A dräger service engineer was examining the device on-site.The reported issue of ventilator failure could be confirmed; the entire motor assembly was replaced which has put back the device into fully operable condition.The log file evaluation provided by the manufacturer confirms the results obtained on-site.The issue is known from earlier reported instances of the same nature.Root cause for the ventilator failure is wear and tear at the collector disc of the motor which led to partly disrupted electrical contact to the carbon brushes resulting in fluctuations in rotating speed.The supervisor function of the device monitors the motor speed continuously and compares the expected piston position with the one derived by the encoder check.If deviations are detected the device will force a shutdown of automatic ventilation to prevent from damages to the ventilator unit.This is accompanied by a corresponding alarm; manual ventilation as well as the monitoring functions remain available.No patient consequences have occurred and dräger finally concludes that the primus workstation responded as designed upon the malfunction of a single component that became worn after approx.Eleven years of operation.In comparison to the specified lifetime of ten years this can be considered acceptable especially when reflecting that the use model for calculation (5 hours/day & 5 days per week) equals to 13.000 hours in ten years while the operation hours counter for particular motor indicates that it was run for 13.700 hours - 105% of the specified lifetime.The number of similar cases, related to the same root cause, is within the expected range of the respective risk assessment and thus accepted.
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