1998/12/07 Caterpillar

Procedure Available To Improve Service Life Of 7U-6300 Expansion Tank Group {1354,1350}

Usage:

D300D (5MG),
D250E (5TN),
D300E (7FN) Articulated Trucks

The shunt tank repair procedure for the 7U-6300 Expansion Tank Group can be used to repair cracks around the weld between the fill neck and the top plate.

The cracks have developed on the tank as shown in Illustration 1.

1. A reinforcement plate and ring need to be fabricated to the dimensions in Illustrations 2 and 3. The plate should be fabricated from SAE1008 or SAE1010 3.0 mm (.12 in) plate steel. The ring should be fabricated from SAE1018 bar or tube, and be 3.0 mm (.12 in) thick.

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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. Weld Information

Weld Information

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 general area. Wear correct eye, ear, and body protection. Do not touch live electrical parts.

See 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 CRF 1910, available from U.S. Dept. of Labor, Washington, D.C. 20408.

NOTE: See 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 CRF 1910, available from U.S. Dept. of Labor, Washington, D.C. 20408.

All repair welding operators must be qualified for groove and fillet welding, as outlined in the current ANSI/AWS D14.3. The qualification will be for the SMAW (Shielded Metal Arc Welding) process in the vertical welding positions. The welding operator must also have used this welding process during the last six months or be re-certified for this process before welding. Documentation must be maintained of the weld operators qualifications. The alternate process for this repair could be FCAW (Flux Cored Arc Welding).

The area to be welded and the surrounding area must be at a minimum temperature of 16°C (60°F) before and during welding.

NOTE: Since weld distortion is a possibility, minimizing the heat is important.

The SMAW process shall be used with E7018 (ANSI/AWS A5.5) 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

22% elongation in 50 mm (2 in)

27 J (20 ft lb) Notch Toughness at -29°C (-20°F)

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.

The following chart relates to the electrodes diameter and approximate current settings for welding:

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 two times the electrode diameter.

As an alternate process the FCAW process may be used with E71T-1 (ANSI/A5.20) welding electrode and the manufacturer's specified shielding gas(es). The weld deposited by three electrodes will have the following minimum mechanical properties:

500 MPa (72 KSI) Tensile Strength

420 MPa (60 KSI) Yield Strength

22% elongation in 50 mm (2 in)

27 J (20 ft lb) Notch Toughness at - 18°C (0°F)

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 electrodes 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.

Clean the metal of oil, grease, paint, and dirt in the area to be welded. Attach the welding ground cable directly to the area to be welded. Protect all machined surfaces from sparks or splatter produced by the welding, chipping, and/or grinding operations.

The welds shall be free from cracks, porosity, undercut, and incomplete fusion. All weld quality shall conform to ANSI/AWS D14.3.

2. Weld the fabricated reinforcement plate over the top of the tank with a 1.5 mm (.06 in) fillet weld all around as shown in Illustration 4.

3. Grind the existing weld around the fill tube only if necessary to fit the reinforcement tube in a flat position.

4. Place the reinforcement ring evenly around the fill tube. Weld the inside against the fill tube and the outside against the reinforcement plate as shown in Illustration 4. Use 2.0 mm (.08 in) fillet weld all around.

Illustration 1.
7U-6300 Expansion Tank Group. Arrow depicts weld crack area.