Over the years, propulsion systems have become more sophisticated and complicated. In spite of regular updates of Class Rules and Regulations to cover the present state of the art technology, upgrading of International Standards, QA/QC procedures and supervision of production and assembly by end users, regular failures occur that lead to excessive wear, loss of functionality up to total lack of propulsion. Besides the lack of 'System thinking' one of the key factors is introduction of electronic control of several functions on separate engines, as fuel injection, valve control, cylinder lubrication, condition monitoring etc., and on complete propulsions systems consisting of several engines and propulsors where different operational modes can be chosen. Replacing mechanical functions by electronic control absolutely increases the flexibility of systems regarding tuning them for specific applications and for a specific goal (for instance fuel optimized versus emission optimized) with a single push of a button or completely automatic. However, as the most famous Dutch soccer player of all times, being Johan Cruijf, has once said: 'elk voordeel hep zun nadeel', meaning every advantage has its disadvantage. The advantages are clear: more flexibility, more accurate control, higher load limits, lower fuel consumption and - emissions over the load range than on mechanically controlled systems and higher redundancy, for instance if a camshaft fractures on a mechanically controlled engine, it stops whereas on an electronically controlled engine one cylinder is shut down when a failure occurs and it keeps on running. The disadvantages are also becoming clear in daily practice: There is a responsible party for the entire system, being the ship yard or 'self-appointed' system integrator, but there often is no competent party with total knowledge of-, control over- and interest in system integration which covers electronic systems, mechanical systems and the interaction between these two. There is a clear lack of understanding what the effect of actions by electronic systems can be on the mechanical integrity of these governed systems because electronic- and software engineers and mechanical engineers are worlds apart: they often do not understand each other even if they communicate at all. The different parties that deliver controls for a propulsion system (engine related controls, power management systems, DP systems) have no intimate relationship which means that the communication is limited to exchange of protocols and wiring diagrams and does not involve the effect of the combined overall control system on the mechanical load of the propulsion installation. During sea trials, the measurements performed are so limited that especially dynamic effects due to interaction between separate components and/or systems that can lead to failures or excessive wear are not recognized. In this paper several cases of disintegration of propulsion systems in practice will be discussed. The examples range from fracture of propeller shafts through rupture of rubber elastic couplings to repeated damage of bearings and unworkable situations due to instable behavior of control systems. Each case is discussed in detail and the damage mechanism as well as the consequences from an operational point of view will be presented as well as the measurements and calculations necessary to determine the root cause. Factors of influence on the development of the damage- or wear mechanism for each case will be presented. A procedure to prevent the encountered damages and unwanted interaction between components in a system and detect them in an early stage will be proposed.


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    Title :

    Propulsion system (dis)integration


    Contributors:


    Publication date :

    2013


    Size :

    15 Seiten, 38 Bilder


    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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