Train 1258 Fiasco at Harold

When this whole thing settles down, can someone tell me what P-wire is? I like this nuts and bolts stuff. Thanks.

FlipFlap

I finally got a chance to look at the print for the Emergency Brake Trainline Loop. CB11.
First, it is monitored by Event Recorder and Differential Current Detector. I wonder if any useful info was obtained from those devices.

I'll go ahead with my theory, if you all promise not to take it as factual at this time.

My theory is it was a shorted surge suppression device across a relay coil.
Sometimes they eventually cook themselves open, and you can reset the breaker and proceed. Sometimes they do not open, and remain shorted. (Dead short between Positive and Negative is not a good thing.)
Since this relay was tied into the EMV trainline, presto...the problem at hand. There doesn't have to be 750 in trainline and GTL for this to happen, although that is also a possibility. We get shorted suppression diodes periodically on the older cars. But it is usually manifested as a local (one car) problem. It generally does not cripple trains. You might get a door breaker trip in one car, HVAC breaker trip in one car, or M/A with shorted exciter field input (which translates to no 220 VAC output), for examples.

If the theory proves correct, the suppression device can be beefed up.
At worst, I'd remove them, and sacrifice the relay if surged. That would only give you one dead (I.E. no propulsion) truck in the train per relay sacrificed...big deal. If any one EMV solenoid coil burned out, that EMV could also be cut out. Again, I'm not trying to jump to conclusions. It's a reasonable, very plausible theory. What info I've seen so far fits in perfectly. And it should not be that hard to modify out this type of trouble.

Tom

BTW I'm told it was the last pair in the train. Who knew?
There are no drum switch connections to break this trainline.
So, Clem wins the prize. Retracting would be the only way I can see to isolate this type of problem.
Edit: I'm looking into this. There may be another way.

Tom:Again I tip my hat to you! What were the #s of the culprit pair if you know? MACTRAXX

Mac,

7295

Thanks for the prize, N340SG. Hope it's something to eat or wear.

I've been doing this for a long time.

I like your theory. Yes, to place a surge suppression diode on a coil that would affect the entire trainline if shorted isn't a good idea. In this type of service they short far too often, and they'll just lie there waiting to get us eventually. Afterall, they give no warning, aren't something that's ever looked at and are never replaced, ever, unless they explode. Rip 'em out! This is a railroad you know. Themz relays should be iron and glass, dang it!

I've got a question for you... entirely unrelated:

There was a time when a train would be considered unequipped with speed control if the head car's EMV was plugged. Now with the Microcab modification, I'm told that if any Microcab is in the train, its EMV would open so a plugged EMV in the head car no longer disables the ASC, just the deadman. Now, we went out with the EMV unplugged as well as plugged and did everything we could to get the ASC to dump a train as a penalty application, but could only get Max brake.

So really I have two questions:

1. In normal operation, when or would the ASC dump the train? When it is not slowing at the proper rate dictated by the penalty max brake application? Or does the ASC NEVER dump the train?

2. How does the Microcab modification know to open an EMV five cars away if the others are not modified?

I hope I'm being clear enough for you to understand what I'm trying to ask. You're a wiz, N340SG!!

Clem

P-wire, or potential wire is a way to send a control signal through an entire locomotive consist-or in the case of the LIRR-a set of mu cars.

Given 32V as the control voltage, 32V might imply a maximum acceleration rate-with 0 volts implying maximum service braking rate on mu equipment.

On diesels, this how the dynamic brake is controlled. I've said enough...I'll leave it to Tom or one of the other LIRR guys to explain further.

After all, I'm only a lowly machinst by trade. (':(')

As, NRECer said, the P-Wire sends a control signal. I know this was covered in an earlier post, but here's a quick explaination. Anyone step in to correct or elaborate.

The P-Wire runs through the MU consist. The controlling pair applies voltage to this wire to release service breakes and reduces the voltage to apply them. The voltage travels from car to car through a set of pins in the electric portion of the couplers.

When it reaches the last car, the "wire" is looped back through the uncoupled coupler (technically through the coupler relay) and runs back to the controlling car. On its way back, it sends its message to release or apply the brakes.

When this circuit is open somewhere in the train, say by a bad (incomplete) hitch, there's no voltage and no brake release.

On the M-7's the P-Wire signal also controls propulsion.

By "looping" the P-Wire mid-train manually (instead in the last car, as is done automatically) a problem with the circuit can be diagnosed, as you would be making the circuit shorter to exclude the problemed pair. You'd proceed back (or forward) one pair at a time until the problem abated. Then you'd know which pair was offending.

Clem

You guys did a good job of explaining P-wire. Only correction is that the signal is sent as current (milliamps), as voltage drop through a consist could result in uneven braking. A 10 car train would be 850' down, and another 850' back, plus bouncing around in each individual pair for A-23 unit, relays, and dynamic brake rate call in each car. You're probably looking at least a half mile of wire, plus numerous contact points, to lose voltage.
So, the ever popular "V to I panel", or equivalent, changes the voltage signal to current signal. Ideally, current signal does not lose current over that distance. The A-23 units (air brake) and 332 cards or equivalent (dynamic brake) have "I to V translators" that change the current signal back to voltage.

M-7 is "Same thing, only different". Same idea, different names. And the important difference is, as Clem said, the M-7 also uses P-wire for acceleration rate, as well as brake rate.

All LIRR EMUs use Analog P-wire. We don't have any EMUs that use digital P-wire.

Tom

Getting back to our discussion of 1258.
There were a couple of things that appeared to seem weird on the blueprint of EMV trainline loop.
First, before we get to that, if this incident had occurred in a tunnel, how can the crew get to the couplers to retract? How could they get to the 3-way valve to turn it?
What if there were no wrenches available? (Somebody is taking the damn things home. It's a miracle there were three wrenches available on that train.)

We need a better way.

Follow me on this (I can't scan and post the blueprints):

The "F" end propulsion boxes in each car are tied in to this trainline loop. The shorted relay was indeed in an "F" end box.
The "B" end propulsion box in each car, however, is not in the trainline loop. The "B" end boxes are enabled when brake pipe is above 110#, by means of pressure switch. They are, however, also powered by CB11. Why was this done this way? Hmmmmmmmm.

So, let's recap:
In this incident, all 10 "F" end propulsion boxes would be disabled, as well as the "B" end propulsion box in the car with the tripped breaker. The other 9 "B" end propulsion boxes should have been available, if I can get brake pipe.
Cut out all EMVs in the train. OK, electrically they are dead. But I have cut them out from venting.
Why can't I charge it up now and move it with slightly under 50% power?
Brake pipe charge is not powered by CB11.

Edit: Oops...forget all that. I just looked at another part of the blueprint, and the propulsion contactor LB11, cannot energize unless the ERs in both propulsion boxes on the car are energized. Who designs these things? It certainly looks like no propulsion would be available in the entire train. Hey, I tried to find something.

Tom

P.S. The prize is still yours, Clem. I will continue to see if there's any other way...It doesn't look good.

1. In normal operation, when or would the ASC dump the train? When it is not slowing at the proper rate dictated by the penalty max brake application? Or does the ASC NEVER dump the train?

Oh, yeah. The ATC will dump the train. This explanation applies to original M-1. All other equipment is similar.
As the train tools along, the EMR is normally energized by the ATCR. EMR is in turn what keeps the EMV energized.
The brakes are applied in an overspeed situation by opening the input to the aforementioned "V to I panel" via ATCR de-energizing, putting 0 milliamps into the P-wire and applying max brake. There is a timing circuit that keeps the EMR energized for several seconds before it deenergizes and dumps the train. During this time, if the train has attained a deceleration rate of at least 1.2 mphps, the 386 card will detect that and energize the EHR (Emergency Holdoff Relay). The EHR now is keeping the EMR, and hence, EMV, energized. That setup remains until the overspeed is cleared, and the Engineer resets the P-wire. The ATCR re-energizes, and it doesn't matter that the EHR de-energizes now.
The 386 card is a rate of change sampler. If it does not see a deceleration rate of at least 1.2 mphps across samples, it will let the EHR de-energize, and your train is in the hole.
The original M-3 did not have a rate of change card. It had simple upwardly curved slosh tubes. Inertia from braking would cause the Mercury, or whatever is in the tube, to move forward and make the holdoff circuit. This is why OEM M-3s were particularly susceptible to dumping during leaf season and/or wet rails. If you start rocking and rolling because of wheel slip/slide, the mercury moves back and forth, and breaks the circuit, dumping the train. We would get M-3s in for "dumps on code change", and there was nothing we could do but send it out again. The slosh tubes were set correctly. They are not to be played with to mitigate a wet rail condition.
A wheel slide condition would also sometimes affect the OEM M-1 system, as sliding wheels would not show a rate of change between samples, and the 386 card would let the EHR de-energize.
All the Microcabs use a solid state decelerometer. If it spits out the right calibration numbers, you leave it alone.

2. How does the Microcab modification know to open an EMV five cars away if the others are not modified?

First, a brief explanation. Then to your point.
All trailing pairs of M-1 and M-3 do in fact go into overspeed at 15-18 mph. Their EMVs are held energized when their EMRs deenergize by trainline 9 (CSR- Control Station Relays). It makes a parallel circuit to the EMVs in all trailing pairs.
The ATC has to continue to work in the trailing pairs for NMR operation. If the No Motion Relays did not drop out at 3 mph in trailing pairs, the doors would be able to be opened from any panel in any trailing car at any speed. The doors would also open in any car except the head two, at any speed. That obviously would not be anywhere near acceptable.

The only way you could trainline dump the older EMU trains, without major wiring modifications, would be to open trainline 9. And you would have to be above 15 mph.
I am not an expert on Microcabs, but I can try to find out if that's done. It would be news to me if true. But, as you know, they don't tell us anything when they make modifications, either. It's not only you guys they don't tell.


Tom

Thanks Tom,

I learn so much from you. Makes me feel young again.

Experiments have found that even with the head car's EMV plugged, the deadman will open the EMV in any Microcab car of the train. I can only assume the same will happen with a speed penalty dump.

We'll take a set of equipment and using the PKO, try to get it to overspeed in max brake with a penalty application, and let you know what6 happens in the Microcab...

Clem

Thanks. Let me know the results.
And I'm learning something from you.
I'm not aware of that. No one ever mentioned a word about it.
My God, this homework is piling up!! I'm starting to feel young again, too!!
I just leafed through the entire M-3 Microcab ATC test procedure, and there's not a lick of information about testing anything like that.

Tom

To bring up to date:

I have been told by reliable sources that both of the things we discussed are correct.
A shorted surge suppressor in 1258;
and for Clemuel, the Microcab trailing pair dumping due to interruption of a certain trainline.
And yes, the only way to work around the shorted pair of cars would be to retract coupler faces and isolate the problem pair electrically.

Tom

Thank you for the replies. You guys are dudes.

FlipFlap