Eastern Railroad Discussion > Welded Rail, Expansion Joints and "Sun Kinks"

Welded rail has been around for a while now. However, I hadn't heard the term "sun kink" until the Amtrak wreck in Florida. With today's Amtrak wreck on CSX in Maryland the term has come up again.

The western railroads have dealt with extremes in temperature for years. One would think that extrems in desert temperatures from day to night would be more of a challenge than Florida or Maryland.

I have heard that even welded rail has expansion joints. What is this "sun kink" business and why hadn't I heard of it before on any other railroad than CSX?

The reason you're hearing about the phenomenon now on CSX is because of its involvement, or suspected involvement, in Amtrak derailments.

I remember seeing a picture of a particularly gnarly sun kink on the Boston & Maine about 12 years ago, but evidently the crew got wind of it before hitting it, because the picture showed the locomotive stopped short of the wobble in the rails.

I also remember my first visit to the RF&P in 1991 and noting there were fittings in the rail beyond either end of the Occoquan River bridge designed to absorb the impact of rail expansion so that a kink wouldn't occur on the span.

An MRL derailment about a month ago in the vicinity of Plains MT was attributed to a sun kink.

Sun kinks happen as a result of the rail heating up and expanding. Eventually it has nowhere to go, and if the proper precautions haven't been taken it tends to bow out and form a kink.

One of the proper rail-teasing methods is called 'stretching' the rail, or something to that effect. It basically takes the tention off the rail ahead of time before a potential kink becomes a reality. The main prevention tool, however, is ballast. Looking at Track Two at the accident scene, it didn't appear to have a lot of ballast around the ends of the ties. With no ballast to prevent the ties from moving, sun kinks are easily made possible.

Fixing them usually involves cutting the rail and stretching two pieces together. However, it can also be done by jacking the track over and then securing it with newly-dumped ballast. From experience on several I can tell you these processes are no fun.

Am I saying that the lack of ballast could have caused this? No, but I wouldn't rule it out of possibility. If there's one thing I hate its speculation...such as CNN trying to say welded rail is like 'playing with fire'. Morons...


Scott H

My understanding is that CWR is laid and then heated(or is allowed to heat) to an optimal temperature before being secured to ties. Still there are events that can occur that contribute to kinking.
I was riding a couple of weeks ago, and unfortunately we did not get wind of the 15 1/2" kink that we did hit. Luckily we were coming off a 25mph and after putting the emergency air to them were able to slow to around 20 mph or so. It was a bit rough, but everything stayed on the rails. The Track Inspector was amazed that we could get a kink like that, on the main halfway between switches of a siding. They had just done some tamping in the area however, and apparently loosened things up just enough.

Here is one from out west:

http://www.nscalesupply.com/Base/9911/991107MoffatPart3.html

Al

Just posted this to the Amtrak board and thought it might add something to this discussion. --

To answer questions raised in several previous messages:

Sun kinks can happen almost anywhere. The southwest, northwest and northeast have plenty. Welded rail is much more susceptible to kinks but jointed rail can have kinks also.

When installing conventional (jointed) rail the temperature of the rail is measured and expansion shims are placed at each joint. This can be between 0" and 1/2" in 1/8th" increments. Rails and insides of joint bars are greased to allow rails to slide in response to expansion.

Welded rail is prevented from expanding and contracting by the use of rail anchors. Expansion joints are not used in welded rail except at some bridge locations.

To properly install welded rail and minimize sun kinks the following steps should be followed:

Rail is layed when temperature (of rail) is above a certain level. This would vary from region to region of the country.

If rail is installed in lower temperatures it should be heated to minimum temperature. Anchors must be installed before rail cools.

If rail must be installed at a cooler temperature than standards allow it must be noted and when warm weather approaches it must be adjusted. This is done by cutting rail and removing anchors either on a hot day or with use of a rail heater. Then the excess rail is cut out and reconnected. Anchors are replaced.

A major factor in preventing kinks is to have a proper ballast profile. Too little ballast will greatly contribute to sun kinks. Disturbing the track structure during track work (tie replacement/tamping) will cause the track to be more susceptable to kinks until track has settled. This is done by passage of trains or use of a ballast packer.

CSX seems to have more than it's share of track problems. They are either not following proper track maintenance procedures or not funding track work at a safe level. It is probably some combination of the two.

Remember the pre-merger quote of the century by CSX????? "This railroad is over maintained". Over maintained, or was it preventive maintainence by Conrail. I talked to a track supervisor in Erie this past May. After the merger went through he said CSX cancelled track his maintainence budget for a period of one year. His section of RR was "over maintained".

On our light rail system in San Diego we have a couple of expansion joinst on either end of one of our bridges, They are called Conley joints and I believe are made by Conley Switch and Frog. I can't find a picture of them though. They are there precisely for the heat problem in the area and the concrete bridge has some affect on it. Wish I had a picture to show.

The Indiana RailRoad derailment back in '99 or '00 was attributed to "sun kinks". And that happened on JOINTED rail.

As for "over maintained lines", the old Big Four here in Indy now has a fair share of mudholes. Funny, I didn't see as many when Conrail was intact.

I've never heard of shims in rail joints or greasing the joint bars. And I've been around rail maintenance for a lot of years.

Are you sure about that? I'd be curious just what conditions warrant that practice.

mediumclear wrote:

> I've never heard of shims in rail joints or greasing the
> joint bars. And I've been around rail maintenance for a lot of
> years.

Oiling the joint bars and bolt threads was a common practice in the spring on northern railroads. Switches were greased at the same time.

<I've never heard of shims in rail joints or greasing the joint bars. And I've been around rail maintenance for a lot of years.

Are you sure about that? I'd be curious just what conditions warrant that practice.>

Yes, allblack is correct, these were common practices on at least some railroads up to the '40's and '50's. My dad, a trackman, used some sort of tool (not sure if it was called a shim) when installing jointed rail to make sure the rails had the proper amount of gap between them to allow for expansion and contraction (the shims or whatever they were called weren't left in the track).

I don't think greasing the joint bars has been used anywhere on any railroad for many years, but I distinctly remember seeing a lot of UP track in the west, perhaps some other railroads as well, with the characteristic greasy looking joint bars (UP was relatively slow to adopt the use of welded rail, so it was not uncommon to see jointed rail even on heavy main lines into the 1970's). Grease was applied not only when installing the rail, but in some cases as a regular maintenance program as well.

The purpose of the grease was to keep the joints from rusting, which would create the same effect as welded rail as far as longitudinal stresses go. The rails could slide slightly to fill the gap between the rails when heated. Rust was a particular problem on lines where a lot of brine drippings from reefers was common.

The practice of greasing joints and using shims comes from my experience as late as 1979. We did leave the shims in between the rails--I'm sure the fiber shims were crushed to nothing when it got hot. Greasing the joint bars (with curve grease) was a messy job. We laid lots of new jointed rail on the mainline at that time. The railroad had some reason for not using welded rail on sharp curves, adjacent to diamonds and on bridges.

I've seen expansion joints at the ends of bridges. It is my understanding that this is because the bridge expands and contracts. Look under a bridge and you will notice one end of the span is fixed and the other end rests on rollers. Welded rail was not used on open deck bridges at first--either because of worries of bridge expansion or inability of the ties to resist the forces of a sun-kink. At some point railroads began using welded rail in all locations, even the formerly prohibited 10 degree curves.

My first sun-kink was on jointed 75 or 85 lb. rail. The foreman walked the track in each direction looking for "frozen" joints. These would be joints with gaps still in them. We'd loosen the bolts and pound on them with spike malls. When the joint was finally free the gap would instantly close. The next step was to leave a flagman (me) to protect against a suspected train (no radios, phones etc.) while the crew took the motor car to get the saw and drill.

While welded rail is alway going to offer less protection against sun-kinks I believe that with proper maintenance sun-kinks can be prevented. When track work in hot weather increases the risk slow orders must be used until the track is stable. Usually a derailment at 10mph doesn't make the evening news.

Well! Thanks guys! Never too late to learn something new. Don't believe I've ever seen or heard of this practice until just now.

allblack wrote:
Welded rail is prevented from expanding and contracting by the use of rail anchors. Expansion joints are not used in welded rail except at some bridge locations.

Only partly true. The use of rail anchors keeps welded rail from expanding and contracting in the traditional sense. But it does expand and contract on the vertical plane, ie., up and down. This is why ballast is so critical. With the use of rail anchors ( tie clips ) the ties have a lateral and longitudinal force on them. If the ballast is not up to par, the ties will shift any way they can.

Robbman wrote:

> allblack wrote:
> Welded rail is prevented from expanding and contracting by
> the use of rail anchors. Expansion joints are not used in
> welded rail except at some bridge locations.
>
> Only partly true. The use of rail anchors keeps welded rail
> from expanding and contracting in the traditional sense. But
> it does expand and contract on the vertical plane, ie., up and
> down. This is why ballast is so critical. With the use of
> rail anchors ( tie clips ) the ties have a lateral and
> longitudinal force on them. If the ballast is not up to par,
> the ties will shift any way they can.
>
> [%sig%]

Sure. I agree completely. I was trying to be as brief as possible.

I think the main point here is that sun-kinks can be prevented. Lay the rail at the proper temperature, use a good ballast profile and use caution in hot weather and following track work. Someone commented that people should leave poor old CSX alone. They didn't go so far as to call this an act of God but I'm sure that's coming. CSX has had a terrible safety record and has been cited by the FRA for poor track maintenance and was re-cited after failing to fix problems uncovered in the first FRA inspection. Similar to Enron et. al. this is corporate corruption. They are skimping on safety to boost profits. Someday (when the current crowd has retired) there will be a huge outcry, the company will change course, write off billions in accidents and embark on a maintenance blitz. Most likely it will involve a huge taxpayer bailout (Conrail). And the new managers will all get bonus's for saving the good old CSX. Just my opinion of course but if you change the names to PRR and PC it is history.

Absolutely. CSX has a very poor maintenance record. I was in Ashland, VA this weekend, along the RF&P main. I talked to a local railroader who commented that NS officials had recently visited this main and made the comment 'they actually run trains on this'.

On the opposite end of the "sun kink" problem is the dreaded "pull apart." A "pull apart" occurs during extremely cold weather spells when the rail/rails contract to the point that they will actually break creating a gap. The only way to solve this problem is for the MOW people to cut off both of the bad ends of the broken rail. Then, a new piece of rail is used to fill the gap by being welded in place. I have heard of "sun kinks" that are so bad that the affected section of track had to have the rails cut out, replaced, and then realigned.

yashicaman wrote:

> On the opposite end of the "sun kink" problem is the dreaded
> "pull apart." A "pull apart" occurs during extremely cold
> weather spells when the rail/rails contract to the point that
> they will actually break creating a gap. The only way to solve
> this problem is for the MOW people to cut off both of the bad
> ends of the broken rail. Then, a new piece of rail is used to
> fill the gap by being welded in place. I have heard of "sun
> kinks" that are so bad that the affected section of track had
> to have the rails cut out, replaced, and then realigned.
>
> [%sig%]

I'd rather go over a thousand pull aparts than one sun-kink. Pull aparts cause the signals to go red, sun-kinks don't. Also I don't recall a derailment ever occurring from a train passing over a pull-apart. I suppose it has happened but I've never heard of one. Yet I've heard of many sun-kink derailments--often fatal.