BHP is releasing very little information.
I cannot see how a locomotive brake failed and then the on train test or pre-train locomotive safety system test didn't pick up the failure/did not detect the failure. Tests are carried out to ensure the safety failsafes are working.
I can. If you understand how the ECP system is set up, it likely functioned exactly as designed. What fell down is BHP didn't feel it necessary to utilize every available safeguard that some of their competition do.
This could be an equipment failure. That answer is the one that makes the most sense in my head. There could have been a critical fault with the ECP brakes and that’s why they stopped. Maybe the brakes on the rear half of the train were not functioning?
Skim reading a document on ECP brake operation there are circumstances where a wagons’ brakes can cut themselves out of service due to faults. It’s only takes a couple of abnormalities to stack up and affect the outcome.
I never heard the true reason but the Drayton accident in NSW where they put 3 near new TT class in the dirt I believe was an ECP issue of some sort, train or driver induced I’m not sure.
ECP has multiple fault modes available to it. The local rumour mill has an ECP cable coming apart, that will apply a 120% ECP Application, due to the loss of the ETM Beacon. Unfortunately, if you keep the BP charged, the CCD will revert to a pneumatic application after 60 minutes, by design. This is not what you want when standing on the steepest grade in the network...
My understanding of Drayton was that the brakes were released by a crewman who was trying out options in ECP operation.
The locomotive independent brakes remained applied but these would not hold the train.
It is possible that the crewman didn't understand how quickly the brakes would release compared to the Westinghouse system which of course progressively releases car by car.
They were very lucky that no major damage occurred in that case.
PN's ECP training at the time was "this is how you cut it in, this is how you cut it out, you cant hurt it playing around with it, off you go..." What they didn't mention was that when you cut it out, it cut out instantly, and then
the BP started dropping to match the equivalent pneumatic application. Other systems are designed to blow down the BP first, then transition to ECP cut-out, to guard against exactly this type of incident.
The train was more than half way down the steepest grade on the system and was able to stop.
So the brakes were working.
If the brakes on a part of the train were not working, but the train was under control why stop in the place where the brakes are under the greatest stress, rather than run ten kilometres further where the grade reduces to a third of that on the hill?
The most likely answer is that a hot box detector or dragging equipment detector triggered and it was decided to stop as soon as possible to check. I think that control should have advised against stopping on the 1 in 66.
IF the rumors are true the ECP cable parted, you have no choice where you stop, other than where you are, right now.
I dare say BHP's rulebook is similar to my current employers in that if you trip a DED, you stop immediately, if you trip an HBD and are able to lift it, you stop as soon as the train clears through the HBD site.
I wonder how many handbrakes should be applied to hold a 268 car train weighing more than 40000 tons on a 1 in 66?
At my current employer, pretty much all of them
So was it a 4 locomotive consist or 2, that's important. 4 locomotives would hold the train on a 1:66.
WTF? Not even phucken close, champ. I work trains over a 1:50 descending grade, and it takes all of 45% ECP to simply hold the speed at 60, yet alone start slowing. 4 locos holding back 39,000 tonnes? Not a bloody chance. Here's a tip - find a photo of a Hunter Valley coalie. The ones with the 100-tonne hoppers. See the ones with the big symbols on them? They're wagon's fitted with auxiliary braking capacity actuated from the #3 pipe on the loco to hold the train stationary on a grade. Hell, even the new 120-tonne hoppers have that, and the Hunter heavies are only pushing 11,920 for a 91-long train.
They're wondering why the safety systems didn't work, the VC system should have gone off and so on.
Likely because the #1 BCP was above 200kpa.
If it was 4 loco's and ECP in release, i.e cab handle is release that means only the locomotive brake system is in brake.
And why do you feel it would be in release? On a descending 1:66 grade? With 39,000 tonnes behind it?
It fails (and there's many a ways these things can fail) despite the 7 or so microprocessors within the brake system itself. Suddenly they start bitching with each other and there's a release of control pressure and the off comes the brakes from a failed poppett or pressure transducer or erroneous data on the data bus running through the middle of the locomotive and that internal transient was never that high before.
You clearly have no bloody idea.
But then again it might have been a popped CP pipe like the one BHP might hand to the ATSB. They will only see what BHP allow them to see. Pretty sure BHP's engineers would have had the management & control meeting well before access. Good luck to them, that's why they're who they are.
Um, you do realise that a failed #2 pipe will show reduced BCP on the lead loco, compared to the normal pressure? And probably zero on the trail loco if everything is as you suggest? And you do realise that this will be reflected in the datalogger on the loco? And you do realise that this will be available to the ATSB?
The ATP shutdown signal or who 'sever system they have commands the shutdown through the computer in the lead loco which also runs the vigilance based on an input from the reverser handle which would as sure as little apples been in Neutral. A penalty or shut down is commanded from this computer to the locomotive's brake system which obviously didn't respond due a fault. There's one explanation why safety systems didn't work.
Then the Driver, well he is the ultimate safeguard because he will catch any on board faults and save the day and the safety systems will save his day if he nods off. Well the other day the catcher was out-literally! The Driver if he is smart and not at fault and can prove it could throw himself under the Corporate bus for a big payout to take the heat from the hardware. If he can't prove it, he won't get to see the data logger!
Oh phuck off, champ. You want to know the most likely scenario based on what the locals are reporting?
An ECP Cable pulled apart. This in turn gives a 120% ECP Emergency penalty due to the loss of the ETM Beacon. The wagons that are now out of comm with the HEU - by design - start a timer and transition to ECP cutout after 60 minutes. As a 120% ECP application does not result in an emergency pneumatic application, the BP remains charged, so when the hour is up, you have 210-odd wagons behind the parted cable suddenly revert to pneumatic. As to why no ATP? Apparently not configured to initiate an pneumatic emergency application, if ECP is active (Ours does, why theirs doesn't? Dunno...) I'm somewhat reliably informed the Driver should have initiated a pneumatic emergency himself prior to walking, but as I'm not a BHP Driver, I can't say if that is true, but it does make sense when you consider the nature of some ECP faults.
Unlike you, I am confident the ATSB report will explain what went wrong, and why. It doesn't take a great deal to understand how the systems work, if you want to put the effort in, and from that, potential failure modes. Whether or not the rumours are ultimate found to be true? Well, we'll see...