Lakeland Mills was warned about the risk of an explosion caused by pine sawdust just 11 days before the April 2012 blast that leveled its sawmill and killed two workers, a coroner's inquest heard Monday.
Ahn-Tai Vuong, a sales and business development manager for DuroVac, recounted his visit on April 12, 2012 where he toured the sawmill and would have given Lakeland management a pitch for two models of industrial dust vacuums systems the company could provide.
Vuong said Lakeland had invited him to visit the facility and when asked by Lakeland counsel Gavin Marshall if there was any resistance to his proposals, replied "absolutely not."
"I found that the meeting was very good and potentially we could provide some equipment," Vuong said as he spoke to the inquest from Quebec City via phone.
During his visit, Vuong asked to be shown the areas with the most dust so he could determine which models would be best and, in the process, took photos.
What he found was so bad, that Vuong said he warned Lakeland personnel there is a danger of a dust-fueled explosion that needed to be dealt with in an "urgent way" and went on to explain the "domino effect of a deflagration."
The inquest has heard such events can begin with a primary explosion is not necessarily damaging itself but can create enough force to shake dust from mill apparatus which then fuels a secondary explosion that can actually be more destructive.
Vuong gave the warning in his capacity as an engineer, "not because I'm trying to sell equipment but just because we're trying to protect human lives here," Vuong said according to a statement he gave to WorkSafe following the blast that was read out at the inquest.
Witnesses from Lakeland who have testified so far have said they don't recall Vuong warning them and much of the questioning from counsel centred on the circumstances in which he raised the issue.
However, Vuong said Lakeland representatives appeared receptive to buying a system and noted Lakeland was "one of the first, if not the first," to express interest following the Babine Forest Products blast on Jan. 20, 2012, which also killed two employees.
Whether Lakeland followed up, Vuong could not say because he had been brought in by Langley-based Airplus Systems Ltd. which Lakeland had initially contect about purchasing a system which would have been in addition to the dust collection system already in place.
At the time, Vuong said he would have been offering either a 40 horsepower or 75 horsepower machine that would have had to be carried around by forklift and would have had to remain outside the mill and with a wide perimeter around it.
Because of the possibility for a spark getting inside the machine, Vuong said it featured explosion vents which would have directed the flame outside to prevent the machine from blowing up. He said models featuring a flameless vent are now available and can be placed inside the building.
Once Lakeland placed an order, Vuong said it would have taken six to 12 weeks to get one delivered and would cost between $60,000 and $100,000 to purchase.
Workers could initially use long flexible hoses to vacuum out trouble spots but the idea would be eventually to install piping reaching the mill's critical points where workers could attached shorter lengths and also get better reach.
He said the system would have been an improvement over using compressed air to "blow down" equipment and clean out areas because that merely moves dust to other locations.
Piping would probably have cost a further $200,000 and take about six weeks to supply. The time it would take to install the piping depends on the complexity of the facility, Vuong said.
Vuong visited West Fraser's sawmill in Quesnel later the same day. There, he found similar conditions and also warned them about the potential for an explosion, the inquest heard.
After the blast, Vuong sent copies of the photos he took to WorkSafe and have been shown on a handful of occasions at the inquest so far. He said the incident still gives him goose bumps because people died.
Outside the inquest, Lakeland spokesman Cam McAlpine told The Citizen the search for a vacuum system began Feb. 8, 2012, about three weeks after the explosion at Babine.
The inquest also heard from two experts on dust-related explosions who said the potential for explosions fueled by wood dust has been known for some time.
In separate testimony, both Amy Cronin of Boston-based Strategic Code Solutions, an industrial safety consultancy, and Paul Amyotte, a professor at Dalhousie University in Halifax who has written a text book on dust explosions, agreed with United Steelworkers counsel John Rogers that explosions fueled by sawdust are not an emergent issue.
Cronin also indicated explosions involving wood dust are fairly common. According to an insurance company survey of 166 dust-related explosions between 1993 and 2006, the substance was found to be the source of fuel in 70 of them.
She also said friction was found to be the top ignition source. A WorkSafe B.C. investigation concluded the friction created when a fan at the end of a gear reducer came lose and jammed in a screen at the end of the housing provided the ignition for the blast at Lakeland.
According to the standard set by the National Fire Prevention Association, Cronin said wood dust of 3.2 mm in depth - about the depth of a nickel - covering more than five per cent of a facility's surface, including floors and level surfaces above, is enough to pose a hazard. Dust at Lakeland was deep enough to be measured in inches, she noted.
If the sawdust in a sawmill is deep enough that you can see your footprint or write your name in it, "it can be a problem," Cronin said.
In addition to the basic recipe for a fire - fuel, ignition and oxygen - the addition of compression and dispersion or mixture created the conditions for an explosion, the inquest heard.
