- Engine
- 3054 and 3056
- 3200
- 3300
- 3400
- 3400 All, 3300 All, 3200 All, 3100 All, 3000 All, and D-series All
- 3500 and G3500 Engines
- All 3600 Engines
- All C280 Engines
- All Marine Propulsion, Marine Auxiliary, and Marine Generator Sets
- C-10 All
- C-9 and C9 All
- C11 All
- C12 and C-12 All
- C13 and C-13 All
- C15 and C-15 All
- C16 and C-16 All
- C175 Engines
- C18 and C-18 Engines
- C27 Engines
- C32 Engines
- C4.4 Engines
- C6.6
- C7 All
- C7.1
- 3200
Introduction
This is an example of a good AFA report. Please review the notes that explain how each section of this report adequately communicates the information necessary for a proper failure analysis. (Notes are indicated by a box with bolded text at the beginning of each section.)
| Contains all expected information related to customer name, vessel name, serial number, engine hours, dealer work order number. |
| Customer: ABC Co. | |
| Date: March 14th, 2013 | Failure Date: February 28th, 2013 |
| Failed Part Number: |
Hours in Service: 761 |
| Engine Model: 3512C | Engine Serial Number: NJT00XXX |
Section 1
| Contains expected summary of complaint and high-level failure description. |
Parts Received:
Failure on Diesel Engine #1, powering ABC Co. locomotive #1359. Failed parts were removed and brought to dealer A for analysis.
Condition Upon Receipt:
Injector from cylinder #7 had broken into two main sections, the body and the solenoid.
Section 2
| Contains reasonable pertinent history, observations, and facts, including environmental and adjustment observations, SOS report results, pertinent historic maintenance practices, and well-articulated findings of failed parts. Timeline builds story of what failed first. High-quality pictures of pertinent related components with reasonable observations included in subsequent pages. |
Facts:
The engine cylinder #7 was not functioning. The cylinder #7 valve cover had a hole, which was punched out from the inside. There was fuel and engine oil on the floor, walls, and ceiling of the locomotive engine room. The engine oil level was overfull due to fuel contamination. An oil analysis reported 19.44% fuel dilution of the engine oil. There was a higher than average metal particle count in the oil filter media. Removal of the valve cover revealed the cylinder #7 injector was severely damaged. The injector hold-down bolt had broken, allowing the injector to lose its seating ability. Only the injector rocker arm kept the injector from escaping through the valve cover. The injector from cylinder #7 had broken into two main sections, the body and the solenoid. The injector solenoid was badly hammered and rounded from bouncing around under the valve cover. Eventually, the solenoid punched a hole in the valve cover.
The valve cover was also damaged inside from the injector rocker arm adjustment screw, which had turned to reach its highest point possible. The adjustment screw locknut was found to be loose, which allowed the adjustment screw to turn freely, and slowly work its way higher and higher. As the adjustment screw was backing out, this caused more clearance between the injector rocker arm and its injector. The injector hold-down bolt could not tolerate the additional and continuous stresses, first the head of the bolt broke off, and then the bolt broke again in the threaded area. The head of the bolt broke off due to a stress-related fatigue fracture. The broken threaded area of the bolt was a ductile fracture. Both of these bolt fractures indicate high stress. Since the injector was now free to continuously rebound in its bore, damage to the injector body and bore of the cylinder head were inevitable. The injector bore of the cylinder head was pounded and damaged. The #7 cylinder head must be replaced.
The 11 remaining valve covers were removed to verify the valve lash and injector adjustments. The 0.044” valve lash measured on the exhaust valve from cylinder #10, slightly exceeded Caterpillar’s 0.040” +/- 0.003” specification. All the injector height adjustments on the remaining 11 cylinders were within tolerances. The torque of the 11 remaining locknuts for the injector rocker arm adjusting screws was validated. The locknut on injector rocker arm #12 was torqued to 79 lb/ft, which is 10 lb/ft under the 89 lb/ft spec, but within the minimum +/- 11 lb/ft tolerance.
The ABC Co. maintenance division had verified the valve lash and injector adjustments in February 2013, during the 250-500 hour inspection. On the ABC Co. completed form titled “Inspection 250-500 hrs, employee # 179923 performed the “inspect/adjust” of the valve lash and injector height. The technician signed and dated the form Feb.13th, 2013. There was no indication on the form whether the valve lashes and injectors were readjusted or not. It is not necessary to loosen the injector rocker arm locknut if the injector height is only being validated, this locknut is loosened only if the injector height is readjusted.
Oil sample taken from this engine on Feb. 5th, 2013 showed normal wear, and no unusual amounts of metal particles in the oil. On July 19th, 2011, Bill’s Service Corp. (third-party service provider) checked all valve lashes and injector heights, then readjusted them back to Caterpillar’s exact specifications. The adjustment for injector #7 was found to be 64.46 mm, and was reset to 64.34 mm at that time. The injector’ adjustment screw locknut would have been loosened and then retorqued at that time.
Section 3
| Contains multiple possible root causes which are reasonable and based upon facts. |
List of Possible Root Causes of Failure
- The locknut of the #7 injector rocker arm adjustment screw was not torqued adequately during the ABC Co. valve lash and injector adjustment, completed two weeks earlier. Therefore, the adjustment screw changed positions and created excess rocker arm to injector clearance.
- The locknut on the #7 injector rocker arm adjustment screw was not sufficiently torqued by Bill’s Service Corp., during the valve lash and injector adjustments on July 19th, 2011. This locknut became loose and allowed the adjustment screw to change position and create excess rocker arm to injector clearance.
Section 4
| Proper summary of facts gathered articulate most likely root cause of failure. Additional steps/limiting information is also articulated. |
The Root Cause:
Utilizing the facts made available to Caterpillar, the clear cause of this failure was insufficient torque on the lock nut for the #7 injector rocker arm adjusting screw. The broken injector hold-down bolt, plus the failure of the #7 injector and the #7 cylinder head are collateral damage.
The root cause would be how this locknut became loose, at the time of this report, the root cause has not yet been determined. This is due to the limited information supplied to Caterpillar by the ABC Co. maintenance division, who confirmed that the valve lash and injector height had been verified, two weeks prior to the final failure.
If Bill’s Service Corp. had incorrectly torqued the locknut for the #7 injector rocker arm adjustment screw, the ABC Co. verification of the injector adjustments may have revealed this issue. If this injector height was adjusted by ABC Co., then the locknut in question was improperly torqued by the ABC Co. technician.
Further investigation is required.
Section 5
| Conclusion of root cause clearly stated. Dealer contact/reference information provided for further questions/requests. Summary of repairs included. |
Summary:
Additional photos available upon request.
Bill's Service Corp. readjusted the #7 injector height when the engine had 0-1 hour. This fact indicates that there was no manufacturer defect in material or workmanship involved in the root cause of failure.
Repair Process: Cylinder head replaced with new injector and properly torqued/adjusted.
Investigation Completed By:
Joe Marine
Cat Dealer
Technical Communicator
Photos
- Valve cover from cylinder # 7, ventilated by the injector solenoid. Red circle at the right of the photo shows where the locknut of the injector rocker arm adjustment screw contacted the valve cover, while backing out of the rocker arm.
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Illustration 2 g06098819 - Valve cover removed, the injector was loose and injector solenoid was badly pounded. Locknut on injector rocker arm adjustment screw was loose, and this adjustment screw had backed out as high as could possibly go.
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Illustration 3 g06098813 - Injector #7 and related parts.
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Illustration 4 g06098835 - Injector #7 rocker arm, upper surface of adjustment screw locknut fretting inside the valve cover.
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Illustration 5 g06098839 - Injector pushrod gouged out underside of the rocker arm after the adjustment screw backed out as far as possibly could.
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Illustration 6 g06098866 - The loose injector damaged underside of injector rocker arm.
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Illustration 7 g06098891 - Spalling on injector rocker arm foot, damaged after the adjustment screw backed out and the clearance between this foot and the injector became excessive.
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Illustration 8 g06098894 - Broken injector #7 hold-down bolt with detached head, stress fatigue fracture.
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Illustration 9 g06098898 - Head of injector hold-down bolt. The red arrows point to bolt some of the multiple ratchet marks which indicate high stress.
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Illustration 10 g06098901 - Contact damage to cylinder head # 7, caused by the loose injector. The remaining threaded section of injector hold-down bolt still in the head.
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| Illustration 1 | g06098816 |
