SKF Machine Condition Indicator
How to Select the MCI’s Alarm Mode
SKF Machine Condition Indicator
7
User Manual
The MCI measures vibration velocity, enveloped acceleration vibration (bearing vibration),
and machine surface temperature.
The overall vibration velocity measurement is a general purpose measurement designed
to measure and alarm on structural machinery faults like unbalance, misalignment,
looseness, etc. (this is a band limited velocity measurement close to the ISO standard, ISO
10816-3 (10 to 1,000 Hz)).
The enveloped acceleration vibration measurement is designed to provide early detection
(failure stage three) of bearing faults on machines operating at a fixed speed between
900 and 3600 RPM.
Temperature measurements measure the machine’s surface temperature. Increase in
temperature provides a useful indication of load, and may detect problems that don’t
affect vibration (e.g., lack of oil).
MCI Alarm Modes
The MCI allows you to select one of two alarm modes: threshold mode or percentage
mode. Threshold alarm mode is the MCI’s default mode.
Threshold alarm mode (default mode)
Indicated by 1 green blink every five seconds.
In threshold alarm mode, velocity, enveloped acceleration, and temperature
measurement results are compared to the following default alarm threshold levels, which
are applicable to most “standard” machinery running at “standard” speed (between 900
and 3600 RPM).
Velocity – 9.0 mm/sec RMS (0.35 in/sec RMS; 0.5 IPS equivalent peak)
Enveloped Acceleration – 4.0 gE
Temperature – 105
˚
C (220
˚
F)
Percentage alarm mode
Indicated by 2 green blinks every five seconds.
In percentage alarm mode, the MCI sets its alarm levels specifically for the machine on
which it is mounted. In percentage mode, for the machine upon which it is mounted, the
MCI establishes baseline values (i.e., normal or known-good running condition values) for
the three measurements. After establishing these baseline values, future MCI
measurement results are compared to a multiple of the established baseline values for
alarm purposes, as follows:
Velocity – 2X baseline value (200%)
Enveloped Acceleration - 2X baseline value (200%)
Temperature – baseline value plus 50
˚
C (plus 90
˚
F)
In percentage mode, the maximum alarm values are 40 mm/s RMS and 30 gE.
Therefore (as described above) the maximum baseline values are 20 mm/s RMS (1.1 in/s
P) and 15 gE. If these maximum baseline values are exceeded, the MCI automatically
reverts to threshold alarm mode and indicates so by flashing simultaneous red LEDs
three blinks every five seconds, for about twenty seconds, and then solid red LEDs for
about 10 seconds.
