January 20, 1992

Circular Letter
(c-7793)

Subject: Implementation Clarification: Prohibition of Vent Fittings in Roller Bearing Backing Rings

TO THE MEMBERS AND PRIVATE CAR OWNERS

File: GC-WABL
TB-48
(c-7793)

Circular Letter C-7772 issued on December 20, 1991, prohibited vent fittings on new backing rings effective January 1, 1992, and required vented backing rings to be converted, per the revisions to Section H-Part II, Rule 3.25, at the time of reconditioning after March 1, 1992.

In order to cover all circumstances more precisely, the following provisions are specifically established:

1. Vent fittings are prohibited on backing rings manufactured after January 1, 1992.

2. Backing rings with non-plugged vent fittings may not be installed in roller bearings after March 1, 1992.

3. After March 1, 1992, all roller bearings shipped from manufacturing and reconditioning facilities must have non-vented backing rings.

Sincerely,

Leavitt A. Peterson

SECTION H-PART II

Paragraph 3.25

Present

Vent Fitting: Check to be certain it is not clogged, hardened, or damaged. Should it be necessary to replace vent fitting, it must be renewed according to manufacturers instructions. It must be properly protected during painting operations.

Revised

Vent Fitting: If a backing ring is equipped with a vent fitting, the vent and/or vent cavity must be sealed and the ingress of water and other contaminants prevented. This may be accomplished through replacement of the vent fitting with a suitable plug or by sealing or plugging the cavity with the vent fitting in place. The method and material used must provide an effective and secure seal that will not interfere with the proper seating of the backing ring on the journal fillet during the mounting operation. If a silicone caulk is used, the cavity must be sufficiently clean to provide satisfactory adherence to maintain seal and retention. The sealed vent must be checked at subsequent reconditioning cycles to verify integrity.