[SystemSafety] Lac-Megantic disaster
peter.sheppard at uk.transport.bombardier.com
peter.sheppard at uk.transport.bombardier.com
Thu Jul 11 18:20:01 CEST 2013
Railway wagons normally have two brake lines, main line and train line.
Each wagon has a local reservoir and brakes are applied through a triple
valve and work through a difference in pressure between the main line and
the train line. (Pressure from the local reservoir is fed through the
triple valve to the brake cylinders). So the essential issue is that the
reservoir needs pressure in it for the brakes to be applied.
All brake systems leak, so you need an engine attached to maintain the air
pressure (or vacuum) - it makes no difference on the system in use.
If that engine stops (which apparently it did) the air leaks off and
whilst the brakes will initially be applied, they will eventually leak off
as all the pressure dissipates.
That is why all wagons either have handbrakes or spring applied parking
brakes.
It appears (from what I have read) that one locomotive was left running,
but that was shut down when the fire brigade attended. Locomotive hand
brakes were applied, but they are designed to hold a locomotive, not a 70
wagon train on a 1.2% gradient and it rolled!
Regards
Peter
Peter Sheppard
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Rolf Spiker <rolf.spiker at exida.com>
Sent by: systemsafety-bounces at techfak.uni-bielefeld.de
11/07/2013 17:11
To
Matt Squair <mattsquair at gmail.com>, Bielefield Safety List
<systemsafety at techfak.uni-bielefeld.de>
cc
Subject
Re: [SystemSafety] Lac-Megantic disaster
Hi Matt,
Your answer is a little puzzling to me
Your first two paragraphs:
Train brakes rely on pressure in what's called the brake pipe to keep them
'off'. When brake pipe pressure falls below a set value the brakes engage.
This is the Westinghouse system of air brakes basically.
That gives you a fail safe train brake that will actuate in the event that
the train inadvertently parts, in freight operations a not insignificant
risk due to excessive inter-train dynamic forces.
Are clearly my mentioned : With no any power (in this case vacuum), all
brakes are fully engaged.
The following paragraphs are discussing the opposite I think
You need power to get the brakes engaged.
Is that right?
Regards
Rolf Spiker
Rolf Spiker of Exida.com
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From: Matt Squair [mailto:mattsquair at gmail.com]
Sent: Thursday, July 11, 2013 11:48 AM
To: Rolf Spiker; Bielefield Safety List
Subject: Re: [SystemSafety] Lac-Megantic disaster
Train brakes rely on pressure in what's called the brake pipe to keep them
'off'. When brake pipe pressure falls below a set value the brakes engage.
This is the Westinghouse system of air brakes basically.
That gives you a fail safe train brake that will actuate in the event that
the train inadvertently parts, in freight operations a not insignificant
risk due to excessive inter-train dynamic forces.
However the brake actuation force is also normally provided by a pneumatic
reservoir on each car, these are kept topped up by what's called the main
reservoir pipe. Which is pressurized from air reservoirs located on the
locomotives in the train, which are in turn pressurized by locomotive air
compressors.
Like all pneumatic systems there's a certain amount of leakage, so, if the
locomotive doesn't keep the main reservoir topped up with its air
compressor the pressure will slowly bleed off and the train brake will
disengage.
Which is kind of why mechanical spring style park brakes are always used
to park, and why the comments in the media that the loco was running to
keep the brakes on is misleading.
The actual reason has to do with operational efficiency as it takes time
to pump up a trains reservoirs from ambient. Leave one loco on to run its
air compressor and you can get away quickly in the morning.
Of course if all the needed park brakes aren't applied and then for some
reason the online loco is shutdown...
As a side note, an increasing number of locomotives have what's called an
Auto Engine Start Stop function to save fuel. With AESS the locomotives
control system will monitor air reservoir pressure and only start the main
engine if needed to run the air compressor. Modern freight trains are
quite sophisticated and complicated systems.
So one should be careful of believing what's being said about the 'cause'
of the shutdown, just yet.
Hope that helps. :)
--
Matt Squair
Sent with Sparrow
On Thursday, 11 July 2013 at 7:09 PM, Rolf Spiker wrote:
I always thought that the brakes of a train (also for trucks) have to be
energized to makes them free.
(Vacuum driven energizing)
c
Regards
Rolf Spiker
Rolf Spiker of Exida.com
Senior Safety Consultant & Partner
Phone : +31 (0)318 414 505
Mobile: +31 (0)6 116 225 52
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6721DX Bennekom
The Netherlands
Established Company address:
64 N. Main Street
Sellersville, PA 18960
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From: systemsafety-bounces at techfak.uni-bielefeld.de [
mailto:systemsafety-bounces at techfak.uni-bielefeld.de] On Behalf Of Peter
Bernard Ladkin
Sent: Thursday, July 11, 2013 7:17 AM
To: Matthew Squair
Cc: Bielefield Safety List
Subject: Re: [SystemSafety] Lac-Megantic disaster
There are a lot of questions. The BBC is saying that the locomotive was
left running as the train was parked 7 miles up the line, to power braking
systems; that fire services powered down the locomotive in the course of
extinguishing a small fire; that the train started moving downhill shortly
after that:
[begin BBC quote]
The train, carrying 72 cars of crude oil, was parked shortly before
midnight on Friday in the town of Nantes about seven miles (11km) away.
Local firefighters were later called to put out a fire on the train.
While tackling that blaze, they shut down a locomotive that had apparently
been left running to keep the brakes engaged.
Shortly afterwards the train began moving downhill in an 18-minute
journey, gathering speed until it derailed in Lac-Megantic and exploded.
[end BBC quote]
Questions.
1 (HaroldThimbleby) Powered braking systems on freight are often
air-powered. But they are fail-safe - losing power means they engage. So
what system here requires power to remain engaged?
2. Fire services called to a plant usually have an operator's emergency
number to contact about plant details, and the operation of unattended
running equipment. Is there no such system for freight trains? Why not?
3. That an engine attached to a train with HazMat on board could be left
running and unattended. 4. How the railroad company could tell at this
stage whether and how many handbrakes were or were not applied.
BTW, this is another accident situation predicted explicitly by
sociologists Perrow and Clarke ( The Next Catastrophe, Princeton U.P.,
2007, resp. Worst Cases, U. Chicago Press 2005), as with flooding Mark 1
BWRs. But they were more concerned with Hazmats such as chlorine and
hydrogen fluoride than oil.
It should give engineers pause that sociologists are better at identifying
hazards than they are. (Except for computer networks, of course, where I
think Bellovin's 1992 paper on possible TCP/IP exploits takes some beating
for prediction.)
PBL
Prof. Peter Bernard Ladkin, University of Bielefeld and Causalis Limited
On 11 Jul 2013, at 00:26, Harold Thimbleby ....... wrote:
<a comment about air brakes>
.... BBC News iPad App .......
Engineer blamed for Canada blast
A rail operator's chief executive blames a local engineer for a runaway
train that derailed and exploded in a Quebec town, killing at least 15.
http://www.bbc.co.uk/news/world-us-canada-23264397
Prof. Peter Bernard Ladkin, University of Bielefeld and Causalis Limited
On 11 Jul 2013, at 04:03, Matthew Squair <mattsquair at gmail.com> wrote:
Bigger picture is that there's been a modal shift of oil transport to rail
due to restrictions on pipeline construction, which drives a greater
operational tempo in rail movements in turn.
On Thu, Jul 11, 2013 at 6:44 AM, Gergely Buday <gbuday at gmail.com> wrote:
http://www.bbc.co.uk/news/world-us-canada-23264397
Rail World boss Ed Burkhardt: "It is very questionable whether the hand
brakes were properly applied. In fact I'll say they weren't". [...]
"He said he applied 11 hand brakes. We think that's not true. Initially we
believed him but now we don't." [...]
The fire department and the train's owners have appeared in recent days to
point the finger at one another over the disaster.
- Gergely
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Email: MattSquair at gmail.com
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