Eastern Railroad Discussion > Difference between Graduated Release and Direct Release

I have seen reference to Graduated Release air brakes and Direct Release air brakes when talking about Amtrak trains with and without freight cars in the consist.

What are the main differences between the two systems? How are they used in practice? And why do express cars and roadrailers on short trains such as Amtrak trains need them?

Any other need for Graduated Release besides Amtrak, commuter, etc?

Cameraman Wrote:
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> What are the main differences between the two
> systems?

Direct release brakes mean that if the pressure in the brake pipe rises by only a couple of pounds, the brakes will completely release on all cars in the train. Graduated release means that as the brake pipe pressure rises, the brakes will release in proportion to the pressure rise. In other words, with a graduated release train, the engineer can partially release the brakes.

Direct release is necessary on longer trains, like those over about 1000 feet in length, so the brakes will quickly release and not drag. Freight equipment is mostly set up for direct release only, and passenger equipment can often be set to either.

> How are they used in practice?

Passengers mostly run in graduated release, so the engineer has more control over the train's brakes. This is particularly useful when arriving at station stops. Freight is run in direct release.

> And why do express cars and roadrailers on short trains such
> as Amtrak trains need them?

They have freight type brake valves.

> Any other need for Graduated Release besides
> Amtrak, commuter, etc?

Not really.

Actually in graduated release the brakes do not partially release. A choke is applied to the exhaust port of the brake valves and the brakes release at a slow rate. But they do release completely! It just happens slower, this enables the engineer to keep the slack either stretched or bunched. Providing the passengers for a smooth ride with no slack action. I have a private car and Amtrak requires the valves to be in graduated on most of their trains with the exception of Auto Train and some of the longer train sets that use freight brake valves. Now that the road railers and box cars are going away. They are converting more of the trains back to graduated release.

morail Wrote:
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> Actually in graduated release the brakes do not
> partially release.

Yes they do partially release.

> A choke is applied to the
> exhaust port of the brake valves and the brakes
> release at a slow rate. But they do release
> completely!

You are mixing up retainers with graduated release. Retainers have a number of settings, and one position, slow direct, will allow the brakes to release at a slower rate than direct release.

> It just happens slower, this enables
> the engineer to keep the slack either stretched or
> bunched. Providing the passengers for a smooth
> ride with no slack action.

A typical train control technique approaching stations with a passenger train would see the engineer set a brake to bring the train speed down approaching the platform, then partially graduate the brake off to maintain a low speed along the platform, lightly pulling against the brakes with the locomotives, then drop power to come to a stop, finally partially releasing the brakes to feather the final stop.

morail Wrote:
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> Actually in graduated release the brakes do not
> partially release. A choke is applied to the
> exhaust port of the brake valves and the brakes
> release at a slow rate. But they do release
> completely! It just happens slower, this enables
> the engineer to keep the slack either stretched or
> bunched. Providing the passengers for a smooth
> ride with no slack action. I have a private car
> and Amtrak requires the valves to be in graduated
> on most of their trains with the exception of Auto
> Train and some of the longer train sets that use
> freight brake valves. Now that the road railers
> and box cars are going away. They are converting
> more of the trains back to graduated release.
>
>
When a passenger car that was fitted with an ABDW (freight) brake valve is upgraded
to Amtrak compatability, is a replacement valve required? Have BNSF and UP refitted
their business cars to "graduated release"?

If the brakes only partially released then that means they never fully release and you would burn off the brake shoes. They do fully release but at a slower rate. Passenger cars no longer use retainers these are only used on freight equipment.On the valve bracket there is a small plate with two bolts. You take it out and turn it around and a small choke is put in line with the exhaust port of the valves. When you come into a station stop the engineer will make a service reduction in the brake pipe pressure which will bring the train speed down. He then bails off the engine brake and this will stretch the slack. Basically he is using the brakes on the cars and not engine to stop the train. This is called power braking and graduated release really does not play into making station stops. Graduated released is used when slowing down but not stopping! If your doing track speed and you need to slow down for a speed restriction you make a service reduction in brake pipe pressure this will apply the brakes on the train. You then bail the engine brakes keeping the slack stretched. When you release the train brakes they will release slowly (but completely) meanwhile the engine is pulling again (against the slowly releasing) brakes. This keeps the slack stretched and provides a comfortable ride. TRUST me I do know what I'm talking about I own a Amtrak certified car, not to mention owning at least 12 other passenger cars over the years and I have been the Chief Mechanical Officer of several passenger operations. How many cars have you owned?

None of my cars have ever been equipped with ABDW valves. I have always had either D-22 or 26-C. The freight valves as I recall do not have a graduated release feature. Different train handling is used to keep the slack stretched. Not sure about UP & BNSF's I know BNSF has 26-C on some of their cars. Most of the times the Class 1 railroads will use freight valves. This way if their is a problem they can go to any RIP track anywhere on their railroad and get the parts.

morail Wrote:
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> If the brakes only partially released then that
> means they never fully release and you would burn
> off the brake shoes.


"Highball" is correct. When the brake pipe pressure increases, the brake application will reduce in proportion to the increase. Once full brake pipe pressure is obtained, then the brakes will fully release. Graduated release is a godsend when descending an undulating grade, since the brakes can be partially released when the grade flattens out, and reapplied when the train hits a steeper section. With direct release trains, the only options, in the absence of DB, is to fully release and reapply. I suppose retainers are another option.

> They do fully release but at a slower rate.

No they don't. If the brake pipe pressure is only partially raised, then the brake valves will lap at the new, reduced, cylinder pressure, and hold it. (Assuming the system is tight.)

> Graduated released is used when slowing down but not stopping!

Crap. Graduated release is an essential part of good passenger train handling when stopping trains. It is also a nice feature when balancing on grades.

> TRUST me I do know what I'm talking about I own a Amtrak
> certified car, not to mention owning at least 12
> other passenger cars over the years and I have
> been the Chief Mechanical Officer of several
> passenger operations. How many cars have you
> owned?

If you want pedigree, I have been in the business for over 40 years, was an officer of the Air Brake Association, and have been involved with the maintenance of something like 70,000 freight cars and 2,200 passenger cars. What you say above is completely wrong.