Locomotives, why not shut off?

Trains Magazine General Discussion
21

The air brakes on a train are a split system…as long as the pressure in the train line and the pressure in the car reservoir system are equal, the brakes remain off.

But drop the pressure in the train line, and the pressure in the reservoir system applies the brakes.

The problem occurs when a train is left un- attended, and air leaks between the two allows the cars reservoir system to leak down, equalizing the two sides of the system and releasing the car brakes.

Leaving the locomotive attached and the compressor charging accomplishes two things…it keeps the main reservoir charges so the next crew can release the brakes by equalizing the train line and the cars, and it keeps the cars reservoir charged so the car brakes remain applied.

NORAC and GCOR rules require and train left standing over four hours without a air supply charging the cars systems must have an initial terminal air brake test performed before it can be moved…this is a long, drawn out procedure requiring inspection of the entire brake system, including rigging, shoes, piston travel and visual inspection of both sides of the cars by a qualified person, twice.

Once with the brakes applied so he (she) can see the brake systems function in the applied position, and once released, so he can see the entire brakes system release…in the field this can take several hours as the rules require 100% of the cars have fully functional brakes…find one bad order in the middle of all this and you pretty much stuck there.

Leaving a locomotive running and charging the system allows for a simple set and release and a air pressure test at the rear, which can be done by most EOT now.

It is also cheaper to burn the fuel than to delay a 120 car train while a service person comes out, and replaces one brake shoe.

That in itself can cost you an entire shift…so you end up paying the service person, the train crew and holding up the train…most likely the crew will die on the hours of service before

22

Hmmm…lets use a flammable liquid as a heat transfer medium…in an industry that has been known to produce sparks from dragging brake shoes…in a huge mechanical device which generates KW of electrical engergy and has motors which create so much heat at slow speed they have to be time limited…

Are there any other industries which use kerosene for cooling?

In lieu of that, one could use the fuel actually going to the engine from the fuel tanks to absorb a lot of heat…but I am not sure you want all of that in places you have to have cooling…or even if there is enough of a flow to cool the engine enough.

Just a guess, but it would probably be cheaper to design a system using antifreeze than one using kerosene…

Brakes: the key to what Ed pointed out about the brakes, is that airbrakes on trains could be considered “Short Time” fail safe…after the emergency application, someone has to take action to ensure the train won’t move again once the pressures equalize. They dont even have to bleed down to zero, just equalize between the resivour on board the car and the break pipe pressure. (Of course, in the case of an airline parting, that would be down to zero, but in the case of setting the breaks in a siding, that may be only 20psi difference) Barring major leaks, in every coupled car’s resivour system, this time is measured in hours not minutes or seconds, but is also not “Forever”

23

The brakes don’t release when pressure equalizes between the brake pipe and the brake cylinder. They release when the control valve on the car “senses” that the pressure in the brake pipe is greater than the pressure in the brake cylinder. It doesn’t take much of a rise in brake pipe pressure either, 1 1/2 to 2 psi.

If the car/train is in emergency, the brake pipe pressure is at 0 and the brake cylinder will always be higher until the air leaks out of the cylinder. That could happen anytime from a few minutes to a few weeks, you don’t know. That’s why you put on hand brakes for unattended cars/trains.

Jeff

24

GE locos have a control that will not allow the unit to load very much until the unit is warmed up. This is usually only a problem when inbound units that have been dead need to be taken to the house. If there is any kind of a grade at all, the unit will not load up enough to get there.

True the units will leak air off in a short amount of time, depending on how many air leaks are in the unit/s. No air, no brakes. Cars are somewhat different in that they don’t tend to leak off anywhere near as bad. However, it can and does happen. So the only time that the system is truly “fail safe” is when the system is charged. Again, lose the air, lose the brakes. That is why they all have hand brakes.

This stuff about units starting up when the coolant temp gets too low is something that is new. MOST units won’t do that. Instead, a lot of units have a plug in the coolant system that will drop out, dumping all of the coolant, when the temperature gets too cold. A bad thing for units left dead to “conserve fuel” far away from a water hose!

Newer EMD units with the air starter are also prone to not starting because they have been left dead to conserve fuel with the autostart system defeated. Sometimes you have to wonder who are the masterminds that are designing and running the show.

25

My own understanding, and this applies to compressor blades in jet engines, and all the way down to your little inch-long snarly one-lung sewing matchines in those fly-by-wire toy airplanes, heat causes metal to expand omnidirectionally. In engines that are designed to last a long time under heavy loads, such as diesels, the cycles of expansion and contraction at start and shut down are not advised unless absolutely necessary because the heat changes tolerance gaps. Far better to run a diesel 24/7 than to continually start it after a period of cooling.

It could be, I suppose, that some modern metallurgy has largely reduced this problem to insignificance, but I am not aware of it.

26

I believe this engine is UP 1995 (the C&NW heritage unit):

27

The self starting units are only going to start if they are set up for that. if i manually shut a engine down they will not start up on thier own you will haft to go and crank them up. now they will auto start if they shut down on thier own. and certain things happen to cause them to start. engines are real easy to start . you make sure the ecm switch is in start go prime the unit then crank when it starts release the start switch close the door and go inside the cab and get warm. real simple