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Mishap on GCR


PhilH

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It does state that air brakes aren't the way you secure an unattended vehicle, and that the crew in this instance did not attempt to secure it that (wrong) way, so going into detail about air brakes would surely be irrelevant? 

 

True but, if there was an expectation that the air brakes would not normally leak down over the extent of the break, it might have affected their actions or the care taken. As I see it, there were three causal factors 1) the air brakes leaked off, 2) the scotch probably wasn't placed correctly 3) the handbrakes werent set. All three factors had to happen for the train to move. Yes, you have to set a scotch or handbrake correctly, but I'm pretty certain that was seen as a backup to the train brake in this situation rather than the primary means of holding the train. In general terms, this is very similar to the cause of the Lac Megantic tragedy (loss of air, inadequate secondary braking).

 

Adrian

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The really interesting thing I found about that report is that it doesn't list the loco's air brakes leaking off as a causal factor (in paragraph 136). In fact, aside from the maintenance section, the loco air brakes, which were the other mechanism holding the train in place, do not appear to have been considered in the report.

 

Adrian

No, but it does point out that airbrakes on the loco would leak off unless the compressors were operating in order to maintain air pressure.  As Boris has said it all boils down to some very simple and basic things - the train was not correctly secured (and it would have been better secured if it had been correctly formed and other relevant brakes also then applied).

 

As I've said - it was a pre-planned runaway pure & simple (and that was partially due to, among other things, inadequate Instructions as well as ensuring that staff applied correct procedures - but then there was further evidence of sloppiness in safety procedures with comments such as passenger trains being run through TIII possessions. 

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True but, if there was an expectation that the air brakes would not normally leak down over the extent of the break, it might have affected their actions or the care taken. As I see it, there were three causal factors 1) the air brakes leaked off, 2) the scotch probably wasn't placed correctly 3) the handbrakes werent set. All three factors had to happen for the train to move. Yes, you have to set a scotch or handbrake correctly, but I'm pretty certain that was seen as a backup to the train brake in this situation rather than the primary means of holding the train. In general terms, this is very similar to the cause of the Lac Megantic tragedy (loss of air, inadequate secondary braking).

 

Adrian

It is, as you say, very similar in basic cause to Lac Megantic apart from not using the automatic brake (or straight air brake) to secure the train.  In fact if they had been following Instructions correctly there would also have been the automatic brake applied on the POS although it too would gradually leak off (but in 30 minutes????).

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True but, if there was an expectation that the air brakes would not normally leak down over the extent of the break, it might have affected their actions or the care taken.

 

The RAIB seem to be satisfied that the crews weren't expecting the airbrake to have held the train, if we accept that at face value (which is all the info we have I presume?) then I disagree that it was causal - effectively it did exactly what they expected it to.

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The English Electric handbrake was notorious on most their locos. The class 40s took so many turns to apply the handbrake that they were rarely used in my days on BR; Deltics had a similar arrangement transferring handbrake application through a lever and chain to the bogies. What surprises me is the lack of instruction to apply handbrakes when leaving the loco AND the lack of attention to adjusting the linkage correctly.

 

The KESR has already issues amended instructions about such matters.

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In fact if they had been following Instructions correctly there would also have been the automatic brake applied on the POS although it too would gradually leak off (but in 30 minutes????).

Depends which standard the GC were working to...

 

CMS123 (Maintenance of Locomotive Hauled Coaching Stock at Outstations and Depots - 1988) states:

 

405/Brake Test Vacuum

 

5. Close the vacuum supply, thus isolating the vehicle(s) from the vacuum supply.

Check the brake pipe leakage by observing the vacuum test gauge closely.

The leakage rate must not exceed 4” of vacuum in five minutes.

If the leakage rate is exceeded, examine for causes and rectify.

 

Its predecessor - BR10906 (1969) only permits 2" in 5 minutes.

 

However in CEPS 1019 - (Overhaul, Testing, Transport, Re-Assembly and Storage of Rolling Ring Type Vacuum Brake Cylinders 1990) the requirement is:—

 

4.1.2 Test for leakage

 

Place a sleeve on the piston rod to limit the stroke of the piston to about 4in.(102mm).

Create a vacuum of 20/21in Hg. on both sides of the piston, then isolate the cylinder from its vacuum source.

Make a brake application to reduce the vacuum below the piston by 4in.Hg allowing the piston rod to rise against the sleeve.

After the vacuum has settled there shall not be a loss of vacuum of more than 1/2in.Hg. either above or below the piston during a period of 15 minutes.

Leakage in excess of this rate must be corrected and the cylinder be re-tested.

 

So under CMS 123, it's quite possible for a cylinder to dump all its vac in less than 30 minutes & still remain in spec. CMS123 is probably the most commonly referred to coach maintenance document in the Heritage Railway sector.

 

Either way, the GCR incident reinforces the notion that the automatic brake should not be relied upon to hold a train or vehicle if left unattended.

 

Pete S.

C&W Dept.,

GWS Didcot.

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The English Electric handbrake was notorious on most their locos. The class 40s took so many turns to apply the handbrake that they were rarely used in my days on BR; Deltics had a similar arrangement transferring handbrake application through a lever and chain to the bogies. What surprises me is the lack of instruction to apply handbrakes when leaving the loco AND the lack of attention to adjusting the linkage correctly.

 

The KESR has already issues amended instructions about such matters.

EE Type 4s were notorious for unreliable handbrakes and were equipped with scotches as a result plus widely circulated Instruction to make sure they were scotched when stabled.

 

No such situation with the Type 3s tho' - we normally had no problems with them moving when stabled but occasionally there could be trouble if someone hadn't bothered to fully apply the handbrake.  Over the years I had dealings with two different fleets of them and no reported problems in this respect.

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