The Dynamic Features And Condition Monitoring And Fault Diagnosis Methods About The Press Of 4800 Paper Machine

Recently, with the rapid development of the national papermaking, the demands of the papermaking enterprise for an on-line condition monitoring and fault diagnosis system (CMFDS) are very emergent. But, the enterprises and universities in china have not researched on it yet. In order to change this situation, this masterate thesis investigate into the techniques of the condition monitoring and fault diagnosis on the press of a paper machine (PPM). The press of the paper machine which keeps ahead within the same type in china is selected as the research object. Firstly, the vibration influences on PPM are analyzed, and those caused by roller bearings, gear-box and engine are emphasized especially; Secondly, based on the analysis, the methods for on-line condition monitoring, fault diagnosis and condition estimation are given; Thirdly, the remarkable problems arises during the foundation of the on-line condition monitoring and fault diagnosis system of PPM are discussed; Finally, the superiority of some methods are studied by means of analyzing the vibration signals sampled from PPM. The key results are as follows: 1. Some of the frequencies of the signals belong to the low frequency range, but some belong to the high frequency range, so the frequency range of the condition monitoring of the PPM must include them all. 2. According to the dynamic features of the press, the means of on-line CMFDS combined with off-line CMFDS is used. The velocity standard of the low frequency and the acceleration standard of the high frequency are set down by means of "single machine statistics"and "baseline establishment". 3. The selection of sensors change with the place of the condition monitoring. The temperature of the press is not high, so the ICP accelerators can be used; On the contrary, the temperature of the drying sections is higher, so the traditional piezoelectricity accelerators that are able to bear high temperature and a charge amplifier should be used. The improper selection of sensors will result in the distortion of the signals and the bereavement of the meaning of the diagnosis. 4. The trouble can be detected by analyzing the signals sampled from axis direction of the press, and these signals are superior to others when it comes to diagnose the faults of the press. 5. The structure and the vibration influences of the press are so complex, that the Auto-spectrum usually used in engineering is unsuitable when it is used to analyze the signals sampled from the press. The efficiency of using Auto-spectrum for diagnosis is too low. 6. According to the features of the vibration signals that come from the roller bearings and the gear-box, the paper presents that the cepstrum defined as the Real component of an inverse FFT applied to the logarithm of an Auto-spectrum's Magnitude is a fast, practical and efficient method in analyzing the vibration signals sampled from the press.