Runaway train

Can someone explain something to me about all this. I always understood that the Westinghouse air brake system was a fail safe system, and that springs held the brakes in the "brake" position until such time as a loco began to build up air pressure in the system

The springs are only used to release the brake because the air only travels in one direction and that's into the brake cylinder, springs aren't very strong either, one person can compress the springs with their hands while air can give 45~50PSI pressure which is allot of force, to release the brake you charge the brake pipe and the triple valve closes the aux res to brake cylinder port and opens the brake cylinder vent port which the spring now moves the piston to the release position.

Cheers.
 
Hi everybody.
Well as I suspected would happen when this thread first started the rail company has now gone into liquidation. Working in industrial safety it seems always inevitable that the directors of poorly managed outfits walk away from their responsibilities leaving it to others to sort out the mess and probably have to organise compensation to victims from public funds. I have seen these situations so often I would find it impossible to count them ( though obviously not on this scale)

Regarding what caused the runway, from what has been stated the engine had to be left running to power in the air compressor which continually compensated for innumerable air leaks in the freight cars. It would also seem that these leaks were in the airline couplings between each freight car and that these couplings where of the old plunger type connections which are renowned for developing leaks. Because of the foregoing these connections have not been seen in Great Britain and Europe for over 20 years. However, the more modern Suzie type connections rarely ever leak know matter how many times they are connected and disconnected.

It has been stated in this thread that because of the numbers of freight rail cars throughout the American and Canada that regular maintenance and the new replacement of the old couplings with the more modern Suzie type is impossible due to cost. Well, how much is it now going to cost to compensate the families of the bereaved, the injured, to rebuild the town and heal the mental wounds of all those involved that day? I would suggest that you could replace an awful lot of air valves with the money that is going to be needed in the foregoing.

Replacing those valves would also mean that you do not need to leave engines continuously running therefore saving the cost of the fuel and the environmental damage caused in such procedure. You also then eliminate the danger of unobserved mechanical breakdown and fire which initially started this whole chain of events. Good safety procedures and maintenance always prove to repay their initial costs whenever they are implemented and often within a short period of time. Since that message got through to the heavy goods transport companies in Britain accidents have been reduced by over 80% since 1974, and that in an ever expanding industry. Hopefully this tragedy will now spur a rethink along those lines in the American and Canadian rail industry

Bill
 
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Hi Bill,

It's good to hear from you. :)

I agree that this hopefully should hit home and to the hearts of the rail company owners, and it probably does at the lower management levels. But sadly, our industries today are owned by people seeking instant monetary gratification and will not invest anything back into a company unless they are forced to. Now even more sadly, there are lobbyists who are paid to pay off and influence the government so any possible legislation that is introduced into our Congress will be met with long delays, tabling, and stalling so that it never sees a vote.

John
 
#1 - The money that will be spent now is, as you said, likely to come from public funds, not company coffers so saying that money could be saved if only they had modernized the equipment is a non-sequitur. (Tho I do agree it's appalling that is wasn't done)

#2 - Rail car brakes are applied using air pressure from reservoirs on each car. These reservoirs are "refilled" when the brakes are released, by the pressure in the brake pipe running the length of the train. IE, the brake pipe is evacuated or at a very low pressure when the brakes are applied, and if the brake cylinder leaks air - depleting the supply available to apply the brakes, it won't get "refilled" until the brake handle in the locomotive is moved to the "release-charge" position.

So long as the brake handle was in "application" or "lap" NO NEW AIR could be delivered to the reservoirs used to apply the brake shoes, so what difference does it make that the engine (and therefore the compressor) were shut down?

Seriously, I want to know...
 
Because the air pressure leaks out, disabling the: "fail-safe feature" of the Westinghouse Automatic train braking system.

It takes money ... to make money.

It takes air pressure to keep the brakes applied, and also to release brakes ... there are no, heavy duty, spring loaded brakes.

The loss of air in a trainline, makes the valve to trigger, and apply the other air resivoirs pressure to push out on the brake cylinder.
 
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Hi frogpipe and everybody
You miss the essential point...it won't get "refilled" until the brake handle in the locomotive is moved to the "release-charge" position.

Frogpipe, I think you missing the basics of how these systems work. I am no engineer, but I will try to describe it very briefly in a way I have done in safety presentations to drivers and shunters in the road haulage industry.
In the screen you are looking at now imagine two air tanks one to the left of the screen and the other to the right. They are connected by an airline and in the middle of that airline there is a double headed piston isolating the two tanks.
For argument purposes let us that say that the tank on the left is charged to 100 lbs psi. The tank on the right is charged to 90 lbs psi. The unequal charge of the two tanks would push the piston to the right and this in effect on a freight car would push the brakes off.

If the pressure in the left-hand air tank is suddenly reduced to 80 lbs per square inch by the application of the brake lever, the piston is pushed to the left by the now greater pressure in the right-hand tank and this applies the brakes.
In systems that are well maintained the pressure in the right-hand tank whose action applies the brakes should never need to be recharged as there should be no loss of pressure at any time. There may be a small loss due to expansion when the piston moves on application but even this would be rebuilt when the piston moves back to the right when the higher pressure is restored to the left-hand tank.

Therefore the only section of the braking system that needs recharging with air would be the break lever application section (the left-hand tank), as when the brakes are applied the pressure is reduced by venting it to the atmosphere. Should the compressor fail to recharge that section of the system then the brakes will be applied and remain applied until the brake lever section of the system (the left hand tank) is at a level to once more push off the brakes.

In reality both sections of the system are connected to the compressor just in case the application side (the right hand tank) should develop a leak for any reason. What seems to have happened in the Canadian accident was that poor maintenance and old type plunger connections between the freight cars developed leaks that allowed both sections of the brake system to lose pressure and therefore the brakes would be permanently released if the compressor is not continuously running.

There is on the brake application side of these systems (
The right-hand tank in our description) non-return valves which should stop the air from the tanks leaking back into the airlines should the pressure there drop below the levels of the tanks. However obviously the continuous leaks on the Suzie’s caused working pressures on the non-return valves that they were never designed to carry and therefore these also failed Eventually, which lead to the tragedy that we have seen

hope this is the explanation you are looking for

Bill
 
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Air Brakes on trains do not require any air pressure to be released.

http://www.railway-technical.com/brake2.shtml

http://www.railway-technical.com/brake2.shtml said:
"Each freight car has an air tank (reservoir) on it. This reservoir (often called the auxiliary reservoir or brake reservoir) is charged with compressed air from the locomotive's air compressor thru the train line brake pipe. You can see the air hoses between the cars and they go Kapowssssh when you uncouple them. After the initial charging of the reservoirs, the brakes can be set (applied) by REDUCING the pressure in the brake pipe. Compressed air from each car's reservoir pushes on the brake cylinder piston to apply the brakes on the car. In the rare event that you have no air in the reservoir then you've got no brakes and you've got a run away."

Ergo, while the brakes are applied, the Auxiliary or Brake Reservoir can't be charged while the brake pipe pressure is reduced - as is the case when the brakes are applied.

The link is an excellent document describing the air brake systems on trains, I have only quoted the opening paragraph.
 
Hi Frogpipe and everybody.
Excellent video presentation their frogpipe. But it just demonstrates in graphic terms what I was trying to explain in my probably my not to well composed text posting above. As I stated my experience in the British road transport industry. There the air release would probably have been designed differently due to the more rapid action and frequency of brake applications than there would be on a train, plus you only have one trailer rather than multiple freight cars.

Therefore rather than having a triple action valve on one line in modern road vehicles you have virtually two separate systems on two lines with the air release being on the drivers foot brake section of the system. Therefore as soon as the trailer airlines are released from the drive unit Suzie couplings, the trailer brakes are fully applied which ensures that the trailer while uncoupled will not go anywhere.

As I say I am no engineer and can only go by my experiences in British road transport safety.From memory I do believe when I first joined the industry as a heavy goods driver in the 1960s, triple action valves on a single airline was possibly common on articulated vehicles. However, like plunger couplings the system has not been installed on road vehicles for some years.

With all that said frogpipe, I do genuinely not see the point you are trying to make. Are you trying to make the case that the loss of air pressure should not have or could not have contributed to the trains uncontrolled runaway?


Bill
 
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Hi John and everybody
Hi Bill, It's good to hear from you.
I agree that this hopefully should hit home and to the hearts of the rail company owners, and it probably does at the lower management levels. But sadly, our industries today are owned by people seeking instant monetary gratification and will not invest anything back into a company unless they are forced to. Now even more sadly, there are lobbyists who are paid to pay off and influence the government so any possible legislation that is introduced into our Congress will be met with long delays, tabling, and stalling so that it never sees a vote.
John

John, there was the same problem in Britain prior to 1974 where the large employers for many years successfully stopped any legislation being passed through the British Parliament with regard to improving workplace safety. In the same way as you describe they used well-funded lobbyists to discredit the safety activists along with a programme of misinformation regarding just how safe British workplaces where. However, the Trade Unions and supportive MPs used tactics brought forward by William Wilberforce and Thomas Clarkson many years before which successfully brought to an end the slave trade in Britain.

In that they introduced into Parliament what was at that time to be a relatively small Bill entitled “The Health and Safety at Work Act” in the bill their where two innocuous looking paragraphs which everybody found difficult to argue against. The first one: -
General duties of employers to their employees.
(1)It shall be the duty of every employer to ensure, so far as is reasonably practicable, the health, safety and welfare at work of all his employees.
The second one: -
General duties of employers and self-employed to persons other than their employees.
(1)It shall be the duty of every employer to conduct his undertaking in such a way as to ensure, so far as is reasonably practicable, that persons not in his employment but who may be affected are not thereby exposed to risks to their health or safety.
………………..​
The above two paragraphs not only changed the lives of workers in Britain but if you read into the second paragraph it transformed the obligations the employers had to people other than their employees. To make it salient to the accident we are referring to in this thread, In rail transport it meant that the then British rail operation had a huge increased safety obligation towards not only their employees and passengers but all others who where in the vicinity of any of any of their operations. That obligation remains right up to today.

It is the words reasonably practical in the bill which has transformed everything. Would leaving those engines running to cover for innumerable leaks be considered a “reasonably practical” way of dealing with the air leak problem. I do not think that would be considered so in the courts of Britain where undoubtedly it would have been challenged prior to the accident under the above act.

Perhaps there are few Congresmen in America that could introduce a similar innocuous bill into the legislative programme ?

Bill
 
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With all that said frogpipe, I do genuinely not see the point you are trying to make. Are you trying to make the case that the loss of air pressure should not have or could not have contributed to the trains uncontrolled runaway?


Bill

Not at all. What I'm trying to say is that according to my understanding the following two statements are true.

1. The compressor being on or off does not matter.
2. Any train with it's brakes set, that has leaky brake cylinders, WILL eventually loose braking pressure and run away (assuming it's on a grade) unless the hand brakes are set and/or chocks are applied to the wheels.

Pursuant to #2, once the brake cylinders (and by extension the auxiliary reservoirs) have lost their air pressure, there is NO WAY for it to be replenished until the brakes are RELEASED by the control handle in the locomotive.

The only exception is the Independent brake, the Independent does NOT rely on an auxiliary reservoir for braking force. Rather, the Independent brake used pressure from the Main Reservoir to apply the brakes. There, and ONLY there, would the compressor being off result in loss of braking force, since there and only there would the gradual loss of pressure through leaking brake cylinders be replenished continually by an operating compressor.
 
If the air compressor is turned off, and the 2 reservoirs lose pressure, the train loses brake air pressure, and the westinghouse brake system is totally disabled ... 12 handbrakes on a 1.87% grade is insufficient to stop a runaway, that has lost its air. Any number of mechanical things could have been accidentally done, by a dozen firefighters, and one lone "track worker" that had no qualifications in the field as a RR engineer/conductor, all fiddling with electrical, control handles, angle cocks, cut out valves, cut levers ... etc ...
 
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Quite true. I was considering this in the light of statements like "The reason the train became a run away was because there was a fire where the fire department shut down the locomotive and therefore the compressor for the air brakes"

I originally asked about this here because according to how train brakes work, it couldn't be that simple.

On the other hand I have to wonder what genius decided that an unattended train could be left sitting on a grade, held in place by only it's own air brakes.
 
Hey does the train automatically go into emergency if there is a break in the couplers or train like this one did?

Not when the couplers break but when the trainline hose breaks. The air hose just vents into the atmosphere, which is what happens when a train goes into emergency.
 
Which is also what the emergency position of the handle does, dump the brake pipe pressure to atmosphere. Normal reduction is slower. The fast escape of pressure in the pipe triggers the triple valve on each car to slam the shoes down.
 
Yes it is a fail safe ... but any number of things can accidentally or intentionally disable the fail safe braking operation (which I can't go into how to do so).

With proper settings the air brakes operate (flawlessly, 99.9% of the time), in this case something went horribly wrong, and the generator/compressor was intentionally shut off, by this, and other fiddling with controls, and valves, disabled the emergency braking, allowing all air to escape from both the trainline and all resivoirs, and the emergency brake release reservoirs. Like I said ... there are two presurized systems on a train, one applies the brakes when it loses pressure, by triggering the other pressurized system which pushes out on the brake pistons, if that 2nd pressurized system is also depleted, the emergency brakes pistons release, and you have an uncharged air brake system, a non-presurized runaway train of Radio Flyer wagons rolling downhill.
 
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