The expert report that blamed electrical components inside the Pike River Mine lighting up like a 'Christmas tree' as a contributing factor in the November 2010 disaster was "overly simplistic'' and "antiquated'', the manufacturer said today.

In February, Australian mining consultant Tony Reczek, one of a panel of five experts investigating the cause of the explosion for the Labour Department, told the Royal Commission of Inquiry that the explosion occurred just seconds after the water pumps were switched on in the control room on the surface.

Mr Reczek said he thought the variable speed drives (VSDs) had arced and sparked, igniting gases, saying the mine's electrical system would have lit up like a Christmas tree when the power pumps were restarted.

Rockwell Automation, which made the VSDs, learned it was a key part of the inquiry only a week before the Royal Commission heard the evidence publicly.


Rockwell filed its response with the Commission on March 15, but it was not discussed at the final hearing. It was released to the Greymouth Star this morning.

Their report said Mr Reczek did not consider Rockwell's current technology.

Rockwell had now simulated what happened at Pike River that day and said his conclusions were "implausible''.

The company's own simulation showed that the water pump motors could not have overheated for the reasons Mr Reczek proposed. It also showed the system would not have arced and "could not have been an ignition source''.

Even if there were higher than normal current loads, an 'overload' function in the system would have terminated them.

The company's detailed evidence, filed from Wisconsin, USA, disputes many technical points. For example, Mr Reczek said a diode rectifier caused harmonics, but the VSDs at Pike River did not even use them.

The Royal Commission, which is considering all the evidence, must report back by September.

Other theories have been put forward for the cause of the disaster, including someone underground with contraband, or a diesel machine.