Cleveland Motion Controls ULTRA ISC SERIES SLIM CELL TRANSDUCER REV AA - Manual (Page 29)

MAN-70434-0 R EV AA U LTRA ISC S ERIES S LIM C ELL T RANSDUCER
4.3 P RE -I NSTALLATION P RECAUTIONS
4.3.1 S HIPPING
Shock and vibration transmitted to the transducers by the sensing roll during transportation can
damage the transducers. It is essential that you remove the sensing roll when the machine is
shipped with the transducers mounted.
4.3.2 R OLL B ALANCE
The sensing roll must be adequately balanced. Understand that the balance of the sensing roll will
be more demanding than that typically needed in general rotating machinery. The goal goes
beyond just limiting the force to which bearings will be subjected, but rather to minimize the
generation of an unintended noise component in the transducer tension signal. The centrifugal
force caused by imbalance can be estimated using the following formula:
F = (1.77 x 10
-6
) x W x R x (RPM)
2
Where:
F = centrifugal force (in units of lb-f)
W = weight imbalance (in units of ounces)
R = radius of displacement, distance of imbalance weight from roll axis of rotation (in inches)
RPM = Revolution per minute
The force increase is equal to the square of the RPM or in other words, doubling the RPM causes
four times the imbalance force. Because rolls tend to have a high length-to-diameter ratio, two-
plane (dynamic) balancing is recommended. Balancing is particularly needed where higher RPMs
and lower web forces are involved.
To illustrate how much imbalance induced “noise” could be generated, Table E shows the force
disturbance for various ISO balance grades for an illustrative case of a 20 pound roll (4” diameter
x 36” long, aluminum ) rotating at 1500 RPM.
Table E Force Disturbance For Various ISO Balance Grades
Balance Grade
(ISO 1940/1):
Residual Imbalance:
Resultant Force due to
Residual Imbalance:
G16 1.25 oz-in +/- 5 lb-f at 25 Hz
G6.3 0.5 oz-in +/- 2 lb-f at 25 Hz
G2.5 0.2 oz-in +/- 0.8 lb-f at 25 Hz
G1 0.08 oz-in +/- 0.3 lb-f at 25 Hz
4.3.3 C RITICAL R OLL S PEED
Even with a balanced roll, a vibration can be set up in a stationary shaft. If this vibration (in cycles
per minute) occurs at the harmonic frequency of the shaft, the transducers can be damaged. To
determine the critical roll speed, use the following formula:
Critical roll speed in RPM = 4.8 x 106 x Shaft O.D.
(Shaft Length) 2
(Dimensions are in inches)
To assure that this issue is avoided, the critical roll speed should be at least 20% above the roll
speed attained at maximum web speed.
4.3.4 A VOIDING D AMAGE TO THE T RANSDUCERS
To avoid damaging the transducers, refrain from repetitive overloading above the maximum
working force or severe overloading.
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