The Royal Commission of Inquiry has faced gruelling technical evidence examining what caused the Pike River mine to explode.
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An Australian consultant, providing expert advice to the Department of Labour investigation, suggested the most likely electrical sources that could have sparked an explosion, but his evidence has been challenged by lawyers for the Pike families and Pike River Coal.
3 News online reporter Emma Mackie is following the inquiry with live updates throughout the day.
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Earlier today, the expert witness suggested employees of Pike River did not understand the electrical issues they were faced with.
Last week a mines safety expert told the inquiry the most likely cause of the explosion was a roof collapse, releasing methane that was ignited by an electrical switch.
However, any conclusive cause of the explosion is difficult for experts to pinpoint without access to the mine, and many issues, such as contraband underground, have not been ruled out as a cause.
Expert Tony Reczek was on the stand today explaining his role in the Department of Labour investigation and describing his findings.
He faced scrutiny about his findings from lawyers of the Pike familes and Pike River Coal, who cast doubt on the strength of his theories given the lack of definitive evidence available.
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5:31pm – Inquiry adjourned until tomorrow at 10am.
5:29pm – Mr Reczek has not actually finalised his report to the Department of Labour, and he continues to work on the investigation.
He was assigned to look for potential sources of ignition only, not to determine a definitive source.
5:27pm – Mr Reczek is explaining his references to power frequencies.
5:21pm – The sparking source of ignition, as proposed by Mr Reczek, has to be located within the explosive mixture of gases in order to ignite it.
5:16pm – Mr Reczek says the harmonic currents can emit a high pitched whining sound, but they are difficult to hear.
5:10pm – The commission asks Mr Reczek if he looked at any of the flameproof boxes at the surface of the mine. The witness says he did not.
He has also not seen any portable gas monitor equipment.
5:05pm – The commission is shown the DoL letter of recommendation to the industry with regards to design, installation and commission of VSDs.
Stacey Shortall suggests Pike River Coal sought appropriate consultation through the likes of Rockwell Automation.
5:00pm – Stacey Shortall asks Mr Reczek if he believes Pike River made good choices for the consultants and providers it chose for the design, installation, and commission of the VSDs.
The witness agrees.
4:52pm – Mr Reczek’s brief was to identify potential ignition sources in the mine.
The witness says he was not critiquing the design of the electrical system at Pike River or the installation of the underground fan.
4:47pm – Ms Shortall asks Mr Reczek about the explosion investigations he has been involved in.
Mr Reczek says none of his investigations have found induced harmonic currents as the ignition source.
4:46pm – Mr Reczek says there is sufficient uncertainty about how the power supply was measured for the DoL report. He says it requires further investigation.
4:43pm – Ms Shortall points out that under-supply of power to the mine has been ruled out in the DoL report. She suggests there is some dispute between those findings and what Mr Reczek suggests about the inadequate power supply.
4:34pm – The commission is shown a map of the hydro panel and an area where the continuous miner was working.
Ms Shortall is presenting possible scenarios of where the explosion could have taken place, based on Mr Reczek’s expert report to the Department of Labour.
4:30pm – The Dept of Labour report claims there were accumulations of methane at Pike River. If that had been the case, and Mr Reczek’s theory of harmonic currents is correct, then an explosion could well have occurred prior to November 19 2010.
Mr Reczek says it is hard to be definitive about this.
4:27pm - The stray harmonic currents, that Mr Reczek says were circulating at Pike River, were not being detected.
Mr Reczek has not seen any evidence of anyone bringing the risk of harmonic currents to the attention of Pike River Coal’s management.
4:18pm – An alternate expert view of harmonic currents suggests stray currents would not have been circulating throughout Pike’s mine as Mr Reczek proposes.
4:11pm - Stacey Shortall, lawyer for Pike River Coal, cross-examines the witness.
Mr Reczek says he is not aware of the other views experts have about harmonic currents. Ms Shortall presents the perspectives of other experts who do not support Mr Reczek’s views on harmonic currents.
4:08pm – Mr Reczek says he finds check inspectors very useful. He says they bring a perspective of the workforce to the management team. In his experience they have always been helpful to have check inspectors.
4:02pm – The commission sees a picture of part of the mine where there are power cables in close proximity to the gas drainage system. He says this should have been fixed and the cables should have been separated from the gas pipework.
3:57pm – Mr Reczek has never come across a main fan stationed underground at a coal mine. He says he was incredulous when he heard about the one at Pike River.
He says in order to do any sort of electrical maintenance you would have to stop the fan.
3:52pm – If Mr Reczek had come across an instillation such as that at Pike River, he would have wanted to know how the installation would be managed in terms of its explosion risks, its maintenance, and how it would be integrated into the electrical engineering management plan.
He says he would not have approved it, or even been satisfied with what had been done.
3:48pm – Inquiry resumes.
Mr Reczek is cross-examined by counsel for the union, Nigel Hampton QC.
The witness says VSDs underground in New South Wales and Queensland would typically be on-board the machine they are driving.
At Pike River, the VSD was some distance from the motor it was controlling.
3:30pm – Inquiry adjourned for 15 minutes.
3:22pm – Mr Reczek says he has not made a definitive decision on the location of the ignition. He reiterates that a spark caused by stray harmonic currents could have occurred anywhere in the mine. If the spark came into contact with the right level of methane, it would have caused an explosion.
3:17pm – Richard Raymond, lawyer for the families of the deceased, casts doubt on the theory that switching on the pump was responsible for igniting the explosion.
3:09pm – Mr Reczek did not seek information from Rockwell Automation or consult with them to assist his investigation.
The witness says he is not competent to comment on the design of VSDs.
3:05pm – Counsel asks Mr Reczek about the code of ethics he is bound by as a chartered engineer.
The code of ethics recommends peer review. Mr Reczek is asked why he did not seek peer review in accordance with the institute of chartered engineers.
The expert witness concedes that his report to the Department of Labour is inconclusive and only based on evidence available. He says this is why he has not yet had his report peer reviewed.
3:03pm – Mr Reczek is cross-examined by Richard Raymond, lawyer for the families of the deceased.
Mr Reczek is asked to confirm if he was the only electrical engineering expert on the Department of Labour investigation panel.
He confirms that he was.
He says he has not had his findings peer reviewed.
2:57pm – The commission is shown a safety notice from Australia regarding VSDs, issued after the Pike River explosion.
Mr Reczek says the problems have been recognised for years, but not in the same magnitude as appeared to have been present at Pike River.
2:54pm – Mr Reczek says the inspectorate should not necessarily have oversight of the issues he has raised. He believes this is in the hands of mine management. He says the inspectorate should be testing that mine management are looking at appropriate measures. The inspectorate should operate as an external audit function he says.
2:52pm – A letter to the mining industry was sent from the Department of Labour one month after the explosion, warning of the dangers of the use of VSDs.
2:43pm – Mr Reczek says people are reluctant to voice their concerns or suggest shutting down a mine when they find methane.
“It ends up being a very big call for anybody to do such a thing,” says Mr Reczek.
2:35pm – Mr Reczek is asked to comment on restricted zones at the mine.
2:32pm – The witness says according to the structure at Pike River, it seems the engineering manager would have had a role in making sure the electrical equipment was operating satisfactorily.
2:25pm – Mr Reczek says he would expect to see an electrical engineer in charge, with a close connection to mine management.
An electrical engineer in charge would have the authority to shut down any system that was presenting concerns about the electrical system.
2:23pm – An electrical inspector may have been able to pick up on the issues if he had been present at the mine.
2:20pm – Mr Reczek says he has not seen any risk assessment documents related to the electrical issues he has raised. He says this should have been done.
He says the issues at the mine should have warranted interest from a regulator.
2:15pm – The witness says there are measures that can be taken to reduce or eliminate arcing induced by harmonic currents, which he believes may have caused the explosion.
2:11pm – Mr Rezcek confirms the evidence presented is challenged by a lack of primary evidence. He says the availability of such would remove any speculation.
2:03pm – Rockwell Automation have told the inquiry Mr Reczek’s conclusions are overly simplistic and do not account for more recent technology.
Mr Reczek says he is trying to present the simplest version possible of what is a potentially very complex problem.
2:00pm – Inquiry resumes.
1:00pm – Inquiry adjourned until 2pm.
12:59pm – Mr Reczek says a report from Rockwell Automation indicates the issue of inadequate power supply was not fully understood.
12:56pm – Counsel is referring to evidence given to the inquiry by Oki Nishioko, former hydro mining operator at Pike River.
12:53pm – The environmental conditions, including heat and dust, would have made the electrical equipment sensitive and vulnerable.
The conditions were the most adverse you could find for that type of equipment.
12:48pm – The witness is “not comfortable” the issues of harmonic currents were well understood at Pike River mine.
“Testing, in the very least, should have been carried out,” says Mr Reczek.
The witness is very uncomfortable with the way the main fan was installed underground at Pike River. He says the configuration of the installation underground at the mine has not been seen anywhere else in the world.
12:44pm – Mr Reczek is asked how the Department of Labour investigation created the time sequence leading up to the explosion. He says there are still some uncertainties in identifying the time sequence.
He says it “warrants a closer look” to be more definitive about the time sequence.
12:38pm – Mr Reczek is asked to explain what he meant earlier by “it would light up like a Christmas tree”.
He says every mechanical connection in the mine electrical system could have sparked, and therefore lit up at the same time – like when Christmas tree lights are switched on.
However, the witness says it would not have been visible to the naked eye.
12:31pm - Counsel asks Mr Reczek about the events occurring in the seconds prior to the explosion.
1. Flooming pump start up
2. Five second delay
3. Start up of the VSD and fan motor
12:29pm – Simon Mount, counsel assisting the inquiry, cross-examines Tony Reczek.
12:27pm – Cross-examination of the witness is invited from counsel.
12:21pm – The expert witness believes there were two most likely sources of ignition.
- Arcing caused by harmonc currents coming from the use of VSDS; and or
- Arcing caused by over-heating of joints caused by inadequate power supply.
Mr Reczek says these two issues could have combined to ignite the explosion.
He says the harmonic current circulating in Pike River could provide potential ignition sources throughout the mine wherever power circuits were present.
12:19pm – It would have been very difficult to get protection settings correct at Pike River mine says Mr Reczek.
12:14pm – On the day of the explosion, records show there was very little power supply.
Mr Reczek says those records do not indicate the starting of the flooming pump.
As a result, the expert says he questions the validity of the records in demonstrating the power supply use on the day.
12:13pm – Over-heating can cause mechanical joints to fail due to melting.
12:09pm – Motors would be running in the “overload” range and prone to over-heating and instability. This could have caused an increased chance of stray harmonic currents in the mine and arcing that could ignite the explosion.
12:04pm - Mr Reczek says if you do not properly understand your power supply and load flow at a mine, it is difficult to set the protection settings appropriately.
He says the load flow studies at Pike River indicate the power supply was reaching its full capacity and there was insufficient power to provide the energy stability required.
11:59am – The witness believes there was an assumption made by Pike River of an infinite supply of power into the mine, and this was not correct.
11:57am – A diagram of the surface power source is shown.
11:47am – The commission is shown a photo of a piece of equipment found at the surface of the mine.
The function of the equipment is to ensure that electric power going to the methane detector head is intrinsically safe.
The equipment is connected to the mine’s earthing system. It shows evidence of sparking and scorching.
“In any circumstances, you should not have arcing on any piece of intrinsically safe equipment,” says Mr Reczek.
Arcing: Arcing is sparking of a great magnitude. It is associated with large power systems.
Sparking: Is low energy, typically involving only 1-2 joules of energy.
11:43am - When the pump was switched on, the relative size between the pump and fan (the pump is about ten times the size) meant the entire circuit would have “lit up like a Christmas tree” says Mr Reczek.
Neville Rockhouse reported seeing a bright flash at the time the pump started.
Mr Reczek says a flash of that magnitude was most likely a high voltage flash that was more likely a consequence of the explosion than a cause of it.
The witness believes the most likely location of ignition was around the fan.
11:38am – Inquiry resumes.
The commission is shown a map of the mine, the witness is asked to point out the flooming pump and the variable speed drive (VSD) supplying that pump.
The cabling for the pump would be an 11,000 volt cable into the pit-bottom switchboard, a cable would then come from the switchboard to the VSD, and from there to the pump.
11:20am – Inquiry adjourned for 15 minutes.
11:17am – The switch on of the flooming pump could have led to the transmission of harmonic currents that sparked the explosion.
The pump was switched on in the control room around the time of the explosion.
11:14am – The expert witness is explaining the levels of energy required to ignite methane. He says a watch battery would have more than the amount of energy required to ignite methane.
“Watch batteries are not permitted underground for that reason,” says Mr Reczek.
11:11am – At Pike River they were experiencing instability in the speed of the motors, over-heating, and evidence of stray harmonic currents.
The mine was in the process of trying to understand whether or not the harmonics were being caused by something external, and whether or not the instability was being created by the harmonics themselves.
Mr Reczek says he believes there was no clear-cut understanding of how to tackle these issues at Pike River.
11:03am – At Pike River there was evidence of over-heating on the VSD and the motor to the main fan.
There were difficulties getting the fan motor up to its normal speed.
An 11,000 volt cable came along the drift and into the substation. From the substation a low voltage cable went into the VSD. A cable came out of the VSD and travelled to the motor of the main fan.
Any harmonic currents travelling between the VSD and the fan itself could be conducted anywhere throughout the entire mine.
10:57am – During start-up of machinery sparking is likely to be more intense.
The commission is shown a photograph of a typical VSD system.
10:54am – Induced voltages in the earthing detectors could not be detected, and could also cause sparking.
10:49am – Secondary currents are currents induced or conducted to adjacent cables. This would cause high frequency currents to circulate in the normal earthing circuits.
The expert’s evidence suggests stray currents increase the chance of arcing in the electrical systems, this means sparks could pass between machines as they make contact, and electric shocks could pass to people.
10:45am - At Pike River there was a distance between the VSD and the main fan it was connected to. This meant stray currents flowing in the circuit would have been conducted into the mine’s earthing system.
The stray harmonic currents would always come back to the start of the circuit at the VSD, but in the meantime they could “go walkabout” in the mine.
10:40am – Stray harmonic currents will “follow the path of least resistance” says Mr Reczek. At Pike River they would have been able to flow in the earth connectors connecting the VSDs and the main fan.
Because the whole of the mine’s electrical system is interconnected, there is no limit to where these stray currents could have travelled.
This meant everywhere in the mine would have been a potential source of sparking.
10:36am – The production of harmonic currents is a normal feature of the variable speed device. However, it can be a disadvantage of the system.
The commission is shown a diagram that depicts how harmonic currents work.
10:30am – The commission is shown a diagram of how a VSD works.
The expert witness says VSDs can cause harmonic distortions of electrical currents, secondary currents being induced, and induced voltage in earthing systems.
10:27am – Mr Reczek says VSDs (variable speed devices) were causing harmonic currents, which is normal. However, if the harmonic currents were dispersed outside of their immediate area, and circulated in the power supplies, this could have created a potential source of ignition.
VSDs are used to control the speed of motors on pieces of machinery in the mine, including the underground fan. It is an advantage to be able to use them because it gives continuous control of the speed, it could therefore have been used to control air flow through the mine via the main fan.
VSDs can be effective in saving energy.
10:22am – The commission is shown a map of Pike River mine, the witness is asked to point out non-restricted zones and the areas where methane may have been present.
He would expect methane to be more likely in areas where there were machines
The presence of methane sensors in a non-restricted area indicates the people designating the non-restricted zone suspected methane could be present there.
The equipment in that area was not explosion protected and it appears they were relying on methane detectors to indicate if methane was present.
10:17am – If access to pit bottom were possible there would be a number of issues to review, including the way the cables were connected, the way the earth cables were made, whether pilot systems were being used, and what the protection settings were on the various pieces of equipment.
The expert’s investigation included looking at appropriate use of explosive proof and flameproof enclosures on electrical equipment. The witness says this was a key feature examined in the Pike River electrical system.
10:15am – Mr Reczek is summarising the typical features of the electrical system of an underground mine.
10:12am – Typically an earthing electrode is located on the surface with the main substation that supplies the underground mine. This means all electrical equipment underground is earthed back to this source.
10:09am – Research from New South Wales indicates the temperature required for coal dust to ignite is between 110 and 160 degrees Celsius. Any higher temperature would certainly cause the coal dust to ignite says Mr Reczek.
There are many other variables that contribute to whether or not coal dust will ignite.
10:07am – Methane is very easily ignited. It tends to appear wherever electrical equipment is in use in an underground mine, particularly in a production environment.
It is also important to control the ignition of coal dust through over heating.
10:05am – Underground mining electrical systems are different to surface systems because they are in a hazardous environment due to the presence of methane.
10:04am – The expert witness looked at possible electrical sources of the ignition. He reached a number of conclusions, but it is not possible to be absolutely conclusive about the source.
10:00am – Inquiry resumes with evidence from Tony Reczek, an Australian consultant who gave expert advice to the Department of Labour investigation into the Pike River disaster.
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