Train splits

NW Mailing List nw-mailing-list at nwhs.org
Wed Oct 20 22:54:57 EDT 2010


Mike:

Jeff's answer is of course accurate in its description of the various
reasons why a train may "split/break in two" but I think there's more to be said
about why this results in an emergency brake application.

Air brake systems apply the brakes when the brake pipe pressure is reduced
from its fully-charged level. If the brake pipe is suddenly fully
exhausted, which would happen if a train "breaks in two," the triple valve senses
this rapid loss of pressure and applies emergency brakes, which results in
a higher brake cylinder pressure than a normal service brake application.

Although emergency applications should only happen in the event of a train
separation or a deliberate emergency brake application, unfortunately a
transient pressure pulse in the brake pipe can also look like a sudden deep
reduction, inducing an "unintended emergency brake application." Modern
systems have reduced this tendency, but it still happens occasionally.

Dave Phelps


In a message dated 10/20/2010 9:10:21 P.M. Eastern Daylight Time,
nw-mailing-list at nwhs.org writes:

Mike,

When a train "breaks in two", it could be one of a number of reasons.
Occasionally the air hoses may separate, possibly due to its hanging to low and
hitting a road crossing, or some other obstacle between the rails. There
are times when a knuckle of a coupler may break, due to a weak spot in the
metal, or previous fracture, unnoticed by the car inspectors. Also, an
entire drawhead can break for the same reasons. Of course, a derailment most
times will cause the train line to separate, all of which causes an emergency
brake application. It does not happen too terribly often, but more often
than one might think.

Due to improvements in car construction and modern safety checks, such as
dragging equipment detectors, it doesn't happen as often as it did 50+
years ago.

Jeff Sanders

--- On Wed, 10/20/10, NW Mailing List <nw-mailing-list at nwhs.org> wrote:



From: NW Mailing List <nw-mailing-list at nwhs.org>
Subject: Train splits
To: "NW Mailing List" <NW-Mailing-List at nwhs.org>
Date: Wednesday, October 20, 2010, 6:38 PM

I was curious about something I heard the other day on one of Winston
Link's recordings. He was riding in a caboose descending into Roanoke (I think)
and the train split in two and went into "emergency". Could somebody
comment on what exactly happened and how often would that occur? Thanks!


Mike Weeks
Greenville NC


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