2004/08/23 Caterpillar

Off-Highway Truck:

793C (S/N: ATY1-UP; 4AR1-UP; 4GZ1-UP)

Description of Change: The addition of plates improves the service life of the cowl assembly. The addition of the plates provides increased reinforcement of the mounting surfaces for the cowl assembly.

Adaptable To: The two 254-0092 Plates are effective with the following machines:

• 793C (S/N: ATY731-UP)

• 793C (S/N: ATY1-730; 4AR218-UP; 4GZ1-UP)

Prepare the Area for Welding

Clean the area that will be welded. Make sure that the substances that follow are removed from the area that will be welded.

• Oil

• Grease

• Paint

• Dirt

If the temperature of the base metal is below 0 °C (32 °F), heat the base metal to a temperature of at least 21 °C (70 °F). Maintain the temperature of the base metal at 21 °C (70 °F) during the welding process.

Note: Heat distortion of the base metal is possible when you weld. Avoid excessive heating of the base metal.

Attach the welding ground cable directly to the base metal. Protect machined surfaces from sparks. Protect the machined surfaces from the weld splatter.

Weld Specifications and Qualifications

Show/hide table

Protect yourself and others; read and understand 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 kill. Read and understand the manufacturer's instruction and your employer's safety practices. Keep your head out of the fumes. Use ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing zone and the general area. Wear correct eye, ear and body protection. Do not touch live electric parts. Refer to the American National Standard Z49.1, "Safety in Welding and Cutting" published by the American Welding Society, 2501 N.W. 7th Street, Miami, Florida 33125: OHSA Safety and Health Standards, 29 CFR 1910, available from U.S. Dept. of Labor, Washington D.C. 20210.

Note: Personal breathing protection should be worn by the personnel that are welding. Personal breathing protection will prevent fumes from entering the lungs of the person that is welding. Use a 1U-8088 Type H Respirator for breathing protection.

Welders must be qualified for fillet welding and groove welding. The welders should be qualified in the use of the welding processes that follow: Shielded Metal Arc Welding (SMAW), Flux Cored Arc Welding (FCAW) and Gas Metal Arc Welding (GMAW). Refer to "American National Standards Institiute (ANSI)/American Welding Society (AWS) Specification D1.1, or Specification D14.3" for information that regards the qualifications for the processes that follow: SMAW process, FCAW process and GMAW process. The welders must have used the process at some time within the last six months. The welders must complete the process of certification if the welders have not used the welding processes for six months.

Proper Welding Procedure on Machines and Engines with Electronic Controls

Proper precautions are necessary to prevent damage to electronic controls. When you weld on a machine with electronic controls, use the steps that follow:

1. Turn off the engine. Put the key start switch in the OFF position.

2. If the machine has a battery disconnect switch, open the switch. If the machine does not have a battery disconnect switch, disconnect the negative battery cable at the battery.

3. Connect the ground cable for the welder directly to the actual machine component that will be welded. Attach the clamp for the ground cable as close as possible to the area that is being welded. This will reduce the chance of damage from welding current to the components that follow: bearings, hydraulic components and electrical components.

   Note: Do NOT use electrical components as a ground point for the welder. Do NOT use ground points for electronic components as a ground point for the welder.

4. Protect the wiring harnesses from the weld splatter.

Weld Specifications

Low Hydrogen Electrodes for the SMAW Process

The tables that follow list the mechanical properties of welds that are deposited by low hydrogen electrodes.

Low hydrogen electrodes must be stored in an electrode oven at 120 °C (248 °F). If low hydrogen electrodes get damp, scrap the low hydrogen electrodes or recondition the low hydrogen electrodes to the manufacturer's specifications.

The table that follows shows setting for the welding current for the electrode diameter.

Use a polarity setting of DC reverse polarity. Remove the slag after each pass of the welding electrode. The width of the weld should not exceed two times the electrode diameter.

As an alternative process, use the Flux Cored Arc Welding (FCAW) with E71T-1 H8 (ANSI/A5.20) welding electrode and the manufacturer's shielding gases that are specified for inside welding. The H8 implies that the electrode is designed to provide less than 8 ml/100 g of diffusible hydrogen in the weld deposit. The weld that is deposited by the flux cored welding electrode will have the following minimum mechanical properties:

Flux Cored Welding Electrode for the FCAW Process

The table that follows lists the mechanical properties of welds that are deposited by the flux cored welding electrode.

The table that follows shows setting for the welding current for the flux cored welding electrode that has a diameter of 1.3 mm (.051 inch).

Note: The settings for the welding current can vary due to the position of the weld. Also, the settings for the welding current can vary with the manufacturer of the welding electrode.

Use a polarity setting of DC reverse polarity. Remove the slag after each pass of the welding electrode. The fast freezing characteristics of flux cored welding electrode increases the possibility of evolving gas that is trapped in the weld. Control the size of the weld in order to reduce the possibility of evolving gas that is trapped in the weld. The volume of the fillet weld should not exceed 8.0 mm (.315 inch).

Arc Welding Electrodes for the GMAW Process

The table that follows lists the mechanical properties of welds that are deposited by the GMAW Process.

The welding parameters will vary with the position of the weld and with different electrode manufacturers.

Weld Inspection

The weld should not have any of the conditions that follow:

• Cracks

• Porosity

• Undercut

• Incomplete Fusion

In order to verify the quality of the weld, refer to"American National Standards Institiute (ANSI)/American Welding Society (AWS) Specification D14.3".

Installation Procedure

1. Install the truck body retaining cable. Refer to Disassembly and Assembly, "Truck Body Retaining Cable - Remove and Install".

2. Install the wheel chocks. Refer to Disassembly and Assembly, "Wheel Chock (Front and Rear) - Remove and Install".

3. Remove the hood panels. Refer to Disassembly and Assembly, "Hood Panels (Front and Rear) - Remove and Install".

4. Remove the ladder. Refer to Disassembly and Assembly, "Ladder - Remove and Install".

5. Remove the platform assembly. Refer to Disassembly and Assembly, "Radiator - Remove", Step (1) through Step (31) .

Show/hide table



Illustration 1	g01080382

6. Remove bolts (1) and washers (2). Repeat for the other side.

Show/hide table



Illustration 2	g01080420

7. Remove 20.0 mm (0.79 inch) from the bottom of channel (3). Repeat for the other side.

Show/hide table



Illustration 3	g01080429

8. Remove the top of layer of sheet metal (4) in order to allow plate (5) to lie flat on the horizontal surface. Repeat for the other side.

9. Align the holes in plate (5) with the holes in the cowling with four washers (7) and four bolts (6). Repeat for the other side.

Show/hide table



Illustration 4	g01080446

10. Weld plate (5) to channel (3). Weld (W1) is a 5.0 mm (0.20 inch) fillet weld. Repeat for the other side.

Show/hide table



Illustration 5	g01080468

Show/hide table



Illustration 6	g01080498

11. Weld each end of plate (5) with weld (W2). Weld (W2) is a 5.0 mm (0.20 inch) fillet weld. Repeat for the other side.

12. At two locations, weld plate (5) with weld (W3). Weld (W3) is a 5.0 mm (0.20 inch) fillet weld that is 76.0 mm (3.0 inch) long. Welds (W3) should be located in the center of weld nuts (8). Repeat for the other side.
    Show/hide table

    Table 8

    Weld Tolerances
    Weld	Description
    W1	5.0 mm (0.20 inch) fillet weld
    W2	5.0 mm (0.20 inch) fillet weld
    W3	5.0 mm (0.20 inch) fillet weld 76.0 mm (3.0 inch) in length (X2)

Show/hide table



Illustration 7	g01080517

13. Remove all weld splatter and paint the affected areas in order to prevent rusting. Repeat for the other side.

14. Install the platform assembly. Refer to Disassembly and Assembly, "Radiator - Install", Step (8) through Step (37) .

15. Install the ladder. Refer to Disassembly and Assembly, "Ladder - Remove and Install".

16. Install the hood panels. Refer to Disassembly and Assembly, "Hood Panels (Front and Rear) - Remove and Install".

17. Remove the truck body retaining cable. Refer to Disassembly and Assembly, "Truck Body Retaining Cable - Remove and Install".

18. Remove the wheel chocks. Refer to Disassembly and Assembly, "Wheel Chock (Front and Rear) - Remove and Install".