Recent Utility Studies of Bearing Performance

Because their fleets typically are in captive service, coal hauling utilities are able to maintain extremely accurate mileage data on wheel and bearing changeouts. Over the past several years, a number of midwestern utilities with extensive coal hopper fleets conducted independent studies of wheel sets removed from service for bearing related AAR Why Made Codes. The three studies we have seen showed that a large number of wheel sets equipped with reconditioned bearings were set our for bearing related defects. The average service life for those wheel sets removed with reconditioned bearings ranged from 115,000 to 168,000 miles. This contrasted dramatically with the average mileage range of 352,000 to 391,000 miles for those wheel sets removed that were equipped with new bearings.

What was even more striking in the findings was the extreme variation in mileages for reconditioned bearings. Some reconditioned bearings had been removed after only 11,000 miles of service. Figure 1 presents one utility's distribution of mileages for the bearing removals in its fleet over a period of several years. This analysis shows that 39% of the reconditioned bearing removals occurred in less than 100,000 miles of service, and 21% in less than 50,000 miles.

Figure 1

One Utility's Analysis

Arkansas Power & Light (AP & L) operates 19 unit coal trains which move 10.5 million tons of coal per year. The fleet consists of 2,228 100-ton gondolas, each of which averages approximately 2,500 miles a week. The cars were built in 1979, 1980, 1982 and 1984. All information in the operation of the fleet is tracked through their Automatic Railcar Location Information System (ARLIS), which was developed in-house. Data collection began in 1980, but the present system of reporting started in 1983, when AAR Why Made Codes were incorporated into the data base.

In 1986, Mr. Charles R. Harmon joined Systems Fuels (now AP & L) as Railcar Maintenance Coordinator. Mr. Harmon currently serves as Fossil Fuels Analyst for AP & L and is responsible for the general maintenance of AP & L's unit coal trains. In late 1986, Mr. Harmon began to analyze the data on bearing performance that had been accumulated for the past several years and noted the rapid rise in bearing related wheel set removals. In order to determine the cause of this increase, bearing Why Made Codes were tabulated by year and trends were observed.

Figure 2 presents the data on bearings removed by AP & L during the last seven years. It was apparent to Mr. Harmon that the increase in bearing related removals from 1983 to 1986 were primarily for Why Made Codes 04 and 33, Defective Components and Derailment Damage, which could be attributed to the aging of the bearings in his fleet. Since the cars had been built, all replacement requirements had been met with reconditioned bearings. By 1986 nearly all the original equipment bearings had been removed from service and replaced with reconditioned bearings.

"Systems Fuels had been told, as everyone else had, that if you rebuild a bearing it was as good as new." Mr. Harmon explains. "Consequently, any time a wheel set was removed for whatever reason, the bearings were removed and reconditioned bearings were applied. By 1986 we had changed out the entire car fleet, purged it of all new bearings, and we were running on basically a reconditioned bearing fleet. I think what we saw was a result of that."

In 1986 alone, AP & L spent $3 million in changing out wheels, bearings, and axles. In order to contain the rising costs of maintenance (and their associated costs), the decision was made in late 1987 to apply only new bearings when replacing bearings on these cars. In addition, in 1988 it was also decided that AP & L would initiate a program to remove all reconditioned bearings from its car fleet. The program required the removal of reconditioned bearings whenever a car was in a designated contract repair shop, even though there was no apparent wheel or bearing related cause for taking the bearing out of service. The reconditioned bearings removed from the fleet under this program to purge all reconditioned bearings are identified in Figure 2 by Why Made Code 25, Removed at Owner's Request.

To quote Mr. Harmon about this program: "We had approximately 5,000 pair of new wheels in service, and all the new wheels were equipped with reconditioned bearings. We decided to pull the bearings arbitrarily. There was no external evidence of bearing problems, but when the bearings were removed, we found a lot of axles that were potential burnoff journals, because of the inboard cones grooving the axles." There was such a large population of rejectable axles due to journal grooving at the inboard cone seat that AP & L began to use an axle plating process to salvage these axles for further service.

As shown in Figure 2, bearing removals for Why Made Code 04 peaked in 1986 and have shown a substantial decline over the last three years. A similar trend is evident with Why Made Code 33. In addition, bearing related derailments have now been eliminated. Some reconditioned bearings still remain in the fleet and according to Mr. Harmon these account for the large number of removals under Why Made Code 97, for loose backing rings. Mr. Harmon also states that inspection of the overheated bearings reported under Why Made Code 50 confirm that these bearings, too, come almost exclusively from the remaining reconditioned bearing population.

The problems experienced by AP & L during the mid 1980s are now diminishing rapidly as the reconditioned bearing population in its fleet is reduced. In looking forward to the coming year, Mr. Harmon says: "I think we will have virtually eliminated Why Made Code 04s, and I think we will have gone a long way to eliminating the Why Made Code 97s. I also thing our Why Made Code 50s will drastically decline."

Some of Mr. Harmon's counterparts in the utility industry have viewed his program as expensive overkill. The program has obviously cost a good deal of money. "But we have saved a lot of money," Mr. Harmon insists. "In 1986 our car costs were 3.7 cents per mile; we have been at 2 cents per mile for two years now."

AP & L measures its costs by its AAR billings and private car shop charges. Costs include not only the cost of replacement bearings, but also axles that have to be scrapped or plated because of grooved journals. Mr. Harmon is quick to point out that these do not include some of the most significant costs of all: the effect on the utility's primary operations.

"Our job isn't to maintain railcars. It is really to produce electricity. We maintain as a result of that. Its like the railroads: they didn't start out in the business to maintain railcars, but to provide transportation. Maintenance is a necessary evil, if you want to put it that way. And I think we do have an obligation to maintain our cars and keep them on schedule. Looking at the derailments and the number of cars we have had out of service for long periods of time, it certainly impacts our moving the coal. Thats the real concern in today's age."

In Summary

It is not BRENCO''s position that new bearings are always the preferred application. Reconditioned bearings, when remanufactured to a high standard, perform satisfactorily in a variety of service conditions. However, it is a fact that bearings reconditioned to current AAR standards are permitted to return to service with wider dimensional tolerances than new bearings, as well as with such service related conditions as repaired spalls, brinelled raceways, water etching, and fragment indentation conditions that clearly can impact performance.

It should also be pointed out that AP & L's particular strategy may well have to be modified in view of the new AAR rule that prohibits second-hand bearings in interchange service. AP & L equips its fleet with one-wear wheels and instructs its private car shops to reprofile the wheels when shelling (under stricter criteria that AAR rules) is detected. AP & L believes this preventive maintenance program provides maximum wheel life, and its chief reason for going exclusively to new bearings was that based on its performance statistics, reconditioned product could not be depended upon to go the extended wheel life. Previously, when the wheels were turned, the bearings were left in place. Now under the new rule, the bearings will have to be removed, adding a significant cost to this procedure.

What is applicable to all railcar owners is the methodology AP & L used to approach its performance problems. The collection and analysis of data served not only to identify and define the problems, but suggested a solution and then followed through to monitor the effectiveness of the solution. Without continuing data collection, management would not have been able to evaluate whether the strategy was working and costs were actually being reduced.

Of course the real payoff to improving bearing performance, as Mr. Harmon so clearly stated, is not just in the savings in components and AAR billings. The biggest benefit to the fleet operator is the gain in productivity, by increasing the fleet's ability to deliver, on schedule and with the lowest capital investment, the rail service on which his company depends.

BRENCO Performance Engineers assist private car owners in developing programs to collect and analyze data on bearing performance. For further information, contact Mr. Dave Shannon, Manager - Performance & Product Engineering, BRENCO Incorporated at (804) 732-0202.

The Technical Forum is an information resource for the rail industry and is provided as a courtesy of Amsted Rail Group. Suggestions, inquiries or comments are welcomed and should be directed to:

Editor, Technical Forum
BRENCO, Incorporated
P.O. Box 389
Petersburg, Virginia 23804
804-863-1713

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