So, the 7500-foot freight arrives at the yard. The engines cut off, and powwwooosh, there goes all the brake pipe air, applying the brakes on every car. I would assume that some hand brakes were set before the disconnect.
But the yard crews need to switch these cars now. Does someone (A car-knocker? A switchman?) walk the entire cut and bleed off every reservoir? What about the emergency reservoirs? I'm thinking those may not need to be bled.
Related question. Say it's a flat yard, and a 20-car cut has three handbrakes set. Are there times when a switch engine will pull cuts without releasing the hand brakes, just overpower them? And if so, will the wheels on the braked cars turn (squeakily), or do they drag? Sometimes one, sometimes the other?
Still in training.
After the train goes into emergency a employee will either walk the train or ride in a Kubota and manually bleed off every car. There is no separate bleed rod for the different sections of the air brake reservoirs, its all or nothing. You pull the bleed rod, and wait to hear the air make a popping noise, then you can let go. If it doesn't pop you have to hold the bleed rod open till all the air is released.
Yes cars are moved with hand brakes applied, even though it's usually against the rules. Most of the time the wheels will still roll, but if you tie a really tight brake they will slide creating flat spots which is obviously not a good thing.
Thanks, GB.
It used to be necessary to bleed all the air from the brake system to release the brakes for switching cars and you had to hold the bleed rod for around a minute to let all the air out.
Some time ago, 50's or 60's I'm not sure exactly when, the system was modified to allow air to be bled from just the brake cylinder and not the reservoirs.The bleed rod can now be held for a few seconds and released, and the pressure in the brake cylinder will be reduced to zero. This saves much time when bleeding a large cut of cars. It also saves time when recharging the brake system as some air remains in the reservoirs.
If all the air needs to be bled this can still be done by holding the bleed rod.
The end of the bleed rod indicates which type of system the car is equipped with. The old system has a bleed rod with the end bent 90 degrees. The new system has the end of the bleed rod formed into a closed loop.
There was a way to retrofit the new system onto older control valves. For a time you could see cars with two bleed rods. One with a bent end for the old system and one with a looped end for the new.
Mark Vinski
GBSD70ACe After the train goes into emergency a employee will either walk the train or ride in a Kubota and manually bleed off every car. There is no separate bleed rod for the different sections of the air brake reservoirs, its all or nothing. You pull the bleed rod, and wait to hear the air make a popping noise, then you can let go. If it doesn't pop you have to hold the bleed rod open till all the air is released.
There are/were two types of bleed rods. One, with a short push,, would only bleed off the air in the brake cylinder. The other you needed to hold and bleed off all the air.
.
Pulling the bleed rod for a couple seconds bleeds the cylinder. Hold it until you hear a momentary louder SSSHH (How do you write a sound?) and that's the auxilary reservoir starting to bleed off. I've always been taught to bleed both off, especially when cutting the brakes out of a car on the road, to ensure that air doesn't somehow bleed back into the cylinder. It's not supposed to, but things that aren't supposed to sometimes have a way of happening.
Bringing a train into a terminal yard where the carmen are going to walk the train, bleeding off the cars and inspecting for bad orders needing repair, you might not let the train go into emergency when detatching the engines. It's in the rules, but I can't think of any of the terminals where we terminate a train where we do it.
The procedure is to tie a sufficient number of handbrakes, then make a 70 psi reduction, using the handle off position on the automatic brake valve. Then cut away leaving the anglecock open on the car. The train won't go into emergency. The reason is so that brake piston travel on the cars isn't out of range because of the extra pressure the emergency application adds to the brake cylinder. (It's also the procedure used during extreme cold weather to ensure the emergency portion of the car's control valve doesn't stick open.) As I said, I don't recall doing that when terminating a train where carmen (who's job it is to bleed inbound cars) are employed.
Jeff
We aren't supposed to let the train go into emergency when cutting off if the temperature is below freezing. But it doesn't really seem to make a difference until you get below about -20 C.
If you do get a stuck emergency valve you can often get it to close again by shutting off the air to it and then cutting it again slowly, or feathering the air supply to it a few times. This also works with EOTs after the emergency test.
Different yards may have different procedures. In Saskatoon the carmen may ask you to leave the air bottled with no handbrakes applied (it's a bowl), and in Scotford you were allowed to kick into clear tracks with no one riding a handbrake, as long as you released the cars at 3 mph or less (another bowl).
While moving cars with handbrakes applied is against the rules it can be very useful and save a lot of work at times, like when spotting boxcars at doors, tank cars at racks, or spotting anything right at the end of a track. In winter it is also very important to condition your brakes (remove ice and snow by warming them up) first, and if you are switching with the cars bled off the only way to do this is by applying a light to moderate handbrake.
Empty cars lock up and skid easily, but I've seen loads travel some pretty long distances with the handbrake applied, and they rolled the whole way. The brake shoes melted, but the wheels never skidded.
Greetings from Alberta
-an Articulate Malcontent
Jeff, what do you mean by the brake piston travel being "out of range?"
Lithonia Operator Jeff, what do you mean by the brake piston travel being "out of range?"
Brake piston travel has prescribed requirements.
Brake Inspection Requirements
Inspect both sides of cars while performing the air brake test to determine that:
If a carman walking a train sees a car with an obvious defect, such as excessive piston travel, he can immediately bad order the car.
SD70Dude We aren't supposed to let the train go into emergency when cutting off if the temperature is below freezing. But it doesn't really seem to make a difference until you get below about -20 C. If you do get a stuck emergency valve you can often get it to close again by shutting off the air to it and then cutting it again slowly, or feathering the air supply to it a few times. This also works with EOTs after the emergency test. Different yards may have different procedures. In Saskatoon the carmen may ask you to leave the air bottled with no handbrakes applied (it's a bowl), and in Scotford you were allowed to kick into clear tracks with no one riding a handbrake, as long as you released the cars at 3 mph or less (another bowl). While moving cars with handbrakes applied is against the rules it can be very useful and save a lot of work at times, like when spotting boxcars at doors, tank cars at racks, or spotting anything right at the end of a track. In winter it is also very important to condition your brakes (remove ice and snow by warming them up) first, and if you are switching with the cars bled off the only way to do this is by applying a light to moderate handbrake. Empty cars lock up and skid easily, but I've seen loads travel some pretty long distances with the handbrake applied, and they rolled the whole way. The brake shoes melted, but the wheels never skidded.
Once in a while, one will stick even in warm weather. Back when I was a conductor we had one stick at an intermediate terminal after making a pickup. I had a carman giving me a ride and we found the car. He handed me a ball peen hammer and said to smack the emergency portion of the control valve until it reset. For him to do it, he would have to blue flag the entire train. I could just get a "red zone" to crawl under the car to do it.
We can move cars with hand brakes applied as long as they don't go over a switch. If brakes are tied on the far end of a track, the trainman/switchman will usually just have the track pulled down to where they can release the hand brakes.
And then there's the rule that requires hand brakes to be set when shoving a car within 150 feet of the end of a stubbed track to help control movement. (Don't shove it off the end of the track.)
We got a bulletin a couple weeks ago that said a handbrake should be shoved no more than is necessary to test it. The bulletin recommended 10 or 15 feet as a maximum permissable distance.
We, too have a rule that says we cannot shove past the end of the track (who'd have thunk it), and we are required to stop 25 feet before the end and only shove closer if we are spotting an industry that requires this. So to fully comply with our rules at certain locations one would have to stop short, shove another 10 feet, stop again, apply the handbrake, and then shove a bit more to test it and spot the car.
I'm not sure most of the people in our yard understood the workings of air-brake systems well enough. In a hump operation such as ours, air was anathema. It was usually attended to by the carmen in the receiving yard. One bump of the bleeder rod was all it took to get the car properly bled. However, everyone on the hump seemed to believe that giving a pull on the bleeder rod to makesure the air was exhausted was a good thing to enjuse the the brake was entirely released. Nope. A little pull on the rod might be enough to move air from one reservoir to the other, and I'd often see the piston going out as the car rolled by me in Tower A! I'd immediately release the lower retarders and warn the CRO in Tower B oe C about the car...if we were lucky it would roll off the lead before "dying". (There was one time I was pullin' pins on the hump, and the yardmaster told me that the cars were dying down below and he wanted me to "bleed every f***ing car". I didn't, but you couldn't explain things to these guys who started work in the early 1950s. The trainmaster became involved, and repeated to me the yardmaster's instructions, with a few embellishments of his own. So, I did. As long as air was being heard, I'd hold the bleeder rod...not many cars were cut off at that rate, and I really wished somebody could teach those guys something!)
Carl
Railroader Emeritus (practiced railroading for 46 years--and in 2010 I finally got it right!)
CAACSCOCOM--I don't want to behave improperly, so I just won't behave at all. (SM)
CShaveRRI'm not sure most of the people in our yard understood the workings of air-brake systems well enough. In a hump operation such as ours, air was anathema. It was usually attended to by the carmen in the receiving yard. One bump of the bleeder rod was all it took to get the car properly bled.
You usually have to pull/push it and hold it for a second to get all the air out (you'll hear the pop). If you just quickly pull/bump it, you may release just a little air on the cylinder, but it won't bleed out. You can tell right away...
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
You're right, Zug...you have to listen to the sound it makes. If it stops when you release the lever, do it again. Unless, of course, it's already been bled...then don't touch it.As a pin-puller, I would make my brake checks by looking at the piston before touching anything--unless there were an obvious noise or sight that brakes were applied. There was a lot more to pin-pulling than lifting the lever, for sure!
mvlandswThe end of the bleed rod indicates which type of system the car is equipped with. The old system has a bleed rod with the end bent 90 degrees. The new system has the end of the bleed rod formed into a closed loop.
Good thinking by some design engineer. Cheap and effective.
ChuckAllen, TX
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