Trains.com

News Wire: Lac-Mégantic disaster trial enters fourth week

30989 views
690 replies
1 rating 2 rating 3 rating 4 rating 5 rating
Moderator
  • Member since
    January 2011
  • From: Wisconsin
  • 1,532 posts
Posted by Brian Schmidt on Thursday, October 26, 2017 12:51 PM

Testimony details events leading up to fatal 2013 oil train wreck

http://trn.trains.com/news/news-wire/2017/10/25-lac-megantic-trial-enters-fourth-week 

Brian Schmidt, Editor, Classic Trains magazine

  • Member since
    January 2014
  • 8,221 posts
Posted by Euclid on Thursday, October 26, 2017 2:18 PM

Maybe this testimony will be coming, but this is what I would like to know about the knowledge and intentions of the people in the trial:

Did the engineer know the proper procedure for securing the train?

If he did, why didn't he follow it?

Was he given any instructions by his supervisors about how to secure the train?

 

An interesting point in the testimony is that engineer was not told about the engine problem even though at least one other person knew about it.  However, the engineer certainly knew of the problem when he tied up the train for the night at Nantes.  It was reported that the engineer told his supervisor(s) about the problem, and at least implied that he advised his supervisor(s) that he wanted to shut down the engine before leaving it.  It was reported that the supervisor(s) told him to leave the engine running.

In court, I would like to hear the engineer explain whether after shutting down the engine, he would have started another engine to pump air, if he had been permitted to shut it down the engine with the problem. 

If he answered yes to that question, I would like to hear him state whether he was told that the faulty engine had been shut down by the fire department, as I understand that he had conversations about the fire with his supervisor(s)

  • Member since
    December 2007
  • From: Southeast Michigan
  • 2,983 posts
Posted by Norm48327 on Thursday, October 26, 2017 5:12 PM

Euclid

Maybe this testimony will be coming, but this is what I would like to know about the knowledge and intentions of the people in the trial:

Did the engineer know the proper procedure for securing the train?

If he did, why didn't he follow it?

Was he given any instructions by his supervisors about how to secure the train?

 

An interesting point in the testimony is that engineer was not told about the engine problem even though at least one other person knew about it.  However, the engineer certainly knew of the problem when he tied up the train for the night at Nantes.  It was reported that the engineer told his supervisor(s) about the problem, and at least implied that he advised his supervisor(s) that he wanted to shut down the engine before leaving it.  It was reported that the supervisor(s) told him to leave the engine running.

In court, I would like to hear the engineer explain whether after shutting down the engine, he would have started another engine to pump air, if he had been permitted to shut it down the engine with the problem. 

If he answered yes to that question, I would like to hear him state whether he was told that the faulty engine had been shut down by the fire department, as I understand that he had conversations about the fire with his supervisor(s)

Bucky,

I submit you are beating the proverbial dead horse. Can you not let go of anything that fits your agenda of your desired perfection?

You beat the subject to death in an another thread and refuse to let go. What is your problem?

You keep telling us you have experience but refuse to state your qualifications.

Please put up or shut up.

Your refusal to tell us about your 'experience' speaks volumes.

Norm


  • Member since
    January 2014
  • 8,221 posts
Posted by Euclid on Thursday, October 26, 2017 5:30 PM

Norm,

Like you should lecture me about dead horses.  You seem to be very angry.  Who is the "us" you always refer to? 

  • Member since
    April 2006
  • From: Mission BC Canada
  • 218 posts
Posted by williamsb on Thursday, October 26, 2017 5:54 PM

These three are only scapegoats doing things the way this railroad wanted them to. Running as cheaply as possible. I think this engine was bad ordered many times and nothing was ever done. Not setting the train brakes because it would take longer to get going in the morning. Track was maybe 10 MPH. Didn't they find something like 17 things wrong and the 1 man crew the way they had it set up was just wrong. The higher ups stayed in the USA and weren't held to account. Doesn't accountability come from the top down not the bottom up. I think the trial of these guys is digusting.

  • Member since
    January 2014
  • 8,221 posts
Posted by Euclid on Thursday, October 26, 2017 6:20 PM

williamsb

These three are only scapegoats doing things the way this railroad wanted them to. Running as cheaply as possible. I think this engine was bad ordered many times and nothing was ever done. Not setting the train brakes because it would take longer to get going in the morning. Track was maybe 10 MPH. Didn't they find something like 17 things wrong and the 1 man crew the way they had it set up was just wrong. The higher ups stayed in the USA and weren't held to account. Doesn't accountability come from the top down not the bottom up. I think the trial of these guys is digusting.

 

I think you are correct that the blame for this goes higher than just the engineer or even his supervisors.  The larger organization should be held to account for a lax safety culture if there was one.  But depending on the testimony during this trial, the discovery of blame may lead higher up in the organization.  That is why I am very interested in hearing the answers to the questions I posed above.  It does not seem like it could be the engineer's fault if he was securing train according to company rules or if there were no rules. 

  • Member since
    August 2005
  • From: At the Crossroads of the West
  • 11,013 posts
Posted by Deggesty on Thursday, October 26, 2017 7:22 PM

Euclid

Norm,

Like you should lecture me about dead horses.  You seem to be very angry.  Who is the "us" you always refer to? 

 

I am one of the "us." Why do you not tell us what your experience is? Are you ashamed of something that you did? Were you a railroad employee? Were you a person who gained knowledge of practices by exercising them? What is your experience? Are you a Monday Morning engineer or trainman?

Johnny

  • Member since
    January 2014
  • 8,221 posts
Posted by Euclid on Thursday, October 26, 2017 7:44 PM

Deggesty
 
Euclid

Norm,

Like you should lecture me about dead horses.  You seem to be very angry.  Who is the "us" you always refer to? 

 

 

 

I am one of the "us." Why do you not tell us what your experience is?

 

 

 

Well, I think you should think about it a little bit and maybe the answer will come to you. 

 

  • Member since
    January 2002
  • From: Canterlot
  • 9,575 posts
Posted by zugmann on Thursday, October 26, 2017 8:21 PM

Euclid
Well, I think you should think about it a little bit and maybe the answer will come to you.

Confused

It's been fun.  But it isn't much fun anymore.   Signing off for now. 


  

The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.t fun any

  • Member since
    June 2001
  • From: US
  • 13,488 posts
Posted by Mookie on Thursday, October 26, 2017 8:31 PM

Oh goody.  A seance to liven up the forum....

She who has no signature! cinscocom-tmw

  • Member since
    December 2001
  • From: Northern New York
  • 25,023 posts
Posted by tree68 on Thursday, October 26, 2017 8:47 PM

Euclid
Well, I think you should think about it a little bit and maybe the answer will come to you. 

Alas, we have, and the answer that's come to us is that you're an idealistic wannabe who can't seem to accept any information that doesn't fit your agenda.

And I think you'll find that a great many of us would like to know the answer to the question of where your experience comes from - especially since you actually said you had some.

The folks at the trial may or may not want answers to the questions you asked.  I'm sure you'll be greatly disappointed if the answers are not forthcoming from said trial.

And don't bother asking why.  

LarryWhistling
Resident Microferroequinologist (at least at my house) 
Everyone goes home; Safety begins with you
My Opinion. Standard Disclaimers Apply. No Expiration Date
Come ride the rails with me!
There's one thing about humility - the moment you think you've got it, you've lost it...

  • Member since
    August 2005
  • From: At the Crossroads of the West
  • 11,013 posts
Posted by Deggesty on Thursday, October 26, 2017 9:52 PM

In a face-to-face conversation with Larry (Tree68) last month, he and I pretty much agreed that we have a person who wants to be known as an expert on the various matters that have been discussed and has great diffculty accepting the realities that people with acknowledged experience present. I do not think that I need to name those who we are confident are well-experienced in the various matters that have been discussed.

And, I am confident that posters who are comparatively new to the forums will also recognize the old heads who know what they are posting about.

Johnny

  • Member since
    January 2014
  • 8,221 posts
Posted by Euclid on Thursday, October 26, 2017 10:13 PM

tree68
 
Euclid
Well, I think you should think about it a little bit and maybe the answer will come to you. 

  • Member since
    April 2006
  • From: Mission BC Canada
  • 218 posts
Posted by williamsb on Thursday, October 26, 2017 11:29 PM

Can we discuss the topic and the Lac Megantic trial.

  • Member since
    December 2001
  • From: Northern New York
  • 25,023 posts
Posted by tree68 on Friday, October 27, 2017 4:53 PM

Euclid
Frankly, I think you are projecting your own insecurity.

Nah.  

Just gonna wait until the end of the trial to see what happens.  I don't have an agenda to justify.

 

LarryWhistling
Resident Microferroequinologist (at least at my house) 
Everyone goes home; Safety begins with you
My Opinion. Standard Disclaimers Apply. No Expiration Date
Come ride the rails with me!
There's one thing about humility - the moment you think you've got it, you've lost it...

  • Member since
    June 2002
  • 20,096 posts
Posted by daveklepper on Saturday, October 28, 2017 10:45 PM

Despite all of this off-the-topic argument, it does seem as if the trial is pointing to a general lack of corporate establishment of "Safety First" in its operations, a contrast to what I see as normal practice for every railroad in North America.

And I can understand the attitude of a USA owner who feels that interference with the way Canadians (mostly speaking French, not English) are running things may smack of too much foreign dmination, but that should not have stopped him from having more control over the situation than he did.

This is my impression from the way the trial has progressed thus far and the information presented.  And I think I have a right to this opinion.

  • Member since
    January 2014
  • 8,221 posts
Posted by Euclid on Sunday, October 29, 2017 2:47 PM

Here is the new ten-second procedure that might have averted the Lac Megantic disaster:  

https://beta.theglobeandmail.com/news/national/new-info-shows-backup-brake-may-have-averted-lac-megantic-disaster/article29044518/?ref=http://www.theglobeandmail.com&

In reading this article, there is some good information about what seems to be a new rule by the STB.  However, the pertinent point is obscured by author’s preoccupation of trying to blame MM&A management for the Lac Megantic disaster.

Here is the main point that needs to be clarified.  The article refers to the addition of an automatic air brake application for supplementary securement.  This is the so-called “ten-second procedure” that the writer refers as being a part of the new rules imposed by the TSB since the Lac Megantic disaster. 

This suggests that the use of the automatic brake for supplementary securement was not required by the rules prior to these “new rules.”  If so, MM&A was not required to use this procedure prior to, or at the time of the disaster. 

Yet the article says this:

…on page 105 of the 179-page report [by TSB], a single paragraph suggests the accident "likely" would have been avoided had the air brakes on the rail cars (the automatic brake) been set as a backup safety precaution before the train was left unattended. However, Montreal Maine and Atlantic Railway (MMA) instructed its staff not to use the automatic brakes. Transport Canada either didn't notice this practice or saw no problem with it.

"While MMA instructions did not allow the automatic brakes to be set following a proper hand brake effectiveness test, doing so would have acted as a temporary secondary defence, one that likely would have kept the train secured, even after the eventual release of the independent brakes," the TSB said in its report.

 

This sounds like this practice of supplementing securement with the automatic brake was unusually absent from MM&A operations while either being required or voluntarily done by most or all other railroads.  The writer says this about it being absent form MM&A practice:  The TSB did not notice the practice being absent from MM&A, or saw no problem with it; and that the MM&A instructions did not allow it.

This is ambiguous, so what I conclude is that practice of using automatic brakes to supplement securement was not required by TSB rules existing at the time of the Lac Megantic disaster.   Therefore, there was nothing unusual about MM&A not using the practice prior to the new rules or at the time of the disaster.  Therefore, there is no negligence or oversite involved in MM&A not using the procedure, although that seems to be what this article is so strenuously trying to imply.     

Therefore, assuming that TSB, after the Lac Megantic wreck, has made a new rule requiring the use of automatic brakes to supplement securement, I offer the following criticism of that new rule on the so-called, “ten-second procedure”:

In the past, the TSB has made a public statement that the push/pull test needed to verify securement is not reliable on high grades such as the one where the oil train ran away.  This leaves successful securement dependent upon the handbrake securement prescription which includes the number of brakes set, the number of cars in the train, total tonnage, and the steepness of the grade.  However, what is left uncontrolled is how tight the handbrakes are set, and how much force is applied during the push/pull test. 

Therefore, even if a person complied with the securement rules, there is no certainty that the train will not roll away.  So, it seems that, based on that fact, the TSB has layered on another form of securement as a backup.  On one hand, this appears to be logical and good; the more backup, the better the securement. 

But there is a flaw in that thinking.  It is that the more backup you add, the less accountable any one measure is to the total success.  Adding air brakes to the handbrake securement will encourage a person to slack off on the setting of handbrakes because that is where a large amount of manual labor is required.  In fact that appears to be exactly what happened in the securement that failed at Lac Megantic, although the engineer set the independent brakes and not the automatic brakes.  He knew he had achieved more than enough securement.  Clearly it was far less work than setting more handbrakes to achieve adequate securement.  So, given the choice between securement the hard way or securement the easy way, people will choose the easy way.  So I believe this new rule (if indeed it is true) increases the danger rather than reducing it. 

Even the TSB appears to be offering the same conclusion in so many words toward the end of the article.  So, I it is unclear why they changed their mind.  For instance, they said this:

…asked why a simple safety procedure that could have prevented the disaster was buried deep in the report, and limited to a single paragraph, the TSB said it didn't want to distract from the main point that trains should be secured with the correct number of hand brakes.

"We tried to steer away from any suggestion that air alone is sufficient to hold a train and instead to focus on more permanent solutions to train securement," said John Cottreau, spokesman for the TSB. "The TSB recognizes that an air brake application would have likely ensured that the train would have remained secured until the next morning, but it was not guaranteed."

Moderator
  • Member since
    July 2014
  • 83 posts
Posted by David Lassen on Monday, October 30, 2017 12:21 PM
Some people here are very close to moderation or forcing the thread to be locked. PLEASE discuss the topic, not what you think of each other. Thank you.
  • Member since
    December 2007
  • From: Georgia USA SW of Atlanta
  • 11,919 posts
Posted by blue streak 1 on Monday, October 30, 2017 2:32 PM

IMO just securing trains on slopes can always fail.  Why not require split rail derails at low end of any siding say for example 1 % slopes or more ?  No matter how many securement procedures in effect a train somewwhere will get loose.  If it hits a split rail and goes into an embankment not too much damage.  Of course what does any RR do for securements on Main lines ?  Another split rail if so many securements on a main line ?

  • Member since
    May 2003
  • From: US
  • 25,292 posts
Posted by BaltACD on Monday, October 30, 2017 3:10 PM

blue streak 1
IMO just securing trains on slopes can always fail.  Why not require split rail derails at low end of any siding say for example 1 % slopes or more ?  No matter how many securement procedures in effect a train somewwhere will get loose.  If it hits a split rail and goes into an embankment not too much damage.  Of course what does any RR do for securements on Main lines ?  Another split rail if so many securements on a main line ?

Trains are not always on sidings when the need to be secured.  Split rails may work for sidings - they are a derailment waiting to happen on the Main Track.  In theory, every signal capable of displaying a Absolute STOP indication should be protected by a split rail derail.

Never too old to have a happy childhood!

              

  • Member since
    March 2003
  • From: Central Iowa
  • 6,901 posts
Posted by jeffhergert on Monday, October 30, 2017 4:50 PM

I've read references that leaving a train secured by hand brakes with the automatic brake released was normal practice on some or parts of Canadian railroads.  In theory, with a sufficient number of hand brakes applied the train won't move.  Even railroads that require air brakes to be applied to unattended trains require a sufficient number of hand brakes applied.  After applying them, they are tested to make sure they hold.  If they don't, more are applied.  (Our instructions, depending on locations, may have minimum numbers required.  It does not relieve doing the securement test.  If the minimum number doesn't hold, tie more hand brakes.)  Our test is to release both automatic and independent brakes and check for movement.  After the securement has been deemed satisfactory, and it might take a few minutes to allow slack to fully adjust, the automatic and independent brakes are reapplied.  The assertion that allowing air brakes to be applied leads to less hand brakes being set (IMO) is pure BS. 

Without re-reading everything about this incident, a number of practices that had been considered normal and appropriate were used.  I believe at least one procedure was done incorrectly from what I've read.  That is, going by memory, doing the push/pull securement test with the independent brake set which gave a false sense of securement.  Had the independent not been applied during the push/pull test, it may have allowed movement showing that more hand brakes were needed.  Allowing hand brakes on the engines to be counted toward total train securement (which leads to less brakes being set on cars) may not have been wise.  I must say though that some places allow engine hand brakes (in the lead consist) to count, other places don't even though the locomotive's hand brakes must still be applied.    

I'm not sure that I can agree with the premise that the railroad, or it's employees, knew they were cutting corners when securing the train.  In hindsight, yes things were definitely done poorly, maybe in part incorrectly.  But I think that was due to interpretation rather than a malicious attempt to cut corners.  That what had been considered normal procedures and then have been found to be lacking, is not an unusual event.  It normally takes some incident to point out discrepancies in procedures or practices.  Unfortunately, this time the incident resulted in a tragedy.    

Of course, whether anyone did or didn't know they were cutting corners before this incident is immaterial.  There has to be someone held criminally accountable.  We just need to wait to see who the scapegoat ends up being.

Jeff

PS.  When the only running engine shut down, it stopped supplying air to the locomotive brake cylinders and the train line.  The train line bled down, which usually leads to the car's air brakes setting up.  In this case they didn't, so why would the "10 second procedure" have made a difference?  I wonder if anyone can tell us?  (Of course this question is aimed for a certain forum member.)

  • Member since
    January 2014
  • 8,221 posts
Posted by Euclid on Monday, October 30, 2017 6:37 PM

jeffhergert
PS. When the only running engine shut down, it stopped supplying air to the locomotive brake cylinders and the train line. The train line bled down, which usually leads to the car's air brakes setting up. In this case they didn't, so why would the "10 second procedure" have made a difference? I wonder if anyone can tell us? (Of course this question is aimed for a certain forum member.)

 

Jeff,

regarding your reference to leaking off of the trainline without setting the car brakes, I would like to consider just that possibilty alone before we consider how the ten-second procedure might have affected that.

I asked that same question back in earlier threads about this.  That is, how does the trainline leak down without setting the air and pressurizing all the brake cylinders?  Somebody answered the question, and I recall that one or more others reaffirmed the answer.  I have never heard of this before, so I do not know if it is true, but I find it hard to believe. 

In any case, the answer given was that because the trainline reduction was so gradual, it was able to leak to zero pressure without the control valves sensing that fact.  This was said to be a well-known possibility.  So the train ran away with fully charged reservoirs, and no charge in the trainline or the brake cylinders.  I still don’t understand how that is possible.  Regardless of how slow the pressure drop is, eventually it results in a big pressure differential between the reservoir and the trainline.  How can the valve not sense that big difference in pressure?  Do you think that is possible? 

  • Member since
    December 2001
  • From: Northern New York
  • 25,023 posts
Posted by tree68 on Monday, October 30, 2017 7:05 PM

With a running locomotive, it is possible to completely open the brake line to the atmosphere without applying the brakes.  I've done it.

This is, of course, due to the pressure maintaining feature in modern locomotives.  The backup hose dump valve was opened slowly enough that the locomotive was able to compensate and the brakes did not apply.

So the possibility of the trainline bleeding off slowly enough that the brakes don't apply is definitely within reason.  

A normal "first service" (6 lb reduction) occurs relatively quickly, but not so quickly as to initiate an emergency application.

OTOH, normal acceptable leakage on a train is between three and five pounds per minute.  With a relatively tight train the leakage might be as low as one pound per minute (or less).

A half pound of leakage per minute would mean the train line would take three hours to go from 90PSI to zero.  

 

LarryWhistling
Resident Microferroequinologist (at least at my house) 
Everyone goes home; Safety begins with you
My Opinion. Standard Disclaimers Apply. No Expiration Date
Come ride the rails with me!
There's one thing about humility - the moment you think you've got it, you've lost it...

  • Member since
    January 2014
  • 8,221 posts
Posted by Euclid on Monday, October 30, 2017 7:31 PM

 

tree68
A half pound of leakage per minute would mean the train line would take three hours to go from 90PSI to zero.

We are told that leakage caused the independent brake to release.  Was that leakage also reducing pressure in the trainline at the same rate?   Where would the leakage be located that would cause the independent brake to release?

  • Member since
    December 2001
  • From: Northern New York
  • 25,023 posts
Posted by tree68 on Monday, October 30, 2017 7:39 PM

Euclid
We are told that leakage caused the independent brake to release.  Was that leakage also reducing pressure in the trainline at the same rate?   Where would the leakage be located that would cause the independent brake to release?

Air Brakes 101.  The independent brake is completely separate from the automatic brake.  They are linked (if the automatic is applied, the independent also applies) but can, and do, operate separately.  The independent can be applied, as well as released (actuated/bailed off), without affecting what's going on with the train brakes.

The leakage that would cause the independent brakes to release would occur somewhere on the locomotive consist.  There are many possibilities.

LarryWhistling
Resident Microferroequinologist (at least at my house) 
Everyone goes home; Safety begins with you
My Opinion. Standard Disclaimers Apply. No Expiration Date
Come ride the rails with me!
There's one thing about humility - the moment you think you've got it, you've lost it...

  • Member since
    January 2014
  • 8,221 posts
Posted by Euclid on Monday, October 30, 2017 7:51 PM

tree68
The leakage that would cause the independent brakes to release would occur somewhere on the locomotive consist. There are many possibilities.

I generally understand that separation between independent and automatic, but not all the details.  Could leakage that caused the independent to release, have occurred without involving the train line charge and lowering the pressure of the trainline?

  • Member since
    March 2013
  • 711 posts
Posted by SD70M-2Dude on Monday, October 30, 2017 8:48 PM

jeffhergert

I've read references that leaving a train secured by hand brakes with the automatic brake released was normal practice on some or parts of Canadian railroads.  In theory, with a sufficient number of hand brakes applied the train won't move.  Even railroads that require air brakes to be applied to unattended trains require a sufficient number of hand brakes applied.  After applying them, they are tested to make sure they hold.  If they don't, more are applied.  (Our instructions, depending on locations, may have minimum numbers required.  It does not relieve doing the securement test.  If the minimum number doesn't hold, tie more hand brakes.)  Our test is to release both automatic and independent brakes and check for movement.  After the securement has been deemed satisfactory, and it might take a few minutes to allow slack to fully adjust, the automatic and independent brakes are reapplied.  The assertion that allowing air brakes to be applied leads to less hand brakes being set (IMO) is pure BS.

I've got quite a bit to say, so will spread this over a few posts and add some additional info for those unfamiliar with railway air brakes.

Before the Lac-Megantic disaster the rules and regulations around train securement were much looser, apart from a "sufficient number" of handbrakes being applied to cuts of cars left off air the railroads were quite free to make their own rules, and monitoring/enforcement by Transport Canada was rare. 

I can't speak for the regionals or shortlines, but CN and CP had very different rules for securing trains when the locomotives were left attached with air brakes cut in.

CN required a full service application of the automatic brake (air brakes on cars), full application of the independent brake (air brakes on locomotives) and one handbrake on the lead locomotive, but no handbrakes on the cars unless the train was being left on a grade in excess of 0.7%.  Our rules also stated that "every effort must be made" to avoid leaving a train on such a grade.

CP required a full application of the independent brake and sufficient handbrakes applied to the cars to hold the train, but also required that the automatic brake be left released

It seems that as MMA was operating with rules very similar to CP's (if not the same), which makes sense as they were operating a former CP line where many employees probably started out with CP.

Today the rules are different and more strict, both handbrakes and a application of the automatic brake are required when a train is left unattended outside a yard.

Greetings from Alberta

-an Articulate Malcontent

  • Member since
    March 2013
  • 711 posts
Posted by SD70M-2Dude on Monday, October 30, 2017 8:56 PM

jeffhergert

Without re-reading everything about this incident, a number of practices that had been considered normal and appropriate were used.  I believe at least one procedure was done incorrectly from what I've read.  That is, going by memory, doing the push/pull securement test with the independent brake set which gave a false sense of securement.  Had the independent not been applied during the push/pull test, it may have allowed movement showing that more hand brakes were needed.  Allowing hand brakes on the engines to be counted toward total train securement (which leads to less brakes being set on cars) may not have been wise.  I must say though that some places allow engine hand brakes (in the lead consist) to count, other places don't even though the locomotive's hand brakes must still be applied.   

CN did not allow the locomotive handbrakes to be counted towards the total required to secure a train, and also required that handbrakes be tested with a push or pull test (depending on the direction of the grade).  By default this required releasing the independent brake at least enough to allow the locomotive consist to move itself.

I am not sure what CP or MMA's procedures were for testing handbrakes, but I believe they also required some sort of push/pull test.

Greetings from Alberta

-an Articulate Malcontent

  • Member since
    March 2013
  • 711 posts
Posted by SD70M-2Dude on Monday, October 30, 2017 9:20 PM

jeffhergert

PS.  When the only running engine shut down, it stopped supplying air to the locomotive brake cylinders and the train line.  The train line bled down, which usually leads to the car's air brakes setting up.  In this case they didn't, so why would the "10 second procedure" have made a difference?  I wonder if anyone can tell us?  (Of course this question is aimed for a certain forum member.)

I'm pretty sure I am not that forum member, but I do know why the air brakes behaved the way they did at Lac-Megantic, and I have experienced it myself at work.

In the TSB report the air brake manufacturer (WABCO or NYAB presumably) stated that a reduction rate of at least 3 PSI per minute was required to ensure application of the air brakes on a car.  Understanding this requires a bit more of a detailed explanation of how the car control valve works internally. 

The air brake application depends on the difference in air pressures on two sides of a slide valve, the reservoir and the brake pipe.  The two sides are also connected by a small (3/32 of an inch in diameter) passage through which air flows to charge the car's reservoir.  The small size of this passage is also why it takes so long (~7 minutes) to fully charge a car.

Let's start with the car fully charged, both the reservoir and the brake pipe are at 95 PSI (the pressure MMA was running at).  The Engineer moving the brake valve in the cab reduces the brake pipe pressure fairly quickly, so now at the car the brake pipe is at a lower pressure than the reservoir.  This difference in pressure forces the slide valve over, which blocks the 3/32'' passage while also exposing the pipe to the car's brake cylinder.  When the Engineer moves the brake valve to release this process is reversed, allowing the car's reservoir to be recharged from the brake pipe. 

But, and here's the kicker (pun intended), if the brake pipe pressure is reduced at a very slow rate then air will simply flow out of the reservoir through the 3/32'' passage back into the brake pipe, and the pressure stays approximately the same on both sides of the slide valve.  As a result the valve does not move over, no air is sent to the brake cylinder and the car's air brake stays released. 

There are always many small air leaks on a train, but of note here is the effect of the air turbine on the SBU (Canadianese for EOT or FRED).  The TSB found that the turbine used enough air to consistently apply the brakes on a train of 5 cars or less, but not on longer trains. 

P.S: I'm sure you know all this already Jeff, but there are others on here who may not.

Also my personal experience involved an angle cock that closed itself while the train was moving.  The tail end pressure dropped by nearly 20 PSI over time before we got a chance to stop and check out the problem, and the brakes never applied. 

Greetings from Alberta

-an Articulate Malcontent

  • Member since
    March 2013
  • 711 posts
Posted by SD70M-2Dude on Monday, October 30, 2017 9:25 PM

Also, the 3 PSI per minute reduction rate is only required to set the brakes intitially.  Once this has happened any additional reduction, no matter how slow, will result in a stronger brake application.  This is why the Canadian rules now require at least a minimum application of the automatic brake to secure unattended trains. 

The independent and automatic brake systems are connected, and both are connected to the locomotive's main reservoir.  All also suffer from myriad small leaks as one would expect from a air system out in the real world.  A leak in one system, combined with a lack of MR air pressure to compensate for it will result in the slow bleeding off of both systems.

I also realize that I have given a very simplistic explanation of the air brake system, and have left out the emergency reservoir and other portions like quick service, quick charge, retainers, load/empty features, and pressure maintaining etc.  Just trying to keep this from getting out of hand.

Greetings from Alberta

-an Articulate Malcontent

Join our Community!

Our community is FREE to join. To participate you must either login or register for an account.

Search the Community

Newsletter Sign-Up

By signing up you may also receive occasional reader surveys and special offers from Trains magazine.Please view our privacy policy