PRODUCT SUPPORT PROGRAM FOR REWORKING HYDRAULIC TANK MOUNTING BRACKET WELDS ON CERTAIN 794 AC, 796 AC, AND 798 AC OFF-HIGHWAY TRUCKS Caterpillar

PRODUCT SUPPORT PROGRAM FOR REWORKING HYDRAULIC TANK MOUNTING BRACKET WELDS ON CERTAIN 794 AC, 796 AC, AND 798 AC OFF-HIGHWAY TRUCKS

Usage:

TEBE9174-01

Show/hide table

10May2019

(Revised 17May2019)

U-280

A-235

D-248

Show/hide table

Before/After	PRODUCT SUPPORT PROGRAM FOR REWORKING HYDRAULIC TANK MOUNTING BRACKET WELDS ON CERTAIN 794 AC, 796 AC, AND 798 AC OFF-HIGHWAY TRUCKS
7755 0679 5056 7051		PS46259

Show/hide table

NOTE:

Caterpillar’s obligations under this Service Letter are subject to, and shall not apply in contravention of, the laws, rules, regulations, directives, ordinances, orders, or statutes of the United States, or of any other applicable jurisdiction, without recourse or liability with respect to Caterpillar.

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 "PS46259" 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.

Show/hide table

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.

Show/hide table


NOTE:	This Revised Service Letter replaces the 10May2019 Service Letter. Changes have been made to the Rework Procedure.

Show/hide table

TERMINATION DATE

31May2021

PROBLEM

Show/hide table

The existing hydraulic tank mounting bracket welds can fail on certain 794 AC, 796 AC, and 798 AC Off-Highway Trucks.

AFFECTED PRODUCT

Show/hide table

Model	Identification Number
794 AC	HRT00100-00102 MN500051-00056 MT500100-00143
796 AC	HRZ00500-00502
798 AC	ST700400-00402

PARTS NEEDED

Show/hide table

No parts needed for this program

ACTION REQUIRED

Show/hide table

Refer to the attached Rework Procedure.

Show/hide table

Image1

SERVICE CLAIM ALLOWANCES

Show/hide table

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%
0-48000 hrs, 0-60 mo	100.0%	100.0%	0.0%	0.0%	0.0%	0.0%

Show/hide table

NOTE: This is a 10.0-hour job
This is a 10 hour job, including time required for any disassembly, weld repair and any reassembly. An additional 1.5 hours will be allowed for a partial through thickness crack if present. An additional 3 hours will be allowed for a through thickness crack if present.

Show/hide table

PARTS DISPOSITION

Show/hide table

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

Rework Procedure

Show/hide table

Use the following procedure to rework the frame assembly hydraulic tank mounting bracket welds.

NOTE: The hydraulic tank must be removed to inspect and complete weld repair. Reference UENR2271, "Disassembly and Assembly, 794 AC Off-Highway Truck Machine Systems, Hydraulic Tank (Brake, Hoist, Steering) Remove and Install", removal procedure.

Image1.1.1

1. The first course of action is to identify if a crack exist such as shown in Image 1.2.1 and if so what is the extent of the crack. The next objective is to determine if the crack depth has propagated through the thickness of the plate. The crack depth will determine the extent of the repair. Utilize a grinder, or air arc rod and either magnetic particle, or dye penetrant testing equipment.

Refer to "PROCEDURE IF PARTIAL THROUGH THICKNESS CRACK IS PRESENT" section for a partial through thickness crack. Once crack has been repaired proceed to" PROCEDURE IF NO CRACK IS PRESENT" section.

Refer to "PROCEDURE IF THROUGH THICKNESS CRACK IS PRESENT" section for a through thickness crack. Once crack has been repaired proceed to" PROCEDURE IF NO CRACK IS PRESENT" section.

2. If no crack exists, proceed to "PROCEDURE IF NO CRACK IS PRESENT" section.

Image1.2.1

.
.
PROCEDURE IF PARTIAL THROUGH THICKNESS CRACK IS PRESENT

Partial Through Thickness Crack Repair

The following section assumes that preheat (if required), crack excavation, and NDT verification have taken place and it has been verified that the crack has been completely removed and did not extend through the plate thickness. If so, the area excavated should appear similar (depending on crack depth to wall thickness) to that shown in Image 1.3.1.

Note: A previous crack repair must use ultrasonic testing to verify crack has been completely removed.

Image1.3.1

1. The following Images 1.4.1, 1.4.2 and 1.4.3 demonstrate the sequence of steps necessary to obtain the desired joint configuration prior to welding.

Image1.4.1

Image1.4.2

Image1.4.3

2. After the crack removal has been verified, reinstate by welding and sand the excess weld material flush to the profile of the surface of the surrounding plate.

Image1.5.1

.
.
PROCEDURE IF THROUGH THICKNESS CRACK IS PRESENT

Through Thickness Crack Repair

The following section assumes that preheat (if required), crack excavation, and NDT verification have taken place and it has been verified that the crack has been completely removed and did extend through the plate thickness. If so, the area excavated should appear similar (depending on crack depth to wall thickness) to that
shown in Image 1.6.1.

Note: A previous crack repair must use ultrasonic testing to verify crack has been completely removed.

Image1.6.1

1. Images 1.7.1 and 1.7.2 demonstrate the approximate dimensions for a weld joint requiring a permanent backing strip.

Image1.7.1

Image1.7.2

2. The dimension of the permanent steel, backing strip will depend on the configuration of the excavation.

Every attempt should be made to accommodate a single, continuous strip that runs the full length of the weld joint. A 6.4 mm (0.25 inch) thick by 38 mm (1.50 inch) wide by the required length are the typical dimensions required for most applications.

The steel backing strip material can be any common structural steel such as ASTM A36. Attach wire (or other means) to the backing strip and insert through the root opening/gap and pull back flush to the inside of the plate surface.

The thickness of the backing strip should be kept to a minimum to assist with the insertion process. The thicker the backing strip the more difficult it will be to insert through the gap into an enclosed cavity. A 6.4 mm (0.25 inch) thick backing strip is the minimum that should be used and is sufficient enough to prevent burn through using the welding parameters specified.

Select a backing strip width that will ensure a minimum overlap of 3 mm (0.12 inch) of the backing strip to both sides of the weld joint along the entire length. Refer to Image 1.7.2. Minimize the gap (0 mm if possible) between the backing strip and the inside plate surface.

3. Tack weld backing strip in place. Remove wire/rod and grind one-half the thickness of the tack welds prior to finish welding to ensure proper fusion between tack welds and fill passes.

4. After the crack removal has been verified, reinstate by welding and sand the excess weld material flush to the profile of the surface of the surrounding plate. Refer to Image 1.5.1.

.
.
PROCEDURE IF NO CRACK IS PRESENT

1. Remove existing 7 mm (0.28 inch) intermittent fillet weld on both sides of joint from B to C on two plates (A) as shown in Image 1.10.1.

Image1.10.1

2. Prep weld surfaces to be free of debris, dirt, grease and paint. Relocate two plates (A) as shown in Image 1.11.1.

Image1.11.1

3. Weld two plates (A) with a 5 mm (0.20 inch) continuous fillet weld on both sides of joint from B to C as shown in Image 1.12.1.

Image1.12.1

4. Reassemble hydraulic tank and any hydraulic lines that were disassembled to complete weld repair. Reference UENR2271, "Disassembly and Assembly, 794 AC Off-Highway Truck Machine Systems, Hydraulic Tank (Brake, Hoist, Steering) Remove and Install", installation procedure.