35 Using Operating Data to Locate and Quantify Unbalance in Rotating Machinery 381 Fig. 35.4 MAC values (first order) Fig. 35.5 SDI values (first order) ODS’s. It shows that the worst case pair (cases 4 and 6) has anSDID0.88. This bar chart also shows that SDI values cannot be used on second order ODS data to uniquely identify each unbalance case. Figure 35.8 shows that the worst case pair (cases 3 and 6) has a MACD0.93 for the third order ODS’s. Even though overall these MAC values are closer to zero than for the first and second orders, these values still cannot be used to uniquely identify each unbalance case. Figure 35.9 shows that a worst case pair (cases 3 and 6) has anSDID0.85. Again SDI cannot be used on third order ODS data to uniquely identify each unbalance case. Even though SDI is a stronger indicator of shape differences than MAC, it would still be an unreliable method for discriminating among the seven unbalance cases and the balanced case, regardless of which order of ODS data were used.
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