Pike River Inquiry Phase 3: Electrical set-up an “extreme risk”

Pike’s electrical system presented multiple sources of danger, the commission has heard.

Pike River Mine, photo Iain McGregor/The Press

In yet another day of sobering evidence, an Australian electrical engineer has described how Pike’s electrical set-up presented an “extreme risk” of ignition. Tony Reczek, who reviewed Pike’s electrical records for the Department of Labour and Police, spoke of an “unfortunate combination of factors” that created a “ready supply of ignition sources” throughout the mine.

There was no explosion protection technology on some major items of underground equipment, including the mine’s main ventilation fan – described as the “lungs” of the operation. Power supply was insufficient to meet the demands of equipment underground, which would have caused machinery to overheat. And key items of equipment, such as the main fan and water pump, were controlled by variable speed drives (VSD), which are known to create stray “harmonic” currents that can cause arcing on other equipment on the same electrical circuit. Although VSDs are widely used, Reczek explained that they need to be carefully controlled, and in underground coal mines they are usually integrated into the machines themselves. Not so at Pike, however, where they were separated by long distances from the motors they were powering.

Contractors and workers were struggling with electrical problems in the weeks before the November 19 explosion, with worries about machines tripping, overloading, and not being able to run equipment at full speed. Reczek says they seemed to have been pursuing various explanations, but hadn’t come up with a definitive explanation for the problems.

Reczek thinks it’s probable that when Pike’s surface control room switched on a large water pump at about 3.45pm on 19 November 2010, arcing occurred as a result of harmonic currents circulating from the VSD that drove the pump. This would have caused the whole electrical system to light up “like a Christmas tree”, igniting any methane that was within the explosive range. He said he’d never seen a configuration of VSDs such as was in place at Pike in any other underground coal mine.

Nor had he seen a mine where the main ventilation fan was located underground, in a high hazard area where methane would be present. He was “incredulous” when he heard about it at Pike. Given that it was the most important piece of equipment in keeping the mine atmosphere safe, ongoing inspections and maintenance were vital. But to do that would require stopping the fan – leaving the workers involved without ventilation in a gassy area. He also criticised the area of the mine known as Spaghetti Junction, where a clutter of services including a gas drainage pipe and electrical cables passed through a congested area.

Asked whether there was any way of making the system safe, Reczek said it was too late once the installation had been done. “It’s a big call once you’ve actually purchased the equipment to then proceed to try and modify the installation or the equipment.  It would be hugely expensive and inconvenient.” Anyone who had suggested that was needed would be “pretty much unemployable”.

• Reczek’s commentary on the role of VSDs at Pike has drawn an angry response from Rockwell, the large international company that supplied and installed them. Rockwell called his analysis “overly simplistic”, and has asked to file evidence in reply.