Q CRANKSHAFT TECHNOLOGY


Heart rate monitor for diesel engines


Continuous monitoring of the crankshaft in diesel engines can provide C 20


useful insight into the condition of valuable assets, enabling operators to schedule maintenance only when it’s needed, explains Dr Oliver Hirsch, head of diagnostic systems at Jaquet Technology Group


rankshafts in all engines and the rotating shafts of turbochargers experience torsional vibration. As the engine runs, expansion and compression in the cylinders drives pistons that


apply torsional forces to the crankshaft. However, the pattern of torsional vibration


changes subtly over time as components wear. The wear and tear causes changes to the


operating condition of engines long before the symptom of abnormal vibration becomes apparent. Once this starts, an engine is within months of the end of its life. Left unchecked, the engine will start to emit noise, heat and smoke before failure. By monitoring torsional vibration of the


crankshaft and comparing it to ideal performance, the operator gains information about changes to the condition of the diesel engine at an early stage. It also gives deeper insight into components, down to the level of identifying the cylinder where a problem lies. Jaquet’s predictive diagnostic system


Alphabox achieves this by analyzing data from speed sensors installed on diesel engines. Its goal is to help operators achieve optimum thermodynamic and mechanical performance. Alphabox is installed on four ships


operating in Europe (two barges, one ferry and one tugboat). It is also installed on ships belonging to the French and Indian navies.


Non-invasive sensors The system is similar to a wearable heart rate monitor. It uses non-invasive speed sensors to measure the torsional vibration of the crankshaft. The continuous monitoring system picks up normally undetectable but signifi cant changes long before vibration or other signs of


wear become apparent. Mounting a single- speed sensor on the crankshaft of a diesel engine gives insight into the general health of the engine. A second sensor mounted on the camshaft of four-stroke engines or at top dead centre (TDC) of two-stroke engines synchronizes the diagnosis results with the fi ring order of the cylinders. Combining and analyzing data from both


enables the system to pinpoint the precise location of a fault, such as a defect in bearings, a problem with fuel injection in one cylinder or variation of compression between cylinders. Adding a third sensor on the turbocharger


will allow simultaneous monitoring and diagnostics of the turbocharger in parallel with the engine itself. Signals from the sensors are collected in a diagnostics unit, which applies digital analysis to identify overall mechanical health and effi ciency. Data traces are constantly compared with a benchmark ‘ideal operation’. An algorithm identifi es the differences between the two and diagnoses the source of stresses. For example, under normal operation, all


cylinders have the same characteristics. These include the acceleration of the power stroke after ignition, followed by the deceleration due to compression. As the engine ages, anomalies


arise from friction, wear and misalignment of moving parts and bearings. These anomalies show up as variation between the ideal and actual condition of the engine.


Diagnostic reports Condition is reported through an intuitive reporting screen with a traffi c-light dashboard that shows at a glance the engine’s health. Besides various cylinder-specifi c indicators


such as injection and bearing, and other indicators such as torsional angle of the crankshaft or mechanical stresses, it shows the overall status of the engine regarding its mechanical health and effi ciency. For engines that benefi t from sensors on


both the crankshaft and either camshaft or TDC, the speed data is combined with timing of the engine to identify which cylinder is the source of a problem. For example, it indicates whether the cylinders are experiencing abnormal compression, issues with the quantity or quality of fuel injection, or deterioration of the bearing. Insight from the system gives the operator


the knowledge to optimize maintenance cycles, extend engine life, avoid expensive breakdowns, diagnose faults, and reduce operational and maintenance costs. It can be applied to individual assets or entire fl eets on retrofi t or new installations. For example, a time-based maintenance


schedule may require changing of all injectors on an engine at a total cost of £1,000 each, whether or not they are defective. However, Alphabox allows operators to change only the injectors that are coming to the end of their life. Alternatively, insight from the system could


give an operator confi dence to extend the time between major overhauls by 50%, saving hundreds of thousands of pounds.


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