Hi everyone. My name is Paul. I'm a trainee driver in Australia battling my way through a pretty intense course.
Is anyone aware of a decent triple-valve animation out there? I understand the general concepts behind it. But I'd rely like to see everything down to the level of the distributing valve, relay valve, control reservoir and so on - it would be a huge help.
I can't find anything on YouTube. Any suggestions?
Thanks.
Not animation - but a little history
Never too old to have a happy childhood!
Paul,
I doubt that you really mean triple valve since the literal triple valve was last used in the K brake which was banned from interchange in the US in the early 1950's. The term has held on in railroad slang ever since. The K brake was superceeded by the AB system of 1933, then the ABD and ABDW.
All AB family control valves operate in one of three states, charging running/release, and application. When charging air flows into (the auxilary reservoir and emergency reservoir ER) on the car. In this state, Brake Pipe (BP) pressure is greater than (GT) pressure in the reservoirs. The control valve sends air from BP to AR and ER, which continues until BP is equal to AR and ER pressure. The AR and ER are now fully charged. This is the fully charged, or running state.
Brakes are applied by reducing the BP pressure by manipulation of the engine brake valve by the engineer. The control valve detects the lower BP pressure, ceases charging the reservoirs, and moves air from the AR to the brake cylinder to apply the brakes. The increase of pressure in the brake cylinder is proportional to the reduction in BP pressure. If the rate of release of air from the BP exceeds a value, then the valve sends air from the AR and the emergency reservoir into the brake cylinder causing the highest possible pressure in the brake cylinder. This is an emergency application.
Release is similar to charging in that BP is GT reservoir pressure. Air flows from BP to AR, and ER if prevously used in the application. Air is also released from the brake cylinder to the atmosphere. The train can now be moved, but the BP, and more importantly the reservoirs, have not yet attained a fully charged condition.
If your operation has/uses retainers they are basically choke valves that slow the release of air from the brake cylinders, so they "retain" the set while the AR and ER are being recharged. Retainers have to be manually set up or turned down which always takes time with the train stopped. In the US retainers are seldom used.
The key concept in all of this is equalization of pressures in the various states. Time to apply and release is largely dependent on the speed of propagation of apply and release "commands" which are transmitted as a wave front of decreasing or increasing BP pressure.
Mac
For further details see the Air Brake Association and the Railway Education Bureau. Start with ABA as it is only about air brakes.
Thanks for all these very useful replies!
My grasp of the basics of air brake operation (the different flows from valve handle to equalising reservoir, the role of the relay valve, the various pressues, etc) is solid. I'm just lacking in micro-detail - how individual ports convey pressure, how the diaphragms move in response to those pressure changes, and so on. The few diagrams we have aren't particularly user-friendly.
Thanks for clearing up some terminology. Here, it's always referred to as a '26L triple valve'. I guess perhaps we're a bit behind the times...
Here in the US the 26L is the brake valve in the locomotive cab used by the engineer to charge, set, and release the train brakes. My answers all had to do with control valves on the cars. I have never herd the 26L referred to as a 'triple valve'.
PNWRMNM Paul, Here in the US the 26L is the brake valve in the locomotive cab used by the engineer to charge, set, and release the train brakes. My answers all had to do with control valves on the cars. I have never herd the 26L referred to as a 'triple valve'. Mac
Mac, I think referring to the 26L as the triple valve is really just a function of sloppiness on the instructors' part. We also use the No. 4 and W-type brake valves on older locomotives, and they all fall under the same term. 'Triple valve' here sometimes seems to be shorthand for 'train brake system'.
What I'm trying to find is some online resource, preferably an animation, that traces airflows as the brake is applied: air is exhausted from the equalising reservoir, brake pipe pressure equalises, control reservoir pressure moves against brake pipe pressure in the control valve, brake cylinder pressure is exhausted through the relay valve, and so on. And all this down to the level of individual ports.
Is this the sort of thing the ABA might have stashed up their sleeves? They don't seem too responsive to emails.
Regards
Paul
It looks like the ABA will not do anything if you are not a member.
Try website transalert.com which offers lots of books and charts. While not animation, looks like the best source.
https://www.youtube.com/watch?v=b-zdx5gNM6E
This link (which may need to be opened in a new window) goes to a video series on the 26C locomotive brake system. It seems as the series evolves (I have only looked at segments of the individual videos) to get quite technical in spots.
Jeff
Our community is FREE to join. To participate you must either login or register for an account.