Reuse and Salvage Guideline on 794 AC and 795F AC/XQ Retarder Group {1437, 1627, 3121, 425R} Caterpillar

Mining Truck

794 AC (S/N: HRT1-UP)

Off-Highway Truck/Tractor

794 AC (S/N: MN51-UP; MT51-UP)

795F AC (S/N: ERM1-UP)

795FAC XQ (S/N: SNT1-UP)

Introduction

© 2019 Caterpillar All Rights Reserved. This guideline is for the use of Cat dealers only. Unauthorized use of this document or the proprietary processes therein without permission may be violation of intellectual property law.

Information contained in this document is considered Caterpillar: Confidential Yellow.

This Reuse and Salvage Guideline contains the necessary information to allow a dealer to establish a parts reusability program. Reuse and salvage information enables Caterpillar dealers and customers to benefit from cost reductions. Every effort has been made to provide the most current information that is known to Caterpillar. Continuing improvement and advancement of product design might have caused changes to your product which are not included in this publication. This Reuse and Salvage Guideline must be used with the latest technical information that is available from Caterpillar.

For technical questions when using this document, work with your Dealer Technical Communicator (TC).

To report suspected errors, inaccuracies, or suggestions regarding the document, submit a form for feedback in the Service Information System (SIS Web) interface.

Canceled Part Numbers and Replaced Part Numbers

This document may include canceled part numbers and replaced part numbers. Use the Numerical Part Record (NPR) on the Service Information System Website (SIS web) or Next Generation SIS (NGS) for information about canceled part numbers and replaced part numbers. NPR will provide the current part numbers for replaced parts.

Important Safety Information

Illustration 1	g02139237

Work safely. Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools to perform these functions properly. Safety precautions and warnings are provided in this instruction and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. Therefore, the warnings in this publication and the warnings that are on the product are not all inclusive. If a tool, a procedure, a work method, or operating technique that is not recommended by Caterpillar is used, ensure that it is safe for you and for other people to use. Ensure that the product will not be damaged or the product will not be made unsafe by the operation, lubrication, maintenance, or the repair procedures that are used.

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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.

Safety precautions and warnings are provided in this manual and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons.

The hazards are identified by the “Safety Alert Symbol” which is followed by a “Signal Word” such as “DANGER”, “WARNING” or “CAUTION”. Refer to Illustration 2 for an example of a “WARNING” Safety Alert Symbol.

Illustration 2	g00008666

This safety alert symbol means:

Pay Attention!

Become Alert!

Your safety is Involved.

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

Operations that may cause product damage are identified by "NOTICE" labels on the product and in this publication.

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. Also, determine that the operation, lubrication, maintenance, and repair procedures will not make the machine unsafe.

The information, the specifications, and the illustrations that exist in this guideline are based on information which was available at the time of publication. The specifications, torques, pressures, measurements, adjustments, illustrations, and other items can change at any time. These changes can affect the service that is given to the product. Obtain the complete, most current information before you start any job. Caterpillar dealers can supply the most current information.

Summary

This guideline provides the procedures necessary to determine the reusability of the Retarder Group used on 794 AC and 795 AC/XQ Off-Highway Trucks. Life will vary depending on application, load, lubrication, and environment.

This guideline contains the latest standards of engineering, which will help minimize owning and operating costs. A part is expected to reach the next Planned Component Rebuild (PCR) if the part meets the specifications within this guideline and the part is intended for a similar application. Use this guideline to determine whether a part should be reused. Do not install a part that is not reusable. During reconditioning, correct any condition that might have caused the original failure.

The dimensions and tolerances provided are to return a part / component to specification. The dimensional information alone is not solely used to condemn a part from reuse. Follow visual inspections and the "Crack Detection Methods" section for further guidance.

References

Service Advisories, Service Letters, and Technical Service Bulletins

Tooling and Equipment

Note: The Tooling and Equipment in Table 3 is not an all inclusive list of Tooling required to perform every task within this document. Tooling needs may vary for scope of work to be performed for each specific rebuild.

Preparation Recommendations

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Personal injury can result when using cleaner solvents. To help prevent personal injury, follow the instructions and warnings on the cleaner solvent container before using.

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Personal injury can result from air pressure. Personal injury can result without following proper procedure. When using pressure air, wear a protective face shield and protective clothing. Maximum air pressure at the nozzle must be less than 205 kPa (30 psi) for cleaning purposes.

Note: Clean exterior of the retarder group prior to disassembly to minimize cross-contamination.

• Before you inspect a part, clean the part thoroughly to ensure that all components are free from rust, oil, burrs, and debris prior to inspection. A surface irregularity can hide the indication of an unacceptable defect.

• Use a proper lifting device to provide safety to the operator. Also, use a proper lifting device to prevent damage to the part when you lift the part.

• During cleaning, do not damage machined surfaces.

• Do not use pressurized air to dry internal components. Compressed air has moisture and contaminants that can cause premature failure of internal components.

• Put hydraulic oil on all machined surfaces to prevent rust or corrosion if inspection is not done immediately after cleaning. Carefully store the parts in a clean container.

• Inspect all flange mating surfaces for fretting. Ensure that flange mating surfaces are true and free from raised material resulting from rust, nicks, and dents.

• Use appropriate thread taps to chase all threaded holes.

Standardized Parts Marking Procedure

Reference: SEBF8187Reuse and Salvage Guidelines, "Standardized Parts Marking Procedures".

The code is a Cat standard and is used to record the history of a component. The code will identify the number of rebuilds and hours at the time of each rebuild. This information is important and should be considered for any decision to reuse a component.

Ensure that the mark is not covered by a mating part.

Illustration 3	g06124077
DO NOT use numbering stamp punches to mark internal components.

The procedure for marking components is a Cat standard. This code is helpful when the machine is sold into a different territory after the first rebuild. During an overhaul, the previous code of a part should never be removed.

Example 1

Illustration 4	g03856853
Typical Example

Illustration 4 shows code (1-15). The first number (1) indicates that the gear had been rebuilt once. The second number (15) indicates that there were 15,000 hours on the gear at the time of rebuild.

Example 2

Illustration 5	g03856857
Typical Example

Illustration 5 shows code (1-12) and code (2-10). Code (2-10) represents the information from the second rebuild. The first number (2) indicates that the gear had been rebuilt twice. The second number (10) indicates that 10,000 hours accumulated on the gear between the first and second rebuild.

Note: Add the first and second rebuild hours to obtain the total number of hours for the gear in Illustration 5. In this example, the gear has a total of 22,000 hours.

Example 3

Illustration 6	g03519882
Typical Example

(A) Mark the planet pin on either end using a metal marking pen.

Retarder Group Nomenclature

Illustration 7	g06244219
Retarder group exploded view, components removed for clarity. Stator and shaft not pictured. Note: 434-5149 Stator Assembly and shaft not pictured. (1) Insulator (2) Metal Element (3) Electric Retarder Group (Grid Element) (4) Electric Motor Group (Cooling Retarding) (5) Inlet Screen (6) Grid Support Structure

Visual Inspection Before Disassembly

Clean the retarder group grid support structure (6) prior to inspection. Ensure that all grease, dirt, debris, and loose paint has been removed from the retarder group grid support structure. Use a wire brush to remove any remaining scale or oxidation. Grease, dirt, debris, and loose paint can hinder the inspection process. Refer to "Crack Detection Methods" section.

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Illustration 8	g06237805
Retarder Group Grid Support Structure Inspection Areas (inlet side) (A) Grid Support Structure Area Inspect Fillet Weld (B) Grid Support Structure Area Inspect Fillet Weld (C) Grid Support Structure Area Inspect Fillet Weld

1. Inspect fillet welds (A), (B), and (C) for damage and cracks.
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   Illustration 9	g06237829
   Retarder Group Grid Support Structure Inspection Areas (outlet side) (D) Grid Support Structure Area Inspect Fillet Weld (E) Grid Support Structure Area Inspect Fillet Weld

2. Inspect fillet welds (D), and (E) for damage and cracks.

   Note: If weld repairs are required, refer to , SEBD0512 Reuse and Salvage Guidelines , "Caterpillar Service Welding Guide".

3. Inspect all bolts. Replace broken, damaged, or missing bolts with original Caterpillar parts. Refer to , SEBF8727 Reuse and Salvage Guidelines , "Specifications for Inspection of Driveline Fasteners".

4. The (4) electric motor group (cooling retarding) mounting bolts may need replaced if an update has not been completed prior to this reusability inspection. Refer to the "Retarder Grid Blade Assembly Mounting Bolt Update (As required)" section.

Replacement Grid Support Structure Components (Now Available)

Caterpillar now offers grid support structure replacement components. Refer to Illustration 10 for examples and part numbers.

Illustration 10	g06415057
Grid Support Structures (F) 574-1143 Mount As (G) 574-0906 Mount

Grid Elements

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Illustration 11	g06238214
(F) Serial Number Plate Location (G) Serial Number (H) Resistor As. - Power (TAPPED) Grid Element part number

1. Record the serial number and part number of the 4 grid elements.
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   Table 4

   Resistor Assembly - Power Grid Element Part Number Possibilities
   Resistor Assembly - Power Grid Element (Untapped) Quadrant 1, 3, 4	Qty.	Resistor Assembly - Power Grid Element (Tapped) Quadrant 2	Qty.
   317-0676	3	317-0677	1
   383-8342	3	383-8343	1
   452-6806	3	452-6807	1

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   Illustration 12	g06247754
   Quadrant locations (inlet side)

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   Illustration 13	g06415204
   Example of normal (1) insulator wear. OK TO USE THIS PART AGAIN

2. Inspect (1) insulator for damage. No action required, OK TO USE THIS PART AGAIN.
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   Illustration 14	g06413134
   Example of moderate (1) insulator wear. OK TO USE THIS PART AGAIN, however life is reduced.

3. Inspect the (1) insulator for damage. Insulator can be reused, however life is reduced, and failure is expected prior to the next Planned Component Rebuild (PCR).
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   Illustration 15	g06413155
   Example of element (tabs) not constrained. DO NOT USE PART AGAIN (1) Insulator (2) Metal Element (tabs)

4. Inspect the (2) metal element (tabs) , ensure that the metal elements (tabs) are fully constrained by the (1) insulator . If damage is found, replace the entire electric retarder group (grid element).
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   Illustration 16	g06413175
   Example of (1) insulator excessive wear. DO NOT USE PART AGAIN (1) Insulator

5. Inspect the electric retarder group (1) insulator for excessive wear. If excessive wear is found, replace the electric retarder group entire (grid element).
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   Illustration 17	g06413188
   Example of excessive insulator spacing. DO NOT USE PART AGAIN (1) Insulator

6. This inspection step is for non retained insulator grids only. Push all the (1) insulators in one electric retarder group (grid element) to one side. Measure the distance from the first (1) insulator to the second (1) insulator . The distance should be 25.40 mm (1 inch) or less. If the distance is more than 25.40 mm (1 inch), replace the entire electric retarder group (grid element).

   Note: On retained insulator grids, there should not be any movement of the insulators. Replace the entire grid element if insulator movement has been identified.

7. Inspect the (1) insulator for exposed glass fibers, fiberglass resin baked off. If exposed glass fibers, or fiberglass resin baked off, replace the entire electric retarder group (grid element). Refer to Illustration 16 for examples of exposed glass fibers, fiberglass resin baked off, and excessive wear.

8. Inspect the (1) insulator for cracks or missing chunks. Cracks or missing chunks are an indication that the electric retarder group (grid element) needs to be replaced.

   Note: If damage is found, replace the entire electric retarder group (grid element) with the proper part number. The latest grid elements with retained (1) insulators for improved life are 452-6806 electric retarder group or 452-6807 electric retarder group.

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   Table 5

   Insulation Resistance Test Specification from the Grid Element Terminal to the Frame Ground
   2 Mohm @ 2500 volts for 1 minute

9. Use the 349-4206 insulation tester to perform the insulation resistance test from the grid element terminal to the frame ground.

10. Apply megger at 2500V, 2 Mohm is the minimum acceptable value when the element is dry. Refer to Table 5 for the Megger specifications.

    Note: If the grid element is below the minimum resistance, check that the element is dry. Check for foreign matter on or in between the elements attempt to clean with dry air and repeat the test.

Metal Elements

Illustration 18	g06413393
(2) Metal element without deformation. OK TO USE PART AGAIN

1. Illustration 18 is an example of an electric retarder group (2) metal element without deformation.

2. Inspect each of the four electric retarder group metal element.
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   Illustration 19	g06413399
   (2) Metal element with deformation and waviness. DO NOT USE PART AGAIN

3. Look for deformation, and waviness of the (2) metal element.
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   Illustration 20	g06413402
   (2) Metal element with arc damage. DO NOT USE PART AGAIN

4. Inspect the (2) metal element for arc damage, bubbles, and drips.

   Note: If damage is found, replace the entire electric retarder group (grid element) with the proper part number. The latest grid elements with retained insulators for improved life are 452-6806 electric retarder group or 452-6807 electric retarder group.

Insulation Resistance Test (Megohmmeter)

Illustration 21	g03683397
Example of 349-4206 Insulation Tester.

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Personal injury or death can result from electrocution. The megohmmeter is applying a high voltage to the circuit. To avoid electrocution, do not touch the instrument leads without first discharging them. When finished testing also discharge the generator windings.

Stator

1. Perform the stator winding insulation resistance test by measuring between any phase connection and the frame of the retarder grid. Use the insulation tester to perform the stator winding insulation resistance test.

2. The stator winding insulation resistance test should last for a minimum of 1 minute.

3. Apply megger phase at 1000 volts, 2 Mohm is the minimum acceptable value.
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   Table 6

   Insulation Resistance Test Specification
   2 Mohm @ 1000 volts for 1 minute

   Note: The stator must pass the Insulation Resistance Test to determine if the stator can be reused. Motors that may be wet or contaminated can indicate an Insulation Resistance < 2 Mohms. If the Insulation Resistance test fails close to the threshold, but does not indicate a direct short, attempt to dry the motor out using a forced air heater and retest. After visual inspections and electrical tests are complete, determine the reusability of the retarder grid motor. If tests have passed, then proceed to disassemble. Refer to KENR8727 Disassembly & Assembly, "795F AC and 795F AC XQ Off-Highway Truck Machine Systems" and , UENR2271 Disassembly & Assembly, "794 AC Off-Highway Truck Machine Systems". Refer to the Electric Retarder Grid Disassemble section. Another possible cause of a low resistance reading could be the cables running from the stator and in-line splices. The cables should be insulated from the ground, then repeat the test.

4. If the stator has a low resistance, then replace the stator with 434-5149 stator assembly. The new stator assembly includes the shaft with bearing installed on the shaft.

Stator Inspection & Repair After Cleaning

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Personal injury can result from air pressure. Personal injury can result without following proper procedure. When using pressurized air, wear a protective face shield and protective clothing. Maximum air pressure at the nozzle must be less than 205 kPa (30 psi) for cleaning purposes.

1. Clean the Stator with compressed air.

2. Measure the bearing seat internal diameters in the stator after the shaft with bearings has been removed. Refer to Table 7 for the dimensions.
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   Table 7

   Bearing Bore Diameter
   Large Bore Diameter	Small Bore Diameter
   149.99 mm (5.905 inch) to 150.02 mm (5.906 inch)	109.99 mm (4.330 inch) to 110.02 mm (4.33 inch)

3. If the stator is severely damaged, has a low resistance to the shaft, or has bearing seats that do not meet the inside diameter requirements then replace with 434-5149 stator assembly. The new stator assembly includes the shaft with bearing installed on the shaft. If only the smaller bearing seat is out of tolerance a longer shaft is available that gives a second place for the smaller bearing to be mounted and the stator can be reused. Purchase the 565-5145 shaft for this capability.

4. Inspect the high-voltage leads from the stator for:

   • Damaged or burnt insulation

   • Arcing or overheating

5. Winding insulation should be examined for evidence of degradation or damage, such as:

   1. Puffiness, cracking, separation, or discoloration as an indication of thermal aging

   2. Contamination of wire and connection surfaces

   3. Evidence of partial discharge (corona)

   4. Abrasion or other mechanical stresses

   5. Fretting at supports, bracing, or crossings (an indication of looseness or movement)

6. Inspect the insulation for wear, repair with insulation wrap as needed.

7. If the bearing bores measure within reusable tolerances:

   1. Have the stator redipped (shaft and bearings removed and the machined surfaces protected).

   2. Use a class H rated epoxy compatible resin (Elantas PDG B9-116 recommended).

   3. Vertical cure and bake as required per resin data-sheet instructions.

   4. Retest insulation with megger and Hipot (Motor is a 480 volts AC rated motor).

   5. Replace the electrical insulation on the electrical splice joints from the motor winding to the Red/Blue/White cables (as detailed in KENR8727 Disassembly & Assembly, "795F AC and 795F AC XQ Off-Highway Truck Machine Systems" and , UENR2271 Disassembly & Assembly, "794 AC Off-Highway Truck Machine Systems". Refer to the Electric Retarder Grid Assemble section).

      • Wrap with Electrical insulation tape (Rated for 600 volts AC).

      • Finish with new fiber sleeves for mechanical protection wrapped with tape to secure.

Blade Assembly

1. Inspect the inner diameter Die-cast Aluminum area for cracks.

2. Inspect each blade for nicks or other damage.
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   Illustration 22	g06240761
   Blade Assembly

   Note: Replace entire blade assembly if any damage is found. Replacement blade assembly part number is 434-5144 blade assembly.

3. Prior to installation of a used blade assembly thoroughly clean inside the blade assembly to remove all dirt. The blade assembly is a factory balanced component and the additional dirt causes imbalance.

Blade Assembly Mounting Bolts

1. At minimum all blade assembly mounting bolts should be torqued to 111 N·m (82 lb ft) to verify that the bolts are torqued to the proper specification.

2. Another option is to replace ALL the blade assembly mounting bolts with original Caterpillar parts. Replace one bolt at a time to ensure that the blade assembly is still in balance after replacement of the hardware.

   • Up to quantity of 24 bolts, part number 8T-9389 Bolt grade (8) 1/2-13 x 2.5 inch. (match old bolt length)

   • Up to quantity of 24 bolts, part number 7X-0325 Bolt grade (8) 1/2-13 x 2.75 inch. ( match old bolt length)

   • Quantity of 48 washers, part number 5P-1076 Hard Washer.

   • Quantity of 24 locknuts, part number 1K-6872 Locknut.

   • Use Locktite 263 to secure the locknut.

Cabling

1. Inspect the electrical cabling from grid element 2 to the terminal box for damage, repair as needed.

2. Inspect the electrical cabling from grid blade assembly motor to the terminal box for damage, repair as needed.

Blade Assembly Motor Bearings

• Quantity of 1 bearing, part number 434-5147 Ball Bearing.

• Quantity of 1 bearing, part number 434-5148 Ball Bearing.

• Loctite 620

• Loctite 242

Tracking or Markings

Illustration 23	g06241139
Retarder Grid Identification Plates (J) Element Identification Plate (K) Fan Identification Plate (L) Grid Identification Plate

1. Record serial numbers of grid, blade assembly, and each element before the unit is returned to the customer.

2. Add a marking/nameplate to the grid to indicate that Planned Component Rebuild (PCR) was completed.

Retarder Grid Blade Assembly Mounting Bolt Update (As required)

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Illustration 24	g06241507
Retarder grid (1) weld nuts location

1. With a 12.70 mm (0.5 inch) 8T-4835 bolt check that all 5 grid fan mounting bolts (1) are the larger size 12.70 mm (0.5 inch) 8T-4835 bolt. Earlier grids, were built with smaller grid blade assembly mounting bolt weld nuts and need to be updated at PCR. If the 12.70 mm (0.5 inch) 8T-4835 bolt fits in to all 5 mounting holes, then no rework is required for the grid blade assembly mounting bolt locations.

   Note: Only if the grid blade assembly mounting holes do not accept a 12.70 mm (0.5 inch) 8T-4835 bolt must the following be done:

2. Remove the (1) weld nuts from the grid blade assembly support structure. After weld nut removal, use a grinder to remove the paint and any remaining weld material around the existing hole. Ensure that the surface is flat to accommodate the new weld nut.
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   Illustration 25	g06241560
   Grid Support Structure (cross section) (M) Enlarged hole for weld nut (N) Depth of enlarged hole for weld nut (P) Grid support structure

3. Enlarge each of the 5 holes (M) in the grid support structure (P) to 19.05 mm (0.75 inch). The enlarged hole depth (N) in the grid support structure (P) is to be 6.35 mm (0.25 inch). Refer to Illustration 25.
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   Illustration 26	g06241575
   Grid support structure (cross section) (P) Grid Support Structure (R) 8T-5911 Weld Nut (S) Fillet Weld

4. Insert the new 8T-5911 weld nut (R) into each of the five holes with the smaller diameter to be placed in the recessed area of the hole. Ensure that the weld nut is resting flat on the grid support structure.

5. Weld each of the 5 weld nuts (R) to the grid support structure (P). Refer to the , SEBD0512 Reuse and Salvage Guidelines , "Caterpillar Service Welding Guide".
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   Illustration 27	g06241614
   Electric Motor Group (grid fan) and grid support structure bolt hardware orientation for bolts 1, 3, and 5. (6) Grid Support Structure (R) 8T-5911 Weld Nut (4) Electric Motor Group (grid fan) (5) Inlet Screen (V) 8T-4835 Bolt (W) 292-3198 Hard Washer (X) 8T-4821 Washer

6. Assemble the retarder grid, refer to , KENR8727 Disassembly and Assembly , "795F AC and 795F AC XQ Off-Highway Truck Machine Systems" assembly section for the electric retarder grid.

   Note: New bolt hardware is required at five modified locations.

7. Assemble the (V) bolt , (W) hard washer , (5) inlet screen , (X) washer , electric motor group (grid fan) (4), and (6) grid support structure as oriented in Illustration 27.
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   Illustration 28	g06241619
   Electric Motor Group (grid fan) and grid support structure bolt hardware orientation for bolts 2, and 4. (6) Grid Support Structure (R) 8T-5911 Weld Nut (4) Electric Motor Group (grid fan) (5) Inlet Screen (V) 8T-4835 Bolt (W) 292-3198 Hard Washer (X) 8T-4821 Washer

8. Assemble the (V) bolt , (W) hard washer , (X) washer, (5) inlet screen , (4) electric motor group (grid fan) , and (6) grid support structure as oriented in Illustration 28.

9. Assemble the retarder group, refer to , KENR8727 Disassembly and Assembly , "795F AC and 795F AC XQ Off-Highway Truck Machine Systems" assembly section for the electric retarder grid.

Crack Detection Methods

There are four major crack detection methods or Non-Destructive Testing (NDT) listed in this section: Visual Surface Inspection (VT), Liquid Penetrant Testing (PT), Dry and Wet Magnetic Particle Testing (MPT).

Crack detection methods or NDT methods for testing components for cracks without damaging the component. VT, PT, and Dry/ Wet MPT are methods recommended. There may be more than one acceptable crack detection method for the testing of a given part, although PT is the most versatile. For example, the PT method can be used when testing smooth machined components such as cylinder rods and pistons, but using the Wet MPT is more accurate. Refer to Table 8 for advantages and disadvantages and Table 9 for standards and requirements for these NDT methods.

Visual Surface Inspection (VT)

Illustration 29	g06124166
Example of Visual Surface Inspection (VT) Tooling (A) Flashlight (or adequate light source) (B) Magnifying Glass (C) Tape Measure (or other measuring device) (D) Inspection Mirror

Refer to Tooling and Equipment Table 3 for part numbers.

Components and welds that are to be tested using PT, or MPT shall first be subject to a Visual Surface Inspection (VT). VT is often the most cost-effective inspection method and requires little equipment as seen in Illustration 29. Personnel performing VT shall either be trained to a company standard or have sufficient experience and knowledge regarding the components being inspected. Personnel performing VT shall take routine eye exams.

Liquid Penetrant Testing (PT)

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Personal injury can result from improper handling of chemicals. Make sure you use all the necessary protective equipment required to do the job. Make sure that you read and understand all directions and hazards described on the labels and material safety data sheet of any chemical that is used. Observe all safety precautions recommended by the chemical manufacturer for handling, storage, and disposal of chemicals.

Materials and Equipment Required

Refer to Tooling and Equipment Table 3 for part numbers.

• Cleaner: Removes dirt before dye application and dissolves the penetrant making possible to wipe the surface clean.

• Penetrating Oil: This solution is highly visible, and will seep into openings at the surface of a part with capillary action.

• Developer: Provides a blotting action, bringing the penetrant out of the discontinuities and providing a contrasting background to increase the visibility of the penetrating oil indications.

• Wire Brush: Removes dirt and paint.

• Cloth or Wipes: Use with cleaner and for other miscellaneous uses.

Procedure

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Illustration 30	g06103795
Typical example of pre-cleaning the testing area.

1. Preclean the area to be tested. Spray on cleaner/ remover to loosen any scale, dirt, or any oil. Wipe the area to be tested with a solvent dampened cloth to remove remaining dirt and allow the area to dry. Remove paint where there are visible cracks using paint remover or a wire brush.
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   Illustration 31	g06103803
   Typical example of applying penetrating oil to areas to be tested.

2. Apply penetrant by spraying the entire area to be tested. Allow 10 to 15 minutes for penetrant to soak. After the penetrating oil has been allowed to soak, remove the excess penetrating oil with clean, dry wipe.
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   Illustration 32	g06103816
   Typical example of removing penetrating oil with a cloth.

3. The last traces of penetrating oil should be removed with the cleaner solvent dampened cloth or wipe. Allow the area to dry thoroughly.
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   Illustration 33	g06103820
   Typical example of applying the developer.

4. Before using developer, ensure that the developer is mixed thoroughly by shaking the container. Hold the container approximately 203 - 305 mm (8.0 - 12.0 inch) away from the testing area. Apply an even, thin layer of developer over the testing area. A few thin layers are a better application method than one thick layer.
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   Illustration 34	g06084042
   Typical example of cracks found during Liquid Penetrant Testing (PT).

5. Allow the developer to dry completely for 10–15 minutes before inspecting for cracks. Defects will show as red lines in white developer background, refer to Illustration 34. Clean the area of application of the developer with solvent cleaner.

Dry Magnetic Particle Testing (MPT)

Materials and Equipment Required

Refer to Tooling and Equipment Table 3 for part numbers.

Illustration 35	g06085930
(A) Indications shown by Dry Magnetic Particle Testing (MPT). (B) Electromagnetic Yoke (C) Dry Powder Bulb

1. Dry magnetic powder shall be of high permeability and low retentively and of suitable sizes and shapes to produce magnetic particle indications. The powder shall be of a color that will provide adequate contrast with the background of the surface being inspected.

2. Dry magnetic particles shall be stored in suitable containers to resist contamination such as moisture, grease, oil, non-magnetic particles such as sand, and excessive heat. Contaminants will manifest in the form of particle color change and particle agglomeration. The degree of contamination will determine further use of the powder.

3. Dry magnetic powder shall be tested in accordance with ASTM E709 Section 18 (Evaluation of System Performance/Sensitivity) when not performing.

4. Equipment should include a "U" shaped electromagnetic yoke made from highly permeable magnetic material, which has a coil wound around the yoke. This coil carries a magnetizing current to impose a localized longitudinal magnetic field into the part. The magnetizing force of the yoke is related to the electromagnetic strength and can be tested by determining the lifting power of a steel plate. The yoke shall have a lifting force of at least 4.5 kg (10 lbs).

5. Check dry powder blower routinely to ensure that the spray is a light, uniform, dust-like coating of the dry magnetic particles. Blower should also have sufficient force to remove excess particles without disturbing those particles that are evidence of indications.

6. All equipment shall be inspected at a minimum of once a year or when accuracy is questionable.

Procedure

1. Ensure surface to be inspected is dry and free from oil, grease, sand, loose rust, mil scale, paint, and other contaminants.

2. Apply the magnetic field using the yoke against the faces and inside diameter of each bore.

3. Simultaneously apply the dry powder using the dry powder blower.

4. Remove excess powder by lightly blowing away the dry particles.

5. Continue around the entire circumference of each bore. Position the yoke twice in each area at 1.57 rad (90°) to ensure that multiple directions of the magnetic field are created.

6. Observe particles and note if any clusters of particles appear revealing an indication.

7. Record the size and shape of any discontinuities or indications found.

Wet Magnetic Particle Testing (MPT)

Materials and Equipment

Refer to Tooling and Equipment Table 3 for part numbers.

Illustration 36	g06085937
(A) Indications shown by Wet Magnetic Particle Testing (MPT). (B) Electromagnetic Yoke (D) Ultraviolet Lamp

Illustration 37	g06003178
Pear Shaped Centrifuge Tube

1. Wet magnetic particles are fluorescent and are suspended in a vehicle in a given concentration that will allow application to the test surface by spraying.

2. Concentration:

   1. The concentration of the suspended magnetic particles shall be as specified by the manufacturer and be checked by settling volume measurements.

   2. Concentrations are determined by measuring the settling volume by using an ASTM pear shaped centrifuge tube with a 1 mL (0.034 oz) stem with 0.05 mL (0.0017 oz) divisions, refer to Illustration 37. Before sampling, the suspension shall be thoroughly mixed to assure suspension of all particles, which could have settled. A 100 mL (3.40 oz) sample of the suspension shall be taken and allowed to settle for 30 minutes. The settling volume should be between 0.1 mL (0.0034 oz) and 0.25 mL (0.0085 oz) in a 100 mL (3.40 oz) sample.

   3. Wet magnetic particles may be suspended in a low viscosity oil or conditioned water.

   4. The oil shall have the following characteristics:

      • Low viscosity not to exceed 5 mm²/_s (5 cSt) at any temperature at which the vehicle is to be used.

      • Low inherent fluorescence and be non-reactive.

   5. The conditioning agents used in the conditioned water shall have the following characteristics:

      • Impart good wetting characteristics and good dispersion.

      • Minimize foaming and be non-corrosive.

      • Low viscosity shall not exceed a maximum viscosity of 5 mm²/_s (5 cSt) at 38° C (100° F).

      • Non-fluorescent, non-reactive, and odorless.

      • Alkalinity shall not exceed a pH of 10.5.

3. Equipment should include a "U" shaped electromagnetic yoke made from highly permeable magnetic material, which has a coil wound around the yoke. This coil carries a magnetizing current to impose a localized longitudinal magnetic field into the part. The magnetizing force of the yoke is related to the electromagnetic strength and can be tested by determining the lifting power of a steel plate. The yoke shall have a lifting force of at least 4.5 kg (10 lbs).

Procedure

1. Ensure surface to be inspected is dry and free from oil, grease, sand, loose rust, mil scale, paint, and any other contaminants.

2. Apply the magnetic field using the yoke against the surface in the area to be inspected.
   Show/hide table

   Illustration 38	g03536210

3. For case hardened and ground surfaces:

   • Due to the sensitivity required to locate the grinding cracks, inspection of case hardened and ground surfaces require that the yoke is applied so that the magnetic field is 1.57 rad (90°) to the expected direction of the indications. Also, due to the increased sensitivity resulting when the yoke is energized, the yoke is not moved until the evaluation is completed in the first direction. An AC yoke shall be used. See Illustration 38 for an example of yoke placement.

4. Visually inspect for indications of discontinuities using the proper illumination.

5. Record the size and shape of any discontinuities found.