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Author Topic: Collision disables French train's brakes  (Read 7175 times)
stuving
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« on: October 22, 2015, 13:02:00 »

This happened on Tuesday - but still no English version yet - this is the SNCF (Societe Nationale des Chemins de fer Francais - French National Railways)'s statement (my translation):

Quote
At 8:04 on Tuesday 20 October TER 848973, which was en route between Abancourt and Rouen, struck two cows before Serqueux station. As a result the TER was seriously damaged. The driver operated the emergency brake to halt the train, but this did not function normally. This is evidently an exceptional occurrence, as this is the first time that, after such an accident, an emergency brake has not operated correctly. As the train's speed progressively reduced, and while waiting for it to come to a standstill, the crew on board correctly applied all possible measures.

That was a run of 19 km with no working brakes, from a speed of up to 140 km/hr, before it stopped on an upward incline and the driver could jump down and put chocks under the wheels. On the way it ran through Serqueux station at 90 km/hr, above the local speed limit and fast enough to cause some damage. This is a pretty new train, type Z 27500, made by Bomdardier between 2005 and 2010.

I've seen a TV picture of the damaged front, and it does not look that severe, but it's not on line anywhere.

Employees in France have a general right to stop work if they face a risk to life or health that is new, and so has not been quantified and controlled. Some SNCF crews have done just that, leading to continuing train cancellations over several regions.

Scary, huh?
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Oxonhutch
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« Reply #1 on: October 22, 2015, 13:34:05 »

That's a pretty severe wrong-side failure.  Is there not even a handbrake that can be screwed down? Come to think about it, I don't recall seeing a handbrake on any modern stock.

The idea of stopping the whole thing from running uncontrollably back down hill by chocking it as it rolled to a halt is really scary. And I regularly chock and un-chock stationary trains/locos.
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stuving
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« Reply #2 on: October 22, 2015, 13:40:14 »

That's a pretty severe wrong-side failure.  Is there not even a handbrake that can be screwed down? Come to think about it, I don't recall seeing a handbrake on any modern stock.

The idea of stopping the whole thing from running uncontrollably back down hill by chocking it as it rolled to a halt is really scary. And I regularly chock and un-chock stationary trains/locos.

I agree. I bet there's a lot of scurrying about at Bombardier trains HQ (Headquarters) just now, as well as checking excuse generators are up to the latest version.

If there genuinely is no brake on the train, chocking it would be all that's left. But as this is, on the evidence, a control failure due to no electric supply, surely the fallback is to open the train (air brake) pipe?
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Western Enterprise
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« Reply #3 on: October 22, 2015, 14:18:27 »

It appears very scary, but surely we should await the official report into the accident ??

 Undecided
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stuving
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« Reply #4 on: October 22, 2015, 18:44:33 »

It appears very scary, but surely we should await the official report into the accident ??

 Undecided

That would very self-denying, especially as I was questioning what was reported, rather than the details of the cause.

On further examination, SNCF (Societe Nationale des Chemins de fer Francais - French National Railways) have used electropneumatic brakes, similar to those used here, at least until recently. In that case the "emergency brake" is not electric at all, so should have worked on this occasion. That may be why SNCF's statement suggests some bafflement as to what happened.

It would be surprising if even a new train had abandoned this feature - there are rules, whether domestic, UIC, or European (TIS(resolve)), and they are very conservative. However, there is a report of a comment by CGT Rail (the main union in SNCF) that :
Quote
This accident calls into question once again the design of new rolling stock. It is inconceivable, for the [CGT Rail], that railway equipment can be designed such that a fault of any kind does not immediately stop the train.

Even allowing for the hyperbole, much as you would get from RMT (National Union of Rail, Maritime & Transport Workers), I can't see (in the French) if that is suggesting this train was designed "inconceivably".

SNCF say their internal inquiry will report within a few days; they don't say if it will be published, but precedent suggest this incident is serious enough that it will.
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Worcester_Passenger
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« Reply #5 on: October 22, 2015, 19:43:15 »

The SNCF (Societe Nationale des Chemins de fer Francais - French National Railways) press release, at http://www.sncf.com/ressources/2015_10_22cp_heurt_de_bovins.pdf reports that there were just seven passengers.
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JayMac
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« Reply #6 on: October 22, 2015, 21:36:31 »

Huert de duex bovins?

Too right it hurt the two bovines.  Tongue Wink Grin

I do not speak French.

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stuving
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« Reply #7 on: October 22, 2015, 23:59:09 »

Here is that picture of the front of the train, put on Twitter by Sud-Rail (a union for those who find the CGT too meek).


I have read that BEA-TT will investigate, though any initial report is still more likely to come from SNCF (Societe Nationale des Chemins de fer Francais - French National Railways).
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stuving
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« Reply #8 on: March 21, 2019, 20:36:47 »

There was a BEA-TT report in 2016, which we missed. That's a shame, as it was quite illuminating. And then, for some reason, its summary was posted in English earlier this year. It was obviously an in-house translation, so it's a bit quaint (but I'm sure some will like the line about "insufficient protection of the bleeding system").

Quote
Before twilight at 07:35 on 20 October 2015, regional express train No. 848973 between Abancourt (60) and Rouen (76) collided at full speed with two cows that had escaped from their enclosure after the station at Formerie.
After the impact, the driver realised that he was unable to stop his train, which went out of control at about 100 km/h going towards Serqueux.
He notified the operational traffic management centre (COGC) at Rouen, which took the steps planned for such cases.
After attempting unsuccessfully to stop the train by activating the alarm signal, the agent of the commercial trains department (ASCT) moved the passengers to the rear of the train.
After travelling almost 20 km and going through the station at Serqueux at 80 km/h, the train slowed down to walking speed in the ramp going towards Sommery.
The driver then took two stop blocks, alighted from the train on foot and, once it had stopped, immobilised it at 07:49.
The event caused no human casualties.
Material damage was limited to the front face and underside of the train.

The reason for the loss of control of the train was the loss of all its pneumatic and electromagnetic braking capacity after the impact.
The following technical causes led to the brake failure :

    sensitivity and insufficient protection of the bleeding system ;
    position of the cow catcher ;
    vulnerability of some safety functions in the event of short-circuit in the hitch coupler.

BEA-TT made one recommendation on the implementation of THE technical modifications announced by SNCF (Societe Nationale des Chemins de fer Francais - French National Railways) Mobility.

The analysis also highlighted underlying causes by using feedback from the standards for rolling stock dimensions and risk forecast analyses.
BEA-TT made one recommendation and issued four calls for action on these topics.

That summary misses all the important bits, which are in the narrative of the event - see next post.
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SandTEngineer
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« Reply #9 on: March 21, 2019, 20:47:34 »

The outcome was bleeding obvious then...... Tongue
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stuving
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« Reply #10 on: March 21, 2019, 20:48:51 »

This is the sequence of events, from the BEA-TT report:

Before even striking the deflector (well-called cow-catcher in this case), impact with the animals bent the Scharfenberg coupler arm and ripped off the electric connector and the brake pipes.

Not only was the air in both pipes lost, but the main DC (Direct Current) power line (72V) shorted to chassis. That tripped all the breakers on the supplies (float battery), leaving almost nothing still powered.

The two carcasses were trapped under the front of the train for a short while, then pushed under and the train passed over at least one. On all four bogies, the purge valve assembly (which is mounted lower then the bottom edge of the deflector!) was struck, its cover bashed in, and all the brake air vented.

Thus the brakes which the driver had applied (at emergency) a second before impact all released, and stayed off. There were electromagnetic track brakes for emergency, but those ran off the 72 V DC...

Loss of power took out all the train's control system other than the most direct (air brakes) and, for example, the driver's train radio, intercom, and PA (Public Address).

The real piece de resistance of this, however, is that there was an accident in 2009 (Sallanches) with enough similarities to forewarn that this could happen. There it was a car, lumps of which went under a train with ten bogies. On all bogies the brakes were damaged and lost effect, to varying degrees, but with some still braking and the electromagnetic brakes too (no loss of 72V) the train stopped OK. Some changes to the protection of the brakes was ordered, but I can't see a clear statement that these had or had not been made on this train.

Doesn't it make you think, though, that putting all those vital train-wide systems into a coupler, and putting that sticking out of the front of the train, is just asking for trouble!
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broadgage
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« Reply #11 on: March 21, 2019, 22:34:25 »

This sounds rather worrying.
Surely opening the brake pipe to atmosphere should without fail apply the brakes ? Regardless as to whether this is done accidently as a result of striking the cows, or deliberately by the driver operating the emergency brake control.

The force to apply the brakes comes from compressed air stored in reservoirs under each vehicle. Loss of this air can result from debris striking the tank and breaking fittings attached thereto, this would render the brake ineffective on THAT vehicle.
However the brake should still work on the rest of the train.

It seems improbable that striking the cows would have released the air from ALL the tanks along the entire train.

Perhaps the venting of the brake pipe was reliant on electricity ? In which case it sounds a very poor design.
However even if the drivers brake control was thus rendered ineffective, the collision damage should still have vented the brake pipe, and applied emergency braking on all vehicles with intact air reservoirs.
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A proper intercity train has a minimum of 8 coaches, gangwayed throughout, with first at one end, and a full sized buffet car between first and standard.
It has space for cycles, surfboards,luggage etc.
A 5 car DMU (Diesel Multiple Unit) is not a proper inter-city train. The 5+5 and 9 car DMUs are almost as bad.
stuving
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« Reply #12 on: March 21, 2019, 23:43:48 »

It seems improbable that striking the cows would have released the air from ALL the tanks along the entire train.

Improbable, maybe, but that's what the report says. Exactly how depends on the details of this brake system, and I'm not 100% clear on that - which would be true if I was relying on understanding the English jargon terms, but is worse with the French vocabulary.

What I can infer is that it is electropneumatic, with two air pipes. I think that gives it a two-pipe air brake operable if the electricity fails, plus electric control on top. The problem arose with these quick purge valves (possibly vent valves?) that are described as automatic. It says: a pulse on the control input produces a complete brake release and venting of air, even with no pressure in the supply (reservoir) pipe.

Now, that leaves a number of points I don't follow - such as where did the bogie reservoir air go? But the description does say that, once the cover was not covering it, even flying ballast could operate that valve. One of the required changes is to fit "manual" valves instead - now what does that mean in this context? As described it removes the latching behaviour, but manual??

But I'll stick to the more general conclusion: putting really important stuff right on the front, or very low down and in the same place on every coach or bogie, is asking for trouble.
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DaveHarries
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« Reply #13 on: March 21, 2019, 23:59:04 »

The outcome was bleeding obvious then...... Tongue
Yep. All there in black & white (well, except for the cows....)

Dave
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stuving
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« Reply #14 on: October 27, 2019, 19:34:39 »

I thought I'd put this here, as the mention of "loss of 72 V DC (Direct Current) supply" rang a bell (if not an elctric one).

SNCF (Societe Nationale des Chemins de fer Francais - French National Railways) have produced a very quick report on the accident at Saint-Pierre-sur-Vence -  the one that led to the "illegal strike". It's a bit more than you'd expect so soon, at 34 pages, but has little about the road vehicles that caused it (Wikipedia has something on that). They concentrate on what happened to the train, how the driver coped, and what might need to be improved.

The train hit a low-loader carrying a sugar-beet harvester. The level crossing was rated as not suitable for vehicles with low ground clearance, and this one was meant to use another route. But that was blocked by an accident, so the driver (a German, not that odd in the Ardennes) took this route and got stuck.

When the train, inevitably, hit it its front was badly damaged. The driving desk was forced back, which is presumably how the driver was slightly injured, and the coupler destroyed. Most important, the 72 V DC supply was cut, this being derived from 25 kV and powering essential systems throughout the train. This is 72 V DC so it can be provided from the battery as well, but in this case the change-over is not automatic. The train derailed onto the other track, and brought down part of the conductor wire.

Among the systems that lost power was the GSM-R (Global System for Mobile communications - Railway.) radio with its emergency call feature, and the driver knew it wasn't working when he pushed the button. His priority was to protect the train on both tracks, and he used his own phone to call an agent-circulation (in effect a signaller). The train was some way past the crossing, which had a phone still working, and nearer to the next one. There is mention of another method of protecting the train (not described) that was also not possible without the 72 V DC.

Tests established that the GSM-R could have been made operative by changing over essential facilities to the battery supply, but this is not part of the standard response to an emergency. The process is given - a list of ten steps to be done in order, including transferring a key from the desk to another equipment box, and operating a locking lever on a box of switches. This is said to take at least a minute and a half, and "the ergonomics could be improved".

The conclusions for SNCF are all things "to be looked at":
  • Giving crew official mobile phones
  • Not putting important wiring in places vulnerable in a collision
  • Providing an emergency battery mode that's practicable to use
  • Reviewing the advice to drivers for when a collision is inevitable.

In addition, they'd like someone to stop drivers of convois exceptionnels being so stupid.



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