Steam & Excursion > Emergency Braking Inquiry

So as to rule out and modern day technological or electronic devices in use and to get to question(s) I am asking about. Let's say the year is in the 1930s/40s.
  Long heavy train running 55 mph. I can envision the throttle being well open to supply copious amounts of steam to the cylinders as well as we will assume coal is being auto fed to the fire box.
    Now in the event of an unplanned train separation  i.e.emergency brake initiated  by system design are these systems (throttle and coal/oil supply automatically shut down by some device in the system or is it dependent on the engine crew to do it and do it quickly?

100% depended upon the engine crew taking the appropriate action to close throttle; no automatic system

Marty Harrison
Knob Noster, MO

How about when a steam engine separates from its tender "at speed."

https://www.trainorders.com/discussion/read.php?10,2965476,page=1

https://www.trainorders.com/discussion/read.php?10,3834306,page=1

Greg Stadter
Phoenix, AZ

The braking mass of the train, with each cars' brakes having 150% of normal cylinder
'application pressures' acting on the brake pistons, pretty much brings everything to a stop...
So, as a matter of reality, closing-down the loco systems is easily handled by the crew.

Probably one of the first things the fireman does is to get both 
the feedwater devices sending water into the boiler.   Typically ,
when running, the water level carried in the boiler will be lower than 
when just sitting around...Also, the firebox temperatures are very high
to generate the volume of steam used in propelling the train.

So, to suppress the safeties from blowing ( as a result of throttle closing),
the fireman wants to conserve his water supply ---- in order to manage
the long delay that could ensue, in case of a derailment.  

During the Emergency Application the crew has no way to know the actual
state of the cars back in the train..... if there are derailed cars, or a simple break-in-two,
or an 'undesired emergency brake' application ( UDE , air brake control-valve malfunction)
--- witn the train staying intact., 

So, loco management focuses on conserving fuel and water, while calming the
intensity of fire in the firebox.  

After the situation of the train cars is evaluated, and the loco is to be used in the re-railing of cars,
the boiler pressure must be kept near the popping point .... in order that the action and speed
of controlling the airbrakes is instantaneous.  

If the boiler pressure is allowed to droop significantly, that robs the intensity of HP steam thst
is operating the compressors---- they become sluggish and that affects things like lackadaisical
rates of loco brake piston action.

Since you're mostly sitting and waiting, maintaining near-full pressure is just as easy
as keeping a lower pressure,... but, you're conscious of starting the  "stand-by mode"
at the higher maintenance pressure earlier, and it's easier than thrashing around in
catch-up mode...

Lower steam pressures disproportionately limit the piston-speeds of the cross-compound
compressors,  they become very sluggish----  ( slow to restore MR, back to full pressure)---
at lower boiler pressures.  When moving short distances, during re-railing, is a matter of inches,
you need instantaneous brake responses!

Also,  the fireman must intelligently conserve fuel and water, since they 
may be a long-way from replenishment.

​W.
 



Edited 7 time(s). Last edit at 09/18/22 09:19 by wcamp1472.

One thing to keep in mind is with a train separation, its not a bad idea to bail off the engine brakes and work the engine for a few car lengths.
You don't initially know how much of the train is coming at you and you could prevent a violent run in collision.
I know this sounds silly, but until you know how big the separated portion is a good idea is to get out of its way.
We had two EAS train separations down in TX and took the engine and the front portion as far as we could to keep from getting smacked.  There were people on the train.

Absolutely TRUE!

We had a train separation in the early 70's with a excursion of CNJ
coaches + some High Iron Co. cars.

We were cruising along one afternoon, when the train suddenly went into Emergency....
instinctively and immediately our engineer, Charlie Strunk (CNJ), stood up,
pulled 759's throttle wide-open, bailed off the independent, shoved the valve gear into 
'the corner' and we dragged the train , brakes in 'emergency' and all cars' brakeshoes
applied... As Charlie's fireman, I quickly matched the stoker's speed to get the fire instantly 
hotter...both the water pump and injector were pumping water, as we slowed.

The 759 wasn't phased a bit! 
Barked louder, but never slipped.... the few coaches 14-or so....were no match for the big engine.

As a passenger train engineer, Charlie instinctively knew about the dangers of  a possible run-in...
....if the engine had stopped too soon.

It took less than a couple of seconds for the engine to get to powering-up...
but, Strunk's immediate reaction avoided a potential disaster.

Luckily, after several minutes, everything came to a stop, the last 3 cars had separated,
and quickly stopped.

We then re-coupled and proceeded to the last stop without incident.
( the culprit was a steam-heat piping elbow too close to the free swing-range
of the coupler and it's uncoupling lever....quickly corrected..).

That's where deep experience comes into play ---- in order to avert, what could have been,
a serious collision.   As an inexperienced rail fan group, it was good that Charlie was
our engineer!  A few moments of indecision  ( by a novice engineer) about what that unexpected
emergency application meant, by the way of the rolling train's behavior, could have resulted in
a separation/collision & a worse outcome.

Wes Camp



Edited 2 time(s). Last edit at 09/18/22 09:17 by wcamp1472.

Frisco1522 Wrote:
-------------------------------------------------------
> One thing to keep in mind is with a train
> separation, its not a bad idea to bail off the
> engine brakes and work the engine for a few car
> lengths.
> You don't initially know how much of the train is
> coming at you and you could prevent a violent run
> in collision.
> I know this sounds silly, but until you know how
> big the separated portion is a good idea is to get
> out of its way.
> We had two EAS train separations down in TX and
> took the engine and the front portion as far as we
> could to keep from getting smacked.  There were
> people on the train.

I don't know what makes you say this sounds silly, that's exactly my thoughts. Easier to back up than to get hit by the rear section.

Handling a break-in-two is NOT intuitive ....so, it seems incongruous....
to avoid the temptation to stop and "figure things out".

However, the physics of a rolling train, the 'normal' thing is to stop and
find out the problem.

If it is a break-in-two, where the separation occurs means that the heavier train segment 
travels further than the lighter segment.   In the HICO separation, above, the break was
at the last 3 cars...they stopped first,   The locomotive + the cars, in this case would have 
taken longer to come to a rest..... But, not knowing the location of the separation, the 
engineer maintained the speed, and after a good distance stopped.

We closed the open angle cock ( on the rear car), the BP pressure recovered, and the train
reservoirs were recharged the auxiliary and emergency reservoirs.

Slowly we backed up, recoupled, charged up the separated cars...who's storage tanks
 were emptied.  And resumed the trip.

​W.

TomG Wrote:
-------------------------------------------------------
> Frisco1522 Wrote:
> --------------------------------------------------
> -----
> > One thing to keep in mind is with a train
> > separation, its not a bad idea to bail off the
> > engine brakes and work the engine for a few car
> > lengths.
> > You don't initially know how much of the train
> is
> > coming at you and you could prevent a violent
> run
> > in collision.
> > I know this sounds silly, but until you know
> how
> > big the separated portion is a good idea is to
> get
> > out of its way.
> > We had two EAS train separations down in TX and
> > took the engine and the front portion as far as
> we
> > could to keep from getting smacked.  There
> were
> > people on the train.
>
> I don't know what makes you say this sounds silly,
> that's exactly my thoughts. Easier to back up than
> to get hit by the rear section.
I knew it would sound silly to the uninitiated.  It is just common sense.

One poster implied that keeping the compressor going was important to stopping or so it seemed. It ain't and you can totally shut the compressor off..and as long as air hasn't bled down, an emergency application will have the desired effect. It's getting the brakes to release that you want to maintain enough steam to work the compressor robustly. Though it must be understood that the hole the air blows through to get to the brake pipe is what it is and you can't exceed a certain maximum airflow. Academic of course but it is a thing. Where compressor wear comes into play is when you get the brake pipe partially filled, can you maintain sufficient flow to finish the job promptly? WIth AB brake valves nothing is certain and after an emergency application some of them may need to be manually bled off to effect a release! Another thing about keeping air going after stopping is the engineer is going to turn the air back quickly if he can so the brakement looking for the separation can hear it and find it quickly. Likewise when found and the crew makes repairs and is ready to couple up they will blank the angle cock on the end with air, which signals the engineer to back up and couple up. If a knuckle repair is needed there's other things to do just to get started but there's the basics. 

The air pressure that apples each car's brakes is supplied by the air tanks on each 
car.

in case of a train separation, the separtated cars are braked by their own charged reservoirs.

The brake pipe supplies the charging air, while also acting as a reference pressure ---- controlling 
air pressure to the brake cylinder. 

Normal application and release ( of brake cylinder air) is callled 'Service' application...
And the rate of the discharge flow is called the 'Service Rate"

There is a much more rapid evacuation of air from the train's air pipe --- called "Emergency Application".

During function testing of car's brakes, by a testing device called a 'single car testing device' ,
the proper brake operation is verified using a standard testing pressure and by specific test-orifices
that regulate the rate of air flows.

Although an emergency brake application can be seen at a car in front of you, cars separated by 
by many intermediary cars, emergency flow rates might not be comparable ---- as if only on
a couple of cars..

Thus, an 'Emergency Rate' of air travel is important in order to trigger a local valve to
also dump its brake pipe-air.  Thus, each succeeding car applies its brakes, as well as
triggering the trailing cars to dump their supply pipes, as well.

The brake system of tye train and locomotives is considered a unified braking unit.
The high pressure storage tanks on the locomotives are called the "Main Reservoir" of the
train braking system.  The air tanks on each car are called the system's Auxiliary Reservoirs'

Each car also carries a separate volume called the Emergency Reservoir.  On the freight cars
using the AB scheme, the two tanks are bolted together, with a separating divider.

When an Emergency Rate of Brake Pipe air-discharge is detected, the pressure applied to the
local brake piston is added to the Auxiliary  Reservoir's pressure volume, increasing the
force acting on the brake piston's face by about 50% greater pressure, than when the 
'Service Brakes' are used for train braking control.  All three ( the brake cylinder,
the Auxiliary reservoir, and the Emergency reservoir) stabilize at the higher pressure
becsuse they are all 3,  connected...


The train system's operating pressure is regulated and controlled by the 'Equalizing Piston', 
and it's reference pressure contained in the 'Equalizing Reservoir'.  

The engineer actually controls the pressure in the Equalizing Reservoir , which in turn 
controls the the Equalizing Piston's reference pressure.  When intentionally exhausting
air from the brake pipe of a long freight train, the air moves towards the engines in
"pressure-waves" from the train's cars.

The waves of flowing air come in the form of increasing pressures and decreasing pressures ---
as pressures increase ( flows), the pressure wave causes opening of  the Equalizing Piston & cause
it to lift --- widening the exhaust port, and as the wave pressures decrease, the Equalizing Piston
closes-down the size of the port opening.  An engineer, watching a Brake Pipe gauge cannot
manually keep-up with & regulate the brake valve and the varying " pressure-waves" ...

Pressure 'wave-like' action results from the lengthy trainline piping, the air hoses at the
the cars and the restrictions related to the angle cocks.... also, modern brake ABDX-style
brake control valves perform local BrakePipe venting, as an alternative to ALL the air having
to go out through the engineer's brake valve.

The Equalizing Piston and Its Equalizing Reservoir (the piston's reference pressure) take
care of brake pipe reductions AUTOMATICALLY --- controlling the pressure waves,  
when set by the engineer.  

All the engineer has to do is set the Auxiliary Reservoir's desired ( reduced) pressure....
. the rest of the air flows as regulated by the Equalizing Piston ---- as it balances the train line
pressures down to the lower setting of the reference pressure.( Equalizing Resevoir).
Arriving at the lower, set , pressure, may take a couple of minutes, with a long train.

You will hear the engineer discussing "making a 10-pound reduction..."
He's making a reduced setting of the Equalizing Resevoir from 80-pounds 
DOWN to 70 pounds..  A 10-pound reduction in Equalizing Pressure ...
As stated earlier, even though the Equakizng reservoir gets its pressure reduced quickly,
getting the entity train's pressure down to the lower-setting may take several minutes.
Once the engineer sets the desired, lower, pressure, he leaves the handle
'set'.  

On freight cars, when the engineer releases the brakes,
all air is exhausted from the brake cylinders.

In contrast, 'Full-Pressure', Service Reduction, would be a "20-pound reduction..."

At a 20-pound reduction, the actual  pressure sent to each car's brake cylinder
and it's piston would be about 60-psi...  that's about when the air pressure in
each car's Auxiliary Resevrvoir balances with the pressure sent to the brake piston.   

When the pressure in the brake cylinder's pressure matches the pressure in the car's
Auxiliary Resevoir, that's called 'Equalization'....  
At full brake application pressure... Any further reduction in the brake pipe pressure
WILL NOT increase air pressure on the cars' brake pistons....

That's the heart of the system.

Hope this helps..

Extra credit points:  How does an Emergency Application act to affect increased pressures
on the cars' brakes? 
( If you know the answers, let the newbies go first , to increase their chances to learn...)


​W.


 



Edited 7 time(s). Last edit at 09/25/22 16:21 by wcamp1472.