YANKEE SURFACE MANAGEMENT WORLD PULP&PAPER 26 measurement to determine distance to the organic layer. Thus we can have total coating thickness including natural coating, but still not adhesive or rheological information. Crepe blade vibration measurement is very commonly used across the tissue industry now, initially to alarm for high vibration and protect the Yankee from chattermark damage. However, a more detailed examination of vibration trends and spectra can reveal much about the Yankee surface and coating. Working on the assumption that vibration can be caused by hard coating, and that a blade change will refesh the coating layer and allow softer coating to predominate, we can easily see this effect in Figure 1. Looking at the vibration spectra shows a similar impact, but now we can start to discriminate at which frequency the hard coating (assumed to be stripped away after blade change) cause vibration as can be seen in Figure 2. So for the machine shown in Figure 2, we can see the hard coating pre-blade change induces a high frequency vibration at around 19 kHz, which makes for extremely useful troubleshooting information. Its ulimate expression is to map various frequencies to known and observed Yankee surface phenomenae, as per the example shown in Figure 3. In this case, the edge build up and chatter associated with it gives a lower frequency of vibration. This is determined by measuring actual Yankee marks on a shutdown and a more detailed examination of vibration trends and spectra can reveal much about the Yankee surface and coating Figure 1. Vibration trend from crepe blade showing blade change response. Figure 2. FFT spectrum of crepe blade vibration showing blade change response.