you know, In was probably wrong about the additional port, but on the units I worked worked the same as yours it sounds like, on the compression of the main res port fed a ball valve linked to a moving cam that rotated around the uncoupling handle 'axis' to prevent electrical head deployment if mechanical coupling had failed. (we had really tight tolerances and the electrical head was not allowed to deploy if the link arm(the bit that sticks out of the cone and engages with the slot in the disk) was more than 7mm away from 'home' position
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Braking issue on Caledonian Sleeper causes train to "run away" at Edinburgh
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you know, In was probably wrong about the additional port, but on the units I worked worked the same as yours it sounds like, on the compression of the main res port fed a ball valve linked to a moving cam that rotated around the uncoupling handle 'axis' to prevent electrical head deployment if mechanical coupling had failed. (we had really tight tolerances and the electrical head was not allowed to deploy if the link arm(the bit that sticks out of the cone and engages with the slot in the disk) was more than 7mm away from 'home' position
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kingqueen
Member
Agree. The other issue being that such an error is never ultimately down to one person, there are always procedural and practical issues as well; either previously known about not. Scapegoating doesn't sort that - even if the immediately apparent cause is down to one individual.
EE Andy b1
Established Member
Yes thanks for that.
Having seen 92020 at the South end of the Mk5 sleeper stock at Euston this morning with 92006 at the North, i presumed that the 92 was ok.
With the train brake dynamic braking would make sense on the loco.
On a Class 92 if you put the train brake into emergency brake application do you still have dynamic braking or is that lost?
I know in the past with electric locomotives Class 86/87/90 you were normally better off going to full service brake application and keeping rheostat brake rather than emergency, losing rheostat and ending up with wheel flats.
That's right. It's the main shaft valve (MSV). Gauge 5mm and elec head stays in and 7mm it operates if I remember rightly!
Thats the one, but it should operate at 5mm and not at 7mm (so the electrical head does not deploy on the 7mm i.e. incorrectly coupled)
Yes, scapegoating does not help, but developing a system that does not allow itself to operate when in a dangerous state (i.e. modern MU's not allowing a brake release when not having door interlock) is a very simple and straightforward way of ensuring that you don't end up in high risk loss of life situations (which is what happened here), I can understand the argument against automating everything, but the most certain way to remove the risk would be to automate the process in this situation, or at the very least have an electrically operated emergency brake application available to the driver that triggers the coach brakes (like a back up brake pipe dump valve).
Has the specific coupling cock that was isolated been made public yet?(I think speculation has said brake pipe on the loco, but I can't remember reading anything confirmed) it would be interesting to re-create the incident on paper to get a real understanding of the failure of the twin brake pipe system in this circumstance.
Dren Ahmeti
Member
As I said earlier, and as far as I’ve been informed, the locomotive brake was used to bring the whole consist to a halt, after the emergency brake plunger was pressed by the driver did not result in an emergency brake application.
Ah, wrong way round on my part!
EE Andy b1
Established Member
So from what you were told...
was this the locomotive friction only, straight air brake? because as i was saying in #243, normally when you go to emergency with the train brake you lose dynamic braking on the locomotive (unless Class 92s are different). So maybe a train brake application into a full service application would have been better by keeping the dynamic (electric) brake working on the 92!! which is what @TimboM in post #237 says was likely happening.
Would be interesting to know for sure, which i'm sure we will eventually but in the heat of the moment (were not stopping) the thought is to go to emergency and hit that plunger, which is why i'm surprised the Class 92 didn't have wheel flats, or perhaps after modification at Brush have these Class 92s allocated for use with the Mk5 sleepers had there brake pressure to the brake cylinders reduced to aid sleeper comfort. Only my thoughts!
Surreytraveller
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In the heat of the moment you go to emergency. You're not going to sit there mulling different options around in your head when the train isn't stopping when it should
EE Andy b1
Established Member
Which is what i said,
"in the heat of the moment (were not stopping) the thought is to go to emergency and hit that plunger"
But if a driver had had a similar experience before, although unlikely, then his experience may tell him to go to full service, which is what i learned to do with electric locos, although never a train running away, just late braking!
Slightly off topic but i once drove a class 90 on a freight from Carlisle with the Larbert to Oakleigh soda ash 2 axled tanks (10 approx.) and after all my running brake tests as required, i never used the train brake again from the bottom of Shap to Warrington Bank Quay to slow the freight train, i just used the dynamic brake via the speed set of the Class 90 (when it was allowed originally) to slow the train speed (Max 60 mph anyway) until stopping at Warrington when the Rheostatic brake dropped off and the train brake was applied. So i know how powerful dynamic braking can be but it was not enough to hold the train speed descending Shap. Sorry, memories eh!
edwin_m
Veteran Member
In emergency presumably the train pipe is dumped to atmosphere, which should apply the spring parking brakes to give a certain amount of braking on the train.
If, as we are surmising, this is a case of loss of pressures in the reservoirs due to non-connection of the reservoir pipe and train pipe not replenishing enough between brake applications, then any system of independently applying the brake electrically via an EP valve in the train would make no difference. Apart from the parking brake, the air in the reservoirs is what provides the brake force on the coaches.
An independent EP valve would help if the problem was lack of continuity in the train pipe, and this hadn't been picked up by a brake continuity test. But this probably isn't the situation here, because the driver would most likely have noticed a lack of braking when doing a running brake test after Carstairs and would have alerted the signaller, and probably been able to stop the train with the loco brake, well before Edinburgh.
If, as we are surmising, this is a case of loss of pressures in the reservoirs due to non-connection of the reservoir pipe and train pipe not replenishing enough between brake applications, then any system of independently applying the brake electrically via an EP valve in the train would make no difference. Apart from the parking brake, the air in the reservoirs is what provides the brake force on the coaches.
An independent EP valve would help if the problem was lack of continuity in the train pipe, and this hadn't been picked up by a brake continuity test. But this probably isn't the situation here, because the driver would most likely have noticed a lack of braking when doing a running brake test after Carstairs and would have alerted the signaller, and probably been able to stop the train with the loco brake, well before Edinburgh.
edwin_m
Veteran Member
You wouldn't check each coach, just the last one, but you'd probably fit each coach with the gauges in case it happened to be formed up at the end of the rake. There may well be something like that already, probably behind a panel in the vestibule.
However, it might not help for checking the reservoir pipe, as this has non-return valves so even if not connected it might still have air in it. Possibly someone could watch a reservoir gauge during brake application and confirm it returns to its previous reading.
EE Andy b1
Established Member
It's low pressure on the main air reservoir side that apply's the parking brake automatically, or it's the main air reservoir above a certain limit that holds the spring loaded parking brake from applying, whichever way round you like to look at it.
All part of the discussion! Until the facts are revealed.
surely if the driver cannot apply the brakes on the coaching stock there has to be a break in the continuity of the brake pipe? I fail to see how you can have continuity on the brake pipe and not have control of the brakes (short of en mass rupturing of the auxiliary brake reservoirs on all coaches. Thinking about it there must be an EP valve in the brake pipe if the Train manager hit an e/stop and brought the train to a stand (unless the e/stop was a pneumatic valve in the brake pipe)
TractiveEffort
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Not sure exactly what you mean, but if you reduce brake pipe pressure slowly enough, you can bleed all the air out of the distributors, without them applying the brake, unless you recharge the brake pipe (and maybe wait several minutes for the distributors to charge) then you have no brake - apart from the straight air brake in the loco.
EE Andy b1
Established Member
Or are we saying....
at Carstairs that the brake pipe cocks were closed between the rear attaching Class 92 locomotive and Mk5 sleeper whilst the brakes were released on the train, so that air was trapped in the brake pipe keeping the brakes released, then no brake test i presume. Train sets off to Edinburgh with air trapped in Brake pipe, so driver has no control over application of brakes on the train just on the locomotive. With the dynamic brake working, doing a running brake test especially if climbing, the train speed reduced by at least 10 MPH, driver thinks all is ok until eventually braking towards Haymarket and no brakes, a runaway, loco brake only, hits emergency plunger, loses dynamic braking as i described earlier, so only friction brake on all six axles of the 92 and several hundred tons pushing.
So did that eventually stop the train or after the guard by whatever means releasing that it was a runaway and eventually operating an emergency brake plunger, that dispelled the trapped air in the brake and eventually applied the brakes on the train, with what air that was left.
at Carstairs that the brake pipe cocks were closed between the rear attaching Class 92 locomotive and Mk5 sleeper whilst the brakes were released on the train, so that air was trapped in the brake pipe keeping the brakes released, then no brake test i presume. Train sets off to Edinburgh with air trapped in Brake pipe, so driver has no control over application of brakes on the train just on the locomotive. With the dynamic brake working, doing a running brake test especially if climbing, the train speed reduced by at least 10 MPH, driver thinks all is ok until eventually braking towards Haymarket and no brakes, a runaway, loco brake only, hits emergency plunger, loses dynamic braking as i described earlier, so only friction brake on all six axles of the 92 and several hundred tons pushing.
So did that eventually stop the train or after the guard by whatever means releasing that it was a runaway and eventually operating an emergency brake plunger, that dispelled the trapped air in the brake and eventually applied the brakes on the train, with what air that was left.
Isn't it the point that triple valves are only fitted to single-pipe brake systems, but UK passenger stock (and freight too, I suspect, but maybe that was just the freightliner flats) is all twin-pipe. If so you can ignore the article.
This must be a recognised problem of single brake pipe systems, and is presumably only a problem because you have no train pipe to do the recharging for you. (If I have understood you correctly, in which case there is no distributor anyway, as it seems that they are the a twin-pipe equivalent.)
I am sure that driver training on networks with single-pipe systems will emphasise the correct way to brake so that this does not happen.
TractiveEffort
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Problem with single and twin pipe systems.
EE Andy b1
Established Member
There is no problem with single or twin pipe braking systems if all done correctly. Mistakes can and do happen not on purpose.
Most freight wagons are now single pipe, brake pipe only because of mainly costs. Most that are twin pipe with main reservoir are normally either faster wagons for intermodal use or hopper type wagons that use the main reservoir for discharge/unloading but not exclusively.
Passenger trains are twin pipe for speed of application/release of brake and other systems like airbags, doors, toilets.
TractiveEffort
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I was replying that there is a specific problem that can occur on a single or two pipe system. It’s not common, but it can happen. This isn’t what happened here, but I was just adding to the general discussion.
Might need to be retrained, only been driving 35 years, triple valve stock, normal distributor, westcode, EP assisted, single piped, 2 piped - the only time I have been warned about 'running out of brake' was with triple valve stock - I had the benefit of learning southern region EPBs and then driving freight trains where there were specific instruction regarding certain freight vehicles.
EE Andy b1
Established Member
It was just how i read it as part of the general discussion.
Me too and Vacuum!!
The only time i was warned about running out of brake was with triple valve stock.
Years ago we used to have 8Xxx freight trains transporting tube stock from down South to Scotland, i think Rosyth dockyard for refurbishing.
We had loco some barrier wagons, Tube stock, barrier wagons again for brake force.
We had special instructions for these trains as the tube stock were triple valve fitted.
Triple valve brakes, nice brake when applying and when a full brake release, the problem as you will know was if you tried a partial brake release then tried to lap the brake, the brakes would vent via the triple valve and release completely and so you then didn't have full control of the train brake, the brakes stayed applied on the barrier wagons but released on the tube stock, so could cause a run through/overshoot due to lack of brake force. So it was always better to apply the brake and stop short if necessary then release fully and draw forward then applying the brake again.
Erniescooper
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That sounds more likely but it could have been after the brake test if someone was connecting the 61 way jumper and unwittingly knocked and closed the brake pipe isolation and then maybe the train was brought to a stand using the shunting lever that is at the end of every Mk5 that is there to dump the brake pipe.
a_c_skinner
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Coming at this from a slightly different angle. Clearly CS knowns what happened. Everyone in the industry should know by now what happened, speculation should be superfluous. That is how you safeguard against accidents, you share everything in a no blame culture. Coming from the NHS that is what was supposed to happen. Of course in the NHS secrecy and blame were the norm, despite serious attempts to make it otherwise.
Pete_uk
Established Member
Um, what happened to 'fail safe'?
EE Andy b1
Established Member
That sounds about right to me as well.
I used to do a far bit between locomotives coupling/uncoupling at one time and it was very easy to accidentally knock an isolating cock by mistake.
I did wonder how they vented the brake on a Mk5 with the dellner, so a bit like the butterfly on older stock but that re-set the pass com.
I think someone asked this earlier but not sure if answered...
Is there cab to train communication fitted to the Class 92s and Mk5 stock?
We used to have it between electric loco and DVT stock on the West Coast.
Dieseldriver
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Maybe read through the thread at the detailed explanations and discussions and find out.
HSTEd
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Does anyone know why the decision was made to adopt a Dellner without adopting an installation that included the relevant jumper cables in the coupler head?
Surreytraveller
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Are you trying to suggest that the train pipe cock was closed while the pipe was charged?
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