Procedure To Replace Boom Hour Glass Plate Due To Cracks Caterpillar

THIS TIB REPLACES THE JULY 3, 1996 TIB, COMPONENT CODE: 6501 6504, "PROCEDURE TO REPLACE BOOM HOUR GLASS PLATE DUE TO CRACKS". DESTROY THE JULY 3, 1996 TIB. IT WILL NOT APPEAR IN THE QUARTERLY INDEX.

Problem:

Cracks may occur around the boom hour glass plate. If a crack exists, replace the hour glass plate. Do not attempt to repair.

Solution:

This rework procedure is for repair of booms which have cracks in the plate welded to the top of the boom and stick bosses. A crack in this location can not be repaired. The loads which go into this area of the boom will tend to crack the plate again at the toe of the weld.

If a new plate is needed, order the following:

Inspection/Repair Procedure:

If a crack is present as defined above, order a new plate. Do NOT weld repair the hour glass plate.

Use Shielded Metal Arc Welding with AWS E7018 or AWS E7028 electrodes for this welding procedure.

1. The boom can be repaired while on the machine. Extend the boom and stick to an appropriate height to have access to the top of the boom for welding. Remove attachments as necessary. Be sure to support the boom and stick with the appropriate stands.

2. Shut off the machine and work all hydraulic functions to make sure that the pressure is relieved from the hydraulic system.

3. Disconnect the hydraulic lines from the cylinders and remove the cylinders from the machine.

4. Remove the grease and dirt from the area around the plate to be welded.

5. Use an air carbon arc torch or similar tool to remove the weld which retains the cracked plate to the boom assembly.

6. Grind away any of the old weld or spatter left from the previous step.

7. Position the new plate. Center the plate with the outside edge of the boom top plate. The new plate should be centered in fore-aft direction as shown in Figures A & B.

8. Tack weld the plate in position to keep it from moving during the weld process.

9. Put an 8 mm fillet weld from point "J" to "K" on both sides of the plate as shown Figure B.

10. On the underside of the plate, put a 6 mm fillet weld from point "Q" to "R" on both sides of the plate as shown in Figure A.

11. The boom being repaired may have a fillet weld from point "T" to "S" in four places as shown in Figure C. Do not reweld the new plate in this location.

12. Clean up any weld spatter and paint from the repaired area.

13. Follow the assembly procedrue in the Service Manual and reassemble the hydraulic cylinders and lines.

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