Eastern Railroad Discussion > NS & DPU's?

Reading the other thread about CSX & train length, their use of DPU's, etc., and got to thinking; I've made several photography trips to the Pittsburgh line this fall and realize that I haven't seen one. Has NS given up on the idea of DPU's all together or just trying them elsewhere?

Posted from iPhone

There's quite a few NS trains that run with DPUs in the South.  All the Plant Scherer coal trains (NS rails from Memphis and Juliette, GA) are equipped with DPUs.  UP/NS intermodals off of the Meridian Speedway, 226 and 22G, have DPUs.  Same goes for the Norfolk - Louisville intermodal pair, 22A / 23G.  Some manifests regularly run with DPUs.  I know 154 and 169 regularly have them.

Andrew

NS used DPU technology on the Phillips Linden NJ oil trains.  It was convenient for the layout, but they later went back to a conventional arrangement of power and left a utility switcher at the Linden plant to help with the exit train make up.

Bck when Bakken was big, rapid turnover of tank cars was essential. Now there's a little more flex in the system.

Thank you both for the insight and explanation.

Posted from iPhone

NS did some testing of DPUs on merchandise trains on the Pittsburgh Line late winter/early spring this year and ran some MONSTER trains. I have not seen a train with a DPU for several months.

Posted from iPhone

Several coal trains in southern Illinois and Indiana run with DPU and 111 has been running DPU east of St Louis.
Michael T Kerner
Collinsville, IL

Posted from Android

Aside from the newer power, retrofitting locomotives for DPU tends to be labor intensive and costly.

I don't know what it costs, but it requires electronic air brakes, computer display locomotives* and software upgrades.

Then a bunch of training.

Most of the NS locomotives I have come across either had standard control stands or similar side console air. I know the newer stuff is more standardized like everyone else's so that helps.

During a major overhaul would be the time and place to do it.

Earlier "modern" DPU required the air brake interface as well as some computer interface for synchronized operations, but was controlled by a remote box with a LCD display (known as the Harris Box).

This box has since been intergrated into the locomotive screens.

Also it's pretty standard to use on AC locomotives - why I don't know, but speculation is that AC motors are better at th higher tractive effort they usually see than something with a short time rating or computer limited load at the slower speeds with DC. You can have one on the remote consist, but haven't seen one as a Controller.

So back to NS, look at all th DC - and generally older power they use compared to everyone else.

Why does not NS use DPU's over the Alleghenies (former Pennsy main line  ie Pittsburgh to Harrisburg)?  The answer is simple.  The railroad was a magnificent feat of engineering

Eastbound  it is 100 miles from Conway to Johnstown  but the rating for a Dash 8 (DC locomotive)  is above 10,000 tons  (via the conemaugh at 40 mph).  The main line where the TTX trains run at higher speed (60 mph) is a little more hilly   ie  3900 tons (getting out of Pgh on the old main line)

After Altoona to harrisburg (120 additional  miles)    the rating of a single unit is about 10,000 tons.

Going westward from Harrisburg to Altoona it is similar,,  120 miles with a rating of  8000 tons
and then from Johnstown west to Pittsburgh (all trains run over the main line)  it is about 4000 tons

It is that small stretch of 37 miles   (25 miles eastward and 12 miles westward out of about 260 miles total)  that HELPERS are needed for for up hill (rating of 1800 tons WB  and 2600 tons EB)  power and Braking.  Braking is probably the most important especially on the east slope  and it is difficult for a DPU to control a train coming down the slide.  (too much for the engineer to do).  The helpers doing DB  minimize the use of air and thus "kickers" and the emergency braking is rare on the hill.   Most of the time helpers down the east slope are in power to control slack.  The helpers can keep the speed up and keep the tracks fluid (each track handles over 75,000, 000 gross tons per year. 

So why apply a DPU for over 260 miles when it is not needed for 220 of those miles.  DPU's would be at idle most of the way expecially when you consider that you need at least 2 lead units on every train just for reliability.  The DPU is just 200 tons of drag. 

Note that NS consistently puts 135 car -20,000 ton trains (coal) --- oil trains are 15,000 tons  up the west slope at 25 mph.  Such heavy trains westbound are not that common. 

I'll disagree with DPUs are difficult to control down a hill or too much for the engineer to do.

I take trains down a 40 mile grade that reaches close to 2% in a couple of spots that has some undulations (ups and downs) while going down hill. 90% of the time you set air once and then adjust according.

Our heaviest trains run about 26,000T with one mid train DP consist. Our mixed freights run up to 15,000ft and 20,000T with two sets of DP's.

If you know how to properly use the DP fence, it's not a problem.

Train makeup on the other hand is a whole different story - but we haven't had a break in two on this segment in quite awhile.

Using NS ratings is a bit hairy. A single 4000HP locomotive is only .4HPT on a 10,000T train. Maybe if it's straight and level you might move. Downhill can figure no real help with dynamics and you will be using air.

.8HPT will take a train up moderate grades, at 12-15mph.

But remember not all 4000hp motors are created the same. Depending on electrical gear, axle ratios, maintence and the such it never equals power to the wheels.

For instance, a EMD SD90 with the 4300HP motor produces less tractive effort than an EMD SD70ACe with a 4300HP motor.

In the reverse, the new T4 GE's produce the same tractive effort at 4365HP as the AC4400 with the older 4390HP larger motors.



Edited 1 time(s). Last edit at 11/29/16 17:51 by MW810.

MW810 Wrote:
-------------------------------------------------------
> I'll disagree with DPUs are difficult to control
> down a hill or too much for the engineer to do.
>
> I take trains down a 40 mile grade that reaches
> close to 2% in a couple of spots that has some
> undulations (ups and downs) while going down hill.
> 90% of the time you set air once and then adjust
> according.
>
> Our heaviest trains run about 26,000T with one mid
> train DP consist. Our mixed freights run up to
> 15,000ft and 20,000T with two sets of DP's.
>
> If you know how to properly use the DP fence, it's
> not a problem.
>
> Train makeup on the other hand is a whole
> different story - but we haven't had a break in
> two on this segment in quite awhile.

That sounds like it would be worth a thread on its own.  What goes into the make up, who signs off on the mix and sequence, etc.

The difference in train handling between a conventional and a DPU is tremendous!  Running 8000 feet of stack train that could be run with three units on the point, or two by one gave between a 5 and 10 mph increase in speed in slightly curved territiory.   The difference in speed is due to the reduction in friction from binding on curves from all the pull being on the head end, and the cars near the head end all want to stringline.  The fuel savings is considerable.  This is why the UP is running DPs for several hundred miles where they don't need to.

Next comes the reduction in length to the brake valve.
An 8000 foot train has its rear car 8000 feet from the brake valve, which takes time for the air to travel back and forth.  A DPU on the rear cuts that length to 4000 feet, and doubles the charging rate, because the train is now being charged through two pipes by two valves!

If you need a multiple unit DPU cut in the train because of tonnage restrictions,  it further reduces the length between brake valves, the 8000 footer is now down to under 3000 feet between brake valves, and the brake application and release is quick.
G

Correct. You actually do get better train handling, recharge rates and more dynamic brake effort (usually) than a conventional train.

That's when everything works right, which lately seems to be with the last software update.

Most DP issues are with communications / terrain. Just because it works in the desert doesn't mean it will work as well in the Rocky Mountains

111 came into chattanooga , tn last sat with 157 cars ,  2 on the head end , and 2 DPU`s on the rear.



mkerner Wrote:
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> Several coal trains in southern Illinois and
> Indiana run with DPU and 111 has been running DPU
> east of St Louis.
> Michael T Kerner
> Collinsville, IL
>
> Posted from Android

How much does distance factor in?  Seems to me that the western roads' hauls are longer than eastern ones.  If NS is sending a coal train from central PA to Baltimore, we're talking around 200 miles maybe?  So I'd think that it is more efficient use of equipment to have a set of helpers shove that train a short way then return for another shove instead of having those engines go along for the ride to Baltimore.  So 2 units can push a train up the west slope and brake it down the east slope, then shove a WB back and maybe get another EB, so those 2 units assisted 3 trains where a DPU set would be on one train.

I may be way off but that just seems a logical reason to me.

Helpers require a crew ($$$) whereas DP's do not.

Lackawanna484 Wrote:
-------------------------------------------------------
> NS used DPU technology on the Phillips Linden NJ
> oil trains.  It was convenient for the layout,
> but they later went back to a conventional
> arrangement of power and left a utility switcher
> at the Linden plant to help with the exit train
> make up.
>
> Bck when Bakken was big, rapid turnover of tank
> cars was essential. Now there's a little more flex
> in the system.

Discontinuing DPU's on the P66 trains was done, I believe, to eliminate the time consuming need to address the DPU setup and testing.  There were also some operational issues, such as passing sidings in areas where the DPU's would lose communication.

bioyans Wrote:
-------------------------------------------------------

> Discontinuing DPU's on the P66 trains was done, I
> believe, to eliminate the time consuming need to
> address the DPU setup and testing.  There were
> also some operational issues, such as passing
> sidings in areas where the DPU's would lose
> communication.

What happens when a DPU loses communication - does it just drop into idle?  And how long of a disruption in signal before it does so?

With the last software update linking and unlinking takes no time at all. The air tests Between the consists only takes about 15mins.

Our DP software (and I think it's a standard feature) has a feature called last command hold. It will keep doing what it was last told. After a preset amount of time after comm loss it will idle down (usually 15min).

If you need to command it immediately to idle in a comm loss situation you set full service. It will see the BP reduction and idle.