DPU question

[denveroutlaws06]

if the lead Locomotive hits something and derails and it has a DPU on it does the DPU automatic shut off to stop forward momentum?

[M636C]

Basically, no....

There have been a number of derailments of DPU coal trains in Queensland where the lead locomotives derailed and the DPUs continued pushing, resulting in spectacular derailments.

In these cases, it was in an area with bad radio reception, and the trailing (electric) locomotives kept pushing until the catenary had been knocked down and the power cut off.

The Locotrol system has a separate control unit for trailing units and the driver should manually shut down the trailing units when a derailment appears imminent or occurs. Cutting the throttle and applying the brakes in emergency on the lead units should be automatically relayed by radio (or the ECP cable) to the remote units in any case.

But there is no automatic shutdown of remote units.

M636C

[BaltACD]

I suspect with air brakes applying in emergency, would shut down the power on the DPU - I don't know if there would be the same delay in initiating emergency application on the DPU engines as happens on the lead engines.

The delay on the lead engines is intented to have the head portion of a train pull ahead and not be struck by the rear end of the train.  How successful this strategy is in the real world is open to question.

I am not a engineer.  I suspect jeffhergert will have a more definitive answer based on his actual experiences.

[NorthWest]

The DPUs do not do anything unless the lead unit tells them to do something. If the lead units are placed in emergency, any DPU units will do the same (though with a brief radio delay). There are no derailment sensors on locomotives, so they do not know if others are derailed.

The greater fun was with the original versions of the Locotrol system. Often the radio reciever car would derail and cease to send signals. The DPU units would continue to plug away in whatever notch they were in for an additional twenty seconds before shutting down. Several accidents on the Southern and Santa Fe were exacerbated by this.   

[jeffhergert]

I'm not sure about an in-train caused emergency.  I've never really thought about it, but since the controlling unit in a DP remote consist is set up as a "lead" engine it probably would have the 20 second delay before shutting down unless it had received a command from the head end controlling unit to go into emergency.

We had a derailment over the Memorial Day weekend where an old covered hopper in a manifest was ripped in two.  It was rumored that the DP was having comm loss and kept pushing.  Everyone was wondering why it kept shoving once the air went, but it makes sense if there is the delay before losing power.  It was said the train was derailed in 3 or 4 different places.

Jeff  

[carnej1]

I wonder if it would be possible (maybe it's being done with some units already) to program the electronics on a DPU locomotive in such a way that a sudden loss of air pressure on either side would essentially trip a "Dead man" type function?

[oltmannd]

I would imagine the power knock-out feature on locomotives is still "alive" when in DPU.  An emergency brake applicaiton of any kind should knock the locomotives back to idle immediately.  

[AgentKid]

oltmannd

An emergency brake applicaiton of any kind should knock the locomotives back to idle immediately.

There have been CPR trains running west of Calgary with DPU, or as they were known back in the day "robot units", since the end of the '60's and work as Don described. But the scenarios described above are interesting.

What happens when things go wrong faster than the engineer can keep up and he doesn't have time to "soak it"? Or something happpens that the engineer doesn't even know about, like Jeff's example. Interesting thread.

Bruce

 

[knucklemaster]

When the train goes into Emergency, so dose the DPU. It will on the railroad I work for set 45 lbs of Independent Air to help slow the rear portion of the train.

[Fred Boyer]

The South Shore freight railroad had a problem with DPU this spring.  The engineer had reversed the train to enter a siding, the DPU kept pusing.  Several cars on the ground before everything got stopped.