An Cosantóir

16 MULLINGAR TO MONROVIA – A SOLDIER'S MEMOIR By Photos by Lt Cdr Cian O'Mearain NS Press Office KEEPING IT ALL GOING: THE NAVAL SERVICE VESSEL MAINTENANCE FUNCTION "Right, there's a 500 hour on No.3 generator, a 3 monthly on the main ventilation fan and a six monthly on the emergency fire pumps to do tonight". This is a common worklist for an evening at anchor on NS ships. What are these, where do they come from and why do we do them? Apart from their roles within the action organisation of the ship and performing normal steaming watches where they operate and monitor the propulsion and auxiliary equipment these technicians of the Naval Service also conduct much of the maintenance for the ship. It is essential that this is organically part of the crew skill set, as often there is no base workshop within 400 miles or a day's steaming. We are all familiar with the idea of getting a car service every ten or twenty thousand kilometres. It is similar for a ship, just a lot more complicated. A modern P60 class vessel has approximately 700 different types of machinery, usually with a backup, so that there are up to 1800 individual maintainable assets. Each of these has several maintenance interval patterns that vary from one manufacturer to the next. Some maintenance is based on running hours and some is calendar based. Often both must be considered, so that there are nearly 6,000 maintenance activities to schedule and keep track of, for each ship. Then there are the associated spare parts to account for. Clearly a logbook or a ledger isn't going to do the job! So the purpose of the Naval Service Vessel Maintenance Function is to make sure that ships are reliable and available, so that they remain capable at all times. This provides the OC of the unit with confidence that their ship is in sound condition and in date for the many certifications required for safety critical items. A well-managed maintenance system doesn't just reduce the amount of time a ship is unavailable to go to sea through breakdown, but can also reduce the (often unexpected) cost of breakdowns. So how is this organised? The Maintenance Strategy determines what work is done by whom and when and how this is overseen to assure quality. Maintenance Strategy "If it isn't broken don't fix it" is a common but misapplied phrase. Occasionally it is prudent - where equipment is cheap and not mission critical - to choose a Run To Failure (RTF) strategy. However, this should not be confused with the unexpected breakdown of important equipment. This Unscheduled Corrective Maintenance (UCM) is to be avoided at all costs. It is useful to track when UCM occurs as it is an important indicator of where a Maintenance Strategy needs to be improved. Some outcomes of this can include upgrading a piece of equipment or designing it out entirely. Time interval based Planned Preventive Maintenance (PPM) was developed in the 1940s, as the increased pace of industrialisation of the second world war demanded dependable machinery and to avoid UCM. Initially, this was all time or running hours based and involves periodically inspecting, often by disassembly, equipment on a fixed time interval basis. It has advantages in that it does improve reliability and it has a predictable and stable workload over a time period. It unfortunately introduces a problem where the inspection itself can be the cause of equipment failure and the Naval Service doesn't want to take equipment apart on a regular basis to find out why it is still working. Hence the next development was a move to Condition Based Maintenance (CBM). Equipment selected for this strategy will have some monitoring gauge or test that can be performed to assess its condition and determine if an overhaul is required. A good example of this is the steering gear, which has an annual performance test and must be able to perform specified changes of position within defined maximum time limits. If it fails, it is overhauled early. Today with the Internet of Things (IoT) equipment is often being designed for continuous monitoring. Once the leading indicator of failure (or even reduced performance) is identified, a Predictive Maintenance (PM) strategy can be used. This strategy might predict that a piece of equipment is likely to fail in ten weeks and there are opportunities to overhaul it in 2 or 8 weeks' time - leaving the owner with options to decide how to address the imminent failure. Cylinder Head Removal on the LÉ Eithne A deep knowledge of marine engineering is required to keep it all going

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