Procedure to Ultrasonic Test (UT) the Rear Axle Housing of the 795F AC Off-Highway Truck{0599, 0700, 0722, 3260, 3260, 3260} Caterpillar

Off-Highway Truck:

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

795F AC (S/N: SNT1-UP)

Introduction

The following procedure provides the method used to ultrasonic test the 795F AC Off-Highway Truck 286-8072 Axle Housing casting for cracks (≥ 5 mm (0.20 inch) in depth and > 25 mm (0.98 inch) in length) on the inside and outside surface of the casting near the bottom of the axle housing.

References

• ASTM E 317

• ASNT-TC-1A

Important Safety Information

Do not perform any procedure in this special instruction until you have read this special instruction and you understand this information. Use only proper tools and observe all precautions that pertain to the use of those tools. Failure to follow these procedures can result in personal injury. The following procedures should also be observed.

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 in order 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 the tools, the procedure, the work method, or your actions are not recommended by Caterpillar, ensure that the tools and your actions are safe for you and for others.

Ensure that the product will not be damaged or the product will be made unsafe by the operation, lubrication, maintenance, or the repair procedures.

Follow all safety warnings. Most accidents that involve product operation, maintenance, or repair are caused by failure to observe safety warnings. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. Personnel shall be properly trained in order to perform maintenance, repair, or operate any machine. Safety precautions and warnings are provided this instruction and on Caterpillar products. These warnings should be observed before performing any procedures. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. The warnings in this publication and on the product are not all inclusive.

The hazards are identified by the "Safety Alert Symbol" which is followed by a "Signal Word" such as "DANGER", "WARNING" or "CAUTION". The "WARNING" Safety Alert Symbol is shown in Illustration 1.

Illustration 1	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.

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.

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Sudden movement or accidental starting of the machine can cause personal injury or death to persons on or near the machine. To prevent personal injury or death, perform the following: Park the machine on a smooth, level surface. Lower the work tool to the ground and engage the parking brake. Stop the engine and remove the key. Block the wheels and install the steering frame lock.

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When it is necessary to work under the machine with the body (bed) raised, attach the body (bed) retaining cables to the rear tow points. Install the rear tow point pins through the ends of the retaining cables. Failure to properly secure the body (bed) may result in personal injury or death.

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Hot oil and hot components can cause personal injury. Do not allow hot oil or hot components to contact skin. At operating temperature, the engine coolant is hot and under pressure. Steam can cause personal injury. Check the coolant level only after the engine has been stopped and the cooling system pressure cap is cool enough to touch with your bare hand. Remove the cooling system pressure cap slowly to relieve pressure. Cooling system conditioner contains alkali. Avoid contact with the skin and eyes to prevent personal injury.

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When a hoist is used to lift any part or assembly, stand clear of the area under the part being raised. Always make sure that the hoist has adequate lifting capacity and the wire cable is not damaged. Failure to follow this instruction could lead to injury or death. Approximate weights of the components are shown in the table which follows.

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Do not check for leaks with your hands. Pin hole (very small) leaks can result in a high velocity oil stream that will be invisible close to the hose. This oil can penetrate the skin and cause personal injury. Use cardboard or paper to locate pin hole leaks.

Note: If the procedure is performed at a Caterpillar facility, safety glasses with side shields, hearing protection, bump hats, and steel-toed safety shoes shall be required. Any grinding operations need to have full face shield, long sleeve shirt, and face mask. Consult HM100 screen or read the Material Safety Data Sheet, MSDS, for hazard information on materials used in this procedure.

Required Tools

Note: The instrument used for this procedure shall be a GE USM GO, GE USN 58L, or equivalent flaw detector with the DAC/TCG option. The instrument shall have a current record for having been calibrated for vertical and horizontal linearity to ASTM E317 or NDEOP 102.

Note: The straight beam search unit shall consist of either a 9.53 mm (0.375 inch) or 12.70 mm (0.5 inch), 2.25 MHZ transducer.

Note: The angle beam search unit shall consist of a small 45 degree wedge coupled to either a 9.53 mm (0.375 inch) diameter, 2.25 MHZ transducer, or a 12.70 mm (0.5 inch) diameter, 2.25 MHZ transducer.

Note: The couplant shall be Sonic Gel 80, Soundclear Grade 60, or equivalent.

Note: The material velocity of the calibration blocks shall be set using an IIW block (either type I or type II).

Calibration Blocks

Distance Calibration Block

The material velocity, refracted angle, etc. shall be set using a IIW block (either type I or type II) or equivalent type distance calibration block.

Casting Reference Block

Illustration 2	g03787473
View of casting reference block

A piece of actual casting has been cut to a manageable size and notches with depths of 5 mm (0.20 inch) and 1 mm (0.039 inch) have been cut on the inside diameter of the casting to mimic a crack. Refer to Illustration 2.

Qualifications

Personnel performing the inspections will be at least Level II Certified Technicians in the appropriate method, as defined by ASNT-TC-1A or MH-4000. Personnel performing the inspections will be trained by a Level II or III, until displaying sufficient proficiency and understanding of the procedure and rejection criteria.

Surface Preparation

The outside diameter of the casting surface shall be made accessible and clean in the area of interest. Any material that may interfere with the transmission of sound energy from the transducer into the casting shall be removed. (Loose paint, grease, dirt, oil, scale, etc.)

Test Procedure

Straight Beam Calibration

Calibrate the instrument for distance using a steel IIW Type Block to a range of 100 mm (3.94 inch) using both the 25 mm (0.98 inch) and 100 mm (3.94 inch) thickness feature.

The parts nominal thickness should be 35 mm (1.38 inch) but may vary from 30 mm (1.18 inch) to 45 mm (1.77 inch).

Angle Beam Calibration

Calibrate the instrument for distance using a steel IIW Type Block to a range of 100 mm (3.94 inch) using both the 50 mm (1.97 inch) and 100 mm (3.94 inch) radius features.

The refracted angle shall be with in ± 2 degrees from the marked 45 degree wedge.

Critical Instrument setting: Range 100 mm (3.94 inch), part thickness 35 mm (1.38 inch), and Gate A Threshold.

Sensitivity/DAC Calibration

Illustration 3	g03787551

Calibrate for sensitivity using the Casting Reference Block shown in Illustration 3, Illustration 4, and Illustration 5.

Illustration 4	g03787558
View of search unit placement location (A)

Place 45 degree search unit on the casting reference block at the location shown in Illustration 4 to reflect the 5 mm (0.20 inch) depth notch at the bottom of the first leg.

Peak the signal from the 5 mm (0.20 inch) notch and adjust the gain to 80 percent Full Screen Height (FSH). Save this location as the first DAC point. Refer to Illustration 4.

Illustration 5	g03787578
View of search unit placement location (B)

Place 45 degree search unit on the casting reference block at the location shown in Illustration 5 to reflect the 5 mm (0.20 inch) depth notch at the top of the second leg.

Peak the signal from the 5 mm (0.20 inch) notch do not adjust the gain. Save this indication as the second DAC point. Refer to Illustration 5.

Inspection Procedure

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Illustration 6	g03787610
(A) Inspection zones (B) Suspected crack orientation (C) Internal rib (D) 355 mm (13.98 inch) (E) Motor mounts (F) 600 mm (23.62 inch) (G) UT scanning directions (H) Spindle face to spindle face

1. Using the Straight Beam Calibration inspect the areas shown in Illustration 6.

   The intent is to inspect for cracks on the internal and external surfaces of the casting with suspected crack orientation (B) .

2. Increase the gain +12db and use this gain for initial scanning only. Remove the additional 12db gain when applying the rejection criteria.

3. Scan the entire area shown in Illustration 6 with the 45 degree transducer in both directions while oscillating ± 10 degrees from parallel to the long axis of the part.

   Note: Ensure 10 percent overlap on each scan path for full coverage.

4. Care should be taken when inspecting near internal ribs (C).

   Internal ribs (C) can be marked on the part for reference. Measure from the bottom center hole both left and right, and make reference marks at 355 mm (13.98 inch) the ribs thickness is around 30 mm (1.18 inch). These measurements will provide the approximate location of internal ribs (C) .

   Note: UT indications from the geometry of internal ribs (C) may appear near the depth of the 35 mm (1.38 inch) casting thickness on the UT instrument. Illustration 10 shows the indications that may be seen on internal rib (C) area.

5. Care should also be taken when inspecting near internal motor mounts (E) cast features as shown in Illustration 6. Depending on scanning direction these casting features will give geometry indications as well as difficulty utilizing the second leg inspection for cracks on the outside surface of the casting.

6. All indications should be measured out and the location confirmed by scanning in the opposite direction to ensure that an actual discontinuity is present.

   Note: Thickness inspections should be conducted in any area that an indication is found. Use Straight Beam Thickness Calibration.

Rejection Criteria

Reject any relevant indications that cross the DAC threshold continuously for 25 mm (0.98 inch) or greater at reference level and are found in the area of interest. Refer to Illustration 8 for an example of the 5 mm (0.20 inch) saw cut indications.

Determine the Length of a Discontinuity

1. In order to determine the length of the UT indications, the 6dB Drop/50% Drop method shall be used for indication sizing.

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Illustration 7	g03787868

2. From one end of the indication, scan until the signal peak drops to 50 percent of the reject threshold and repeat on the opposite end of the indication. As shown in Illustration 7.

3. Record relevant indications found that do not meet the DAC reject threshold of Gate A but have a continuous length greater than 50 mm (1.97 inch).

4. Monitor the casting during the next scheduled service for indication growth.

Reference UT Indications

Illustration 8	g03787888
Example UT indication from the 5 mm (0.20 inch) notch

Illustration 10 shows the UT indication from a 5 mm (0.20 inch) deep saw cut from the same side of the reference block.

Illustration 9	g03787893
Example of UT indication from 5 mm (0.20 inch)

Illustration 10 shows the UT indication from a 5 mm (0.20 inch) deep saw cut from the opposite side of the reference block.

Illustration 10	g03787895
Example of UT indications from internal rib (A) No indication when inspecting from the opposite direction (B) Rib radius will show indications thicker than 35 mm (1.38 inch) nominal (C) Same transducer location

Illustration 10 shows a UT geometry indication from the internal rib.

Reporting

Illustration 11	g03787920

Report any rejected castings to Product Support Engineering for disposition. Use the inspection map shown in Illustration 11 to report location of indications.

If possible, provide inspection reports with photographs that clearly show UT instrument information and transducer location.