Air Brake Issues 101:

Trains Magazine General Discussion
1

From the STB of Canada report:

“However, if, during a hand brake effectiveness test (when applying throttle), hand brakes are also applied on the operating locomotive(s), the retarding force from the locomotive hand brakes can give the false impression that the retarding force is that of the entire train. This can result in an inaccurate effectiveness test, increasing the risk of runaways. An LE would therefore have to compensate with a greater throttle application to overcome the retarding force of the locomotive hand brakes.”

False impressions? How can you trust a handbrake effectiveness test that is capable of giving false impressions? If you are getting a false impression, you are supposed to compensate. To do that, you would have to know that you are getting a false impression. How would you know that you are getting a false impression?

2

Don’t apply the locomotive handbrake while performing the test?

3

On the MM&A, locomotive handbrakes are counted as part of the securement. So when the securement is tested, the brakes have to be applied to the locomotives.

4

Leaving the Independent Brake applied during the handbrake test, as occurred at Lac-Megantic, is another sure-fire way to get a false pass on the test

5

Its common on US roads to require the handbrakes be set on the engines but not the independent brake.

6

After thinking about this, I conclude that the TSB of Canada has made a mistake in writing the paragraph where they refer to getting “false impressions” during a handbrake effectiveness test.

I don’t see how a false impression could arise. The impression yielded by the pull test would indicate the retarding force of the entire train, contrary to what the TSB has stated. Braking force, it is determined by the friction of the brake shoe against the wheel. It is true that the locomotive wheels are directly powered by traction motors and the car wheels are not, but so what? During the pull test, all wheels are powered to turn against the brake shoe friction. The locomotive wheels are powered by the traction motors, and the car wheels are powered by the locomotives pulling the cars to turn their wheels through their contact with the rails.

While it is true that you can’t tell how much retarding force is coming from handbrakes on locomotives versus handbrakes on the cars, what difference does it make? It is only the total retarding force that matters.

7

I read that part as a warning that doing the test with the locomotive handbrakes applied may lead the employee doing the test to incorrectly assume the cars are secure…It may just be the way I am interpreting it

On my carrier, locomotive handbrakes are not to be used to help secure a train, only the handbrakes on the cars, for the simple reason we may, at some time during the day, need to remove the locomotives from that train for use elsewhere.

We are required by general order to apply handbrakes to cars, and then release all the brakes on the locomotive and let the weight of the locomotives try and move the cars…if it remains in place, good test, secure the locomotives and leave it, if the cars move more hand brakes should be applied, repeat as needed until train is secure.

We also do a push/pull test, if the locomotive under power has a difficult time moving the cars with only the cars handbrakes applied, it is reasonable to assume the cars are secured and can, if needed, be left unattended.

We are also required, when cutting away from cars, to “observe for a sufficient amount of time the cut of cars to be left and verify that no unintended movement occurs”

This rule allows us to cover the portion of the GCOR that refers to cars left unattended also…because the cars alone are providing the retarding force, they meet the criteria for both leaving a train unattended and a “cut of cars” unattended.

I would assume most carriers do the same thing.

Not picking a fight, but the reasoning in your last two sentences may be the major contributing factor to this event.

If the handbrakes on the cars had been sufficient to hold the entire train, including the “dead weight” of the locomotives, then nothing that was done to the locomotives afterward would have cause the train to runaway.

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8

Ed’s example (cutting the power away from the cars) notwithstanding, I don’t see that there is a problem with a policy of including the handbrakes on the locomotives as part of the required number of brakes. Assuming that the locomotives will remain attached to the rest of the consist, AND that a proper securement test is done (even if it’s simply releasing all brakes and observing for movement, as Ed also mentions), then the train is going to stay where it’s left.

What we’re really talking here is having handbrakes set on sufficient axles to hold the train. Setting brakes on a certain number of cars is only sufficient if the number of axles with brakes applied are sufficient (and the retarding force thereof is also sufficient, but that’s another discussion). If eleven cars have handbrakes that apply on all four axles, that’s 44 axles. If some of the cars only apply on one truck, that could be as few as 22 axles.

And I’m pretty sure that we’ve established that the MMA train held as long as the independent was set. If the LE had set hand brakes on ten to fifteen more axles (to cover the locomotive axles not held by handbrakes), we wouldn’t be having this discussion.

9

Ed,

I understand your points and agree with them. I don’t know how common it is to allow the inclusion of the locomotives in the count for the required number of handbrakes to be set. The report says it is the rule for the MM&A, and Dave Husman says it is common elsewhere. I am not suggesting that there is any problem with including the locomotives in the handbrake securement.

Also, just to clarify, the question that I am asking is not about the securement of the MM&A oil train. My question pertains to the general practice of including the locomotive handbrakes in the handbrake securement and the warning of false impressions that can come from that practice. The only relationship of my question to the MM&A oil train is that the information that raises the question was provided in the MM&A oil train accident report.

Also, incidentally, I don’t think that the question of the false impression even came into play in the MM&A securement because the engineer did not pull on the train to test it. He only released the automatic air brakes. He also left the independent brakes set during his test, so his test was faulty even without the false impressions.

To the question of false impressions being given by a handbrake effectiveness test that does include the locomotives, there are a couple of points that puzzle me. Say you had five engines and the rule called for 15 handbrakes. So you set the five engine handbrakes and handbrakes on ten cars. Then you pull, reasonably hard as one might assume to be prudent, and nothing moves. I would say the train is secured. I don’t see how the fact t

10

Setting the minimum number of handbrakes (as specified in rules and special instructions) is a good start.

The runaway problem could occur if a deep reduction was taken to stop the train. The deeper the reduction, the longer it will take to recharge the train. And until the train is recharged to a certain point, you’re not going to get much from a service application (having already p****d away your air with the stop).

And this is where your runaway is going to come from.

Making an emergency application might still stop the train, if it’s done before the train gets much momentum. Not depending on the independent application as part of the securement will also help a lot, even if you’ve set the handbrakes on the locomotives. Again, not all axles on a locomotive are secured with the handbrake, so you have those unsecured axles available for stopping power as long as the main res is above the normal operating pressure for the independent brake.

As for the false impression, if you simply do a static release (train is stopped, no force applied by the locomotive), the train may stay put. I have seen cars that were secured with a handbrake and which h

11

Yes, I understand what you are saying. The engineer of the MM&A oil train should not have used the independent brake to help secure the train. That was flat out wrong. There was also an issue that I did not quite follow about the locomotive handbrakes. There was a valve that would bleed off the independent brake if a handbrake were set. That valve did not work properly, so when setting the handbrake, there was actually no handbrake set. I think that may have been on just one of the locomotives. But it added one more little defect in the securement.

As to the false impression, I think the point they are making is that if you have handbrakes set on the locomotive, you get less pull out of it because the handbrakes are holding it back. And then that reduces tractive pull on the cars, leading to a false impression that the cars are being held by their handbrakes when they really are not. That is my interpretation of their point. But I think it is fuzzy logic.

Here is another way of looking at it: Say that the rules do not allow locomotive handbrakes as part of the securement. But say you decide to set them anyway just for extra assurance. And they you perform the pull test. THAT would lead to a false impression that they are talking about.

12

Part of the issue is that you and the TSB are talking about a “pull test”. Not all railroads require a “pull test”. Many railroads just require the air brakes to be released and the train not move after a certain period of time.

A bit of an apples to oranges situation.

If you are doing a pull test then yes, having any brakes on the engine would skew the results. if you are not doing a pull test then the engine handbrakes being on don’t affect the outcome of the securement test.

13

False tests are something that happens in all varieties of human activity, from securing trains to account functions to quality control functions to any and all kinds of human activity.

It is easy to fall into the trap that you are testing something, when in reality you are just wasting time with no real test having been applied.

The MMA’s LE performed a false test and believed he was doing the right thing.

14

Although it is not required on all railroads, it is the pull test that I am talking about; and it is also the pull test performed on a handbrake securement that includes the locomotives. That is what the TSB is referring to in this paragraph upon which I base my question:

“However, if, during a hand brake effectiveness test (when applying throttle), hand brakes are also applied on the operating locomotive(s), the retarding force from the locomotive hand brakes can give the false impression that the retarding force is that of the entire train. This can result in an inaccurate effectiveness test, increasing the risk of runaways. An LE would therefore have to compensate with a greater throttle application to overcome the retarding force of the locomotive hand brakes.”

Referring to these conditions, you say that “If you are doing a pull test then yes, having any brakes on the engine would skew the results.” Skewing the results seems to be what the STB is referring to as “false impressions.” I don’t see the basis for concluding that false impressions might result.

But in the first place, considering what is at stake, why would they allow such a test if it could produce false impressions? This is especially amazing considering that there is no way to know whether the results are false impressions. This seems like an incredible flaw in the rules.

15

Some locomotive handbrakes operate by opening a valve and letting off the air in the brake cylinders. Not sure if the C30-7 uses this type of brake.

16

Back in the last Lac Megantic’ petitnj made this comment:

"The locomotive is a different case. The air brake pushes on the bottom of brake show lever and the hand brake chain on the top. If the air brake cylinder is “out” or pressurized, the chain will tighten but loosen when the air drains out of the cylinder. (That seems like a formula for disaster – the brakes feel tight but they are not!). "

This bleed valve must be to solve this problem, but I wonder why anyone would design a brake system that way in the first place. When the pressure drained down the handbrakes were effectively released.

17

The valve you are discussing releases or bails off the independent brake when you tighten the handbrake…which is a good thing, as it forces you to apply enough handbrakes to hold the cars and the engine in place.

It is designed that way so you cannot rely on the independent brake to secure the train.

Theses valves often fail, as they are exposed to the elements, and most railroads whose locomotives still have them also have a general order that requires the engineer or crew to manually bail off the independent or manually trip the valve.

The intent was to force the securement of locomotives with handbrakes only, in case, as is under discussion, the engine in the locomotive is disabled and stops, thus allowing the air compressor to stop, which could result in a bleed down and runaway locomotive.

I have only seen the valve on older GEs, never seen one on an EMD.

You can reapply the independent after you tighten the handbrake by moving the brake handle

18

Ed, why would these valves be only on older units? Are the brakes on newer ones designed differently?

19

Those QRB valves were on the old EMDs as well . Search for pictures of the ATSF 5300 SD45s. Seems like the Santa Fe liked them.

The QRBs worked pretty good and they were easy to adjust. We had a special instruction on how to make sure they were set properly. They released the brake cylinder pressure on ONE cylinder.

20

Outstanding, I will look and see….not that we get a lot of older Santa Fe power here, but we did have a bunch of BN B30-7As here for a while, sent most of those to Brazil.