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Locating air leaks...

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Posted by jeffhergert on Friday, May 13, 2011 10:13 PM

Has anyone ever tried to find a dynamiter/kicker?  I've never heard of it being done.  There's all kinds of variables too.  Some dynamiters go every time you touch the air, some don't.  Some only go during slow speeds, others speed doesn't matter.  You could check every car and find nothing, then the first time you use the air again, it dynamites.

Besides, sometimes the DPU is the one throwing the train into emergency.

Old Wive's Tales (or maybe Old Hoghead's Tales) type remedies.  None guaranteed to work.

Go to the first car behind the engine(s) and cut out the air brakes.  Some say this only works when the car is a long car, like a 89 ft flat or autorack.   

When setting air, first place the brake valve in minimum reduction for a second then back to release.  Repeat once more.  Then make your brake application.  

Again, the experts will say those, and any other methods, won't prevent a dynamiter.  If they seem to work, it's just coincidence.  Well, I've used the second method a time or two.  It doesn't always work, but I've had a few trains where every time I tried it the train didn't dynamite and the times I didn't the train went into emergency.  I actually haven't had a train with a dynamiter in it for a while and have probably jinxed myself now.

Jeff

 

 

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Posted by henry6 on Friday, May 13, 2011 4:56 PM

Another secnerio: If there weren't a kicker, and the train could still move, the headbrakie would get on the ground and let the train roll by then hit the cushions in the caboose if nothing found and ride there to the next destination where he could or would have to return to the locomotive. 

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Posted by BaltACD on Friday, May 13, 2011 4:38 PM

This is elementary line of road railroading generally at 3 AM with the temperature at 10 degrees and a 30 MPH 'breeze'.  Brakemen and Car Knockers are not using calculus to solve the situation....they don't have the education or time for it.

Paul_D_North_Jr

Yeah - you  (Semper Vaporo) understand the analytical dilemma/ challenge with this:  What are the relative risks/ benefits of adopting a particular method and testing a specific car - in terms of the time already expended to do that, and the most probable amount of time to finish the isolation process ?  SUuperficially, this problem seems similar to finding a specific card in a randomly shuffled deck, and could be solved by writing an equation in the nature of:

Total time = time walking + time testing = (No. of cars walked x average time to walk 1 car-length) +  (No. of cars tested x average time to test 1 car), or = NW*TW + NT*TT. 

Then, substitute the probability equations for the NW and NT terms, and differentiate the resulting equation with respect to the no. of cars walked (NW), and solve for the optimum/ minimum Total Time.

Note that the number of cars walked has no fixed relationship with the number of cars tested (except that they both have to be less than or equal to the total number of cars in the entire train length), and further, the time to walk 1 car-length and the time to test 1 car are also unrelated in any way.  So there might be multiple valid answers, such as if the equation is also solved for minimum Total Time with respect to the number of cars tested (NT).   

Intuitively, I suspect the answer will be related to the inverse of the ratio of the average time to walk 1 car-length to the average time to test 1 car.  So, if it takes 20 seconds to walk 1 car-length (60 ft. at 3 ft./ sec., about 2 miles per hour), but 1* minute to perform the average brake pump-up and release, that would be a ratio of 1/3.  So, the optimum or 'balance point' (in calculus terms, slope of function = 0)  might be around where equal amounts of time are spent on each task - walking and testing - or, 3 times as many cars being walked as are being tested.  So maybe it's better to do the train by 1/3's or 1/4's - but that still doesn't tell us whether it's better to start at the 3rd car of the 1st 4, or at the 75th car of a 100-car train . . . Whistling 

*Made-up number for example purposes only; feel free to substitute real-world values and recalculate. 

Anybody who knows this subject or analysis better, feel free to jump in and contribute what you can !

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Posted by tree68 on Thursday, May 12, 2011 1:52 PM

Semper Vaporo

If you had instant access to each car at random then the "Binary Search" method would be best, but since access to the cars is linear then a linear search is best.

Indeed - if you're using the binary (or half-split) method on a circuit, you're not usually having to cover 5,000 feet overall in the process...

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Posted by zugmann on Thursday, May 12, 2011 12:52 PM

Ugh... too much reminder of calculus.

It's been fun.  But it isn't much fun anymore.   Signing off for now. 


  

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Posted by Paul_D_North_Jr on Thursday, May 12, 2011 11:44 AM

Yeah - you  (Semper Vaporo) understand the analytical dilemma/ challenge with this:  What are the relative risks/ benefits of adopting a particular method and testing a specific car - in terms of the time already expended to do that, and the most probable amount of time to finish the isolation process ?  SUuperficially, this problem seems similar to finding a specific card in a randomly shuffled deck, and could be solved by writing an equation in the nature of:

Total time = time walking + time testing = (No. of cars walked x average time to walk 1 car-length) +  (No. of cars tested x average time to test 1 car), or = NW*TW + NT*TT. 

Then, substitute the probability equations for the NW and NT terms, and differentiate the resulting equation with respect to the no. of cars walked (NW), and solve for the optimum/ minimum Total Time.

Note that the number of cars walked has no fixed relationship with the number of cars tested (except that they both have to be less than or equal to the total number of cars in the entire train length), and further, the time to walk 1 car-length and the time to test 1 car are also unrelated in any way.  So there might be multiple valid answers, such as if the equation is also solved for minimum Total Time with respect to the number of cars tested (NT).   

Intuitively, I suspect the answer will be related to the inverse of the ratio of the average time to walk 1 car-length to the average time to test 1 car.  So, if it takes 20 seconds to walk 1 car-length (60 ft. at 3 ft./ sec., about 2 miles per hour), but 1* minute to perform the average brake pump-up and release, that would be a ratio of 1/3.  So, the optimum or 'balance point' (in calculus terms, slope of function = 0)  might be around where equal amounts of time are spent on each task - walking and testing - or, 3 times as many cars being walked as are being tested.  So maybe it's better to do the train by 1/3's or 1/4's - but that still doesn't tell us whether it's better to start at the 3rd car of the 1st 4, or at the 75th car of a 100-car train . . . Whistling 

*Made-up number for example purposes only; feel free to substitute real-world values and recalculate. 

Anybody who knows this subject or analysis better, feel free to jump in and contribute what you can !

- Paul North. 

"This Fascinating Railroad Business" (title of 1943 book by Robert Selph Henry of the AAR)
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Posted by zugmann on Thursday, May 12, 2011 11:27 AM

...or just tell the engineer to not touch the air if he/she can help it. 

 

 

It's been fun.  But it isn't much fun anymore.   Signing off for now. 


  

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Posted by Semper Vaporo on Thursday, May 12, 2011 10:53 AM

But the more I think about it... it also depends on how long each test takes.  If it takes longer to do the test than to walk half the length of the train then the Binary Search would be faster.  At some point between how long it takes to walk some distance and how long it takes to perform a test one or the other method might be faster.

Semper Vaporo

Pkgs.

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Posted by Semper Vaporo on Thursday, May 12, 2011 10:50 AM

If you had instant access to each car at random then the "Binary Search" method would be best, but since access to the cars is linear then a linear search is best.

Semper Vaporo

Pkgs.

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Posted by Paul_D_North_Jr on Thursday, May 12, 2011 9:45 AM

GFood observation, zug.  Reminds me of Bill Cosby's early comedy bit about him and his younger brother Russell playing the game of "20 Questions": Cos goes at it methodically and logically , uses up all 20 questions, doesn't get it; but Russell guesses randomly and gets it on the 3rd one . . . Whistling

This is an illustration of some deep mathematical principles in the nature of statistics, probability, game theory, "linear programmming", "real math", etc., but I'm too fried right now to remember and assign the correct name.   Suffice it to say that in this exercise (literally !), the "starting position" does matter, and the choices for the next trail or test are not equal, nor is the decision process "free' - it involves time, and the effort of someone walking, and then the time for each 'cycle' of closing the next anglecock, pumping up the air, and applying the brakes, etc. - kind of like friction in physics, in that the intellectual models assume there is no friction, whereas there of course is in the real world.  All of that is to say that given a single car with a certain characteristic somewhere randomly and evenly distributed in a train of x cars, there is likely a rational method to work out the fastest and easiest way to isolate and identify that particular car, which is a hybrid of the above 2 methods.  Someday I might figure out what that is . . . Smile, Wink & Grin 

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Posted by zugmann on Thursday, May 12, 2011 7:36 AM

MikeInPlano

In the world of computers we call this a binary search.  Repeatedly cutting the part to be searched in half after eliminating one of the existing halves as not having what's being searched for.

 

With trains, if you're at the head end, there's no need to start halfway back.  Walk back 5-10 cars, close an anglecock, apply brakes.  If no kicker - then walk ahead a few more cars and try again.  Repeat ad nauseum.  It'd be silly to walk to the 50th car of a 100 car train only to find out the kicker was the 4th car.

 

 

It's been fun.  But it isn't much fun anymore.   Signing off for now. 


  

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Posted by MikeInPlano on Wednesday, May 11, 2011 10:40 PM

In the world of computers we call this a binary search.  Repeatedly cutting the part to be searched in half after eliminating one of the existing halves as not having what's being searched for.

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Posted by Packy54 on Wednesday, May 11, 2011 8:41 PM

Speaking of run around hoses, is anyone familiar with any safety rules governing the safe and proper use of a run around hose? Would appreciate any help here. Thanks.

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Posted by Paul_D_North_Jr on Tuesday, May 10, 2011 9:59 AM

edblysard
  My carrier took our runaround hoses and re-railr frogs and chains off the motors about 10 years ago...their concern was we would get something on the ground, then re-rail it and not tell anyone about it...like I am going to let a re-railed LPG or chlorine car head out to interchange with out the car department going over it completly... 

  Well, the "railroad mentality"/ culture has changed quite a bit from 'back in the day', though not so much over just the last 10 years.  Recall the likely apocryphal tale about 2 trains which had a head-on collision because one of the crews goofed up on their orders.  No one was injured, but a fair amount of equipment was derailed and down in the ditch.  Both  conductors then walked forward from their respective cabooses to the point of impact.  After looking over the mess, one turned to the other and said: "Don't be in a hurry to call this in - I think we can cover it up !"  Smile, Wink & Grin  Whistling 

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Posted by erikem on Monday, May 9, 2011 11:32 PM

edblysard

...like I am going to let a re-railed LPG or chlorine car head out to interchange with out the car department going over it completely...

It would be kind of fun if the LPG car and chlorine car were loaded and coupled together...Devil

- Erik

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Posted by zugmann on Monday, May 9, 2011 10:11 PM

edblysard

My carrier took our runaround hoses and re-railr frogs and chains off the motors about 10 years ago...their concern was we would get something on the ground, then re-rail it and not tell anyone about it...like I am going to let a re-railed LPG or chlorine car head out to interchange with out the car department going over it completly...

 

I can understand the frogs (well, not really) but runaround hoses?  I've never had to personally string one out, but I have had to handle trains where one was already being used due to a broken brake pipe.  They must have confidence in us..?

 

 

It's been fun.  But it isn't much fun anymore.   Signing off for now. 


  

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Posted by robscaboose on Monday, May 9, 2011 10:02 PM

EmbarrassedHad that happen to me this past weekend on our tourist RR.  I cut the engine in and as I began walking to the rear of the train to begin my terminal brake test, I heard a hissing sound comming from the back of the train (as we have a long backup move crossing several roads, we have a horn & emergency brake valve on the caboose).  The brake valve was cracked open just enough to make a lot of noise, but not enough to build up the air or "dump" the air.  Once I closed the valve, everything was just fine.

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Posted by edblysard on Monday, May 9, 2011 9:13 PM

My carrier took our runaround hoses and re-railr frogs and chains off the motors about 10 years ago...their concern was we would get something on the ground, then re-rail it and not tell anyone about it...like I am going to let a re-railed LPG or chlorine car head out to interchange with out the car department going over it completly...

23 17 46 11

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Posted by zugmann on Monday, May 9, 2011 7:13 PM
 

 

If you can't repair the airhose with the supplied wrench and replacement hose it may be possible to hang the runaround hose to allow you to continue moving.. with airbrakes.

It's been fun.  But it isn't much fun anymore.   Signing off for now. 


  

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Posted by BaltACD on Monday, May 9, 2011 7:09 PM

Runaround hoses are normally in charge of the Car Dept and will be used where a car has at broken trainline that cannot be repaired in the field to permit the bad order to be picked up and brought to a regular car repair facility for actual repair.

zugmann

 edblysard:

Paul,

You would simply bleed off the air from the remaining cars with the bleed rod...no air at all in the cars and they roll free.

 

 

You don't carry runaround hoses?

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Posted by edblysard on Monday, May 9, 2011 5:20 PM

Sorry about that, I should read first, then type!

But the answer, even though directed in error, is still the same.

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Posted by Paul_D_North_Jr on Monday, May 9, 2011 9:31 AM

Ed - I believe you're replying to "TrainManTy's" question as below, not mine (I had the same answer, which is how I recognized it).  - Paul North. 

TrainManTy

 edblysard:

*snip*

air hose damaged beyond repair you close the anglecock on the car ahead and set the car out, if there is no where or way to set the car out you button up the train ahead of the problem car and proceeded at restricted speed to the nearest location where the car can be set out.

 

Not that there's any other way to do it out on the road, but doesn't that mean you're dragging a car with it's brakes applied?  

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Posted by zugmann on Monday, May 9, 2011 7:59 AM

edblysard

Paul,

You would simply bleed off the air from the remaining cars with the bleed rod...no air at all in the cars and they roll free.

 

You don't carry runaround hoses?

It's been fun.  But it isn't much fun anymore.   Signing off for now. 


  

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Posted by edblysard on Monday, May 9, 2011 4:31 AM

Paul,

You would simply bleed off the air from the remaining cars with the bleed rod...no air at all in the cars and they roll free.

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Posted by jeffhergert on Sunday, May 8, 2011 11:03 PM

To me, in the original poster's scenario the problem isn't that the brakes won't release, but that they either can't get enough air on the rear end, and/or get the leakage to reduce enough to do or pass the air test.  Some or maybe all of the car's brakes may have actually released. 

What Ed described, to me sounds like a Transfer Train air test.  It's less restrictive than a full blown Initial Terminal air test, but it is also limited to trains going at or under a set number of miles, etc.  Ed's version actually sounds more restrictive than Uncle Pete's version, but to be honest I haven't done one in years.  I'd have to look up the requirements.  I'm more used to the road brake test requirements. 

An Initial Terminal test requires air pressure at the rear to be within 15 psi of the feed valve setting.  If you're running a 90 lbs train line, that means you need at least 75 lbs at the end of the train to do the test.  There are two methods to determine brake pipe leakage.  One is if the engine is equipped with an air flow meter, then to begin the test in addition to the 75 lbs on the end you need the flow to be 60 cubic feet/minute or less.  If not equipped with the meter during the time the brakes are set, you cut out the automatic brake valve and watch the engine's brake pipe gauge and how much in drops in one minute.  Leakage can't exceed 5 lbs per minute.  If it does, you have to have any leaks corrected and start the test over.  

Air leaks on the road while moving can happen due to an air hose or brake pipe going bad.  It can also happen because of a drop in temperature.  It isn't unusual during very cold weather to see the flow and pressure at the rear change as the sun sets or rises.

I had an auto rack train last winter that went into emergency four times when ever the slack came in just a bit on the rear end.  The air also came back on it's own each time.  The condr walked the train but could never find the problem.  He found one car with a real slight leak.  He didn't know it, but that was causing our problem.

Each time the slack came in just a bit, the air hose would twist the glad hand just enough to allow enough air to escape through the cold gaskets to put us into emergency.  Once in emergency the slack would pull out enough to reseat the glad hands.  (It's problems like this that make me cringe at the thoughf of 10000 foot DPU auto rack trains.)  After the sun came up and the air temp rose a bit, we stopped going into emergency but would lose 10 or 12 lbs on the rear end.

I told the outbound engineer about this when we changed out.  A few days later I saw him and he said he had no problems and the rear end only varied about +/- one pound the whole trip.  The daytime sun had warmed up the gaskets enough to seat them properly with the slack in or out. 

Jeff   

 

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Posted by Paul_D_North_Jr on Sunday, May 8, 2011 9:40 PM

BaltACD
  Air leaks sufficient to apply the brakes are sufficiently unique that they can be heard in almost all noisy environments.  [emphasis added - PDN]   

 I'm sure they are - but the Original Poster's question was different - it was about a leak where "the compressors are working but the pressure will not rise to 90 psi (or whatever it is) and the brakes therefore won't release". 

Further, I'm now considering the 'included' problem of a much smaller leak that is just enough to exceed the allowable rate - from Ed's post above: ". . . compare the rear train line pressure against the locomotive gauge, minimun pressure is 85 pis and the rear has to be withing 5pis of the head end, we then do a leak down test, allowable for us is 1pis per minute . . ."  Only 1 psi in as long as a minute could be a fairly small leak, which would be hard to hear.  (I'll skip the fallacy of a long train having more places for air to leak from, because it also has more compressed air in its lines, and hence each car would have to lose its share of also about 1 psi - otherwise, the leak would be of air from multiple cars, hence more and louder and easier to hear, as you noted.)     

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Posted by Anonymous on Sunday, May 8, 2011 9:09 PM

edblysard

*snip*

air hose damaged beyond repair you close the anglecock on the car ahead and set the car out, if there is no where or way to set the car out you button up the train ahead of the problem car and proceeded at restricted speed to the nearest location where the car can be set out.

Not that there's any other way to do it out on the road, but doesn't that mean you're dragging a car with it's brakes applied?

 

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Posted by BaltACD on Sunday, May 8, 2011 8:43 PM

Air leaks sufficient to apply the brakes are sufficiently unique that they can be heard in almost all noisy environments.

Paul_D_North_Jr

 edblysard:
  [snipped]  As for finding the actual leak, with 90 psi of air blowing through a 1" opening in a glad hand/hose that was not laced up, well its pretty loud, you can hear it from 10, 15 or 20 cars away, it is a very distinct sound. 
  True enough.  But now imagine a much smaller leak, and in a nosiy environment such as a windy day, next to a road engine running pretty fast - or worst of all, next to a busy highway with lots of truck traffic and tire noise and loud exhausts, etc. - hence my mention of the gage.   

Interesting procedure otherwise - thanks. 

- Paul North.   

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Posted by Paul_D_North_Jr on Sunday, May 8, 2011 8:36 PM

edblysard
  [snipped]  As for finding the actual leak, with 90 psi of air blowing through a 1" opening in a glad hand/hose that was not laced up, well its pretty loud, you can hear it from 10, 15 or 20 cars away, it is a very distinct sound. 

  True enough.  But now imagine a much smaller leak, and in a nosiy environment such as a windy day, next to a road engine running pretty fast - or worst of all, next to a busy highway with lots of truck traffic and tire noise and loud exhausts, etc. - hence my mention of the gage.   

Interesting procedure otherwise - thanks. 

- Paul North.   

"This Fascinating Railroad Business" (title of 1943 book by Robert Selph Henry of the AAR)

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