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Figure 1: Car body showing heat damage from thawing operation. |
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Figure 2: Side frame, adapter, bearing and car body burned by thawing operation. |
Figure 3:Wheel and bearing assembly showing evidence of excessive heat from car thawing. |
Another potential source of bearing damage is the roller bearing adapter. If the adapter becomes worn in excess of acceptable limits or becomes displaced from its correct location on the bearing outer race, mechanical damage, off-center loading, accelerated fatigue damage, and premature bearing failure can result. Figure 4 and Figure 5 show the correct positioning of the adapter in the side frame and on the outer race. Figure 6 shows the cast relief area on a new adapter. The adapter would be excessively worn if this area was in contact with the roof of the side frame.
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Figure 4: Adapter properly positioned in side frame. |
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Figure 5: Adapter properly located on bearing outer race. |
Figure 5:Adapter cast relief area. |
Adapters can become displaced during car operations causing wear and mechanical damage to various bearing components. Adapter related bearing damage can be difficult to detect because displaced adapters can return to their normal position during service. Figures 7, 8, 9, 10, and 11 show external indication on the bearing of the adapter having been displaced.
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Figure 7: Adapter has been displaced to outboard end of bearing. Thrust shoulder has been riding on the end cap flange and rim (A) and has also been point loading the outer race at two points (B). |
Figure 8: Adapter has been displaced to outboard end of bearing. Thrust shoulder has worn away the end cap rim (A) and has displaced the outboard seal (B). In board thrust shoulder has been riding on the outer race over the inboard load zone (C). |
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Figure 9: Adapter has been displaced to outboard end of bearing. Thrust shoulders have been in contact with the end cap flange(A) and rim (B) and have broken the outer race inboard counterbore (C). At one time the adapter was correctly positioned as indicated by the contact pattern on the outer race (D and E) |
Figure 10:Adapter chas been displaced to inboard end of beairng. Adapter thrust shoulders have been in contact with the outer race over the load zone (A and B)and with the backing ring and dust guard fillet radius inboard ( C and D) indicating multiple displacements.
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Figure 11: Adapter has been displaced to outboard end of bearing and has cut away the end cap flange (A) and grease seal case (B). The condition would require inspection from the side of the bearing to be detected. Inspection from the end of the bearing would not reveal the damage. |
After operating in a displaced position, truck action can cause the adapter to reseat in its correct position. Any wear or damage to the end cap or backing ring is an indication that the adapter has been out-of-position, and the bearing may have sustained damage. Further inspection of the bearing per Field Manual Rule 36 is necessary at this point.
Grease purging or leaking from the bearing is not cause for removal from service under Rule 36, but interpretation here can be difficult. Grease leaking between the cup counterbore and the seal case major diameter Figure 12 may be an indication of a loose seal. The seal should be checked with a suitable probe Figure 13 as described by Field Manual 36.A.11.a.
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Figure 12: Grease leaking between cup counterbore and grease seal case. |
Figure 13:Probing for loose seal. |
Grease leaking between the backing ring and the axle dust guard Figure 14 is an indicator of a loose backing ring and a loose bearing. The backing ring should be checked in accordance with Field Manual Rule 36.A.10.
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Figure 14: Grease leaking between backing ring and axle dust guard (A and B) |
Wheel conditions, which can generate high impact forces into the bearing, are indicators of possible internal bearing damage. Built-up tread Figure 15 and severe slid flats Figure 16 are two such conditions. Recent research shows that these conditions can be even more detrimental than previously believed.
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Slid flat tread. |
Unless they are detected and removed from service, bearings exhibiting the conditions shown in this Technical Forum can continue to deteriorate and can experience overheating and premature failure. To further aid in the important inspection process for not only these conditions but also unclamped and loose bearings, loose backing rings, and other service related defects, BRENCO has produced a videotape on the subject of installed bearing inspection. The videotape (scheduled for release on June 1, 1989) will also include additional car inspection recommendations and a segment on bearing terminology and operations. If you have further interests in this subject, you may request a copy of the tape by calling or writing to the address listed below in the editors box.
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
Additional copies provided upon request.
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