2005/06/13 Caterpillar

An Improved Butt Weld Reduces Internal Stress on the Boom {6501}

Usage:

315C ANF

Excavator: 312C (S/N: BWH1-UP; BNN1-UP; DBN1-UP; CBT1-UP) 315C (S/N: ANF1-UP) 318C (S/N: FAA1-UP; BTG1-UP; DAH1-UP) 319C (S/N: KGL1-UP)

Description of Change: In some heavy-duty applications, the boom may crack along the edge of the butt welds. The cracks are created from the internal stress that is created by the butt welds for the blocks. Refer to Illustration 1 for an example. This stress can propagate to the upper and lower boom plates. Two of the four butt welds have been removed at each block that is welded on the boom in order to reduce the stress. The occurrence of the cracks will mainly affect machines that are withstanding continuous heavy-duty applications. The cracks can be repaired if the cracks are detected before exceeding more than half of the total height of the side plates.

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Illustration 1	g01176635
(1) Block (2) Butt Weld (3) Crack

Adaptable To:

Rework Procedure

Remove the affected block by grinding or cutting. Ensure that the side plate of the boom will not be damaged. Any scratches in the top plate of the boom will lead to cracks later in the boom.

If the block is not damaged during the grinding operation, this part can still be used. Produce a new block according to the original support block if the block is damaged.

Grind a V shape chamfer over the crack. Create a 20 mm (0.79 inch) chamfer at each end of the crack. Fill the chamfer by welding.

Grind the butt weld flush.

Relocate the existing block at least at a distance of 100 mm (3.94 inch) from the initial location. Weld with only 2 horizontal butt welds along the block.

Repaint the unprotected areas.

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Table 1
Effectivity and Adaptability for the Improved Butt Weld
Sales Model	Effectivity	Adaptability
312C	S/N:BWH790-UP S/N:DBN436-UP S/N:CBT945-UP S/N:BNN568-UP	S/N:BWH1-789 S/N:DBN1-435 S/N:CBT1-944 S/N:BNN1-567
315C	S/N:ANF550-UP	S/N:ANF1-549
318C	S/N:DAH649-UP S/N:BTG280-UP S/N:FAA344-UP	S/N:DAH1-648 S/N:BTG1-279 S/N:FAA1-343
319C	S/N:KGL338-UP	S/N:KGL1-337