HYDRAULIC AR 2845619 - Caterpillar

SOLUTION:
During preventive maintenance and routine inspections, cracks may appear at the rear engine base mount and generator mounts. The following weld procedure should be used in order to repair the cracks.
Note: When corresponding with Caterpillar regarding this problem, be prepared to provide the specific site information listed in Table 2.
Welding on Machines and Engines with Electronic Controls
Proper welding procedures are necessary to avoid damage to electronic controls. The following steps should be complied with when welding on any machine or engine with electronic controls.
Engine Preparation
Turn off the engine. Place the engine start switch in the OFF position.
If equipped, turn the battery disconnect switch to the OFF position. If there is no battery disconnect switch, disconnect the negative battery cable at the battery or negative 24V power supply.
Note: This is the position of the machine Service or storage.
Connect the welding ground cable directly to the actual base to be welded. Clean the area where the clamp is applied to ensure a good current path. Clamp the cable as close as possible to the weld in order to reduce the possibility of current damage to the drive train bearings, generator bearings, electrical components (such as ground straps), and other engine/generator components.
__________________________________________________________
Do not use electrical components (ECM?s or ECM sensors) or electronic component grounding points for grounding the welder.
________________________________________________________________
Protect any harnesses from welding debris or splatter.
Use the following welding procedure to weld materials together.
PROCEDURE
Step 1: Prepare for Welding
Remove the crack, creating a groove weld joint geometry. (Remove material 25.4 mm (1 inch) beyond the end of the visible sign of crack). This may be accomplished using an arc gouge or by grinding.
Shape the weld joint such that the welder will have good access to the root and can produce a continuous full penetration weld.
Clean the grooves by removing all residual carbon, grease, oil, etc. If arc gouging is used, take care to remove all of the residual base metal. The melted base metal has a tendency to adhere to the un-melted base metal and is difficult to remove by grinding. A pneumatic chipper will remove this material.
Remove 12.7 mm (.50 inch) of the outer edge of the gusset (point) by grinding. This will result in a vertical surface.
Remove the paint, by grinding, on the top surface of the plate at least 50.8 mm (2 inches) from the weld joint.
Visually inspect to make sure the entire crack is removed.
Use an NDT process, such as a dry mag with a yoke, to verify that the entire crack is removed.
Note: If by chance the cracks are originating and propagating thru the center of a fillet weld, simply remove the fillet weld and replace it with a fillet weld of the same size. Do not increase the size of the fillet weld. Grind the toe of the fillet weld to produce a smooth transition to the base metal.
Step 2: Weld Repair
Weld the joint with a low hydrogen process and a matched electrode. See Table 1.
The fillet welds along the sides of the angled gusset should