- Off-Highway Truck/Tractor:
- 793D (S/N: FDB1-UP)
Introduction
This Special Instruction will provide the information required to update the accumulator mounting group on certain 793D Off-Highway Trucks.
Three scenarios are possible when performing this Special Instruction. Verify the machine serial number in order to follow the correct rework procedure.
| Serial Numbers | Rework Procedure Required |
| S/N:FDB1-1216 | Refer to Special Instruction, REHS4430, "Upgrade Procedure For The 793D Off-Highway Truck Steering Accumulator" for upgrading to piston accumulators. |
| S/N:FDB1217-1692 | Refer to ""Rework Procedure for Updating the Accumulator Group Clamps and Bracket Assembly" ". |
| S/N:FDB1693-UP | Refer to ""Rework Procedure for Updating the Accumulator Group Clamps" ". |
Safety
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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. |
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Dry nitrogen is the only gas approved for use in the accumulators. The charging of oxygen gas in an accumulator will cause an explosion. An explosion can be eliminated by using nitrogen gas cylinders with standard CGA (Compressed Gas Association, Inc.) No. 580 connectors. When nitrogen gas is ordered, make sure to order the cylinders with CGA No. 580 connectors. Do not rely on color codes or other methods of identification to tell the difference between nitrogen and oxygen cylinders. In any application, never use an adapter to connect your nitrogen charging group to a valve outlet used on both nitrogen, oxygen, or other gas cylinders. BE SURE YOU USE DRY NITROGEN (99.8% purity). |
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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 by reading and understanding 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 instructions of the manufacturer and the safety practices of your employer. Do not touch live electrical parts. See "American National Standard Z49.1, Safety in Welding and Cutting" which is published by the American Welding Society. American Welding Society8669 NW 36 Street #130 Miami, Florida 33166-6672 1-800-443-9353 See "OSHA Safety and Health Standards, 29 CFR 1910" which is available from the U.S. Department of Labor. U.S. Department of LaborWashington, D.C. 20210 See applicable requirements for your local area. |
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Personal injury or death can occur from heavy components falling during removal or installation. Properly support the component with a suitable lifting device during removal or installation. |
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Do not operate or work on this machine unless you have read and understand the instructions and warnings in the Operation and Maintenance Manual. Failure to follow the instructions or heed the warnings could result in injury or death. Contact any Caterpillar dealer for replacement manuals. Proper care is your responsibility. |
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Parts Required
| Parts Required | ||
| Qty | Part Number | Description |
| 1 | 214-7566 | O-Ring Seal |
| 4 | 228-7093 | O-Ring Seal |
| 3 | 238-5084 | O-Ring Seal |
| 1 | 324-8906 | Plate As |
| 6 | 469-9340 | Clamp |
| 1 | 474-6698 | Bracket As |
| 12 | 8T-4184 | Bolt |
| 12 | 8T-4194 | Bolt |
| 24 | 198-4778 | Hard Washer |
Prepare the Machine
Note: Permit only one person on the machine. Either keep others away from the machine, or keep other personnel in the sight of the operator.
- Move the machine to a smooth horizontal location. Move away from any machines that are working and any personnel.
- Move the transmission control to the PARK position.
- Stop the engine
- Place blocks in front of the wheels and behind the wheels.
Rework Procedure for Updating the Accumulator Group Clamps and Bracket Assembly
Note: Rework procedure for S/N:FDB1217-1692.
Parts Required
| Parts Required | |||
| Item | Qty | Part Number | Description |
| 1 | 1 | 324-8906 | Plate As |
| 2 | 2 | 474-6698 | Bracket As |
| 3 | 12 | 8T-4184 | Bolt |
| 4 | 24 | 198-4778 | Hard Washer |
| 5 | 6 | 469-9340 | Clamp |
| 6 | 12 | 8T-4194 | Bolt |
| 7 | 4 | 228-7093 | O-Ring Seal |
| 8 | 3 | 238-5084 | O-Ring Seal |
| 9 | 1 | 214-7566 | O-Ring Seal |
- Discharge the pressure in the accumulators. Refer to Special Instruction, REHS5464, "Accumulator Discharging and Charging Procedures" for the correct accumulator discharge procedure.
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| Illustration 1 | g03845689 |
(A) pressure switch Assembly | |
- Disconnect pressure switch assembly (A) .
- Disconnect O-Ring tee (B), stem assembly (C), elbow adapter (D) .
Note: The two hose assemblies attached to O-Ring tee (B) may be removed individually. If the hoses are removed individually, an additional O-Ring will be required during reassembly. See Step 19 for details.
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| Illustration 2 | g03848919 |
(B) O-Ring Tee (C) Stem Assembly (D) Elbow Adapter | |
- Secure O-Ring tee (B), stem assembly (C), elbow adapter (D) out of the way.
- Remove and discard bolts (E) and washers (F) .
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| Illustration 3 | g03845700 |
(E) Bolt (D) Washer (G) Clamp (H) Accumulator Group | |
Note: The weight of each accumulator is approximately 118 kg (260. lb). Handle the accumulators individually using a suitable lifting device for both removal and installation procedures.
- Remove and discard clamps (G) and lift accumulators (H) from the machine.
- Remove and retain clip (J) and clip (K) .
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| Illustration 4 | g03845707 |
(J) Clip (K) Clip (L) Hose (M) Hose | |
- Secure hose (L) and hose (M) away from the rework area.
- Use a suitable tool to cut plate assembly (N) off the frame assembly.
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| Illustration 5 | g03846219 |
(N) Plate Assembly | |
- Grind the frame assembly smooth and clean off any dirt, oil, or debris.
- Position plate assembly (1) as shown in Illustration 7 and Illustration 6.
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| Illustration 6 | g03846327 |
(1) Plate Assembly (T) 358.1 mm (14.1 inch) | |
- Weld all the way around plate (1) as shown in Illustration 6.
- Clean up the work area and paint as needed.
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| Illustration 7 | g03846299 |
View A (1) Plate Assembly (P) 105 mm (4.1 inch) (Q) 254 mm (10 inch) (R) 214 mm (8.4 inch) | |
- Install bracket assembly (2) to upper plate assembly and existing lower plate assembly using 12 bolts (3) and 12 washers (4) and tighten to a torque value of 100 ± 20 N·m (73.8 ± 14.8 lb ft).
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| Illustration 8 | g03846482 |
(2) Bracket Assembly (3) Bolt (4) Washer | |
- Reinstall hose assembly (L) and hose assembly (M) .
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| Illustration 9 | g03847855 |
(M) Hose (L) Hose | |
- Individually reinstall accumulators (H) with stickers and fill fittings facing outwards.
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| Illustration 10 | g03846719 |
(H) Accumulator Group (5) Clamp (6) Bolt (4) Washer | |
- Secure six clamps (5), 12 bolts (6) and 12 washers (4) .
- Tighten bolts (6) to a torque value of 100 ± 20 N·m (73.8 ± 14.8 lb ft).
- Reinstall O-Ring tee (B) with one new O-Ring seal (7) and one new O-Ring seal (8) .
Note: If the two hose assemblies were removed instead of O-Ring tee (B), reassembly will require two O-Ring seals (7) .
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| Illustration 11 | g03847213 |
(B) O-Ring Tee (C) Stem Assembly (D) Elbow Adapter (7) O-Ring Seal (8) O-Ring Seal | |
- Reinstall stem assembly (C) with one new O-Ring seal (7) and one new O-Ring seal (8) .
- Reinstall elbow adapter (D) with one new O-Ring seal (7) and one new O-Ring seal (8) .
- Reinstall pressure switch assembly (A) with a new O-Ring seal (9) .
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| Illustration 12 | g03847519 |
(A) pressure switch Assembly (9) O-Ring Seal | |
- Charge the pressure in the accumulators. Refer to Testing and Adjusting, RENR8336, "Steering Accumulator - Test and Charge" for the correct accumulator charge and test procedure.
Rework Procedure for Updating the Accumulator Group Clamps
Note: Rework procedure for S/N:FDB1693-UP.
Parts Required
| Parts Required | |||
| Item | Qty | Part Number | Description |
| 1 | 2 | 474-6698 | Bracket As |
| 2 | 12 | 8T-4184 | Bolt |
| 3 | 24 | 198-4778 | Hard Washer |
| 4 | 6 | 469-9340 | Clamp |
| 5 | 12 | 8T-4194 | Bolt |
| 6 | 3 | 228-7093 | O-Ring Seal |
| 7 | 3 | 238-5084 | O-Ring Seal |
| 8 | 1 | 214-7566 | O-Ring Seal |
- Discharge the pressure in the accumulators. Refer to Special Instruction, REHS5464, "Accumulator Discharging and Charging Procedures" for the correct accumulator discharge procedure.
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| Illustration 13 | g03847975 |
(A) pressure switch Assembly | |
- Disconnect pressure switch assembly (A) .
- Disconnect O-Ring tee (B), stem assembly (C), elbow adapter (D) .
Note: The two hose assemblies attached to O-Ring tee (B) may be removed individually. If the hoses are removed individually, an additional O-Ring will be required during reassembly. See Step 12 for details.
 | |
| Illustration 14 | g03848080 |
(B) O-Ring Tee (C) Stem Assembly (D) Elbow Adapter | |
- Secure O-Ring tee (B), stem assembly (C), elbow adapter (D) out of the way.
- Remove and discard bolts (E) and washers (F) .
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| Illustration 15 | g03848101 |
(E) Bolt (F) Washer (G) Clamp (H) Accumulator Group (J) Plate Assembly | |
- Remove and discard clamps (G) and lift accumulators (H) from the machine.
- Secure bracket assembly (1) to the upper and lower plate assemblies using 12 bolts (2) and 12 washers (3) as shown in Illustration 16.
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| Illustration 16 | g03848109 |
(1) Bracket (2) Bolt (3) Washer | |
- Tighten bolts (2) to a torque of 100 ± 20 N·m (73.8 ± 14.8 lb ft).
- Individually reinstall accumulators (H) with stickers and fill fittings facing outwards.
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| Illustration 17 | g03848106 |
(4) Clamp (5) Bolt (3) Washer (H) Accumulator Group | |
- Secure six clamps (4), 12 bolts (5) and 12 washers (3) .
- Tighten bolts (5) to a torque value of 100 ± 20 N·m (73.8 ± 14.8 lb ft).
- Reinstall O-Ring tee (B) with one new O-Ring seal (6) and one new O-Ring seal (7) .
Note: If the two hose assemblies were removed instead of O-Ring tee (B), reassembly will require two O-Ring seals (6) .
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| Illustration 18 | g03848537 |
(B) O-Ring Tee (C) Stem Assembly (D) Elbow Adapter (6) O-Ring Seal (7) O-Ring Seal | |
- Reinstall stem assembly (C) with one new O-Ring seal (6) and one new O-Ring seal (7) .
- Reinstall elbow adapter (D) with one new O-Ring seal (6) and one new O-Ring seal (7) .
- Reinstall pressure switch assembly (A) with a new O-Ring seal (8) .
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| Illustration 19 | g03848541 |
(A) pressure switch Assembly (8) O-Ring Seal | |
- Charge the pressure in the accumulators. Refer to Testing and Adjusting, RENR8336, "Steering Accumulator - Test and Charge" for the correct accumulator charge and test procedure.