The Abormal Vibration Research Of Press Section In Board Paper Machine

The board paper machine is built with forming section,press section,dryer section,sizer section,calender,reel drum and reel winder and the press section is the most important part,which removes the water from wet paper by nip force giving from rolls and increases the apparent density and smoothness of paper.According to the speed of paper machine and the paper type manufacturing by the product line,the press section structure is designed to one type of double nips with LNP or shoe press,three nips with four rolls,shoe press with smooth roll or belt.The press section must be running continuously with very low level vibration to make sure that the wet paper which contain 80%water can go through the nip under very high pressure without breaking and waving.It is very important for the high speed machine,so the sensors will be located at the press rolls to monitor the vibration level all the time.The vibration level of main rolls of press section can also be regularly measured by movable device.The article shows the classical cases of abnormal vibration in the press section which happened in our company and others.The frequency characteristics from vibration parts is exclusive,so in these cases,the root cause of vibration was found by analyzing the spectrum domain,time domain and vibration trend chart which were got from on-line or off-line vibration indicator.The correct action was carried out to decrease the vibration level.The vibration of press section depends on many factors.The author just collected and analyzed the problems he met and heard no matter in or out of his company.They are not overall just some classical ones due to my limited experiences.I hope it could be useful for your reference on daily working and lower the lost if any similar cases happen...