The more precisely the operating conditions of a straightening roll are known or can be calculated, the more exactly and reliably its useful life can be determined.
Three different equations are available: for nominal life-time according to ISO, for modified nominal life according to ISO, and for modified nominal life-time based on a new life theory.
The simplest approach is to determine the nominal life-time according to ISO using equation (1) shown opposite.
Calculation of the nominal life-time using this equation is sufficient for conventional bearing applications.
In other applications it may be wise to take detailed account of other life-affecting factors as well. This led in 1977 to the introduction of the modified life-time equations shown under (2).
In the third equation - modified nominal life-time according to the new SKF life theory - a life-time coefficient is added to take account of a fatigue load limit and various other factors affecting the lubricating conditions and the degree of soiling.
The life-time value calculated with equation (3) is regarded as the period of use actually covered by a straightening roll in its life-time. As a rule this value deviates slightly from the calculated nominal life-time.
See Also
Adapted from “"We do it straight" — Wire Straightening”, p. 105 (ISBN 3-00-005897-4).