12
both measurement types for bearings and gearboxes. As ENV values
begin to decrease, rely on VEL readings.
Overall Vibration Monitoring
— monitors normal, low frequency
machine vibration. Detects rotational and structural problems like
imbalance, misalignment, and mechanical looseness.
Enveloping
— amplifies high‑frequency, repetitive bearing and gear
mesh vibration signals for early detection of bearing problems, but
does not detect non‑repetitive rotational or structural events like
imbalance, misalignment, and looseness. Provides earliest detection of
high frequency metal‑to‑metal contact or poor lubrication in problem
bearings.
13.0 MEASUREMENT TECHNIQUES
In general, vibration of anti‑friction bearings is best monitored in the load
zone of the bearing. Equipment design often limits the ability to collect
data in this zone. Simply select the measurement Point which gives the best
signal. Avoid painted surfaces, unloaded bearing zones, housing splits, and
structural gaps. When measuring vibration with a hand‑held sensor, it is
very important to collect consistent readings, paying close attention to the
sensor’s position on the machinery, the sensor’s angle to the machinery,
and the contact pressure with which the sensor is held on the machinery.
Location
—
always collect at the same point on the machine; mark
location
Position
— vibration should be measured in three directions:
•
A ‑ axial direction
•
H ‑ horizontal direction
•
V ‑ vertical direction
Angle
— always perpendicular to the surface (90
o
+10
o
)
Pressure
— even, consistent hand pressure must be used (firm, but
not so firm as to dampen the vibration signal). For best results use the
magnetic base. If using the stinger/probe is the only method available
to collect data, it is best to use a punch to mark the location for the
probe‑tip to ensure a consistent coupling to the housing.
