BALTECH VP-3470
Operation manual
Operation conditions and prestarting procedures 27
or two directions where the foundation stiffness is the lowest.
If the foundation stiffness is much the same in all three directions, the measurements
should be made in all the directions. If the foundation stiffness is different in three
directions, the measurement can be made only in the direction of the lowest stiffness.
Moreover as opposed to monolithic structures the stiffness of the frame structures
in the horizontal and axial directions are usually much higher than in the vertical
direction. So the vibration levels can be higher in these directions than in the vertical
one.
Most attention should be given to the horizontal direction where the stiffness is lower
and there is always an internal source of dynamic forces generated be the rotating
rotor (as opposed to axial direction where high dynamic forces occur usually only
due to poor alignment).
Never install the vibration sensors on auxiliary production parts: slopes, shrouds,
etc. even if the vibration in these parts is the highest.
5.2.4. Accelerometer installation during the balancing and diagnostics
The measure points are selected based on the following:
а) First of all it is necessary to control the vibration levels on the bearing units
because they fully take the dynamic forces generated by the unbalanced rotor. As
a rule, the measurement directions are vertical and horizontal, i.e. radial to the
rotation axis. The balancing should be performed based on the measurement
results, in the points (and directions) of the highest vibration level;
b) Before and after the balancing procedure it is necessary to measure the vibration
according to the recommendations given in the p. 5.2.3;
c) Additional measurement points can be measured depending on the individual
requirements to a particular machine. If the vibration levels at the rotation frequency
in the axial direction are comparable or exceed the vibration levels in the radial
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