Pressroom draw variation and its impact on web breaks Part I: Newspaper pressroom trials

Web breaks in pressrooms are affected not only by paper properties, but also by pressroom conditions. Recent research at Paprican has identified the key paper properties controlling web breaks. However, the impact of pressroom conditions has not been clarified. In this study, we used a synchronized pair of Laser Doppler sensors to measure high frequency draw variations of newsprint webs, and examined the relationship between draw variations and web breaks in five different newspaper pressrooms. The results show that the draw variation is related mainly to press configuration, operating conditions, and maintenance, while the contribution of the paper was found to be small. In certain cases, the draw variation can be very high (close to 1%) at press start-up and stop, as well as at pasting. We also found that severe out-of-roundness in newsprint rolls did have an impact on draw variations. Using frequency analysis, we showed that the sources of draw variations call be identified and linked to press variables. Finally, a correlation between pressroom draw variation and web break rate was found. with a higher draw variation causing a higher break rate. These results suggest that in addition to improving paper properties, it is important to minimize draw variation through better control of the press.