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Related: Editorials & Other Articles, Issue Forums, Alliance Forums, Region ForumsLac Megantic: Death toll rises in Quebec train derailment explosion
Ravaged site is now being treated as a crime scene as the railway says someone shut down a locomotive keeping the brakes on.But someone managed to shut down the fifth locomotive unit, he said. The railroad alleges someone tampered with the controls of the fifth engine, the one maintaining brake pressure to keep the train stopped.
If the operating locomotive is shut down, theres nothing left to keep the brakes charged up, and the brake pressure will drop finally to the point where they cant be held in place any longer, Burkhardt said.
There are two ways to shut down the fifth unit: Theres an emergency lever on the outside of the locomotive that anyone wandering by could access. Or, there are a number of levers and buttons inside the unlocked cabin.
Both means were used, said Burkhardt.
http://www.thestar.com/news/canada/2013/07/07/lac_megantic_death_toll_rises_in_quebec_train_derailment_explosion.html
Since there was a fire in one of the locomotives which was extinguished by the Nantes fire department, it is possible that one of the firemen shut down the locomotive.
However, leaving a train unattended without setting the manual brakes on enough individual cars to hold the train appears to be an unacceptable operating practice. There should also have been a derailer placed at the downslope end of the train so that if it starts to move, it would leave the tracks.
hedgehog
(36,286 posts)the default mode if power is lost is to set the brakes!
FarCenter
(19,429 posts)If the main brake line pressure drops suddenly, as in a decoupling of a car, the valve disconnects the brake line and uses the local pressure reservoir in the car to apply the brakes. They stay applied until the pressure in the car leaks down.
So either enough in car reservoirs leaked down to let the train move, or at some point in the main brake line leaking down the brakes in the cars are not fully applied. There were reports of seeing sparks from the rails as the cars came into town, so some cars may have had brakes applied.
Not sure what the grade from Nantes to Lac Megantic is, but part of the Nantes siding is 0.7 grade, and I've seen an estimate that the gravitational force on the train would have been 30 to 40 tons when parked.
hedgehog
(36,286 posts)FarCenter
(19,429 posts)hedgehog
(36,286 posts)cali
(114,904 posts)particularly the clear way you explain bewildering (to me) technical aspects.
Again, thanks, FC
HooptieWagon
(17,064 posts)When the air pressure is reduced or vented, the reserve air tanks on each car apply the brakes. The Westinghouse brake system has been in use for well over 100 years, although I don't think its still used on passenger trains. It is a reliable system. I don't know what happened in this case.
mainer
(12,026 posts)Anyone could access it. You'd think there'd be a hand-over from engineer to engineer.
bluedigger
(17,087 posts)From what I have gathered, there was a fire on one of the engines earlier that evening, which local responders put out. It isn't clear if the train was subsequently inspected by rail officials, although I think they have claimed it was. Either they missed the fact that the FD had shut down the train, not understanding the implications, or it wasn't inspected at all. That seems to be the point where things went tragically wrong.
pinboy3niner
(53,339 posts)LAC-MEGANTIC, Quebec | Mon Jul 8, 2013 2:03pm EDT
(Reuters) -
...
Nantes Fire Chief Patrick Lambert said his crew had switched off the locomotive late on Friday as they extinguished a "good-sized" blaze in the motor, probably caused by a fuel or oil line break in the engine.
"We shut down the engine before fighting the fire," he told Reuters in an interview. "Our protocol calls for us to shut down an engine because it is the only way to stop the fuel from circulating into the fire."
The tanker train's operator, the Montreal, Maine & Atlantic Railway, said the engineer had parked the train in Nantes on Friday night and left one locomotive running to ensure the air brakes worked properly.
The company's chairman said the brakes will not work if a train is switched off.
"If the operating locomotive is shut down, there's nothing left to keep the brakes charged up, and the brake pressure will drop finally to the point where they can't be held in place any longer," Ed Burkhardt told the Toronto Star.
...
Lambert said once the blaze was out, the Nantes fire service contacted Montreal, Maine & Atlantic Railway. "We told them what we did and how we did it," he said.
Asked whether there had been any discussion about the brakes, he replied: "There was no discussion of the brakes at that time. We were there for the train fire. As for the inspection of the train after the fact, that was up to them."
...
http://www.reuters.com/article/2013/07/08/us-train-idUSBRE96505L20130708
FarCenter
(19,429 posts)http://books.google.com/books?id=aLzZB07raxwC&pg=PA606&dq=unattended+train+hand+brake+regulation&hl=en&sa=X&ei=FgnbUZerCdK44AOb04CwCQ&ved=0CDUQ6AEwAA#v=onepage&q=unattended%20train%20hand%20brake%20regulation&f=false
There follow regulations for setting hand brakes and depressurizing the air brakes before leaving the train.