Pike's ventilation system 'unable to cope'

DEIDRE MUSSEN
Last updated 16:07 09/02/2012
Australian mine safety expert David Reece
DIEDRE MUSSEN
Australian mine safety expert David Reece

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Gas management and ventilation at Pike River coalmine has been criticised by an expert mining panel investigating the November 2010 fatal blast.

Australian mine safety consultant David Reece today continued to give evidence at the royal commission into the deaths of 29 men after an explosion ripped through the underground West Coast mine.

He was one of a panel of five experts, most from overseas, employed by the Labour Department to investigate what caused the explosion.

Reece said the mine's ventilation system was unable to cope with the amount of mining in such a gassy mine so Pike River Coal should have cut back on mining.

Five areas underground were being mined by November 19, 2010, although most weren't operating when the blast occurred.

He had never seen a mine with an underground ventilation fan like at Pike River, which was problematic and should not have been contemplated in a high hazard area.

The fan was plagued with problems once it began operating in October 22 and was finally commissioned only nine days before the blast, he said.

''It is one of the fundamental pieces of equipment you must rely on.''

It was vulnerable to damage if an explosion occurred, which would stop ventilation.

Australian regulations used to specify fans could only be on the surface, Reece said.

''Even in a surface situation, it's still your primary means of controlling the atmosphere in the mine and giving people maximum opportunity for escape.''

If an underground fan stopped, it was difficult to reach and restart, particularly if the atmosphere was explosive, he said.

''You are starting to cut down your options as far as knowing what's going on down there and starting it up again.''

In his written submission, Reece said Pike's main ventilation system of one intake and one return was not uncommon in New Zealand coalmines ''but would not be considered acceptable for anything but initial development in an Australian context''.

Some of the mine's ventilation devices were ''substandard'' in controlling explosive gases, he said.

He also harshly criticised the mine's gas monitoring system, highlighting variability and inaccuracy of data gained.

Some methane detectors were ''poisoned'' by high levels of the potentially explosive gas, stopping them from accurately measuring it, while other detectors were in poor condition, he said.

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Mine management failed to recognise the seriousness of that failing, he said.

The methane drainage system was unable to properly remove gas coming out of the coal, including the 100mm drainage pipe which was too narrow.

That put further pressure on the mine's ventilation system, he said.

He said the panel found it unacceptable the mine's workers would have to climb up its 108m ventilation shaft to escape the mine.

The mine should have developed a better second egress, he said.

In Australia, there was a strong push for mines to have three entries or exits, he said.

He agreed the location of the mine's fresh air base should have been of concern to the regulator, which was the Labour Department.

Yesterday, he revealed the blast's most likely cause was a roof collapse in the hydro-mining goaf, a void left after coal was extracted, expelling a large volume of highly concentrated methane accumulated there.

The gas would then become diluted by air to within the explosive range before being ignited by an electric spark.

It was most likely a result of the electric supply being switched on to the water pumps, which happened shortly before the explosion.

''It was fairly significant to us and strongly coincidental that these pumps started very close to the same time.''

Analysis of the explosion showed it probably ignited deep in the mine, he said.

Temperatures of 1500-2000 deg C were typical at the ignition point in a methane explosion.

However, he said blast survivors Daniel Rockhouse and Russell Smith, who were further out, didn't experience great heat.

'HIGHLY UNUSUAL' VENTILATION SYSTEM

The ''highly unusual'' ventilation system in the Pike River coalmine has come under scrutiny at the royal commission of inquiry into the tragedy.

Australian mine safety expert David Reece today continued to give evidence at the inquiry into the deaths of 29 men after an explosion ripped through the underground West Coast mine on November 19, 2010.

Yesterday, when the inquiry resumed for 2012 at Greymouth District Court, it was revealed the blast's most likely cause was a methane outburst from a roof collapse in the hydro-mining area that was ignited by an electric spark.

Reece, one of five experts who investigated the explosion's cause for the Labour Department, today said the mine's ventilation system was unsatisfactory for the amount of mining under way deep in the mine.

He has harshly criticised the mine's gas monitoring system, highlighting variability and inaccuracy of data gained.

Some methane detectors were ''poisoned'' by high levels of the potentially explosive gas, stopping them from accurately measuring it, while other detectors were in poor condition, he said.

Four or five areas were being mined at the time of the explosion, and it was known to be a gassy mine

Pike River Coal needed to cut back on mining because it was struggling to properly ventilate the mine, he said.

Reece had never seen a mine with an underground ventilation fan like Pike River had, which was problematic and should not be contemplated because it was a high-hazard area.

In his written submission, Reece said Pike's main ventilation system of one intake and one return was not uncommon in New Zealand coalmines ''but would not be considered acceptable for anything but initial development in an Australian context''.

Australian regulations used to specify fans could only be on the surface, he told the commission.

''Even in a surface situation, it's still your primary means of controlling the atmosphere in the mine and giving people maximum opportunity for escape.''

If the underground fan stopped, it was difficult to start again if the atmosphere was explosive, he said.

It was also challenging to get to the fan to assess the situation.

''You are starting to cut down your options as far as knowing what's going on down there and starting it up again.''

He said most of the mine relied on only one intake of air and one return, which was unusual and had risks, such as if a rockfall occurred in one of the roadways, which could block ventilation.

Other ventilation devices were also criticised for their inadequacy.

- The Press

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