Usage:
776D (5ER),
784C (2PZ) Tractors;
771D (6YS),
775D (8AS) Quarry Trucks;
069D (9SS),
073D (1GW) Underground Trucks;
769D (5SS),
773D (7CS),
777D (3PR),
777D HAA (2YW),
785C (1HW),
785C HAA (5AZ),
789C (2BW),
793C (4AR) Off-Highway Trucks
Description of Change: A 5 mm (.2 in) radius fillet weld dressing has been added to the 8 mm (.32 in) fillet base weld used to fabricate the tank mounts to the frame rails. The added weld distributes the load of the tank over a larger area of the frame. This will reduce frame stress, improve fatigue life and reduce the possibility of cracking in this area.
Illustration 1.
Typical fuel and hydraulic tank bracket.
Field Repair Of Cracks
The following procedure is for the field repair of tank mount weld cracks and to enhance the fatigue life of the tank mount welds.
1. Visually inspect for fractures and use 4C-4736 or 9U-6335 Liquid Penetrant Kit on surfaces where cracks are suspected.
2. Clean the area to be welded of oil, grease, paint and dirt.
3. Protect all machined surfaces from sparks or splatter produced by welding, chipping and/or grinding operations.
4. Attach the welding ground directly to the frame.
5. Remove any cracks with the grinding or carbon arc gouging method. Cut past the suspected end of the crack by approximately 2 inches. Through section cracks should be removed with a grinder to prevent blowing through the casting. Cracks must be completely removed to sound metal prior to welding. Verify that the crack has been completely removed. The weld groove preparation shall include an approximate 90° angle at the root for good penetration and to minimize root defects. The side walls shall be angled at approximately 45° slope. Weld repair the prepared groove by using passes that do not exceed two times the electrode diameter. If the alternate process is selected, the welding pass size should not exceed (.31 in) fillet weld volume. Slag each pass to avoid the possibility of slag inclusions.
6. Clean and inspect the weld repair as in Step 1. The weld is to be free from cracks, porosity, undercut and incomplete fusion.
Illustration 2.
5 mm (.2 in) toe radius weld.
7. Weld a minimum of 5 mm (.2 in) radius weld around the toe of the existing weld as shown in Illustration 2.
8. Use a small grinder to blend the toe of this weld to create a smooth transition from the weld to the rail.
Adaptable To: Effective with 776D (5ER108), 784C (2PZ1), 771D (6YS1), 775D (8AS1), 069D (9SS180), 073D (1GW123), 769D (5SS1), 773D (7CS1), 777D (3PR950), 777D (2YW99), 785B (6HK709), 785C (1HW1), 785C HAA (5AZ90), 789B (7EK553), 789C (2BW1), 793C (4AR80) and adaptable to earlier models
Welding Operator Requirements
All repair welding operators must be qualified for fillet and/or groove welding as outlined in the current ANSI/AWS D1.1 or D14.3 qualifications, or Caterpillar Manufacturing Practices MC1000-105. The qualification will be for the SMAW (Shielded Metal Arc Welding) process in the vertical welding positions. The alternate process for this repair is FCAW (Flux Cored Arc Welding). The welding operator must also have used the welding process within the last six months or be re-certified for this process before welding. Documentation must be maintained of the weld operators qualifications.
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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.
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Read and understand the manufacturer's instructions 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 no touch live electrical parts.
Refer to American National Standard Z49.1 "Safety in Welding and Cutting" published by the American Welding Society, 2501 N.W. 7th Street, Miami, Florida 33125; OSHA Safety and Health Standards, 29 CFR 1910, available from U.S. Dept. of Labor, Washington, D.C. 20210.
NOTE: Welding operator personal protection should be provided to assure that total weld fumes in the operators breathing zone does not exceed OSHA limits.
Weld Process
When the base metal temperature is below 0°C (32°F), the base metal shall be preheated to at least 21°C (70°F) and this minimum temperature maintained through the weld repair procedure.
NOTE: Since weld distortion is a possibility, minimizing the heat into the metal is important.
The SMAW process shall be used with E7018 (ANSI/AWS A5.1) welding electrode. The weld deposited by these electrodes will have the following minimum mechanical properties:
- 500 MPa (72 KSI) Tensile Strength
- 420 MPa (60 KSI) Yield Strength
- 13% Elongation
- 18% Reduction of Area
- 420 MPa (60 KSI) Yield Strength
These are low hydrogen electrodes and must be stored in an electrode oven at 121°C (250°F) when not in use. If the electrodes get damp, scrap or recondition them to the manufacturer's specifications.
Use the direct current positive (DC reverse polarity) setting and remove the slag after every pass. The weld pass size shall not exceed two times the electrode diameter.
As an alternate process the FCAW process may be used with E71T-I (ANSI/A5.20) welding electrode and the manufacturer's specified shielding gas(es). The weld deposited by three electrodes will have the following minimum properties.
- 500 MPa (72 KSI) Tensile Strength
- 420 MPa (60 KSI) Yield Strength
- 13% Elongation
- 18% Reduction of Area
- 420 MPa (60 KSI) Yield Strength
NOTE: This type of electrode has limitations if it is used to carry larger weld pass volumes in the flat welding position. Due to the fast freezing characteristics of this electrode's slag system, there is a chance of trapping evolving gases in the weld melt. Precaution should be taken by controlling weld pass size.
Welding parameters will vary due to weld position and manufacturer of the welding electrode. For 1.30 mm (.052 in) diameter electrode typical welding parameters should be:
Use the direct current electrode positive (DC reverse polarity) polarity setting and remove the slag after every pass. The weld pass size shall not exceed 8.0 mm (.31 in) fillet volume.