Braking issue on Caledonian Sleeper causes train to "run away" at Edinburgh

edwin_m said:

If the problem was the reservoir pipe not being connected leading to loss of reservoir pressure over multiple brake applications in quick succession, then the obvious solution would be to do a continuity test on that pipe as well when coupling up the train. That wouldn't protect against the reservoir pipe getting disconnected in transit, though the driver would presumably be alerted to that by the loss of air pressure. I've read about it in the context of big American freight trains descending long grades, but I have no recollection of this been mentioned as a cause in a UK accident report - and I've read most of them.

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You can't really do a continuity test on the reservoir pipe, unless you had some sort of gauge at the rear of the train. On normal two piped braking systems the reservoir pipe has a star valve in it and if the pipes become disconnected then the rest of the train becomes single pipe brake only from that point and the star valve prevents air from venting from the reservoir pipe, so the driver would still have full main air showing on his gauge. If a reservoir air tank was damaged or an air leak from the pipes then that would be noticed.

EE Andy b1 said:

You can't really do a continuity test on the reservoir pipe, unless you had some sort of gauge at the rear of the train. On normal two piped braking systems the reservoir pipe has a star valve in it and if the pipes become disconnected then the rest of the train becomes single pipe brake only from that point and the star valve prevents air from venting from the reservoir pipe, so the driver would still have full main air showing on his gauge.

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Thanks for the info. Perhaps there is a gauge somewhere in each coach that they can check?

Thinking some more on this, I presume the Mk5s have air suspension, which would normally use air from the reservoir pipe and probably increases the consumption a fair bit. Is there some valve that prevents the suspension depleting the air from the reservoirs themselves?

PURELY speculation but I thought they didn’t change engines at Waverley? Reckon they’re doing a rigorous check? It was coupled when I arrived but they’ve now disconnected.

If anyone has any other questions I’m here till 10.55

ok do not have any experience of mk5 or 4s for that matter but have driven many trains with triple valves and distributors
in general a 8 car sub would take perhaps 30 -40 seconds after a normal application to replenish brake aux res[auxiliary reservoir] denoted by the hiss stopping in the cab it would take perhaps twice as long after say 3 or 4 small applications and release back to application with no recharge time in between
there must be more than what we know as the way to recharge the brake pipe is full application off the loco sab[strait air brake] and train brake handle to release for perhaps 1- 2mins then full application until stationery
now this assumes you still have aux reses charged by the brake pipe in this set up ??

Ben Glasgow said:

PURELY speculation but I thought they didn’t change engines at Waverley? Reckon they’re doing a rigorous check? It was coupled when I arrived but they’ve now disconnected.

If anyone has any other questions I’m here till 10.55

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Do we know if the Class 92 from this incident ended up with severe wheel flats at all after braking with what i presume was just the straight air brake?

Parham Wood said:

Solution should be three sensors for such a safety critical component which is standard in the air industry. Sorry off track but could not let it go!

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Thanks for that ... shows an even more critical level of safety.

Ben Glasgow said:

PURELY speculation but I thought they didn’t change engines at Waverley? Reckon they’re doing a rigorous check? It was coupled when I arrived but they’ve now disconnected.

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The last few times I've used the Sleeper from Waverley, the loco runs round from one end to the other of the stock; that is the same one which brings the empties in from Polmadie works the train to Carstairs, so it has to uncouple in order to be moved from one end of the train to the other.

edwin_m said:

Perhaps there is a gauge somewhere in each coach that they can check?

Thinking some more on this, I presume the Mk5s have air suspension, which would normally use air from the reservoir pipe and probably increases the consumption a fair bit. Is there some valve that prevents the suspension depleting the air from the reservoirs themselves?

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There could be gauges for reservoir & brake pipe in each coach, but i don't know myself. Would be a good idea though!

I know air suspension has a levelling valve to basically keep the same ride height of the vehicle dependent on load. I presume there will be some sort of venting, you can hear it plenty on Mk3 coaches with the hisses and whistles, so must use a bit of reservoir air but not enough to cause a problem normally unless a deflated air bag.

Peter Mugridge said:

The last few times I've used the Sleeper from Waverley, the loco runs round from one end to the other of the stock; that is the same one which brings the empties in from Polmadie works the train to Carstairs, so it has to uncouple in order to be moved from one end of the train to the other.

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You’re absolutely correct! Haha! Not long after posting it did in fact go about and recouple at the other end!

edwin_m said:

Thanks for the info. Perhaps there is a gauge somewhere in each coach that they can check?

Thinking some more on this, I presume the Mk5s have air suspension, which would normally use air from the reservoir pipe and probably increases the consumption a fair bit. Is there some valve that prevents the suspension depleting the air from the reservoirs themselves?

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I’d imagine that there’d be a non-return valve. It’s certainly necessary on conventional two-pipe systems, otherwise the reservoirs would just empty themselves into the main res pipe and potentially beyond when running single-piped (and thus being replenished from the brake pipe) for whatever reason.

Parham Wood said:

Solution should be three sensors for such a safety critical component which is standard in the air industry. Sorry off track but could not let it go!

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The equivalent of 3 sensors in many rail signalling applications to.
May be someone should remind Boeing about 3 sensors...

edwin_m said:

Thanks for the info. Perhaps there is a gauge somewhere in each coach that they can check?

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EE Andy b1 said:

There could be gauges for reservoir & brake pipe in each coach, but i don't know myself. Would be a good idea though!

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That's a bit over the top, and going through the train checking each coach would be quite time-consuming.
How about providing a compartment equipped with the gauges at or near the rear of the train, so that a qualified member of traincrew can check them before departure?
If it was about a quarter of a coach length it could be his or her office, and also provide secure stowage for safety equipment and high-value parcels traffic... Now where have I seen something like this before?

I don't know why people are all of a sudden concentrating on the reservoir system and inventing all kinds of things when we don't even know what went wrong in the first place. All the gauges and pretty lights in the world won't help if the train is fully charged and someone (for whatever reason) has isolated cocks between the loco and coach after all checks have already been made...(bar the running brake test)....and if that is actually what happened.

GB said:

I don't know why people are all of a sudden

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People are speculating because this is a rare event and potentially a very serious one. People like me are wondering how in general this might have happened and there have been some illuminating links and some posts that plainly contradict - one suggesting isolating the train pipe leaves you with good but sluggish brakes, one saying sooner or later you run out of air (and one link recounting just this in USA freight). So a topic of legitimate interest with speculation driven by conflicting explanations and the assumption that brakes fail safe, this latter plainly incorrect.

edwin_m said:

Isn't the brake continuity test the double check

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seems the most interesting question.

pt_mad said:

https://www.bbc.co.uk/news/uk-scotland-edinburgh-east-fife-49202981

Quote from article:


Interesting reading especially the quote they've given from the TSSA.

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So reading what the TSSA said
( "Clearly this is an incredibly serious situation which calls for nothing less than the grounding of the entire new Sleeper fleet until we have the full details of the what went wrong.

"No one should be playing fast and loose with faulty brakes on our railways and Serco need to wake up to that fact and act now.")

, if it is, as has been stated elsewhere it was a staff error, they will be not be defending the staff member if dismissed or suspended ?

Although I understand faulty brakes have been ruled out.

Greg Read said:

So reading what the TSSA said
( "Clearly this is an incredibly serious situation which calls for nothing less than the grounding of the entire new Sleeper fleet until we have the full details of the what went wrong.

"No one should be playing fast and loose with faulty brakes on our railways and Serco need to wake up to that fact and act now.")

, if it is, as has been stated elsewhere it was a staff error, they will be not be defending the staff member if dismissed or suspended ?

Although I understand faulty brakes have been ruled out.

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Are the ground staff at Carstairs, driver or guard likely to be TSSA members?

Greg Read said:

So reading what the TSSA said
( "Clearly this is an incredibly serious situation which calls for nothing less than the grounding of the entire new Sleeper fleet until we have the full details of the what went wrong.

"No one should be playing fast and loose with faulty brakes on our railways and Serco need to wake up to that fact and act now.")

, if it is, as has been stated elsewhere it was a staff error, they will be not be defending the staff member if dismissed or suspended ?

Although I understand faulty brakes have been ruled out.

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Is the union leader technically qualified? If not, has he had this advice from an Engineer who has full information on the incident? If not, it would seem to be a typical union knee-jerk response.

With the single or two pipe brake system, it is possible, given a particular set of circumstances to lose the brake completely, but this doesn’t sound like what has happened here, if there was an operational process error, then there is a different slant in the investigation, than if it was a technical failure..

TractiveEffort said:

Is the union leader technically qualified? If not, has he had this advice from an Engineer who has full information on the incident? If not, it would seem to be a typical union knee-jerk response.

With the single or two pipe brake system, it is possible, given a particular set of circumstances to lose the brake completely, but this doesn’t sound like what has happened here, if there was an operational process error, then there is a different slant in the investigation, than if it was a technical failure..

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Actually he does have engineering qualifications, but in optical electronics. His statement is not one I'd expect from an engineer of any discipline.

https://en.m.wikipedia.org/wiki/Manuel_Cortes

Cortes was born and grew up in Gibraltar. He left school with no qualifications.[2] Growing up, he never spoke English with his family or friends.

He became an apprentice electrician, joined a local union, and gained technical qualifications from the Gibraltar and Dockyard Technical College. It allowed him to pursue further studies at a technical college in Kent. He studied Engineering at Heriot-Watt University, later becoming a full-time student representative. Later he would gain master's degrees in Optical Electronics, and also Business Economics from the University of Strathclyde. He studied Economics because he did not value the main beliefs of capitalism, which he views mostly as forms of greed.

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a_c_skinner said:

People are speculating because this is a rare event and potentially a very serious one. People like me are wondering how in general this might have happened and there have been some illuminating links and some posts that plainly contradict - one suggesting isolating the train pipe leaves you with good but sluggish brakes, one saying sooner or later you run out of air (and one link recounting just this in USA freight). So a topic of legitimate interest with speculation driven by conflicting explanations and the assumption that brakes fail safe, this latter plainly incorrect.

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What conflicting explanations? I see no contradictions, only technical explanations and other people chipping in who still don't fully understand the operation of train brakes in spite of the information given and the links posted. For example, many people here are interpreting "depletion of the air in the brake pipe" as meaning "the brake pipe contained no air pressure at all" (hence all the questions about parking brakes and how the train stopped at all), which is not the same thing whatsoever.

The Railway Technical website pages already linked to up-thread explain all of these things, are easily accessible to anyone and do not require any specialist engineering knowledge to understand. They explain how the air brake works, the advantages of the two-pipe system and how the brakes can stop functioning in certain conditions. All of this information, together with the RAIB's apparent lack of concern over the operation of the fleet itself, gives a highly plausible explanation to what happened to the Cally Sleeper on it's approach to Waverley. Once this is confirmed, all that remains to be found out is precisely what happened at Carstairs to cause this to happen and precisely how the train was finally stopped, and by whom.

As for all the discussion about proving the main air supply with gauges and tests and warnings, I'm afraid that I'm with @GB. All these wonderful ideas are totally unnecessary when all that is required is for the shunter to look between the loco and coaches to ascertain visually that the air supply cocks to the coupler head are in the correct position.

I've lost count of the number of times that I've used the word "procedural" in this thread, but that is very likely what this incident will come down to and how Cally Sleeper (and other operators) ensure the risks of a repeat are reduced. It may be that adding a visual check will be part of the solution, or Cally Sleeper may have to decide whether the air supply cocks to the loco coupler head are always left open (as in MU operation), in which case the shunter should never have to touch them, or always left closed (as in loco operation), in which case the shunter will always be required to open them when coupling and close them again when uncoupling.

Tomnick said:

On a conventional two-pipe system, the air from the main res pipe isn’t “used” as such - that side of the diaphragm in the brake cylinder is maintained at a constant pressure, the brakes being released as pressure is admitted into the adjacent chamber from the brake pipe (equalising the pressure in the two) and applied as pressure is released (creating a differential) - if I’m not mistaken (it’s been a while...).

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Sorry for being slow, but I think I'm finally with you. You mean that the main air enters the opposite side of the brake cylinder to the brake pipe air and acts like a spring against which the brake air pressure works to apply and release the brakes? The Railway Technical pages show a mechanical spring in the brake cylinder, but there's no reason why it couldn't be compressed air held at a constant pressure instead, as the main air pipe would be. In that respect, yes, the main air is not used directly for braking.

However, the main air is used in that it directly replenishes the brake reservoirs, gets admitted into the brake cylinders and then exhausted. This is the great advantage of the two-pipe system, in that this replenishment happens immediately and does not require air to be taken from the brake pipe, which can get on with the job of controlling the brakes themselves through variations in the brake pipe pressure. Without the main air supply (the one-pipe system), the reservoirs can only be replenished from the brake pipe itself which means it takes longer for the operating pressure to be reached potentially leading to braking difficulties in the event that the driver needs to make successive applications.

edwin_m said:

Thinking some more on this, I presume the Mk5s have air suspension, which would normally use air from the reservoir pipe and probably increases the consumption a fair bit. Is there some valve that prevents the suspension depleting the air from the reservoirs themselves?

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All systems that use air take their supply from the main air pipe, whether it's suspension, doors, pressure ventilation, toilets or whatever. However, each is a separate system protected by it's own non-return valves to prevent a fault on one system affecting other systems on the same vehicle. Pressure is maintained automatically by valves and governers and the entire air system is supplied by a compressor (although it could be more than one on an MU).

Greg Read said:

So reading what the TSSA said
( "Clearly this is an incredibly serious situation which calls for nothing less than the grounding of the entire new Sleeper fleet until we have the full details of the what went wrong.

"No one should be playing fast and loose with faulty brakes on our railways and Serco need to wake up to that fact and act now.")

, if it is, as has been stated elsewhere it was a staff error, they will be not be defending the staff member if dismissed or suspended ?

Although I understand faulty brakes have been ruled out.

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TSSA have obviously borrowed the RMT’s hyperbolic press release generating machine.

O L Leigh said:

I've lost count of the number of times that I've used the word "procedural" in this thread, but that is very likely what this incident will come down to and how Cally Sleeper (and other operators) ensure the risks of a repeat are reduced. It may be that adding a visual check will be part of the solution, or Cally Sleeper may have to decide whether the air supply cocks to the loco coupler head are always left open (as in MU operation), in which case the shunter should never have to touch them, or always left closed (as in loco operation), in which case the shunter will always be required to open them when coupling and close them again when uncoupling.

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I'm curious, and this may seem a little pedantic in some ways, on a proper MU you have an electrical head with a brake continuity wire, in the event of a breakaway the train is brought to a stand electrically and the air supplies between units are not vented due to mechanical valves that close upon coupler surfaces coming apart. looking at it, using dellners for coaching stock, with the brake pipe being your 'brake continuity' in the event of breakaway you want that pipe to be vented (on the coaching stock at least) to bring the train to a stand. As I understand it at the moment, If you were to permanently supply the drophead dellner on the loco with main res and brake supply, there shouldn't be a problem as there are/should be valves in the coupler that will isolate the air supply upon uncoupling (If the coupler is set up the same as MU's, that is) however you would need to have the coaching stock couplers set up so that they vent upon breakaway, and so you would still have to have isolation cocks being operated. I only make this point, because although this might be a 'procedural' issue, it might be deemed to warrant a 'technical' response to mitigate against procedure failing again? I'm not sure any member of the public would be happy to be told 'someone forgot to do it once, so we told him off and he doesn't do that job any more'. If someone forgot, it means someone else can also forget.

aleggatta said:

I'm curious, and this may seem a little pedantic in some ways, on a proper MU you have an electrical head with a brake continuity wire, in the event of a breakaway the train is brought to a stand electrically and the air supplies between units are not vented due to mechanical valves that close upon coupler surfaces coming apart. looking at it, using dellners for coaching stock, with the brake pipe being your 'brake continuity' in the event of breakaway you want that pipe to be vented (on the coaching stock at least) to bring the train to a stand. As I understand it at the moment, If you were to permanently supply the drophead dellner on the loco with main res and brake supply, there shouldn't be a problem as there are/should be valves in the coupler that will isolate the air supply upon uncoupling (If the coupler is set up the same as MU's, that is) however you would need to have the coaching stock couplers set up so that they vent upon breakaway, and so you would still have to have isolation cocks being operated. I only make this point, because although this might be a 'procedural' issue, it might be deemed to warrant a 'technical' response to mitigate against procedure failing again? I'm not sure any member of the public would be happy to be told 'someone forgot to do it once, so we told him off and he doesn't do that job any more'. If someone forgot, it means someone else can also forget.

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Agreed, a procedure is being carried out because of decisions at the time of design, it wasn't designed out but probably should have been.

@aleggatta: Apologies. I fear that I may have been incorrect in regard to one detail which could have resulted in my previous post being misleading.

In my own defence, it has taken me several days to find a photo showing sufficient detail of the coupler heads to see precisely what is going on with the Delners in use on the Mk5s. In the end I found one showing Mk5s in the shed on the RevolutioN Trains website, which I have reproduced below. (The full resolution photo can be accessed via the link and scrolling down to the relevant entry.)

From this photo it would appear that there is a star valve only on the top air port but not the bottom one. I presume that this top port is the main res pipe and the lower one is the brake pipe, and that the lack of a star valve on this connection means that any air contained within it would vent should the connection be broken. This being the case, the brake pipes should vent in the event that a train ever parted, which would automatically initiate an emergency brake application on both portions although the pressure in the main res pipe would be preserved. I have still not been able to find a corresponding photo of the loco-mounted coupler head to verify whether or not it is similar, but I suspect that it must be.



To correct my earlier post, this would mean that it would make sense for the procedure for coupling and uncoupling to remain as per current loco practice; in other words, the air supply cocks should be closed when uncoupled and opened when coupled.

aleggatta said:

I only make this point, because although this might be a 'procedural' issue, it might be deemed to warrant a 'technical' response to mitigate against procedure failing again? I'm not sure any member of the public would be happy to be told 'someone forgot to do it once, so we told him off and he doesn't do that job any more'. If someone forgot, it means someone else can also forget.

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As I've said already up-thread, I do not believe that a technical solution is warranted in this situation. Based on the evidence to hand thus far, it is my own opinion that this incident was caused by an isolation cock in the wrong position, for reasons that the RAIB will establish, which caused the main air supply from the loco to the train being isolated. The primary reasons for this are likely to be a) unfamiliarity with the new rolling stock and it's unusual coupling method, b) incorrect or inadequate procedures for coupling and uncoupling this stock, or c) human factors that resulted in a member of staff making a mistake with the positioning of the cock and/or failing to check that it was correctly set. These are procedural issues that can be addressed by improvements to training and assessment of staff competency and tightening up procedures on the depot as well as out on the route.

Could there be a repeat of this event? While we continue to use Human 1.0 there is always the possibility, even where we increase the use of automatic safeguards. But the railway industry is getting better at understanding human factors and designing procedures that reduce the risk of incidents. And the answer is not simply to identify the culprit and remove him/her from duty, but rather to identify what went wrong, learn the lessons and take appropriate remedial steps. Personally, I'd rather have someone who has made the mistake, learned the lesson and is now more vigilant as a consequence than some newbie who is still gaining knowledge and confidence.

O L Leigh said:

@aleggatta:

From this photo it would appear that there is a star valve only on the top air port but not the bottom one. I presume that this top port is the main res pipe and the lower one is the brake pipe, and that the lack of a star valve on this connection means that any air contained within it would vent should the connection be broken. This being the case, the brake pipes should vent in the event that a train ever parted, which would automatically initiate an emergency brake application on both portions although the pressure in the main res pipe would be preserved. I have still not been able to find a corresponding photo of the loco-mounted coupler head to verify whether or not it is similar, but I suspect that it must be.

To correct my earlier post, this would mean that it would make sense for the procedure for coupling and uncoupling to remain as per current loco practice; in other words, the air supply cocks should be closed when uncoupled and opened when coupled.

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Ah, that is a very helpful response (and photo!). Just to add, the bottom air connection is Main Res on multiple units (with an additional air connection below it on MU's to actuate the electrical head) so I would deduce that the top air connection is the brake pipe (Multiple units have a recess in the dellner to allow this air connection to not foul coupling faces) It is also worth noting that the bottom air connection is identical to that of multiple units (which self isolate upon uncoupling)


Edit: if you look at the middle coach you can see an air connection block on the coupler with brake/main res pipe connections, with brake pipe on top

O L Leigh said:

I'd suggest having a look at this page and read down to the section headed "Successive Applications" which explains some of the problems associated with a single pipe train. It's not necessary to run out of air entirely for the brakes to fail to work.

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That article talks about 'triple valve' fitted vehicles - these vehicles are very specific. I am not aware of the type of brake distributors fitted to the Caledonian stock, but standard brake distributors whether single piped or 2 piped will not run out of air.

EE Andy b1 said:

Do we know if the Class 92 from this incident ended up with severe wheel flats at all after braking with what i presume was just the straight air brake?

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Yes we do know... and no it didn't.
It is also likely it was braking with its rheo (aka "dynamic") brake as well as the straight air - otherwise there isn't much of an explanation of how the train's speed was held in check on the decent from Cobbinshaw towards Edinburgh. The rheo would provide enough brake force to do that, but not to then bring the speed down significantly on the approach to Edinburgh.

aleggatta said:

Ah, that is a very helpful response (and photo!). Just to add, the bottom air connection is Main Res on multiple units (with an additional air connection below it on MU's to actuate the electrical head) so I would deduce that the top air connection is the brake pipe (Multiple units have a recess in the dellner to allow this air connection to not foul coupling faces) It is also worth noting that the bottom air connection is identical to that of multiple units (which self isolate upon uncoupling)


Edit: if you look at the middle coach you can see an air connection block on the coupler with brake/main res pipe connections, with brake pipe on top

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Not that it matters here, but...

On the Dellner fitted units I work on, the compression of the main res connection itself is what operates the electrical coupler head (think of it as an automatic auto-coupler!) And the additional port is used to supply to the opposite units uncouple cylinder during the uncouple process.

Good old fashioned hook and drawbar, or SR style buck-eye couple, with back up hook/drawbar recall we had an ECS running Ipswich to Norwich many years ago, left a track down behind it, so was stopped at Diss, Driver came on the SPT, to have a moan about being stopped on a red, and all of sudden shouted "My train, my train" ! transpired he had left Ipswich with a 170 and a 153, and arrived at Diss with just the 170 ! He was unaware that the train had split, and there was no automatic brake application, if I recall it was down to a coupling problem at Ipswich, all seemed OK, but there was an actual problem within the system, there was a ban on coupling 170's for sometime after that !

aleggatta said:

Edit: if you look at the middle coach you can see an air connection block on the coupler with brake/main res pipe connections, with brake pipe on top

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Yes, you're right. Thanks for the clarification. I was too busy looking at the coupler head of the coach on the right to have even noticed that detail.