Beloit-Lenox WIT-WOT Analysis

Roll structure is one of the most important components and indicators of roll quality. Roll structure is the result of operating parameters (TNT), hardware conditions and paper properties. The proper measurement and interpretation of roll structure provides the key to corrective actions and achievement of defect-free and consistent roll quality.

The Roll Structure Analyzer has been known as the WIT-WOT, which stands for "Wound-in-tension/ wound-off-tension." It is a unique winder which, through a special arrangement of load cells and web run, allows the recording of "wound-in" tension in a roll as it is "wound-off" the unwind. Wound-in tension is an excel-lent indicator of roll structure, and can be measured on the WIT-WOT with high reliabil-ity. This machine can accommodate rolls up to 1500mm (60") in diameter and between 400mm (20") and 1000mm (40") wide. Roll Structure Using the WIT-WOT Machine

Benefits

• Establishes a base line roll quality history.
• Regular testing catches most prob-lems before shipment
• Preventative maintenance
• Quick turnaround for up to four rolls to assure timely corrective action can be taken.
• Critical in determining printing press problems as related to the paper roll structure.

Features

• WIT/WOT Analysis – Wound in Tension/wound off tension – creates a profile of the roll structure.
• Wound in tension is an excellent indicator of roll structure
• Measurement of cross machine direc-tion roll hardness reveals the condi-tion of the outside of the roll and indicates problems related to caliper profile.
• Creates a density curve to corroborate the wound in tension.
• Physical properties are established i.e. tensile, elongation, coefficient of friction , elastic modulus, caliper, and compressibility.

The plot below shows the results of an incor-rectly made splice near the outside of the roll which resulted in crepe wrinkles below the splice. This roll also demonstrates a lack of wound in tension near the core.

A comprehensive report, issued to every cus-tomer, creates a "picture" of the wound in tension throughout each roll tested, as well as other aspects of roll quality. These include a wound in density curve, roll roundness, a hardness profile and caliper profile, Smith Needle measurements and more. Recommenda-tions for improving roll structure are spelled out clearly and sucinctly.

This second roll was wound from the same reel, succeeding set, same parameters but cut from the center of the reel where as the previous roll was cut from the end position. No splices were made in this set. Tightness near the core is improved. The paper machine caliper profile for this exercise indicated a higher caliper in the center, thus explaining the tighter area near the core. This type of analysis can dramamtically demonstrate the influence that caliper profile, as well as other variables, have on wound roll tightness therefore, quality.

GL&V Pulp and Paper Group, 1000 Laval Blvd., Lawrenceville, GA 30043. Tel: 770-963-2100; Fax: 770-963-4155.