Rio Grande Valley, CFI,CFII
The 'pow' is the sound of the car control valves making an emergency brake application, when this happens a vent valve on each car trips to speed up the propagation of the emergency braking signal. A second or two later you'll start hearing the squealing of heavy braking, it takes a little bit of time for air to flow from the reservoirs to the brake cylinders.
10 minutes isn't long enough to change an air hose, let alone a knuckle. It could have been that the hoses parted or a coupler pin lifted by itself right at the head end of the train (a good crew could recover the air on the locomotive consist and do up the hoses or couple the engine back onto the train in a few minutes), but I think it is more likely that the engineer made a service brake application and got a 'kicker' (a defective car control valve that goes into emergency when it is not supposed to, which then results in the whole train going into emergency) or the crew put the brakes in emergency for one reason or another.
Greetings from Alberta
-an Articulate Malcontent
With the train going into emergency and then having the brakes released and the train moving again in less time than any kind of inspection would take - I would have to presume that the Engineer placed the brakes in Emergency for something he saw the train approaching and that an Emergency application would PREVENT the train from impacting. Once the way was seen to be clear, the Engineer released the brakes and could see the brake pressure returning to normal values on the End of Train Device, thus indicating an intact train line on a train that does not contain HAZMAT.
Under CSX Rules in effect when I retired, if a train contained HAZMAT, all the HAZMAT in the train had to be visually inspected before the train could move after an Emergency Brake Application - no matter if desired by the Engineer or undesired.
Never too old to have a happy childhood!
I think the Dude has it right. A kicker, or as we call it a dynamiter, that's a car's control valve that goes to the emergency position instead of the service position during a service braking application.
A dynamiter can go every time the air is set or there are some that only go when going at slow speeds, generally under 10 to 15 mph. There are a few tricks of the trade that may prevent a known dynamiter from happening.
It could also be a glitch in the locomotive or a DP locomotive air brake system that put them into emergency. All the modern road power have the air brakes controlled through the computer. If it happens too often, and cycling the air brake computer circuit breaker doesn't clear it up, the locomotive won't be allowed to lead until it's been through a shop.
For us, a unit bulk commodity train, loaded or empty, doesn't require an inspection if the air immediately recovers and there was no harsh slack action felt when coming to a stop and excessive power isn't needed to start moving again.
Jeff
I had thought for some reason that the major cause of valves 'dynamiting' was unintentional rapidity with which a set is 'taken' -- the impulse of decreasing pressure being what actuates the 'emergency' part of the valve. This might be exacerbated when running at low speeds before full trainline recharge, but I don't have the firsthand knowledge people like jeff or zug do.
One theory was dirt within the control valve might cause it to stick a little, then when it moves it moves too much into the emergency position. It makes some sense. Most of our dynamiters used to be coal trains which in addition to dust from the ballast can pick up coal dust.
Not that other equipment was immune to it either.
It also might be localized leakage contributing to an imperfect control valve. The leakage, say at a joint of two air hoses or maybe in the piping near the valve increase amount of pressure reduction, tricking the valve to go to emergency.
Overmod I had thought for some reason that the major cause of valves 'dynamiting' was unintentional rapidity with which a set is 'taken' -- the impulse of decreasing pressure being what actuates the 'emergency' part of the valve. This might be exacerbated when running at low speeds before full trainline recharge, but I don't have the firsthand knowledge people like jeff or zug do.
That was always the thinking. That's why we were taught to do a "split reduction" when possible. (go to minimum-10# first, then go deeper). But I always found kickers kick no matter how much air you try to put on.
Roadrailers were nortorius for kicking. One of the theories I heard from managers was becuase when not under a trailer on a train, the bogies were stored on a dirt/gravel/grass/mud lot, and dust and crap was constantly being blown into them (and their air parts).
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
Most dynamiters seem to go in minimum reduction. The split reduction is to start setting the brakes to control slack.
If you know you have a dynamiter, going to minimum then back to running/release a couple times then going to minimum and staying seems to keep it from kicking. One old head explained to me that it was thought getting the air to "stir" a bit kept it from going.
Another trick, although some said it worked better with the 89 foot flats they used to have in TOFC service, is to cut out the first car behind the engine. It slows the movement of the service application. That's why there are rules against cutting out the brakes on two consecutive cars. It may not transmit an actual emergency application.
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