A freight car lasts about a half-century

The expected lifetime of a freight car is needed to determine deprecation and leasing rates.

I saw reference to the 40/50-year rule for the allowed age of a freight car. That made me curious about the details of the rule. I found several answers. This is one of the better:

There are two regulations in play here. Association of American Railroads (AAR) and Federal Railroad Administration (FRA). AAR rules restricted freight cars built before July 1, 1974 to 40 years of interchange service. Changes to AAR freight car construction standards effective in 1974 allows freight cars built on or after July 1, 1974 to operate for 50 years. A lot of the older cars are still in sound condition so by performing certain upgrades and repairs, with AAR approval the older cars can operate up to 50 years as well. (AAR Rule 88 Rebuild or AAR Rule 88 Extended Service Status [RailroadForums, Feb 8, 2015]) A railroad may operate cars over 40 years in revenue freight service on their own lines. In fact two railroads could agree to interchange such equipment up to age 50. At age 50, FRA regulations prohibit operation of the cars in freight service. [TrainOrders, Date: 10/18/10 19:00]

DeBruler

But this raises the question: why make the rule in 1974? I suspected it was part of an effort to get friction bearings off the railroads. Dschmitt found the AAR rules that confirmed the 1974 date. [trains, September 21, 2017 6:20 AM]

1972   "Roller bearings required for all cars w/6-1/2x11 journals"
1974    "Cars w/axle load >55,000 lbs must have roller bearings" 
1991   "Plain-brg trucks banned from interchange"

But it appears the AAR later decided that 40 years was too long for cars with friction bearings.. I found more details concerning the 1990s rules. [trains]:

Friction Bearings Banned

Posted by rogerhensley on Thursday, September 21, 2017 5:38 AM

Friction Bearings Banned

Q) When were friction bearing (solid journal) trucks banned from interchange service?

A) Friction bearing trucks were banned from interchange service on 1/1/91 for cars carrying hazardous materials. All other non-hazardous carrying cars equipped with friction bearings were banned from interchange on 1/1/94. Cars with converted friction to roller bearing side-frames were banned from interchange on 1/1/95.

There were some instances of exemptions granted for shippers in "hardship circumstances" who could not comply with these dates. So, some cars did linger a little longer in interchange after the actual deadline dates.

Q) I understand the logic behind eliminating solid journal (friction) bearings from interchange service, but what was the reason for outlawing trucks with conversion roller bearings?

A) Hot bearing detectors couldn't "see" them when they overheated.

From information supplied by Ed Kaminski, ACF Industries

Note that AAR rules control what can be interchanged between railroads. Railroads can use older cars in non-revenue (i.e. maintenance-of-way) service. However, railroads now won't handle any car with friction bearings, including passenger cars. This creates a hardship for railroad museums that acquire older equipment for their collection. They have to pay for cranes to load the equipment on flatcars or trucks for transport.

The 50-year rule is evidently motivated by metal fatigue considerations.

Some cars built before 1980 already have been approved for a 65-year service life, but the process of gaining that approval was very expensive. [ProgressiveRailroading-analyzing]

A relatively recent development has been Increased Life or ILS wherein car owners can apply for 65-year life. TTX Company led the charge in this with its fleet of autoracks in order to get two rack life cycles out of the car body. ILS is also covered by Rule 88. [trains, December 05, 2011 5:26 PM]

It makes sense that 89' 4" TTX flatcars used for autoracks would last longer than, say, a gondola car used to carry scrap metal. First of all, they cube-out instead of tare-out. That is, even with their long length and extra height, they run out of room before they hit the weight limit of the trucks. (Cars have a lot of air in them.) Also, they are not humped. They are flat-switched. For example, the IHB/MC Gibson Yard is the vehicle mixing center for all of the Chicago trunk railroads. And I'm sure the flat-switching is done gently because they don't want to stress (damage) the cars that are inside the autoracks. Because of their gentle treatment and light load on the frame and trucks, their metal fatigue should be slower than normal cars. So Rule 88 was modified:

The AAR has instituted a new provision under Interchange Rule 88 that permits cars to operate for up to 65 years since their built date. The procedure incorporates two basic portions; demonstrating that the carbody has the structural integrity to last for a total life of 65 years and upgrading specific components on each car. After applying to the AAR Equipment Engineering Committee (EEC) requesting that ILS be granted to a particular group of cars, the car owner has two optional methods to demonstrate the structural integrity of the selected cars. The first option is to perform structural inspections on a specified number of representative cars and to perform a full-scale fatigue test on a test car. In place of the fatigue test, the second option is to perform structural inspections on a larger number of cars and conduct follow-up inspections every five years after receipt of approval. The physical fatigue test incorporates modern engineering best practices by utilizing finite element modeling and full-scale accelerated fatigue testing (AFT). Following the creation of a representative model, several load conditions, both real and worst-case, are then applied to determine the high-stress locations. Using instrumentation at the high-stress locations, a full-scale test is conducted with the car operating in a typical service environment. The objective of full-scale testing is to obtain real strain data and input loads produced by typical environment conditions. AFT enables the required load cycles to be applied to the test car in a dynamic test fixture in weeks or months versus years of actual service. A rapid accumulation of fatigue-damaging cycles representative of the remaining years necessary to bring the total life of the test car to 65 years are applied to the car. The requirements for the components to be replaced or upgraded under Rule 88 are similar to those for new cars and for rebuilt cars. Some components, such as air brake control valves, are to be upgraded to more recent standards. Others are to be replaced in kind with reconditioned parts. Even though the carbody is permitted to operate beyond 50 years, components must still comply with existing AAR and Federal Railroad Administration (FRA) age limits. In addition to obtaining Increased Life Status (ILS) from the AAR, the car owner must also apply to the Federal Railroad Administration for authorization to operate the cars beyond the 50-year limit of the FRA Freight Car Safety Standards. [ASME]

I gather that "full-scale accelerated fatigue testing (AFT)" on a test car means building a rig that would allow hydraulic rams to repeatedly apply and release forces to the frame and trucks that emulate forces experienced during transit. Their is no wait between the applications of the force cycles so they can do as many cycles in a few weeks or months that a normal car would experience in many years. Then that car would have to be scrapped because it has been worn out by the testing. (When I toured the International Harvester engineering building in Fort Wayne, IN, they showed us a test apparatus for drive shafts. And they showed us a failed drive shaft. They explained it had a 45-degree break because it suffered from torque fatigue.) The expense of sacrificing a test car is probably in the noise compared to the expenses of building the test rig and writing the computer program that does the finite element modeling. But for TTX, which has a large inventory of autorack flatcars, extending the lifetime of their cars by 30% would justify that expense.

However, there is also a 50-year rule for castings, and that cannot be extended. That is, to get 15 more years of life out of a car, all of the castings have to be replaced. And 70% of the useful life of the replacement castings will be wasted. (Unless they keep careful records of their castings and take the castings off a 65-year old car to use in a rebuild of a 50-year old car.) The paper industry is the predominant user of boxcars. They are concerned that the pool of boxcars is shrinking. Between 2007 and 2016 110,000 cars were retired but only 8,500 cars were built. "New box cars are problematically expensive, and the modal-competitive nature of this freight makes new-car investment difficult to justify" (New car prices remain near an all-time high because of "energy-driven growth." (I suspect that "energy-driven growth" means they keep having to build new tank cars because new safety designs proved not to be safer when they suffer derailments. Also, new covered hoppers and  tank cars are needed to support the ethanol industry. New covered hopper cars are needed to support the plastics industry that is growing because of cheaper oil. [RailwayAge])) In 2015, the Paper and Forest Industry Transportation Committee convinced the AAR board to consider changing the ILS rule for castings from an age-based to a conditioned-based life limit. Like autoracks, paper boxcars have a lighter loading weight. Furthermore, they spend a lot of time in railyards because they are single-car manifest shipments. That means they are also low-mileage cars compared to coal cars that are almost continuously travelling in unit trains. "ILS may provide an additional option to resolve car-supply problems. Remember: 'Rail car supply = rail freight market share.'" [ProgressiveRailroading-boxcars]

Another consideration affecting the useful life of a freight car is their weight carrying capacity. When reading about boxcars being used to carry grain in the 1800s and the first half of the 20th Century, they talked about 40-ton and 50-ton box cars. Grain was heavy enough that the top third or fourth of the boxcar would remain empty. It was a big deal when covered hoppers were introduced in the 1960s to carry grain because not only were they easier to load and unload, some were 100-ton cars. 263,000-pound gross weight cars were introduced in 1963 and 286,000-pound cars entered service in 1995. The design of any bridge being built today probably anticipates 315,000-pound cars. [ProgressiveRailroading-analyzing] I wonder if continuous welded rail (CWR) started becoming prevalent by 1995. There is no point building strong (286k pound) cars if the rails can't carry them. I found wight maps for the various railroads a few years ago. I see the BNSF and UP links are now broken. But the CN map is still available. A lot of grain elevators lost their rail service because the railroad choose to abandon their branch line rather than upgrade the track's weight capacity.



Another impact of the lifetime of a freight car is that its purpose or design becomes obsolete. But that limit is hard to predict. If you knew a design was short-lived, you would not  uilc the cars in the first place. We have already seen that tank cars that carry crude oil and ethanol that were built with a new safety design that became obsolete after just a few years because derailments demonstrated the new design was not, in fact, much safer. [DeBruler]