of ventilation reports as a training tool.

He said if management freely distributed the report, the challenge would be to make it interesting enough for people to read it.

To this end he suggested the inclusion of any ventilation-related information that was both of some use and some interest to the supervisors and underground personnel.

He also suggested the report could be personalised by mentioning individuals and commenting on raised or lowered standards with attributions to particular groups.

In one example, Rowland said at “a very transparent Bowen Basin mine”, general ventilation knowledge and resultant respect of the circuit from supervisors had been well elevated since the site made its ventilation reports widely available several years ago.

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