Repair Procedure for the Boom Nose on the 324D Excavator{0679, 6501} Caterpillar

Excavator:

324D (S/N: TSN1-UP; JZR1-UP)

Introduction

This Special Instruction describes the necessary procedures to repair the boom nose on certain hydraulic excavators with a heavy-duty boom. Do not perform any procedure and do not order any parts until the information contained in this document is understood. Refer to the appropriate Parts Manual, Operation and Maintenance Manual, and Service Manual.

Safety

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Be sure all personnel are clear of the equipment while the equipment is being lowered. Failure to stay clear of the equipment while the equipment is being lowered may result in personal injury.

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Personal injury can result from flame cutting or welding on painted areas. The effect of gasses from burned paint is a hazard to the person doing the cutting or welding. Do not flame cut or weld on painted areas.

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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; 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 cause death. Read and understand the manufacturer's instructions and your employer's safety practices. Do not touch live electrical parts. See "American National Standard Z49.1, Safety in Welding and Cutting" published by the American Welding Society. American Welding Society 2501 N.W. 7th Street Miami, Florida 33125 See "OSHA Safety and Health Standards, 29 CFR 1910", available from U.S. Department of Labor. U.S. Department of Labor Washington, D.C. 20210

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Hydraulic oil pressure can remain in the hydraulic systems after the engine and pump have been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic systems. To prevent possible injury, refer to the section, Testing and Adjusting, "Hydraulic System Pressure - Release" before any fitting, hose or component is loosened, tightened, removed or adjusted. When possible, the bucket or attachment must always be lowered to the ground before service is started. When it is necessary for the boom to be in the raised position while tests or adjustments are done, be sure that the boom, stick and bucket or attachment have correct support. The swing lock (if equipped) must be engaged before service is started. Always move the machine to a location away from the travel of other machines. Be sure that other personnel are not near the machine when the engine is running and tests or adjustments are being made.

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Accidental machine starting can cause injury or death to personnel working on the machine. To avoid accidental machine starting, turn the battery disconnect switch to the OFF position and remove the key. If the machine is not equipped with a battery disconnect switch, disconnect the battery cables from the battery and tape the battery clamps. Place a do not operate tag at the battery disconnect switch location to inform personnel that the machine is being worked on.

Problem Identification:

The weld along the U- shape plate is cracking, due to incomplete fusion of the weld.

Refer to Illustration 1.

Illustration 1	g02470336
Weld crack photos

Disassembly of the Bucket, the Stick, and the Boom

1. Move the machine to level ground. The ground must support the weight of the machine.

2. The removal of the bucket, stick, and boom requires special equipment to handle the extreme weight.

3. Put the machine in the SERVICING position. Lower the boom until the bucket is flat on the ground. The stick must be in the VERTICAL position, with the bucket flat on the ground. Refer to illustration 2.

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Illustration 2	g02416540
SERVICING position

4. While the machine is in the SERVICNG position, remove the bucket from the stick. Refer to the applicable Disassembly and Assembly manual for your machine for the correct removal procedure.

5. Remove the stick from the boom. Refer to the applicable Disassembly and Assembly manual for your machine for the correct removal procedure.

6. The work can be done with the boom on the machine or with the boom off the machine. Refer to the applicable Disassembly and Assembly manual for your machine for the correct removal procedure.

7. Remove all the hoses and hardware from the boom.

Preparing for Welding

1. Remove the paint, rust, dirt, and scale with a wire brush or by buffing or grinding. Shot blasting all the work areas will also remove the foreign material.

2. Remove any oil or grease that is on the boom with a Caterpillar approved solvent.

3. Cover all the finished bores and threads. Finished bores and threads must be protected from all of the following items: foreign material, welding, gouging, and paint spatters. Do not remove the covers until the boom is painted.

Illustration 3	g02470583
Steel strip diagram

Refer to Table 1 for the specifications of the steel strip.

Note: The steel strip should be fabricated by the dealer.

Illustration 4	g02470639
Steel strip positioning (1) Steel strip (2) Tack weld

Note: Make sure that the steel strip is securely tacked to theboom nose before starting the repair procedure.

Weld Procedure:

Illustration 5	g02470678
Weld gouging (3) Old weld (4) After gouging

1. Use an air carbon arc torch or a grinder to gouge out the crack on the U-shape plate completely. Refer to Illustration 5.

2. Use the dye penetrant to inspect the gouged area in order to ensure that the crack has been removed completely.

Illustration 6	g02470696
Bevel diagram

1. Use a grinder to form a 25 (+5/-2°) degree bevel on the U-shape plate. Refer to Illustration 6.

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Illustration 7	g02470736
Section view of the weld

2. Weld along the crack in the U-shape plate to ensure the root weld penetration. Refer to Illustration 7.

Note: The ambient temperature must be a minimum of 16° C (61° F) to perform the repair.

Illustration 8	g02470740
Grind the weld

1. Grind the weld until the top face is smooth with U- shape plate. Remove the crosshatched section of the weld. Refer to Illustration 8.

Painting and Coating the Boom

1. Relieve the stress in all the welds by needle peening. A wire brush or a grinder can also be used to clean the welded area.

2. Use a Caterpillar authorized paint product to paint the welds and reinforcement plates.

3. Cover all the bores, threaded holes, and cylinder rods before painting.

4. Remove all the protective covers from the bores and threads once the paint has dried.

5. The bores must be free of paint and grease prior to assembly of the bearings.

Apply the required amount of lubricant to the bores, bearings, and threads. Refer to the Operation and Maintenance Manual and the Service Manual for lubrication instructions and quantities.

Installation of the Boom, the Stick, and the Bucket

1. Prepare the machine and parts for reassembly. The weight of the boom, stick, and bucket is excessive and the correct equipment must be available to handle the extreme weight. Consult your Cat dealer for the weight ranges of the assemblies.

2. Reattach the boom to the machine. Refer to the Disassembly & Assembly module for your machine systems.

3. Reattach the stick to the boom. Refer to the Disassembly & Assembly module for your machine systems.

4. Reattach the bucket to the stick. Refer to the Disassembly & Assembly module for your machine systems.

5. Make sure that the machine operates according to the Operation and Maintenance Manual.