Procedure to Rework the Cabin Floor Plate Cracks on Certain 424B Backhoe Loaders {0679, 7301} Caterpillar

Backhoe Loader

424B (S/N: JRN1-UP)

424B HD (S/N: JRY1-UP)

Introduction

This Special Instruction contains the rework procedure to repair the cabin floor plate crack near the tool box corner on the machines listed above.

Do not perform any procedure in this Special Instruction until you have read the information and you understand the information.

Safety Section

Show/hide table

Do not operate or work on this product unless you have read and understood the instruction and warnings in the relevant Operation and Maintenance Manuals and relevant service literature. Failure to follow the instructions or heed the warnings could result in injury or death. Proper care is your responsibility.

Show/hide table

Personal injury or death can result from fumes, gases, and ultraviolet rays from the weld arc. Welding can cause fumes, burn skin, and produce ultraviolet rays. Keep your head out of the fumes. Use ventilation, exhaust at the arc, or both to keep fumes and gases from your breathing area. Wear eye, ear, and body protection before working. Protect yourself and others by reading and understanding this warning. Fumes and gases can be dangerous to your health. Ultraviolet rays from the weld arc can injure eyes and burn skin. Electric shock can cause death. Read and understand the instructions of the manufacturer and the safety practices of your employer. Do not touch live electrical parts. See “American National Standard Z49.1, Safety in Welding and Cutting” which is published by the American Welding Society. American Welding Society 8669 NW 36 Street #130 Miami, Florida 33166-6672 1-800-443-9353 See “OSHA Safety and Health Standards, 29 CFR 1910” which is available from the U.S. Department of Labor. U.S. Department of Labor Washington, D.C. 20210 See applicable requirements for your local area.

Show/hide table

Failure to follow all safety guidelines prescribed in this document and by governing authorities and regulatory agencies may result in severe injury or death of personnel or machine damage.

Show/hide table

When removing a major component or attachment, ensure that it is properly blocked or secured before removing mounting hardware. An assembly that is disconnected without proper blocking may shift or fall, resulting in serious injury or death of personnel or machine damage.

Show/hide table

Personal injury or death can result from improper maintenance procedures. To avoid injury or death, follow the procedures exactly as stated below.

Show/hide table

Before servicing/performing maintenance on the machine, electrical power must be physically disconnected; battery plugs must be disconnected from the batteries, or the trailing cable must be unplugged, and warning tags and padlocks shall be applied by a certified electrician. Certified electricians shall perform or direct any electrical work, including any energized testing, repair work in controllers, motors, or other approved compartments, and shall insure that all compartments are properly closed and inspected prior to re-energization. All applicable lock out and tag out procedures must be followed.

Welding Requirements

Welding quality is critical to the success of the installation procedures. Welds must be smooth and continuous. Do not undercut the welds. No overlap is allowed. Grind the ends of the welds to a smooth radius.

Prepare the metal for welding according to the next section. Refer to the illustrations in this special instruction for welding symbols and specifications.

All electrodes must be dried completely. The electrodes can be dried by heating the electrodes to 300°C (572°F). The electrodes must be dried for at least 30 minutes.

Do not weld in windy conditions. Do not weld when temperatures are below 16°C (60°F).

Penetration characteristics may vary greatly depending on the following conditions:

• Electrode diameter

• Shielding gas

• Welding current

• Plate thickness

The following items also affect the welds:

• Geometry of welded joints

• Surface conditions

• Composition of the base metal and of the electrode

A root pass should be applied before each weld is finished.

Maintain a 3 mm (0.12 inch) minimum root opening on all cross welds and circle welds.

For more welding information, consult the Caterpillar Service Welding Guide, SEBD0512.

Preparing the Metal for Welding

All grease, paint, and foreign objects must be removed before welding. Any of these materials will discharge gas which will cause porosity in the weld deposit. Water and rust will cause hydrogen embrittlement. Hydrogen embrittlement causes cracks in the weld deposit.

Remove foreign objects with a wire brush, a buffer, or a grinder. Shot blasting the appropriate areas will also remove foreign material.

Remove any oil or grease with a Caterpillar approved solvent.

Note: After welding, allow all areas to cool to room temperature. After the areas have cooled, paint the area with primer. After the primer has dried, coat the area with Caterpillar 4C-4200 Yellow Paint.

Required Tools

• Portable weld machine (CO₂)

• Portable hand driller

• General service tools

Plate Fabrication

Note: Plates to be fabricated from 2.0 mm (0.08 inch) sheet metal.

Illustration 1	g06330751
New plate profile (D1) 40 mm (1.6 inch) (D2) 35 mm (1.4 inch) (D3) Radius is 17 mm (0.7 inch) (D4) 72 mm (2.8 inch) (D5) 5.0 mm (0.19 inch) (D6) 20 mm (0.8 inch) (D7) 65 mm (2.5 inch)

Note: (D1), (D4), (D6), and (D7) dimensions may vary based on the length of the crack without changing the (D2) (Y axis) and (D5) (X axis) from radius axis point.

Rework Procedure

1. Remove the floor mat from the cab.

2. Grind the existing weld surface on the affected zone.

3. Drill a hole at start and stop of the weld crack zone to avoid crack propagation.
   Show/hide table

   Illustration 2	g06330752
   Floor mat

4. Position the new profile plate to cover the existing crack as shown in Illustration 2.
   Show/hide table

   Illustration 3	g06330753
   Detailed view of area A New profile plate (B) Weld zone (W1) 2.0 mm (0.08 inch) stitch weld with 25 mm (1.0 inch) long and 40 mm (1.6 inch) pitch

5. Stitch weld the plate at the crack zone as shown in Illustration 3.

6. Install the floor mat after the gas welding is completed.

   Note: Ensure that the floor plate is not hot.

Inspection Procedure After Rework

1. Remove any loose scale an dirt by wiping. Remove oil and coatings using the solvents or grinding.

2. Wipe the area to inspect with a solvent dampened cloth to remove the remaining dirt and allow the area to dry.

3. Apply a penetrant by spraying the entire area to be examined. Allow 10 to 15 minutes for penetrant to soak.

4. After the penetrant has been allowed to soak, remove most of the excess penetrant with a clean dry wipe. The last traces of penetrant should be removed with the cleaner solvent dampened cloth or wipe. Allow the area to dry thoroughly.

5. Apply an even thin layer of developer over the area being inspected. Few thin layers are better application method than one thick layer. Allow the developer to dry completely for 10 to 15 minutes before inspecting for surface discontinuities.

6. The developer will act to draw entrapped penetrant out of the discontinuity. A red stain on the developer indicates a possible surface discontinuity.

7. Clean the area of application of the developer with solvent cleaner.

8. If cracks are noticed, repeat the rework procedure.