2002/10/07 Changes to the Hood Assembly Improve Service Life {7155, 7251, 7267} Caterpillar

Description of Change: A new hood assembly with improved mounting is used for improved service life. In addition, the handrail has been relocated for improved accessibility. The new hood assembly must be used with the new cowl and with the new handrail.

Adaptable To: The new 211-9138 Hood As and the new 212-2759 Cowling are effective with 789C (S/N: 2BW569) Off-Highway Truck. Use the following procedure to adapt the new hood assembly to all earlier trucks.

Note: Existing cracked hoods can be repaired. For more information, see the subsection with the title "Procedure to Repair the Hood Assembly".

Weld Information

All repair welding operators must be qualified for fillet welding. Refer to the current ANSI/AWS standard D1.1 or refer to the current ANSI/AWS standard D14.3. The repair welding operator must have used the welding process during the last six months or the operator must be recertified for the process before welding. Documentation must be maintained for welding operator's qualification. Provide personal protective equipment for the repair welding operator in order to ensure that the total welding fumes in the operator's breathing zone are within safe limits.

The SMAW process shall be used with E7018 welding electrode. Refer to ANSI/AWS standard A5.1. The weld that is deposited by these electrodes will have the following minimum mechanical properties:

• 500 MPa (72500 psi) Tensile Strength

• 482 MPa (69900 psi) Yield Strength

• 22 percent Elongation

The weld should be free from cracks, porosity, undercut and incomplete fusion. All weld quality shall conform to ANSI/AWS standard 14.3.

As an alternative process, the GMAW process may be used with ER70S-3 welding electrode and the manufacturer's specified shielding gas. Refer to ANSI/AWS standard A5.18. The weld that is deposited by these electrodes will have the following mechanical properties:

• 480 MPa (69600 psi) Tensile Strength

• 400 MPa (58000 psi) Yield Strength

• 22 percent Elongation

When possible, use the DC reverse polarity setting in order to obtain the deepest penetration. This setting is also known as the electrode positive.

Procedure to Replace the Hood Assembly and Cowling

1. Remove 150-8733 Hood As and 151-3178 Cowling. Refer to Disassembly and Assembly, SENR1520, "3516B Engine Supplement for 789C Off-Highway Truck" for the proper procedures. Retain the hardware.

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Illustration 1	g00916578

2. Remove 9D-4721 Rail As (A) .

   Note: 9D-4721 Rail As (A) will not be replaced.

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Illustration 2	g00916486

3. Remove 8W-4778 Plate As (B) .

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Illustration 3	g00916642

4. Weld 212-0395 Plate As (1) to the frame. See Illustration 3 and Table 2.
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   Table 2

   Item	Dimension
   W1	6.0 mm (0.24 inch) Fillet Weld
   W2	6.0 mm (0.24 inch) Fillet Weld with 1.5 mm (0.06 inch) penetration
   C	166 ± 5 mm (6.5 ± 0.2 inch)
   D	241.0 ± 3.0 mm (9.49 ± 0.12 inch)

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Illustration 4	g00916649

5. Weld 211-4228 Plate (2) to 210-7861 Support. See Illustration 4 and Table 3.
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   Table 3

   Item	Dimension
   W3	4.0 mm (0.16 inch) Fillet Weld
   W4	4.0 mm (0.16 inch) Fillet Welds on both sides
   F	680.0 ± 1.5 mm (26.77 ± 0.06 inch)

6. Install 211-9138 Hood As (3) and 212-2759 Cowling (4). Refer to Disassembly and Assembly, SENR1520, "3516B Engine Supplement for 789C Off-Highway Truck".

   Note: The weight of the new 211-9138 Hood As is 80 kg (177 lb). The weight of the new 212-2759 Cowling is 252 kg (555 lb).

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Illustration 5	g00919556

7. Use the following parts to install 211-9138 Hood As (3) : two 8T-4222 Plated Washers (5), one 8T-4186 Bolt (6), two 6N-6984 Mounts (7), two 8T-4133 Nuts (8), two 8T-4121 Hard Washers (9) and one 8T-4196 Bolt (10) .

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Illustration 6	g00922070

8. Use the existing hardware to install 211-9141 Rail As (11) .

Procedure to Repair the Hood

Inspect 150-8733 Hood As for cracks. If cracks are found, use the following procedure to repair the affected area. Then reinforce the affected area.

Illustration 7	g00918675

Illustration 8	g00918677

Illustration 9	g00918680

Repair the Cracks

1. Remove 150-8733 Hood As. Refer to Disassembly and Assembly, SENR1520, "3516B Engine Supplement for 789C Off-Highway Truck" for the proper procedures. Retain the hardware.

2. Use a grinder to remove any cracks. Grind 25.4 mm (1.00 inch) beyond both ends of the crack.

   Note: The cracks must be completely removed to good metal prior to welding. Use a liquid dye penetrant to verify that the crack has been completely removed.

3. Clean the prepared groove before welding. Weld the ground area.

4. Grind the weld in order to match the existing profile of the hood.

5. Clean the weld and inspect the weld. The weld should be free from cracks, porosity, undercut and incomplete fusion. All weld quality shall conform to ANSI/AWS standard D14.3.

Fabricate the Reinforcing Plates

Illustration 10	g00918740
Plate (1)

Illustration 11	g00918742
Plate (2)

Illustration 12	g00918744
Plate (3)

Illustration 13	g00918745
Plate (4)

1. Fabricate Plate (1), Plate (2), Plate (3), and Plate (4). Fabricate the plates from structural steel that has the following properties: a yield strength of 290 to 450 MPa (42100 to 65300 psi) and tensile strength of 435 MPa (63100 psi). Acceptable materials are ASTM A572 Grade 42, ASTM A572 Grade 50, and ASTM A656 Grade 50.

   Note: Remove all burrs and sharp edges.

Weld Fabricated Plates

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Illustration 14	g00918999

1. Assemble Plate (1) to the right hand side of 150-8733 Hood As. Use 5 mm (0.2 inch) fillet welds (W1) to weld Plate (1) to the hood assembly. See Illustration 14.

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Illustration 15	g00919003

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Illustration 16	g00919007

2. Assemble Plate (2) and Plate (3) to the left hand side of 150-8733 Hood As. Use 5 mm (0.2 inch) fillet welds to weld the plates to the hood assembly. See Illustration 15, Illustration 16, and Table 8.
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   Table 8

   Item	Dimension
   S	10 mm (0.4 inch)
   T	5 mm (0.2 inch)
   W2	5 mm (0.2 inch) Fillet Weld

3. Replace the hood assembly. Refer to Disassembly and Assembly, SENR1520, "3516B Engine Supplement for 789C Off-Highway Truck" for the proper procedures.

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Illustration 17	g00919014

4. Assemble Plate (4) to the right hand side of 150-8733 Hood As. Use 3.0 mm (0.12 inch) fillet welds (W3) to weld Plate (4) to the hood assembly. See Illustration 17.

   Note: The nominal thickness of Plate (4) is 14.0 mm (0.55 inch). Measure the actual clearance on the machine. Adjust the thickness accordingly. Plate (4) is designed to provide additional support at the front corner of the hood assembly. Plate (4) should be flush with the existing components.

5. Grind the weld in order to match the existing profile of the hood. Paint the affected area.