Procedure to Rework Main Frames of Certain 422F, 428F, 432F, 434F, and 444F Backhoe Loaders {7054} Caterpillar

Introduction

This special instruction contains the procedure to rework the main frame of certain 422F, 428F, 432F, 434F, and 444F Backhoe Loaders.

Do not perform any procedure in this special instruction until you have read the information and you understand the information.

Safety Section

Show/hide table

Do not operate or work on this machine or work tool unless you have read and understand the instructions and warnings in the Operation and Maintenance Manuals and Owner's Manuals. Failure to follow the instructions or heed the warnings could result in injury or death. Contact your AVSpare dealer for replacement manuals. Proper care is your responsibility.

Show/hide table

Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the attachments have been lowered, and the oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.

Show/hide table

Escaping fluid under pressure, even a pinhole size leak, can penetrate body tissue, causing serious injury, and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

Show/hide table

Pressurized System! Hydraulic accumulators contain gas and oil under high pressure. DO NOT disconnect lines or disassemble any component of a pressurized accumulator. All gas pre-charge must be removed from the accumulator as instructed by the service manual before servicing or disposing of the accumulator or any accumulator component. Failure to follow the instructions and warnings could result in personal injury or death. Only use dry nitrogen gas to recharge accumulators. See your Cat dealer for special equipment and detailed information for accumulator service and charging.

1. Move the machine to a flat, level area that can support the weight of the machine.
   Show/hide table

   Illustration 1	g03352993

2. Shut down the machine and perform Lock Out Tag out procedure. Attach a "Do Not Operate" warning tag or similar warning to the start switch or the controls before attempting the installation procedure.

3. Move the control levers for the lift arms, implement, and travel to the full stroke positions. This movement will release any hydraulic pressure in the hydraulic lines.

   Refer to Disassembly and Assembly Manual, UENR2303, "System Pressure - Release" for more information.

4. Slowly loosen the fill/vent cap on the hydraulic system. This action will relieve pressure in the hydraulic tank.

Welding Requirements

Show/hide table

Personal injury or death can result from fumes, gases and ultraviolet rays from the weld arc. Welding can cause fumes, burn skin and produce ultraviolet rays. Keep your head out of the fumes. Use ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing area. Wear eye, ear and body protection before working. 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 cause death. Read and understand the manufacturer's instructions and your employer's safety practices. Do not touch live electrical parts. See "American National Standard Z49.1, Safety in Welding and Cutting" published by the American Welding Society. American Welding Society 2501 N.W. 7th Street Miami, Florida 33125 See "OSHA Safety and Health Standards, 29 CFR 1910", available from U.S. Department of Labor. U.S. Department of Labor Washington, D.C. 20210

Welding quality is critical to the success of the installation procedures. Welds must be smooth and continuous. Do not undercut the welds. No overlap is allowed. Grind the ends of the welds to a smooth radius.

Prepare the metal for welding according to "Preparing the Metal for Welding". Refer to the illustrations in this Special Instruction for welding symbols and specifications.

Use LB-26 Electrodes (AWS E7016 or AWS E7018) or equivalent electrodes to weld the boss assemblies to the stick assemblies. Basic welding wire ESAB OK tubrod 15.00 with a 1.2 mm (0.05 inch) diameter can also be used. The basic welding wire must be the equivalent to AWS A5.20 E71T-5 with positive polarity. The welding wire must be protected with CO2 gas.

All electrodes must be dry. The electrodes can be dried by heating the electrodes to 300°C (572°F). The electrodes must be dried for at least 30 minutes.

Do not weld in windy conditions. Do not weld when temperatures are below 16°C (60°F).

Penetration characteristics may vary greatly depending on the following conditions:

• Electrode diameter

• Shielding gas

• Welding current

• Plate thickness

The following items also affect the welds:

• Geometry of welded joints

• Surface conditions

• Composition of the base metal and of the electrode

A root pass should be applied before each weld is finished.

Maintain a 3 mm (0.12 inch) minimum root opening on all cross welds and circle welds.

All welds to the stick must be welded in the direction from the rear of the stick toward the front of the stick.

For more welding information, consult the AVSpare Service Welding Guide, SEBD0512.

Preparing the Metal for Welding

Show/hide table

Personal injury can result from flame cutting or welding on painted areas. The effect of gasses from burned paint is a hazard to the person doing the cutting or welding. Do not flame cut or weld on painted areas.

All grease, water, paint, rust, dirt, and scale must be removed before welding. Any of these materials will discharge gas which will cause porosity in the weld deposit. Water and rust will cause hydrogen embrittlement. Hydrogen embrittlement causes cracks in the weld deposit.

Remove paint, rust, dirt, and scale with a wire brush or by buffing or grinding. Shot blasting all work areas will also remove foreign material.

Remove any oil or grease with a AVSpare approved solvent.

Welding on Machines and Engines with Electronic Controls

Proper welding procedures are necessary in order to avoid damage to the electronic controls and to the bearings. The following steps should be followed in order to weld on a machine or an engine with electronic controls.

Note: If you are welding on a work tool, AVSpare recommends removing the work tool from the host machine before welding.

1. Turn off the engine.

2. Turn the battery disconnect switch to the OFF position. If there is no battery disconnect switch, remove the negative battery cable at the battery.

3. Clamp the ground cable from the welder to the component that will be welded. Place the clamp as close as possible to the weld. Make sure that the electrical path from the ground cable to the component does not go through any bearing. Use this procedure in order to reduce the possibility of damage to the following components:

   • Bearings of the drive train

   • Hydraulic components

   • Electrical components

   • Other components of the machine
   Show/hide table

   NOTICE
   Do NOT use electrical components (ECM or sensors) or electronic component grounding points for grounding the welder.

4. Protect any wiring harnesses from the debris which is created from welding. Protect any wiring harnesses from the splatter which is created from welding.

5. Use standard welding procedures in order to weld the materials together.

Machine Preparation

1. Place the machine on firm level ground in an area suitable for performing the rework procedure.

2. Turn off and remove the key from the battery isolator switch. This action will help protect the machine electronics during the welding procedures.

3. To aid in gaining access to the welds of the frame, other items will need to be removed. Remove the rear wheels and rear axle.

   Reference: UENR2303Disassembly and Assembly, Rear Axle - Remove.

   Show/hide table

   Illustration 2	g06018730
   (A) Tube

4. Remove filter to implement valve tube (A).
   Show/hide table

   Illustration 3	g06018734
   (B) Filter

5. Undo hydraulic oil filter (B) and secure the assembly out of harms way.
   Show/hide table

   Illustration 4	g06018738
   (C) Loader control valve (D) Ride control valve (if equipped) (E) Coupler valve hoses (if equipped) (F) Coupler control valve

6. Disconnect the four loader valve hoses connected to valve (C). Cap and tie back the hoses.

7. Remove ride control valve (D), if equipped.

8. Remove, cap, and reposition coupler hoses (E), if equipped. Then remove coupler control valve (F).

Rework Procedure

1. Clean the frame both inside and outside to ensure that the frame is free of dirt, oil, grease or any other debris.

2. Inspect the area carefully for any cracks that may have been missed on the original inspection.

   Note: If there are small cracks that have penetrated into the side plates (less than 50 mm (2 inch) long), the side plates should be repaired before completing the rest of the rework procedure.

   Note: If a crack in a side plate extends longer than 50 mm (2 inch), STOP and contact AVSpare BHL Product Support.

   Locate the crack and fully grind out the crack. If possible, grind 10 mm (0.4 inch) past the end of the visible crack.

3. Ensure that the crack has been fully removed by using a dye penetrant kit. If not, grind away more material and check again.

4. Grind the weld back so that the weld is flush with the parent metal.

   Once any small cracks have been repaired in the side plates, continue with the repair for the other welds.

   Note: The repair must be carried out in the correct sequence. This sequence is important to allow for cooling and prevent distortion of the frame.

5. Fully reweld the groove that has been made, proud of the parent material.

Inside Frame Rails

Show/hide table

Illustration 5	g06019076
View of inside frame (G) Area to remove

1. Working under the machine, remove all the weld between the side plate and bottom axle mounting plate of the frame on the left-hand inside using an 8 mm (0.315 inch) diameter air arc carbon electrode at around 500 Amps.

2. Under the machine, remove all the weld between the side plate and bottom axle mounting plate of the frame on the right-hand inside using an 8 mm (0.315 inch) diameter air arc carbon electrode at around 500 Amps.
   Show/hide table

   Illustration 6	g06019150
   (H) 30 mm (1.181 inch) (J) 80 mm (3.150 inch) (K) 115 mm (4.528 inch) (L) Groove 8 mm (0.315 inch)

3. Using the air arc tool, prepare a bevel or J-groove (L) in the left-hand inner side plate. Refer to Illustration 6 for the four locations to place the bevel.

4. Repeat the bevel groove in the right-hand inner side plate.

5. Ensure that all slag and carbon deposits are removed from the area.
   Show/hide table

   Illustration 7	g06019178
   View of inside frame rail (M) Area to weld

6. Fully weld the 8 mm (0.315 inch) weld preparations that have been made on the left-hand inside frame rail using one of the two following methods:

   1. MAG Weld: 1.2 diameter wire inclined-vertical, 22 V 130-140 amps horizontal-vertical 28-30 V 260-280 amps.

   2. Stick/Arc Weld: inclined-vertical 130-140 Amps, 3.2 mm (0.126 inch) diameter low hydrogen electrode, horizontal-vertical 250-280 Amps, 5 mm (0.197 inch) diameter electrode.

7. Minimize any stop-starts to ensure weld strength.

8. Repeat on the right-hand inside frame rail.

9. Ensure that all slag and carbon deposits are removed from the area.

Use the following procedure to reweld insideof the rails.

Note: Following the sequence is critical to allow cooling and prevent distortion in the frame.

Illustration 8	g06019220
View of both inside frame rails

Refer to Illustration 8 for the location of each weld pass. The welds should start at the outside edge of the rail, and end at the top/center of the rail. Avoid any welding stops until you are at the center of the frame.

1. Weld a 10 mm (0.394 inch) fillet on the left-hand inside frame rail for the first pass (first and second welds).

2. Weld a 10 mm (0.394 inch) fillet on the right-hand inside frame rail for the first pass (third and fourth welds).

3. Weld a 10 mm (0.394 inch) fillet on the left-hand inside frame rail for the second pass (fifth and sixth welds).

4. Weld a 10 mm (0.394 inch) fillet on the right-hand inside frame rail for the second pass (seventh and eighth welds).

   Both sides of the frame on the inside are now repaired.

Outside Frame Rails

Before starting any welding or cutting on the outside of the frame, temporarily refit the rear axle to the machine:

1. Attach the axle to the frame using the inside bolts only. Tighten the bolts to a specified torque of 460 N·m (340 lb ft).
   Show/hide table

   Illustration 9	g06019251

2. Install a C-clamp between the frame and the axle on the outside for the frame. Refer to Illustration 9 for clamp placement.

   Note: This action is important so the frame is not distorted during the next welding procedure.

   Note: The axle must be flat to the frame during and after this repair.

   Note: The repair must be carried out in the correct sequence. This sequence is important to allow for cooling and prevent distortion of the frame.

   Show/hide table

   Illustration 10	g06019274
   View of outside frame rail (N) Area to remove

3. Working under the rear fenders, remove all the weld between the side plate and bottom axle mounting plate of the frame on the left hand outside using an 8 mm (0.315 inch) diameter air arc carbon electrode at around 500 amps.

4. On the opposite side of the machine, remove all the weld between the side plate and bottom axle mounting plate of the frame on the right hand outside using an 8 mm (0.315 inch) diameter air arc carbon electrode at around 500 amps.
   Show/hide table

   Illustration 11	g06019530
   (H) 30 mm (1.181 inch)

5. Using the air arc tool, prepare an 8 mm (0.315 inch) bevel or J-groove at locations (H) in the left-hand outer side plate. The bevel or J-groove should be made according to the dimensions shown in Illustration 11.

6. Repeat the 8 mm (0.315 inch) bevel or J-groove in the right-hand outer side plate around the radius.

7. Ensure that all slag and carbon deposits are removed from the area.
   Show/hide table

   Illustration 12	g06019178
   View of inside frame rail (M) Area to weld

8. Fully weld the 8 mm (0.315 inch) weld preparations that have been made on the left-hand outside frame rail using one of the two following methods:

   1. MAG Weld: 1.2 diameter wire inclined-vertical, 22 V 130-140 amps horizontal-vertical 28-30 V 260-280 amps.

   2. Stick/Arc Weld: inclined-vertical 130-140 Amps, 3.2 mm (0.126 inch) diameter low hydrogen electrode, horizontal-vertical 250-280 Amps, 5 mm (0.197 inch) diameter electrode.

9. Minimize any stop-starts to ensure weld strength.

10. Repeat on the right-hand outside frame rail.

11. Ensure that all slag and carbon deposits are removed from the area.

Use the following procedure to reweld outside of the rails.

Note: Following the sequence is critical to allow cooling and prevent distortion in the frame.

Illustration 13	g06019220
View of both sides of the frame rails

Refer to Illustration 8 for the location of each weld pass. The welds should start at the outside edge of the rail, and end at the top/center of the rail. Avoid any welding stops until you are at the center of the frame.

1. Weld a 10 mm (0.394 inch) fillet on the left-hand outside frame rail for the first pass (first and second welds).

2. Weld a 10 mm (0.394 inch) fillet on the right-hand outside frame rail for the first pass (third and fourth welds).

3. Weld a 10 mm (0.394 inch) fillet on the left-hand outside frame rail for the second pass (fifth and sixth welds).

4. Weld a 10 mm (0.394 inch) fillet on the right-hand outside frame rail for the second pass (seventh and eighth welds).

   Both sides of the frame on the outside are now repaired.

5. Remove the rear axle from the machine.

Final Assembly

1. Ensure any burnt paint, weld slag, carbon deposits and any other oil or debris are removed before repainting the repaired area.
   Show/hide table

   Illustration 14	g06020420
   View of outside frame

   Show/hide table

   Illustration 15	g06020412
   View of inside frame

2. Repaint all repaired areas using an etch primer and high gloss Cat yellow paint.

1. Install the rear axle, and reinstall the components that were removed at the start of the repair.

   Reference: Refer to UENR2303Disassembly and Assembly, Rear Axle - Install for correct method and torque setting for the rear axle.

2. Purge the brakes after the hoses have been refitted.

3. Lower the machine to the ground, check for leaks and correct operation.