Marine Power Systems were asked to measure shaft power on a fast ferry. The crew believed that the engines were overloaded when the vessel had high numbers of passengers onboard. In order to test this theory, a small strain gauge was bonded to the stbd shaft and together with the TorqueTrak measuring system, data was collected over the course of an afternoon/evening. Once analysed, the data revealed that high numbers of passengers caused excessive load on the engines which meant that each could not achieve rated speed. The owner made a small correction to the propeller pitch during the next slipping which reduced the load on the engines and allowed them to reach rated speed, even with high numbers of passengers onboard. Furthermore, this allowed the owner to specify higher rated engines for two new vessels that were under construction at the time.
This work is a good example of where shaft power measurements can be used to ascertain correct matching of propulsion engines and propellers.
Examples of data collected during the trial
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