BELL ASSEM. 8M4744 - Caterpillar

Weld the prepared joint.
Blend sand the excess weld material flush with the surrounding plate profile.Cracks that Extend Through the Thickness of the Underlying Plate
Illustration 8 g06320816
View of prepared joint prior to welding
(AA) Section thickness
(C) Finish grinding area
(EE) Root opening greater than 6 mm (0.236 inch)
(FF) Root face of 1 1 mm (0.039 0.039 inch)
Illustration 9 g06320847
View of prepared joint prior to welding
(AA) Section thickness
(BB) 60 degree minimum angle
(EE) Root opening greater than 6 mm (0.236 inch)
(FF) Root face of 1 1 mm (0.039 0.039 inch)
Excavate to profile prior to grinding.Note: Illustrations 8 and 9 demonstrate dimensions that require permanent backing strips.
MT inspect to verify that the defects have been removed.
Verify the size of the excavation root and determine if backing plates are required.
Illustration 10 g06320857
View of prepared joint backing plate location
(AA) Section thickness
(BB) 60 degree minimum angle
(F) Backing Plate
(GG) 6 mm (0.24 inch) backing plate overlap
The dimensions of the permanent steel, backing strip (F) will depend on the configuration of the excavation. Every attempt should be made to accommodate a single, continuous strip that runs the full length of the weld joint.Typical dimensions of a backing strip (F) for a crack excavation of this size are: 6.4 mm (0.25 inch) thick X 38 mm (1.5 inch) wide X the length of the crack excavation. The steel backing strip material can be any common structural steel such as ASTM A36. Attach wire (or other means) to backing strip and insert through the root opening/gap and pull back flush to the inside of the plate surface.The thickness of the backing strip should be kept to a minimum to assist with the insertion process. The thicker the backing strip the more difficult it will be to insert through the gap into an enclosed cavity. A 6.4 mm (0.25 inch) thick backing strip is the minimum that should be used and is sufficient to prevent burn through using the welding parameters specified. Select a backing strip width that will ensure a minimum overlap of 6 mm (0.25 inch) (GG) of the backing strip to both sides of the weld joint along the entire length, refer to Illustration 10.Minimize the gap between the backing strip (F) and the inside plate surface. No gap is preferred.
Illustration 11 g06320868
View of weld buildup
(AA) Section thickness
(D) Welds
Tack weld the backing strip in place.
Remove wire/rod and grind ½ the thickness of the tack welds prior to finish welding to ensure proper fusion between tack welds and fill passes.
Preheat repair area to 20° C (68° F). Inter-pass temperature shall be maintained between 20° C (68° F) and 300° C (572° F) maximum.
Weld the prepared joint.
Illustration 12 g06320879
View of weld buildup
(D) Welds
(E) Flush ground weld material
Blend sand the excess weld material flush with the surrounding plate profile.Plate Fabrication and Installation Procedure
Illustration 13 g06317749
(1) 561-4529 Plate
Fabricate two plates (1) per Illustration 13.Note: Use material ASTM A572 grade 42 or 50 to fabricate plates (1).
Illustration 14 g06317867
Right-hand plate location
(D1) 250.5 3 mm (9.86 0.12 inch)
(D2) 309.5 3 mm (12.19 0.12 inch)
(1)