Usage:
June 14, 2004
U-188
A-130
D-145
before
or after failure |
PRODUCT SUPPORT PROGRAM FOR REPLACING THE WEAR BARS IN THE 4Z6938 LINER GROUP OF CERTAIN MSD LL BODIES USED ON 793 OFF-HIGHWAY TRUCKS |
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7258 |
PS41628
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NOTE: The information supplied in this service letter may not be valid after the termination date of this program. Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.
Termination Date
June 30, 2006PROBLEM
Three of the wear bar part numbers in the 4Z6938 Liner Group of certain 4Z6980 MSD II Body And Canopy Assemblies were made from the wrong material. These Bodies are used on 793 Off-Highway Trucks. The wear bars can be replaced if abnormal wear is detected.AFFECTED PRODUCT
Model | Identification Number |
4Z6980
MSD II Body |
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PARTS NEEDED
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4 | 2537694 | BAR |
1 | 2537695 | BAR |
2 | 2537696 | BAR |
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Dealer sales people will need to submit a Misc. MSO to order the 2537694, 2537695, and 2537696 Bars. Facility will be 13 for Decatur plant and Source Facility is 89A.
ACTION REQUIRED
Refer to the attached procedure and replace the 253-7694, 253-7695, and 253-7696 Bars in the 4Z6938 Liner Group of the 4Z6980 MSD II Body And Canopy Assemblies.SERVICE CLAIM ALLOWANCES
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0-12 Months |
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PARTS DISPOSITION
Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.Attach. (1-Rework Procedure)
REWORK PROCEDURE
Assemble/Position the new bars. Tack and weld as shown in the following instructions and illustration.
WELDING ELECTRODES
Proper preparation of the weld area must be conducted prior to any weld repair. Clean the area to be welded with a grinder. All paint, rust, oil, scale, slag, dirt, moisture, etc. must be completely removed. Any dye penetrant must also be removed with the appropriate cleaner. After the crack is completely removed, prepared and cleaned it may be weld repaired by one of the two following options:
OPTION 1
Preheat the weld groove and 3" in each direction from the weld centerline to 350 degrees F (176 degrees C). The maximum interpass temperature should not exceed 450 degrees F (250 degrees C). Weld the prepared groove with either the SMAW or FCAW electrode as specified below.
Electrode /Characteristics
The SMAW process may be used with E7018 (ANSI/AWS
A5.1) welding electrode. The weld deposited by these electrodes will have
the following minimum mechanical properties:
TENSILE STRENGTH | 480 MPa (70 KSI) |
YIELD STRENGTH | 400 MPa (58 KSI) |
ELONGATION | 22% |
IMPACT TOUGHNESS | 20 FT LBF @-20F (27J @-18C) |
DIAMETER | AMPS |
3.2MM (0.125") 1/8" | 70-140 |
4.0MM (0.156") 5/32" | 110-180 |
4.8MM (0.166") 3/16" | 190-270 |
Use the direct current electrode positive (DC reverse polarity) polarity setting and remove the slag after every pass. The weld pass weave width shall not exceed two times the electrode diameter.
OPTION 2
As an alternative process the FCAW process may be used with E71T-1 H8 (ANSI/AWS A5.20) welding electrode and the manufacturers specified shielding gas (es). The weld deposited by these electrodes will have the following mechanical properties:
TENSILE STRENGTH | 480 MPa (70 KSI) |
YIELD STRENGTH | 400 MPa (58 KSI) |
ELONGATION | 22% |
IMPACT TOUGHNESS | 20 FT LBF @-20F (27J @-18C) |
Welding parameters will vary due to weld position
and manufacturer of the welding electrode. For 1.3mm (0.052 inch) diameter
electrode typical welding parameters should be:
WIRE FEED SPEED | VOLTAGE | APPOX. AMPERAGE |
MIN 200 IMP | 24 | 210 |
OPT 275 IMP | 28 | 250 |
MAX 325 IPM | 29 | 300 |
Use the direct current electrode positive (DC reverse polarity) setting and remove the slag after every pass.
Illustration 1 - Welding Bars In Position
Illustration 2 - Alternate Position of Wear
Bars
If Front of Rock Box is Worn Down Under 1/2
inch.