Procedure to Inspect and Rework the Frame 4 Bar Casting to Main Rail Connection Offset on the 793F Off-Highway Truck {0679, 7051} Caterpillar

Off-Highway Truck/Tractor

793F (S/N: SND100-131; SSP112-1004; RBT111-171)

793F AC (S/N: EMD75-77)

Introduction

Reference: Special Instruction, REHS4439, "High Voltage Isolation Procedure for Welding on a Large Off-Highway Electric Drive Truck"

Special Instruction, REHS7193, "Procedure for the Inspection, Repair, and Component Replacement on the Frame of the 793F, 793F AC, and the 793F Command For Hauling Off-Highway Trucks"

Reference: Special Instruction, REHS1841, "General Welding Procedures"

Reference: Operation and Maintenance Manual, SEBU8406, "System Pressure Release"

Reference: Special Instruction, REHS9546, "Procedure to Prime the Hydraulic System on Certain 793F Off-Highway Trucks."

This special instruction contains the necessary instructions to Inspect and Rework the Frame 4 Bar Casting to Main Rail Connection Offset on the 793F Off-Highway Truck

Note: The body does not need to be removed for inspection or frame repair as long as retaining cables are in serviceable condition and used properly.

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The Power Train Electric Drive System will contain hazardous voltage levels during machine operation and for a short period of time after engine shutdown. Do not remove any covers that will expose energized high voltage electrical components while the engine is operating. Any type of maintenance on the following components can only be performed after the Power Train Electrical System Service Shutdown procedure has been followed: High voltage compartments in the inverter cabinet The rear axle housing that contains the electric drive traction motors The generator The retarding resistor grid, the grid blower motor and the grid system cabling The excitation field regulator The high voltage cables and connection enclosures Failure to follow these instructions could result in personal injury or death.

Important Safety Information

The following information is an explanation of various labels that are found in this document.

Warnings

The warning label informs the technician that an injury or death can occur as a result of a condition that may exist.

Notices

A notice informs the technician that component damage can occur as a result of a condition that exists.

Notes

A note contains general information for the technician about the operation that is being performed.

Proper repair is important to the safe operation and the reliable operation of this machine. This document outlines basic recommended procedures. Some of the procedures require special tools, devices, or work methods.

Before you perform any repairs or before you perform any maintenance, read all safety information. Understand all safety information before you perform any repairs or before you perform any maintenance.

Safety information is provided in this document and on the machine. If these hazard warnings are not heeded, bodily injury or death could occur to you or other persons.

The “Safety Alert Symbol” that is followed by a “Signal Word” identifies a hazard. “DANGER”, “WARNING”, and “CAUTION” are “Signal Words”.

Illustration 1	g00008666

The signal word “WARNING” has the following meanings:

• Pay Attention !

• Become Alert !

• Your Safety Is Involved !

The message that appears under the safety alert symbol explains the hazard.

Operations or conditions that may cause product damage are identified by "NOTICE" labels on the machine and in the service information.

The person that services the machine may be unfamiliar with many of the systems on the machine. Use caution when you perform service work. Special knowledge of the systems and of the components is important. Before you remove or disassemble any component, obtain knowledge of the system and knowledge of the component.

Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. The safety information in this document and the safety information on the machine are not all inclusive. Determine that the tools, procedures, work methods, and operating techniques are safe. Determine that the operation, lubrication, maintenance, and repair procedures will not damage the machine. Determine that the operation, lubrication, maintenance, and repair procedures will not make the machine unsafe.

Basic Precautions

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Improper operation, lubrication, maintenance or repair of this product can be dangerous and could result in injury or death. Do not operate or perform any lubrication, maintenance or repair on this product, until you have read and understood the operation, lubrication, maintenance and repair information.

Always observe the list of basic precautions that follows:

Safety Signs

Safety signs include the items that follow: signs, information plates, and decals. Read all “Safety” signs on the machine before operating, lubricating, or repairing the machine. Understand all “Safety” signs on the machine before operating, lubricating, or repairing the machine. Replace any safety signs that are in the conditions that follow: damage, unreadable and missing.

Protective Equipment

When you work around the machine, always wear protective equipment that is required by the job conditions. Protective equipment includes the items that follow: hard hat, protective glasses, and protective shoes. In particular, wear protective glasses when you use a hammer or when you use a sledge hammer. When you weld, use the appropriate protective equipment that is required by the job conditions. Protective equipment for welding includes the items that follow: gloves, welding hood, goggles, and apron. Do not wear loose clothing or jewelry that can catch on parts of the machine.

Mounting and Dismounting

Use steps and handholds when you mount a machine. Also, use steps and handholds when you dismount a machine. Before you mount the machine, clean any mud or debris from steps, walkways, or work platforms. Always face the machine when you use steps, handholds, and walkways. When you cannot use the accesses on the machine, use ladders, scaffolds, or work platforms to perform safe repair operations.

Specifications for Cables, Chains, and Lifting Devices

Use approved cables, chains, and lifting devices to lift components. Refer to the manufacturer's weights to determine the application when you select the following items: cable, chain, and lifting devices. When you lift a component, the lift angle is critical. Refer to the Illustration that follows to see the effect of the lift angle on the working load limit.

Note: The lifting devices that are shown in this publication are not Caterpillar parts.

Note: Ensure that the hooks are equipped with a safety latch. Do not place a side load on the lifting eyes during a lifting operation.

Illustration 2	g00629745
Lift angles for lifting slings. (A) The load capacity is 100% of the working load limit for the sling. (B) The load capacity is 86% of the working load limit for the sling. (C) The load capacity is 70% of the working load limit for the sling. (D) The load capacity is 50% of the working load limit for the sling.

Hot Fluids and Parts

To avoid burns, be alert for hot parts on machines which have been stopped and hot fluids in lines, tubes and compartments.

Be careful when you remove filler caps, breathers, and plugs on the machine. Hold a rag over the cap or plug to prevent being sprayed by pressurized liquids. When the machine has been stopped, the danger of hot fluids is greater.

Corrosion Inhibitor

Corrosion inhibitor contains alkali. Avoid contact with the eyes. Do not allow corrosion inhibitor to contact the skin for extended periods of time. Avoid repeated contact with the skin. Do not drink corrosion inhibitor. If there is contact, immediately wash skin with soap and water. For contact with the eyes, flush the eyes with large amounts of water for at least 15 minutes. Seek medical attention.

Batteries

Do not smoke when an inspection of the battery electrolyte level is made. Never disconnect any charging unit circuit or battery circuit cable from the battery when the charging unit is operating. A spark can cause an explosion from the flammable vapor mixture of hydrogen and oxygen that is released from the electrolyte through the battery outlets. Do not allow battery electrolyte to contact skin or eyes. Battery electrolyte is an acid. If there is contact with battery electrolyte, immediately wash the skin with soap and water. For contact with the eyes, flush the eyes with large amounts of water for at least 15 minutes. Seek medical attention.

Pressurized Items

1. Always use a board or a piece of cardboard when you check for a leak. Leaking fluid under pressure can penetrate body tissue. Fluid penetration can cause serious injury and possible death. A pin hole leak can cause severe injury. If fluid is injected into your skin, you must get treatment immediately. Seek treatment from a doctor that is familiar with this type of injury.

2. Relieve all pressure in air, oil, or water systems before any lines, fittings, or related items are disconnected or removed. Always make sure that all raised components are blocked correctly. Be alert for possible pressure when you disconnect any device from a system that utilizes pressure.

3. Fuel lines that are damaged and fuel lines that are loose can cause fires. Lubrication lines that are damaged and lubrication lines that are loose can cause fires. Hydraulic lines, tubes, and hoses that are damaged can cause fires. Loose hydraulic lines, loose tubes, and loose hoses can cause fires. Do not bend or strike high-pressure lines. Do not install lines which have been bent or damaged. Check lines, tubes, and hoses carefully. Do not use your bare hand to check for leaks. If fluids are injected into your skin, you must get treatment immediately. Seek treatment from a doctor that is familiar with this type of injury.

4. Pressure air or water can cause personal injury. When pressure air or water is used for cleaning, wear a protective face shield, protective clothing, and protective shoes. The maximum air pressure for cleaning purposes must be below 205 kPa (30 psi). When you use a pressure washer, keep in mind that the nozzle pressures are high. The nozzle pressures are frequently above 13790 kPa (2000 psi). Follow all the recommended practices that are provided by the manufacturer of the pressure washer.

Inspection Procedure

Illustration 3	g03731215
View of inspection areas on the top side of the frame

Illustration 4	g03731217
View of inspection areas on the bottom side of the frame

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Illustration 5	g03729720
View of top of frame rail (A) distance between straight edge and 4 bar casting (B) Plate thickness (C) 150 mm (5.91 inch) (D) Toe of weld seam on rail side

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Illustration 6	g03732337
View of measurement locations across the frame rail (C) 150 mm (5.91 inch) (D) Toe of weld seam on rail side

1. Measure dimension (A) at three locations across the frame rail where dimension (A) is a minimum (or the high point on the cast surface) within the 150 mm (5.91 inch) region. Measure on both frame rails (left and right).

   Note: Use a plate that is at least 20 mm (0.79 inch) thick or more so that the straight edge is above the high spot of the casting.

2. Top Offset = B - A, if offset is greater than 5 mm (0.20 inch), proceed to the rework instructions.
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   Illustration 7	g03729743
   View of bottom of frame rail (B) Plate thickness (F) distance between straight edge and 4 bar casting

3. Measure dimension (F) at three locations across the frame rail on both sides of the frame.

4. Bottom Offset = F - B, if offset is greater than 5 mm (0.20 inch), proceed to the rework instructions.

Rework Procedures

Rework Procedure for Top of Frame Rail

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Illustration 8	g03729786
View of top of frame rail (A) 100 mm (3.94 inch) (B) 50 mm (1.97 inch) (C) Thickness measurement location 9 places (D) Toe of weld seam (E) 220 mm (8.66 inch) (F) 25 mm (0.98 inch) (G) 110 mm (4.33 inch) (H) 195 mm (7.68 inch)

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Illustration 9	g03729873
Example of thickness measurements

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NOTICE
Measurements should not be taken if the temperature of the part exceeds 93° C (200° F)

Note: Personnel that performing this inspection should be qualified to a minimum of a Level I for ultrasonic testing. Ensure that personnel performing inspections are qualified to perform calibration and interpretation of the acquired results. An ultrasonic inspection unit capable of calibration in the thickness range of 10 mm (0.40 inch) to 60 mm (2.40 inch) is needed. A 5 MHz, dual element transducer is required. The desired diameter is 12.7 mm (0.5 inch), but a large diameter transducer may be acceptable if the transducer can achieve good contact with the casting surface in the area. A standard UT flaw detector can be configured to check thickness with a straight beam transducer, or a flaw detector dedicated to thickness testing can be used.

Note: The instrument shall be calibrated using a two-point calibration. The calibration block shall have a minimum of 4 steps, with thicknesses that range from 10 mm (0.40 inch) to 12.7 mm (0.5 inch) through 50 mm (2.00 inch) to 60 mm (2.40 inch) (a 4-step block 12 mm (0.4724 inch), 24 mm (0.9449 inch), 36 mm (1.4173 inch), 50 mm (1.9685 inch) steps). The block used for the calibration shall have a letter of certification that is traceable through a serialized number to National Institute of Standards and Technology (NIST). The calibration procedure should be done according to the instructions in the equipment manual.

1. Identify the casting areas that require rework. Set up a grid pattern surrounding the area that will be removed. Refer to Illustrations 8 and 9.

2. Use Ultrasonic (UT) to measure the thickness of the rail, transition area, and 4 bar casting at nine locations (C).

3. Apply couplant to the grid area.

4. Place the transducer firmly on each grid point and observe the reading on the ultrasonic flaw detection unit. Reading for each grid point must be done in an organized manner.
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   Illustration 10	g03729879
   View of top of frame rail (E) 100 mm (3.94 inch) (F) 50 mm (1.97 inch) (G) 48 mm (1.90 inch) minimum (H) 50 mm (1.97 inch) (J) Material to be removed

5. Remove material (J) between the rail side toe and 150 mm (5.91 inch) on to the casting, by using a 36 grit or finer flexible sanding disc. A minimum thickness (G) of 48 mm (1.90 inch) must be maintained throughout this transition, material (J) may be thicker depending on the location of material (J) on the casting.

   Note: If a minimum of 48 mm (1.90 inch) cannot be maintained, submit a Dealer Service Network (DSN) ticket and reference this Special Instruction, REHS9555.

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   Illustration 11	g03729897
   View of top of frame rail finished profile (K) Transition to casting (L) 2 mm (0.08 inch) maximum gap (M) Transition to rail

6. Ensure that the transition to casting (K) and the transition to rail (M) have a larger radius greater than 50 mm (1.97 inch). The transitions should be smooth and free from any gouges.

   There should be no more than a maximum gap (L) of 2 mm (0.08 inch) between a straight edge placed along the slope and the ground profile (outside of the radius area).

Rework Procedure for Bottom of Frame Rail

System Pressure Release

For information on releasing the system pressure, refer to Operation and Maintenance Manual, SEBU8406, "System Pressure Release"

Component Removal From the Hydraulic Tank

1. Drain the hydraulic tank.
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   Illustration 12	g03730916
   Typical view of the backside of the hydraulic tank (A) Tube assembly (B) Tube assembly (C) Hydraulic tank

2. Remove and retain tube assemblies (A) and tube assemblies (B).
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   Illustration 13	g03730930
   Typical view of the backside of the hydraulic tank (D) Hose assembly (E) Hose assembly (F) Hose assembly (G) Hose assembly

3. Disconnect one end of hose assemblies (D), (E), (F), and (G). Once the hose assemblies are disconnected secure the hose assemblies out of way of the work area.

4. If more components interfere with accessing the bottom of the frame, remove and retain as needed.

Component Removal From the Fuel Tank

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Illustration 14	g03733311
Typical view of the backside of the fuel tank (H) Filter assembly (J) Bracket assembly (K) Shutoff valve

1. Close shutoff valve (K).

2. Remove and retain filter assemblies (H), bracket assembly (J), and hose assembly (K).

3. If more components interfere with accessing the bottom of the frame, remove and retain as needed.

   Note: Draining of the fuel tank may be required, if more components are removed.

Rework Procedure

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Illustration 15	g03729917
View of bottom of frame rail (A) Additional weld material (B) Over-fill with weld material past the bottom of rail (C) 4 bar casting (D) Rail

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NOTICE
Do not weld on the rail forward of weld joint

Note: Refer to Special Instruction, REHS7193, "Procedure for the Inspection, Repair, and Component Replacement on the Frame of the 793F, 793F AC, and the 793F Command For Hauling Off-Highway Trucks" for welding specifications.

1. Add additional weld material to area (A) on 4 bar casting (C) over fill area (B) past the bottom of rail (D). This area will be sanded later to a profile.
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   Illustration 16	g03729937
   View of bottom of frame rail (A) Additional weld material (B) Over-fill with weld material past the bottom of rail (C) 4 bar casting (D) Rail (E) Straight edge

2. Use a 36 grit of finer flexible sanding disc to remove weld material (A) until flush with the bottom surface of rail (D). Ensure that the finished profile is smooth with no gouges. Transition with casting should be smooth with a radius greater than 50 mm (1.97 inch).

3. Use straight edge (E) to ensure that weld is flush with bottom rail (D). There should be a maximum gap of 2 mm (0.08 inch) between straight edge (E) placed along rail (D) and the finished profile.
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   Illustration 17	g03729956
   View of completed repair to joint

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   Illustration 18	g03729957
   View of completed repair to joint

4. Illustrations 17 and 18 are examples of the completed weld.

Component Installation

1. Install any components removed and retained in the"Component Removal From the Hydraulic Tank"and the "Component Removal From the Fuel Tank" sections.

2. Fill the hydraulic tank and the fuel tank. Refer to Operation and Maintenance Manual, SEBU8406, "Capacities (Refill)"

   Note: Prior to starting the machine, refer to Special Instruction, REHS9546, "Procedure to Prime the Hydraulic System on Certain 793F Off-Highway Trucks."