PRODUCT SUPPORT PROGRAM FOR REWORKING THE 171-7850 FRAME ASSEMBLY ON CERTAIN 785C LARGE OFF-HIGHWAY TRUCKS Caterpillar

PRODUCT SUPPORT PROGRAM FOR REWORKING THE 171-7850 FRAME ASSEMBLY ON CERTAIN 785C LARGE OFF-HIGHWAY TRUCKS

Usage:

REBE5521-00

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30Oct2009

U-361

D-324

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*Before/After*	PRODUCT SUPPORT PROGRAM FOR REWORKING THE 171-7850 FRAME ASSEMBLY ON CERTAIN 785C LARGE OFF-HIGHWAY TRUCKS
0679 7051		PS42976

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NOTE:

This Program must be administered either before or after failure. In either case the decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS42976" as the Part Number and "7755" as the Group Number. If administered before failure, use "56" as the Warranty Claim Description Code and "T" as the SIMS Description code. If administered after failure, use "96" as the Warranty Claim Description Code, and "Z" as the SIMS Description Code.

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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.

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TERMINATION DATE

31Oct2011

PROBLEM

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The existing 171-7850 Frame As. can crack on certain 785C Large Off-Highway Trucks. If the existing 171-7850 Frame As. cracks between the ring on the torque tube and the tube itself and goes unrepaired it can cause additional damage to the machine.

AFFECTED PRODUCT

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Model	Identification Number
785C	APX00188-00189, 223, 229-233, 237, 240, 251, 261-263, 296, 319-323, 453-455, 466-467, 469, 482, 495-496, 503-506, 508, 512, 520, 558, 560-561, 574, 598-602, 643-645, 681-683, 690-691, 707, 711-713, 745-747, 807, 1522, 1526-1528, 1625-1627

PARTS NEEDED

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No parts needed for this program

ACTION REQUIRED

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Refer to attached Rework Procedure.

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Image1

SERVICE CLAIM ALLOWANCES

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Product smu/age whichever comes first	Caterpillar		Dealer Suggested		Customer Suggested
Product smu/age whichever comes first	Parts %	Labor Hrs%	Parts %	Labor Hrs%	Parts %	Labor Hrs%
0-20000 hrs, 0-36 mo	100.0%	100.0%	0.0%	0.0%	0.0%	0.0%
20001-40000 hrs, 37-72 mo	33.0%	50.0%	0.0%	0.0%	50.0%	50.0%

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NOTE: This is a 16.0-hour job

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PARTS DISPOSITION

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Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.

Rework Procedure

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Two methods can be used to repair the weld.

First, the preferred method is a TIG dressing. The second method can be performed in an emergency. This method does not require an experienced welder or specialized equipment.

METHOD 1

TIG DRESSING OF FILLET WELDS FOR IMPROVED FATIGUE LIFE

The equipment required is as follows.
- GTAW (TIG) Power Supply and torch capable of 225 amps (min. 60% duty cycle) with hand/foot current control.
- Shielding gas ? 100% Argon (& flow meter)
- Electrode ? Lanthanated, Ceriated or Thoriated Tungsten [3/32? (2.4 mm) dia.]
ER70S-2 filler metal (1/16? dia.) if needed
- Grinder - Pneumatic or Electric with Carbon Steel Wire Wheel Attachment
- Aluminum oxide grinding wheel to sharpen tungsten electrode.
- Radius Gages

The first steps to ensure a proper TIG dressing are cleanliness and tungsten electrode preparation. The fillet weld and surrounding base metal must have all contaminants thoroughly removed. It is imperative that all rust, dirt, oil, scale, silicate islands, etc. are non-existent. This can be accomplished quickly via a grinder with a carbon steel wire attachment. Next, prepare a 3/32? (2.4 mm) tungsten electrode to the dimensions shown in Image 1.3.1. Grinding striations should run parallel not transverse.

Image1.3.1

Adjust shielding gas flow rate to 15 CFH and current control to approx. 225 amps. If a ramp down control is present on the power source, utilize to ensure proper crater fill control.

A number of different techniques exist for TIG dressing. This is due to the variability of the contour of the fillet weld toe that must be re-shaped. Therefore, either a stringer or weave manipulation of the torch can be employed so long as the goal of a smooth, contoured radius of 5 mm minimum exists between the base material and weld metal.

Note 1: 10 to 15 deg push angle for both stringer and weave

Note 2: Poorly shaped fillet welds with 70 ? 90 degree transition angles to the base material will probably require several overlapping TIG dressing runs to properly smooth out the weld toe transition region.

Note 3: TIG dressing can be conducted in the vertical position as long as it is performed in a DOWNHILL progression.

Note 4: If undercut or other circumstances require the addition of filler metal, this can be accomplished by hand feeding ER70S-2 (1/16? dia.) into the weld pool and then repeat the TIG dressing to achieve desired toe radius/profile.

Image1.5.1

Image1.5.2

Once TIG dressing is completed and the area is allowed to cool area needs to be cleaned and painted to prevent pitting due to corrosion.

Image1.6.1

METHOD 2

BURR GRINDING OF FILLET WELDS FOR IMPROVED FATIGUE LIFE

The equipment required is as follows.
- High speed hand-held pneumatic rotary pencil grinder ? 20,000 rpm min.
- Compressed air ? 90 psi min.
- Tungsten carbide burr (conical shaped) with an end diameter of approx. 10 mm.
- Leather welding jacket, leather gloves, safety glasses and face shield to protect operator from metal slivers.
- Radius gauges and bridge cam gauge for inspection.

Image1.7.1

Image1.7.2

Burr tip should be located over the weld toe. The axis of the tool should be maintained at approx. 45 degrees to the parent plate and inclined at approx. 45 degrees to the direction of travel. Grinding should extend to a depth of 0.5 mm below the last visible traces of the weld toe resulting in minimum depth of 0.8 mm and maximum depth of 1 mm. The resulting ground surface should be smooth with no grinding marks running parallel to the weld, but transverse (90 degrees) to the weld. All traces of the original weld toe should not be visible via the use of a lower powered magnifying glass. Image 1.7.2 shows the finished appearance.