20
SOUND AND VIBRATION MANAGEMENT
Sound
Sound power level for Danfoss MPZ with R404A, motor code 4, Te = -10°C, TC = 45°C
Running compressors vibrate and
generate refrigerant gas pulsations.
These vibrations, when coupled to
ambient air, are heard as sound. Those
vibrations and pulsations conducted
through connecting tubing as well as
the vibrations reaching the compressor
feet continue to other parts of the
system and structure where they may
also generate sound.
Danfoss MPZ compressors are 100%
suction gas cooled, and require
no body cooling, thus they can
be insulated. For inside mounted
compressors, sound insulation of the
enclosed location of the compressor
is an alternative to sound insulation of
the compressor.
For treatment of vibration please refer
to the next section.
Vibrations
There are best practises to check
whether vibration paths are designed
in the best possible way.
Grommets
: the mounting grommets
delivered with the compressor
should always be used. They reduce
the vibration transmitted by the
compressor mounting feet to the base
frame.
The compressor should never be
directly mounted to the base frame
without the grommets, otherwise
high vibration transmission will occur
and the compressor service life will be
reduced.
The base on which the compressor
is mounted should be suffi
ciently
rigid and well connected to the main
frame of the application to ensure
the full eff ectiveness of the mounting
grommets.
Tubes
: suction and discharge lines
must have adequate fl exibility in 3
planes. Eventually vibration absorbers
may be required. Take care that
the tubes are correctly formed and
located in front of the connector
before fi tting to avoid any constraint
on the compressor. Using a shock loop
with a generous bending diameter is a
good means of vibration transmission
through the piping. Soft copper tubing
and smaller diameter tubing should
be used to make smooth fl exible
connections.
Care must be taken to avoid tubing
having resonant frequencies close to
those of the compressor frequency.
Vibration is also transmitted by
refrigerant gas pulsation. Danfoss MPZ
compressors have built in muffl
ers to
reduce this vibration.
Note: MPZ compressors have been
designed and qualifi ed for stationary
equipment used in refrigeration
applications.
Danfoss doesn’t warrant these
compressors for use in mobile
applications, such as trucks, busses,
railways, subways, etc...
Sound power level at 50 Hz
dB(A)
Sound power level at 60 Hz
dB(A)
MPZ038
71
74
MPZ048
68
71
MPZ054
68
71
MPZ061
68
71
MPZ068
68
71