Installation, operation and maintenance instruction
High voltage flameproof motors for explosive atmosphere
AMD Rg 355-400-450-500
Sleeve bearings maintenance
Issued by: MOLM
Sheet No.
3AAM101043 E
Rev. C
Page 3 of 4
01.2023
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The maximum acceptable clearance is normally 0.3 mm.
Consult the specific technical documentation or ask to
supply Factory to have the exact value for the motor
under subject.
If the clearance would be more than the maximum
allowed value, the bearing’s shell must be replaced.
WARNING !
The replacement of the bearing’s shell
and, moreover, of the complete bearing with support,
must include the check of the exact centring between
the static and rotating components of the inner flame
seals. In case the complete bearing has to be replaced,
the required insertion of safety pins must be carried out.
All the operations are described in the section
“Disassembly and assembly instruction” of this manual.
We suggest to entrust for this jobs a qualified Ex db
Service factory.
The bearings are designed such that, with an oil of the
specified viscosity and at a normal ambient temperature
between 0°C and 40°C the maximum bearing
temperature will be 85°C.
To guarantee the correct heating dissipation the bearings
must not be subjected to direct sunshine, and the support
surface must be always clean.
The operational condition of a bearing cannot be judged
by the temperature level alone, much more important is
the temperature behaviour of the bearing. If
thermometers are fitted, the temperature behaviour can
be observed and the temperatures noted and recorded
regularly.
Should a rise in bearing temperature be noted compared
with earlier readings, the cause must be determined with
the machine stationary.
If the bearings are fitted with temperature monitoring
equipment, then the set values in the relevant sheet, have
to be used.
In case of ambient temperature exceeding 40°C, the set
of alarm and shutdown has to be agreed with the
manufacturer.
Various instruments can be fitted to monitor the bearing
temperature. However, if none of them are fitted, the
temperature must be measured with portable instrument.
If an abnormal, i.e. higher than usual temperature is
noted, then exact measurement is to be made using a
precision thermometer.
In case of strong fluctuations or a sudden change in
temperature level, the bearing is to be inspected and the
oil possibly changed.
Operation at ambient temperature below 0°C
When the motor operation can provide several start-ups
at ambient temperature below 0°C, special synthetic oil
has to be used or alternativelly heating elements fitted
in the oil tank could be use.
Here under suggested oil for low temperature .
In the case of lowest temperature applications, it is not
allowed to exceed a maximum lubricant viscosity of
800-1500 mm
2
/s at start up.
Most of PAO based lubricants are according to above
condition.
Checking the bearing seals
The seals are to be checked at the shaft passage points
for loss of lubricant and if required cleaned of any dirt
deposits.
Monitoring running quality (measurement of bearing
housing vibration and/or shaft vibration)
When provided, set vibration monitors to the values
given below or use these values to evaluate vibration
measurements made with portable instruments. Based
on the standard ISO 10816 the following vibration limit
values for alarm and shut-down were fixed for setting the
monitoring equipment. This instruction is also basically
valid for NEMA, API and other similar standards.
The values are valid for:
Vibrations originating from the machine itself.
Machines on rigid foundations. Definition of a rigid
foundation according to ISO 3945: “For a rigid
foundation the system natural frequency is higher
than the speed frequency”.
The values are
not
valid for:
Reciprocating compressor drives.
Machines on foundations with a low natural
frequency of vibration (i.e. lowest system natural
frequency
≤
0.25 x speed frequency).
For these machines, values must be agreed upon
between the manufacturer and the customer at the
ordering stage.
Bearing housing vibration
The decisive quantity is the rms value of the vibration
velocity measured on the bearing housing. Measuring
point arrangement in accordance with ISO 10186.
ALARM
V
rms
= 4.5 mm/s
SHUT-DOWN
V
rms
= 7.1 mm/s
