Studies On Accurate Measure Of Real Plate Gap And State Monitoring Of Main Spindle Of Refiner

Real plate gap means the clearance between the surface of stationary disc and the surface of rotating disc in refining zone. The quality of fiber separating is deeply affected by plate gap. In order to guarantee constant and uniform fiber quality and output of the refiner, the proper plate gap should be chosen and kept in constant at all times while the refine is in operation. Generally plate gap should be controlled in the range of 0.2~0.5mm and the dimensional precision in operation should be defined at 0.01mm. As a matter of fact that plate gap adjusted at start-up will increase as the plates wear down., There is still a difficult problem in the worldwide to measure and indicate real plate gap. when refiner is runningThe running state of main spindle of refiner not only affects refiner running in good condition but also affects the fiber quality.The thesis researched the technologies of measuring accurately the plate gap and monitoring the running state of main spindle of refiner with the approach combining theoretical analyzing and experimental tests. The technologies supplied a gap in the domestic research area.The thesis puts forward the concepts of contact plate gap measurement and non-contact plat gap measurement. Contact plate gap measurement cannot timely indicate the change of plate gap caused by plate wear. Under the structure and running condition of refiner, to measure plate gap accurately in time, non-contact plat gap measurement must be used.For the first time, the thesis brings forward two plans of measuring real plate gap by using capacitive displacement sensor and eddy current displacement sensor respectively, in order to measure displacement of and surface position after wear of rotating disc.A special capacitive displacement sensor, which was designed for measuring plate gap, has some advantages such as: be able to wear down with plate wearing down, the output of sensor directly reflecting the real plate gap, simple structure, small measuring range.By using eddy current displacement sensor, the gap-measuring plan consists of one eddy current displacement sensor and one ultrasonic thickness sensor. Eddy current sensor measures displacement and surface position after wear of rotating disc, and ultrasonic sensor measures thickness after wear of stationary disc. As a result, the real plate gap will be calculated by using three parameters: the displacement of rotating disc, thickness of stationary disc, and position of eddy current sensor. The probe of eddy current sensor needs a safeguard cover. Since eddy current displacement sensor and ultrasonic thickness sensor can be purchased easily, so the plan can be put in practice easily.Static and dynamic experimental tests were carried out to the plan that is to measure real plate gap by using eddy current displacement sensor.Static experimental test shows that wet wood can make tiny decline to the output voltage of eddy current sensor. As for different species woods, their influences on output voltage of eddy current sensor are almost same. Hot wood can also cause the output voltage to decline; so high-temperature sensor should be selected. When medium contains ferrous powder, the output of sensor arises, the higher ferrous powder content is, the more output is. The fiber produced by refiner, which contains little ferrous powder, does not influence on the output of sensor. The area of probe overlaid by mental panel affects the output of sensor. The more the area is, the smaller the output is.Dynamic experimental test shows that the measure and collection system, which consists of eddy current sensor and displacement converter and data collector and computer, could be used for high frequency dynamic measurement. So eddy current sensor could be used for measuring displacement and surface position after wear of rotating disc. As a result, it is a feasible plan to combine one eddy current displacement sensor with one ultrasonic thickness sensor to measure real plate gap. At the same time, to select a proper kind of material used for safeguard cover of eddy c...