snaping train safety feature

i got that there is delay time for nulifying engin when snaping train happen . my quenstions are :
1- is there any evidence of accident before existing this safety feature on locomotives or from when locomotive was equiped with this feature exactly?
2-is there still this feature on new locomotives with electro-pneumatic systems?
3-and if our locomotive dosnt equiped with this feature should waiting for an accident ?

Are you asking about delayed independant brake application during a break-in two situation (automatic brake hose separation) in order to prevent a run-in situation?

nelson bay
no . when break in two happen for train and the connecting hose of brake pipe seperate from the rest of train automatic brake applying at the same time but for preventing to stike head end of train to front head enginge keeping running untill about 45 seconds to insure that both side of train are stoped and no encountring happen . and after this 45 second and electro-pneumatic valve ( pcs )send a signal to idling the engin and because of action of brake system and running the engine cause wheel cuting and i want to know have ever happened any accident before equiping locomotive to this delay time or they suppose that maybe happen some accident and they did preventing action . because as i told this safety feature causes cutting the wheel and if it has no real evident of happening i think maybe no need to it

It sounds like Xerxes is asking if something like controlled emergency, like on the old 24RL systems, has been incorporated into the new EP systems. Just my read; I honestly don't know-

He is asking about power knock-down delay on a pcs hit, so that if you break in two near the head end you can keep power on the front portion of the train for a predetermined time to make sure your stopping distance will be longer than the rear portion. A number of railroads used this feature, unfortunately I have not kept any records of the time delays used, but the feature may be described in some employee timetables and operating instructions.

But why is an answer for an air brake safety question being sought in a railroad enthusiast oriented internet discussion group? Why not just call EMD?

Been a while since I've seen a loco with this feature. They have the PCS overide, while in dynamics, so you can continue to brake, but the PCS in power, I can't recall the last one I had. As a matter of fact, I've had hoses part, trains derail and kickers, all removing power from my control, without allowing me to continue pulling. Sometimes, on a 26 brake, if they "kick", and you see it on the rear, before they shoot up front, you can crack the cut-out/in valve to shut the valve, towards "cut-out", and you can continue to pull. Depending on the loco, you might have to quickly move to suppression, while doing this. Key to remember, is to actuate the loco brakes, and keep them actuated, while doing this. I've "heard" this might delay a penalty application from overspeeding, or from a cab signal hit, as well..............

That sort of action sounds like an FRA fine just asking to be levied.

If my train kicks... I do exactly what the company's rulebook requires.

The PCS (Power Knockdown) was an option from EMD and GE to customers. Not all loco's have it. With modern loco's and dynamic brakes, it's changed once again.

Most units operated one of two ways (at least that is what i have found), either the PCS opened immediatley and dropped the load or there was a 45 second delay. I have come across a few units with a 20 second delay before the PCS opens as well.

Forget calling EMD or GE, they will NOT answer any questions whatsoever as to locomotive operations, even if you work for a railroad. Your best bet is to simply try it out on the loco or consist in question. I always test the emergency brake on any consist i pull from the engine house while in notch one or two. Ill know right away what to expect one i do this test.