ENGINEERING - Royal Australian Navy

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N A VY E N G I N E E R I N G B U LL E TI N F E B RU A RY 2 00 2 2 1 The forward gudgeon pin circlip was located in the sump. It is suspected that the circlip used in the overhaul did not have sufficient surface contact, and that the design deviates significantly from the original equipment manufacturer (OEM) intended circlip. The circlip had been deformed (see Figure 5) and shows that it had minimum surface contact with the gudgeon pin. Metal around the circlip boss area on the liner side of the circlip has been displaced. The nature of the metal removal suggests that the boss area of the piston has been fretted and cracked away allowing the circlip to dislodge. The gudgeon pin also shows evidence of fretting against the circlip (see Figure 6). The aft gudgeon pin is still in situ. There is no evidence of fretting with the gudgeon pin and the cylinder boss area remains intact. The circlip used for the aft retaining mechanism on the g u d geon pin had an incre a s e d s u rface area contact comp a red to the one used on the fo rwa rd end. This allowed increased re ta i n i n g c o n tact with the gudgeon pin. Metal particulate impact damage was noted on the crown and side of the second s tage piston. forward gudgeon pin. The hypothesised mode of failure is as follows: • The forward circlip frets against the piston boss area from repeated impact from the gudgeon pin; • The boss area on the cylinder breaks away allowing the circlip to dislodge; • The forward circlip binds with the cylinder liner, jamming the first stage piston; • The conrod continues to drive into the cylinder shattering the first stage piston; • The shattered piston drops into the sump, however the compressor continues to run at a reduced output level (15 bar); and • The drop in output is noted and the compressor shut down for investigation. CO NC LU S I O N S The Port MAC was rebuilt during the Maintenance Availability and set to work. The maintenance and operation of the MAC could not be attributed to the failure of the MAC. The spectrographic oil analyses conducted prior to the failure indicate that there was no abnormal wear or lubricating oil problems. The conclusions from th e i nve st i gation are that the Po rt M AC suffe red a cata st ro p h i c The Port MAC, even with this significant damage, continued to run with the second stage piston imparting a system pressure of 15 bar. The standby compressor was required to regain system pressure. The conclusions indicate that the cause of the failure can be attributed to the failure of the forward retaining circlip on the first stage piston. FIGURE 4 FIRST STAGE BIG END BEARING SHELL BOTTOM FIGURE 5 FORWARD GUDGEON PIN CIRCLIP The fi rst sta ge piston gudge o n pin securing device (circ l i p ) did not have adequ a te mating s u rface area. Fragments of metal were found in close proximity to this area however the size and type of fragments indicate that this damage was most probably sustained through carry over from the fir st stage failure. FA I LURE MODE The root cause and primary failure has been attributed to the fa i l u re. The fi rst sta ge pisto n g u d geon pin securing dev i c e ( c i rclip) did not have adequ a te mating surface area. The circ l i p f re t ted and cra cked its housing, d i s l o d ged, and became bound w i th the fi rst sta ge cylinder l i n e r. The connecting ro d i mposed sufficient fo rces to s c o re the liner and shatter th e p i ston assembly. FIGURE 6 FORWARD CIRCLIP BOSS AREA
2 2 N A VY E N G I N E E R I N G B UL LE T I N FE B R U A RY 2 00 2 BY LIEUTENANT DANNY ELSTOB, RAN Fleet Intermediate Maintenance Activity This article is the next in the series on “What does MHQ’s Engineering Division do?” In the previous edition of the Bulletin, CMDR Damien Allan outlined the work of the Fleet Marine Engineering and Fleet Hull Engineering sections. This article aims to give the reader an insight into the goings on at the Fleet Intermediate Maintenance Activity (FIMA). BELOW DARWIN NAVAL BASE – HOME TO FIMA DARWIN As technology changes along with <strong>Navy</strong> culture, we are seeing an ever-increasing trend of smaller ship’s companies and increased requirement for ships to be available for sea. This has established a requirement to provide increased uniformed maintenance support, particularly at the Intermediate Level. This support includes, but is not limited to, maintenance, personnel interchanges or substitutes and training. It is important that Intermediate Level Maintenance (ILM) resources are used efficiently and effectively. FIMA is the organisation responsible for this resource management role. FIMA is primarily comprised of five Fleet Maintenance Activity Elements. These elements are physically located in Cairns, Darwin, Perth (Garden Island), Sydney (Garden Island) and at HMAS WATERHEN (Sydney’s North Shore), and each element services the intermediate maintenance needs of their local areas. FIMA is controlled centrally by Commander Fleet Maintenance (CFM) and the FIMA National Administration Office (FNAO) located within building 103 at Garden Island in Sydney. THE PLAY E R S FIMA National Ad m i n i st ra t i o n O ffi c e FNAO as part of the Maritime Command Engineering Division (ENGDIV), provides business management, Quality Assurance, Management Information System support and Library support to all FIMA Units. Also FNAO hosts the FIMA Web site at fima.defence.gov.au. This site provides an insight to the other FIMA units. FIMA CA I R N S The primary role of FIMA Cairns is the maintenance support of the Cairns Based Fleet Units (CBFUs), in particular FREMANTLE Class Patrol Boats (FCPB) and Landing Craft – Heavy (LCH) with only a minor maintenance involvement in the Hydrographic Ships and Sur vey Motor Launches. In providing this maintenance support, FIMA provides a valuable service to the Maritime Commander in keeping the Northern Fleet operational. FIMA DA RW I N The primary function of FIMA Darwin is to provide a high level of maintenance support to the Darwin based FCPBs and LCHs. FIMA Darwin also provides support to visiting Ships and a base and workshop facility for the Deployed FIMA Assistance Group (DFAG) when in the Darwin area. The relocation of the FCPBs from Sydney and Perth to Darwin Naval Base was completed in November 2001. Thirty billets
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ENGINEERING - Royal Australian Navy

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