How to prevent roll defects caused by rider roll load variations

by Bassam Dib, B.ing, Senior Analyst

See also our Knowledge Base article: How to calculate Rider Roll Load from cylinder pressures

Challenges

Detection

Solution

These variations occur sporadically and for a very short duration, making them almost impossible to detect unless we combine high resolution data acquisition (>10 samples/sec) with automated continuous analysis and monitoring.

Our analysis modules calculating each rider roll cylinder pressure instability flagged a higher than usual level (Graph #1) which corresponded to a sudden change of pressure (Graph #2).

Further analysis indicated also that the drum speed differential and sheet tension levels were disturbed.

Pressure Change, Graph

Additional analysis by our experts of this  pressure instability pointed to a faulty operation of the pressure limiting valve on the counter pressure hydraulic line.

 

A detailed report was sent to the mill with the following recommendations:

 • Service the pressure limiting valve

 • Inspect oil supply for contamination

 • Replace oil filters in the supply unit if needed

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Sudden variations or drifts in the performance of hydraulic components dramatically increase the probability of inducing roll defects.

Our intervention enabled us to successfully isolate the problem, and the mill had enough lead time and information to take corrective actions and prevent further roll defects.

The list of potentially defective rolls was also provided to the mill for tracking purposes.