Technical data are subject to change without notice.
© Copyright SPM 2002-04. 71650.B
SPM Instrument AB • Box 504 • S-645 25 Strängnäs • Sweden
Tel +46 152 225 00 • Fax +46 152 15075 • info@spminstrument.se • www.spminstrument.se
Measuring range
The measuring range of the T30 is large and covers most bearing applications, but there are a few
cases where shock pulse monitoring should only be attempted with installed measuring equip-
ment, or not at all.
High speed bearings: The T30 accepts max. 19 999 rpm, 1 999 mm shaft diameter, and a dBi of 40.
The upper part of table in figure 3 contains examples of possible combinations of shaft diameter
and rpm giving a maximum dBi of 40.
Low speed bearings: The lowest acceptable dBi is -9 dB. However, it is nearly impossible to get a
meaningful reading from bearings in the extremely low speed ranges. The practical limit are
bearings with a dBi around 0 dB (see lower half of the table).
A heavy load with a well defined direction and a low interference level make it easier to get
readings from low speed bearings. Successful SPM monitoring has been carried out on bearings
with dBi = –3 (54 rpm, shaft diameter 260 mm). Note that the dynamic measuring range decreases
when dBi values get below 0. For example, a bearing with dBi = –3 showed very heavy damages at
dBn = 40.
Installed adapters required: The installation of adapters is strongly recommended for all system-
atic shock pulse monitoring. In some cases it is a requirement:
• on bearings with dBi below 5
• on heavily vibrating bearing housings
• on covered bearing housings.
Low speed: Do not use the hand-held probe on low speed bearings. As a rule, the measurement
should cover at least 10 full revolutions of the shaft. A single damaged part in the raceway will
cause a strong pulse only when hit by a rolling element while passing through the load zone. It can
take several revolutions before that event occurs or is repeated.
Shaft, mm rpm dBi
50 19 999 40
100 13 000 40
180 10 000 40
300 6 000 40
500 5 000 40
1 000 3 400 40
1 999 2 200 40
1 999 24 0
1 000 35 0
650 45 0
500 52 0
300 72 0
180 100 0
100 140 0
50 210 0
Adapters
required !
Covered
housing
dBi < 5
Heavy
vibration
General remarks on SPM measurement 25
To Next Page
Loading...
