AAR Circular Letter C-8675

December 18, 1996

CIRCULAR LETTER

(c-8675)

Subject:   Implentation of Manual of Standards and Practices, Section G II, Rule 1C7 - Repair Procedures for Axles with Seal Wear Ring Grooves

TO MEMBERS AND PRIVATE CAR OWNERS

File Number: TB-6.1A

In Circular Letter c-8034, dated May 20, 1993, the industry was advised that the Wheels, Axles, Bearings, and Lubrication Committee and the Car Engineering Committee conditionally adopted a new axle salvage and repair procedure for circumferential journal grooves caused by seal wear ring movement due to axle flexure. In that same letter, proposed changes to Section G II codifying this action were included along with a field test to study the effect of various bearing configurations in relation to the repaired journal prior to unconditionally adopting the procedure. On June 10, 1996, the AAR held a town meeting soliciting input from the industry on this subject, which included a review of the field test results.

Resulting from these efforts, the attached rule changes have been unconditionally approved for publication as an alternative to the repair of seal wear ring grooves by electro-chemical deposition. The attached changes become effective with the publication of this Circular Letter. This is your authority to update Manual of Standards and Recommended Practices, Section G II accordingly.

Sincerely,

Thomas J. Stahura

Director – Equipment Performance

Add new Rule 1C7 to Section G II as follows:

Vacant

RULE 1C7 Axles with grooved journals caused by inboard seal wear rings may be returned to service provided there are no abrupt changes or sharp edges after repair.

AND

• Groove average no more than 0.002" deep and does not exceed 0.004" deep at any point, or
• Groove does not exceed 0.010" at any point and axle is used in conjunction with the AAR Approved or Conditionally Approved parts listed below, or
• Groove is repaired in accordance with Rule 1C6. (Rule 1C6 was published in Circular Letter c-8526, dated April 10, 1996)

NOTES:

1. Groove depth must be measured using a gage with minimum resolution of 0.0001" and a probe small enough to fit completely into the groove without interfering with the groove walls.
2. Average groove depth shall be determined by averaging no fewer than three equidistant points.

This rule modification generated the following companion changes:

Section G II, Rule 1C4 (as modified in c-8528, dated April 10, 1996)

Vacant

Rule 1C4 – After "INSPECTION AND REPAIR – Journal …..tolerance" add a new bullet

• Rule 1C7 gives the accept/reject criteria and process for repairing grooves in journals caused by inboard seal wear rings.

Section G II, Figure 4.10

In the upper right hand corner, under the heading:

"BEARING SEAT AREAS" is modified to read as follows:

Dial or digital snap gage must be rotated around the journal diameter at least 180 degrees within the bearing seat locations to obtain the maximum and minimum journal diameters. The average diameter of each bearing seat must be within tolerances. Care must be taken when using temperature compensating snap gages that rotating speed does not create sufficient heat, due to friction, to effect the readings. There shall be no abrupt changes or steps over the length of the journal, including tapered end, except journal grooving from inboard seal wear ring is permissible when repaired as specified below.

Dial or digital snap gage must be rotated around the journal diameter at least 180 degrees within the bearing seat locations to obtain the maximum and minimum journal diameters. The average diameter of each bearing seat must be within tolerances. Care must be taken when using temperature compensating snap gages that rotating speed does not create sufficient heat, due to friction, to effect the readings. There shall be no abrupt changes or steps over the length of the journal, including tapered end, except journal grooving from inboard seal wear ring is permissible when repaired in accordance with Rule 1C7.

In the lower left hand corner, under the heading: "JOURNAL GROOVING FROM INBOARD SEAL WEAR RING" is modified to read as follows:

Delete the present paragraph

Depth of the seal wear ring groove must be measured using a dial indicator gage with 0.0001" graduations. The three measurements may be averaged. Average reading not to exceed 0.002", with any one reading not to exceed 0.004". Polishing with abrasive cloth (80 grit or finer) is permitted. No abrupt changes or sharp edges are permissible.

Add the following paragraph

Rule 1C7 gives the accept/reject criteria and process for repairing grooves in journals caused by inboard seal wear rings.