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5. The diagrams show frequency spectrum for a cooling pumping unit driven by a gear reduction unit. The electric motor rotates the 100 teeth pinion at 1800 rpm, while the output shaft rotational speed is reduced to 600 rpm by a 300 teeth gear to drive the centrifugal pump which has 8 vanes. Both the electric motor and the pump rotor are mounted on deep groove bearings with the following data: Inner diameter 20 mm, outer diameter 60 mm, pitch diameter 40 mm, width 16 mm, 10 balls with ball diameter 8 mm. The original reference data are collected at first installation as shown in the left spectrum, with max. amplitude of (0.3 g) m/s². Measurement is carried out at output geared shaft. After 2 years, the manufacturing team reported increased level of vibration and unsatisfactory cooling. The maintenance team performed a second measurement (shown on the right). The spectrum showed increased peaks above 2g in the frequency range 70 to 140 Hz. Based on these data complete the following information necessary for the inspection report: 100 tooth pinion o 300 tooth gear 8 vane centrifugal pump Motor-Driven Centrifugal Pump with Gear Reduction Unit 1800 rpm motor
Acceleration (g, rms) 2 0.2 0.02 10 30 2000 80 1000 3000 Frequency (Hz) Reference spectrum BPFO: BPFI: f(Hz)= n/2 *f (1-BD/PD * cos ß) f(Hz) = n/2 * f (1+BD/PD * cos ß) f(Hz)=PD/BD *[ 1- (BD/PD * cos )²] f(Hz)= 1/2*f (1-BD/PD * cos ß) BFF (Balls): FTF (Cage): Final Exam, MF417, Sem. 422, JUC Male Branch Reference Data at Start of Operation (Write your answer inside the text box): 1. Peak at frequency of 10 Hz represents: 2. Peak at frequency of 30 Hz represents: 3. Peak at frequency of 80 Hz represents: 4. Peak at frequency of 3000 Hz represents: Inspection Data after 24 Months: Acceleration (g. rms) 120 Hz 0 25 50 125 75 100 Frequency (Hz) Same Machine after 24 Months 150 Page 6 of 7 (4 Points)
Calculations (if needed): Write a short description of the shown spectrum (4 Points) Conclusion: The high peaks reported in the range 70 to 140 Hz indicate as the main problem in the inspected cooling pump. If a peak of 6g m/s² is detected at 20 Hz while the peak at 10 Hz is increased to 2g m/s², what problem can be expected? What is the evidence that can be seen on the spectrum when the wear of gears is the problem?