Train splits

[NW Mailing List]

Mike & Dave,
 
Ocassionaly, if there is a bad (defective or dirty) triple valve on a car in the train, when the engineer makes a brake application, the valve gets stuck, or otherwise reads the application as an emergency, which causes the the emergency brake application. I believe this is what Dave refered to as an "unintended emergency application".These can be difficult to find, often times resulting in the trainmen having to walk the train to find the problem.
 
Sometimes, although not often enough, if the engineer restores the air, the valve may reseat itself. If not, that's when you have to start walking. We refered to these as "kickers".
 
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: Re: Train splits
To: nw-mailing-list at nwhs.org
Date: Wednesday, October 20, 2010, 10:54 PM



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
-----Inline Attachment Follows-----


________________________________________
NW-Mailing-List at nwhs.org
To change your subscription go to
http://list.nwhs.org/mailman/options/nw-mailing-list
Browse the NW-Mailing-List archives at
http://list.nwhs.org/pipermail/nw-mailing-list/


________________________________________
NW-Mailing-List at nwhs.org
To change your subscription go to
http://list.nwhs.org/mailman/options/nw-mailing-list
Browse the NW-Mailing-List archives at
http://list.nwhs.org/pipermail/nw-mailing-list/

-----Inline Attachment Follows-----


________________________________________
NW-Mailing-List at nwhs.org
To change your subscription go to
http://list.nwhs.org/mailman/options/nw-mailing-list
Browse the NW-Mailing-List archives at
http://list.nwhs.org/pipermail/nw-mailing-list/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://six.pairlist.net/pipermail/nw-mailing-list/attachments/20101021/682cb92a/attachment.html>