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Table 11:
Slewing crane – Sum sound
power of gearbox plus motor
Sequence of calculation:
1. Definition of the sound power Lw of individual components
(motor and gearbox)
2.
3.
Calculation of the sum sound power level
Calculation of the enveloping surface
4. Definition of sound pressure level on the enveloping surface
We take into consideration the slewing crane
described before and calculate, while basing on
the standards IEC 60034 and VDI 2159, the sound
power levels of the drive units belonging to the
two lifting- and closing gears.
The sound power levels, calculated in
accordance with the method described, are not
far away from the sound power levels measured,
while taking into account that the machine house
of the slewing crane has a sound insulation factor
of approx. 10 dB. The least these values show
is a tendency and an order of magnitude. Real
values can only be derived from measurements
and experiences made with projects realized
in the past. It is even possible to forecast the
frequencies that will occur, such as the meshing
frequencies of the gearboxes and the frequencies
of the magnetostrictive motor power resulting
from the converter frequencies.
Spur wheel gearbox
Planetary gearbox
Planetary gearbox with stationary bell-type
wheel
Issue 04 | 2010
TRANSFER OF TECHNOLOGY
The meshing frequencies calculated while taking the
number of teeth as basis are clearly verifiable by the
structure-borne sound measurements, as well as by the
spectra of the airborne sound measurements. So, in the
figure 22, there are shown the vibrations taken on the
frame to which the drive unit is fixed appertaining to the
lifting- and closing gear. In the abscissa there is plotted the
frequency, and in the ordinate the time. For every time step
the vibration signal, plotted consecutively to the top, has
been submitted to the FFT analysis. So, it is formed a space
Fig. 21:
Gearbox scheme / Slewing gear
Fig. 20:
Gearbox scheme / Lifting- and closing gear
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