Procedure to Repair The Welds on Certain Excavators Track Roller and Car Body Frames{0679, 4150, 4151, 7062} Caterpillar


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Procedure to Repair The Welds on Certain Excavators Track Roller and Car Body Frames{0679, 4150, 4151, 7062} [REHS5149]
UNDERCARRIAGE
UNDERCARRIAGE GP
Procedure to Repair The Welds on Certain Excavators Track Roller and Car Body Frames{0679, 4150, 4151, 7062}
1.1. Introduction
2.1. Required Parts
3.1. Welding Requirements
4.1. Procedure for the Repair of the Cracked Weld
5.1. Fabrication of The Reinforcement Plate
6.1. Installation of the Reinforcement Plate
7.1. Repainting the Repaired Weld Area
Excavator:
324D (S/N: CJX1-UP)

Introduction

Table 1
Model     Serial Number     Part Number    
324D     S/N:CJX     236-8464    
324D     S/N:JZR     236-8464    

This Special Instruction outlines the procedure that is recommended in order to repair the cracks in the welds on 324D Excavators. The cracks are occurring between the car body frame and the track roller frame.

The instructions for fabricating the parts that are needed for this procedure are included within this publication. The procedures in this publication are applicable to the serial number prefixes that are listed in Table 1.

Refer to Illustration 1 for the location of the weld joints.




Illustration 1g02145568

Typical frame assembly

(A-A) View of frame assembly

(B) Detail of frame assembly




Illustration 2g02145595

(C) Typical view of cracked weld location

Removal of cracked welds that are present in the car body frame and the track roller frame is required in order to repair welds. Add the reinforcement plate after rewelding is completed in order to prevent the reoccurrence of the failure. Use the information that follows for the repair of the cracked welds.

Before making weld repairs, refer to the appropriate Operation and Maintenance Manual for your machine. Lift one side of the machine. If a cracked weld extends into the inner side of the track frame body, remove the track assembly and the track rollers. Support the machine with a repair stand.

Required Parts

The required parts are depicted in each section of this Special Instruction. Use the designs that are provided in order to fabricate parts that are needed. All of the plates must be fabricated from the approved steel. Steel must meet or exceed ASTM A572 Grade 42 steel standard, or the equivalent steel with a minimum yield strength of 290 MPa (42000 psi).

Welding Requirements

Welding quality is critical to the success of the repair procedure. Welds must be smooth and continuous. Do not undercut and/or overlap as these methods are not allowed. Grind the ends of the welds to a smooth radius.

Prepare the metal for welding according to Preparing the Metal for Welding. Refer to the illustrations in this special instruction for welding symbols and Specifications. Use LB-26 Electrodes (AWS E7016 or AWS E7018) or equivalent electrodes for welding the baffle plate and the reinforcement plates.

Basic welding wire ESAB OK welding rod15.00 with a 1.2 mm (0.05 inch) diameter can also be used. The basic welding wire must be the equivalent to AWS A5.20 E71T-5 with positive polarity. The welding wire must be shielded with CO2 gas or Argon/CO2 80/20 gas. Welding of the gouged grooves requires LB-52 (AWS E7018), or an equivalent electrode. Basic welding wire ESAB OK welding rod 15.00 with a 1.2 mm (0.05 inch) diameter can also be used. All electrodes must be dried completely. The electrodes can be dried by heating the electrodes to the temperature of 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 electrode diameter, shielding gas, welding current, and plate thickness.

Geometry of welded joints, surface conditions, and composition of the base metal and electrode also affect the welds. 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.

All repair welds should be done in a controlled environment. Controlled environments prevent the rapid cool down after the weld. Controlled environments would be inside of a repair shop. All welds should be done in the horizontal or the flat position in order to make a smooth surface finish.

Please refer to Special Instruction, REHS1841, "General Welding Procedures".

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

Procedure for the Repair of the Cracked Weld

Examine the crack and the toe of the weld. Refer to Illustration 2.

Examine the shape of the weld. The welds are unsymmetrical, if the weld size on the carbody frame is larger than the weld size on the track roller frame. If the toe of the weld overlaps the side of the track frame body, the probability of cracks and lack of weld penetration is high.

If there is a cold lap or lack of weld penetration, the weld should be gouged out and rewelded as shown in Illustration 6. The procedure should be done even when the cracks are not evident but there is a cold lap or lack of penetration.

If cracks are present, repair in the following procedure.




    Illustration 3g02146734

    Area that is to be gouged out.

    (A) Cleaned area of removed weld penetration

  1. Gouge out the cracked weld from the car body side and completely remove the crack. Gouge out the weld on the cracked frame side. The cracked weld is to be gouged to a depth so that the weld penetration from the original weld is removed completely. Refer to Illustration 3.

    Table 2
    Required Backup Strips For The 324D S/N:CJX Excavators    
    QTY     Length     Width     Thickness    
    4    
    317 mm (12.5 inch)    

    25 mm (1.0 inch)    

    9 mm (0.3 inch)    

    437 mm (17.2)

    25 mm (1.0 inch)    

    9 mm (0.3 inch)    

    37mm (1.5 inch)

    25 mm (1.0 inch)    

    9 mm (0.3 inch)    

    33 mm (1.3 inch)

    25 mm (1.0 inch)    

    9 mm (0.3 inch)    



    Illustration 4g02147781

    (1) Tack weld 20 mm (0.8 inch)

    (B) Backup Strip




    Illustration 5g02147793

    Location of the backup strips on a track roller frame

    (C) Backup strip length is33 mm (1.3 inch)

    (D) Backup strip length is 37mm (1.5 inch)

    (E) Backup strip length is 437 mm (17.2)

    (F) Backup strip length is 317 mm (12.5 inch)

    (G) 193 mm (7.6 inch)

    (H) 10 mm (0.4 inch)

    (J) 12 mm (0.5 inch)

  1. Install the backup strips. Tack welding within 50 mm (2.0 inch) from both ends is not permitted on the inside of the backup strip. The length of the tack weld on the inside of the backup strip is not to exceed 20 mm (0.8 inch).

    Note: Refer to Table 2 for the backup strip sizes.

    Note: Refer to Illustration 4 and Illustration 5 for the installation of the backup strips.




    Illustration 6g02147795

    (A) Cleaned area of removed weld penetration

    (K) View of area to be repaired

    (L) Surface area that is to be ground down

    (L1) Radius of 5 mm (0.2 inch)

    (L2) Fill length of 12 mm (0.5 inch)

  1. Make the weld repair to area (A) as shown in Illustration 6.

    1. Grind surface (L) of the repaired weld. Form the weld to radius (L1) .



    Illustration 7g02148243

    (M) Typical location of tack welds

    Note: If the cracked weld extends the entire length of the weld joint, tack welds must be added in order to prevent deformation during the repair. The repair weld for the entire length should be completed as two separate welds. Each weld will repair approximately one half of the entire length.

  1. Weld two tack welds (M) that are 50 mm (2 inch) long for one of the half-lengths. Refer to Illustration 7.

  1. Complete Step 1 through Step 3.a for the remaining one half-length of the frame that is near the tack welds completed in Step 4.

  1. CompleteStep 1 through Step 3.a for the half-length that was tack welded in Step 4.

Fabrication of The Reinforcement Plate




    Illustration 8g02148285

    (N) 332.4 mm (13.1 inch)

    (P) 280 mm (11.0 inch)

    (R) 140.6 mm (5.5 inch)

    (S) 137.6 mm (6.6 inch)

    (T) 136.5 mm (5.4 inch)

    (U) 7 mm (0.3 inch)

    (AF) 1.5 mm (0.06 inch)

    (AH) Reinforcement plate




    Illustration 9g02148286

    (V) 228.9 mm (9.0 inch)

    (W) 139.3 mm (5.5 inch)

    (X) 106.8 mm (4.2 inch)

    (Y) 6 mm (0.2 inch)

    (Z) 130 degrees

    (AA) Radius of 6 mm (0.2 inch)

    (AH) Reinforcement plate

  1. Manufacture four plates from a mild steel plate with a yield strength of 290 MPa (42000 psi). The dimensions for reinforcement plates (AH) are shown in this step. Refer to Illustration 8 and Illustration 9 for the manufacturing view.

Installation of the Reinforcement Plate




    Illustration 10g02148831

    (AB) 670 mm (26.4 inch)

    (AC) 650 mm (25.6 inch)

    (AH) Reinforcement plate

  1. Measure distance (AB) from the idler end of the frame in order to find the center point of reinforcement plate (AH). Measure distance (AC) from the motor end of the frame in order to find the center point of reinforcement plate (AH) .

  1. Add reinforcement plates (AH) on the idler end of the frame assembly, and on the motor end of the frame assembly. The dimensions for locating the plates and the welds are shown in Step 1. Refer to Illustration 10 for the proper location of installation for the reinforcement plates.



    Illustration 11g02148333

    (B-B) View of weld location for reinforcement plate

    (AH) Reinforcement plate




    Illustration 12g02148974

    (2) 6 mm (0.24 inch) fillet weld

    (AD) Weld extension of 20-30 mm (0.8 inch-1.2 inch) on both ends of the plate

    (AE) Gap

    (AG) Finish grind area of the weld toe for the track roller frame

    (AH) Reinforcement plate

  1. Finish grind the toe of the track roller frame.

  1. Weld reinforcement plate (AH) in accordance with Illustration 12.

  1. Gradually decrease the weld leg length and join to an existing weld in range (AD). Plug gap (AE) by joining the welds. Upon completion of welding reinforcement plate (AH) in place grind area (AD) on both ends of the plate smooth.

Repainting the Repaired Weld Area

  1. Clean surface from all debris.

  1. Apply primer paint for corrosion control.

  1. Apply touch-up paint on the area with the repaired welds.

  1. Allow paint to dry completely before operating the machine.

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