Research of a fibrous layer at refining in the refiners

A subject of research-a fibrous layer in the refiners at refining. By means of the tension compression chart it is shown that parameters of a fibrous layer are adequately described by Maxwell-Thompson's model for liquid friction and the Hooke model for boundary friction of a plate. Deborah's number of a fibrous layer is also investigated. Deborah's number of a fibrous layer at refining changes in the range from 7 to 2.1•106 and depends on a nature and concentration of the refining material, the angle of knife crossing, the frequency of rotation of rotor and width of the platform of contact. For decrease in power consumption at refining both chips and pulp of high concentration it is recommended to increase the speed of sliding of knife of rotor along stator knife. It is possible to reach by increase in frequency of rotation of rotor and by decrease of an angle of crossing of knife. At refining of pulp of low concentration for decrease in power consumption of refining it is recommended to reduce the frequency of rotation of rotor and to increase the angle of crossing of knife of rotor and stator. At the high density of contact of plate knife in the range from 5 to 106 of Deborah number the deformation component of friction coefficient decreases together with power consumption of refining process. © 2019 IOP Publishing Ltd. All rights reserved

Vibroacoustic processes of grinding fibrous semi-finished products in the knife refiners

Vibroacoustic processes during refining in knife refiners are investigated. When the rotor blades move relative to the stator knives, pressure pulses occur that act on the fibrous semi-finished product, causing it to refine, and on the rotor and stator, causing them to vibrate. A technique has been developed for calculating the sliding speed of the rotor knives on the stator knives. The sliding speed of the knives depends on the headset pattern and the rotor speed and can reach the speed of sound in the metal. The necessity of taking into account the Doppler effect during vibration diagnostics and controlling the functioning of mills is shown. The error in calculating headset frequencies without taking into account the above effect can reach more than 40%, taking into account up to 8%. © Published under licence by IOP Publishing Ltd

Vibration diagnostics of plates of knife refiners

The subject of the research is the diagnosis of the technical condition of the plate of knife refiners. The technical diagnosis of a knife plate consists of determining the stability of the inter-knife gap and the degree of the plate wear. The paper explores the dynamic effects of a plate on a fibrous material. It is shown that the main source of high-frequency vibration of the stator is pressure pulses that occur when the rotor and stator knives cross. The influence of the rotor speed and the number and angle of intersection of the plate knives on the nature of the stator vibration spectrum is studied. It is concluded that the intensity of the effect of the plate on the fibrous material increases from the centre to the periphery. A formula is proposed for determining plate frequencies taking into account the Doppler effect. The vibration diagnostics of the rotor beats is based on the resonance-demodulation method. Estimating the depth of the amplitude modulation of vibrational acceleration of the stator at the maximum plate frequency with harmonics of the working frequency, it is possible to judge the amount of beating of the rotor plate. A device was developed for vibration diagnostics of the beats of a rotor plate of a disk mill. The developed methods and tools can be used in other industries, for example, in mining and metallurgy. © Published under licence by IOP Publishing Ltd

Longitudial fluctuations of rotors of disk knife refiners

The subject of the study is the longitudinal fluctuations of the rotors of disk knife refiners. The dynamic and mathematical models of rotors of disk mills are developed. As a result of the research, a methodology for calculating the longitudinal fluctuations of rotors is proposed and tested. The error in determining the lower frequencies of free fluctuations of the mill rotors does not exceed 9%. The lowest frequencies of free longitudinal fluctuations of the rotors of existing mills are in the range of 85-165 Hz, and the second and subsequent frequencies of free fluctuations are in the frequency range above 1 kHz. When designing and operating disk knife refiners, it is necessary that the minimum inter-knife gap between the rotor and stator does not exceed the amplitude of fluctuations of the mill disk. The developed calculation procedure can be used in other industries, for example, mining and metallurgy. © Published under licence by IOP Publishing Ltd

Vibration processes in the knife refining machines

An object of research is a vibration of the stator of the knife refining machines and its interrelation with the factors which influences the course of refining among them are technical condition of a plate and change of characteristics of the ground material. The diagnostic model of process of refining is developed and positively approved. The new method of determination of degree of wear of the refining plate of refiners is offered. The new method of management of functioning of the knife refining machines is developed. It is shown that management of work on this indirect indicator is not worse, than the management based on the earlier known diagnostic signs of refiners functioning. The developed method of management is indispensible for the refiners with stepwise regulation of a gap, in a disk-conic refiners and in a dual refiners. Realization of this method under production conditions showed stable characteristics of a gain in degree of refining of a semi-finished fibrous product and decrease in specific power consumption during refining. The developed methods can be used in other branches of industry, for example, mining and metallurgy. © 2019 IOP Publishing Ltd. All rights reserved

Study of longitudinal vibrations of stab knife refiners

The subject of research is the longitudinal vibrations of stab knife refiners. A model of the fibrous layer between the rotor and stator is developed. It is shown that it is advisable to use the Maxwell-Thomson model for liquid friction of the rotor and stator, and the Hooke elastic model for boundary friction. The formula for determining the dynamic stiffness of the fibrous layer is obtained. Dynamic and mathematical models of the refiner in the longitudinal direction are developed. The mathematical model is a system of linear differential equations with periodically varying coefficients (Mathieu-Hill equations). A method for calculating the amplitude of oscillations of the refiner rotor and stator is developed. According to this technique, Andritz 54-60-1c stab refiner was designed. Oscillation parameters of the refiner rotor and stator are determined theoretically and experimentally. The stator oscillation amplitude is 1.6-2.3 times smaller than the rotor oscillation one. In case of boundary friction, the amplitude of oscillations of the stator and rotor increases by 2-3 times in comparison with liquid friction. The oscillation amplitude of the rotor and stator in the longitudinal direction is comparable with the gap between these elements. Therefore, it is recommended while designing refiners, to develop methods and means of vibration protection, and during operation, to prevent boundary friction between headsets. The developed calculation procedure can be used in other industries, for example, mining and metallurgy. © Published under licence by IOP Publishing Ltd

Engineering of the knife grinding machine milling process

The paper investigates milling process in knife grinding machines. Engineering process of these machines involves determining a degree of knife garniture wear as well as rotor and stator misalignment without the stop of the machines. To find these parameters a series of experimental researches were conducted at the enterprises of the industry. Vibrating diagnostics methods are the most informative ones for exploiting engineering of the knife grinding machine milling process. Methods of determining a degree of knife garniture wear and rotor and stator misalignment without the stop of the machines are protected by patents of the Russian Federation. Use of the developed methods and means by support and diagnostic team specialists at the enterprises increased the efficiency of the engineering process of knife grinding machine milling. Proposed methods can be used in other businesses, for example, in mining and steel industries. © Published under licence by IOP Publishing Ltd

Dynamic calculation of knife refining machines together with a supporting structure

The research subject is the method of dynamic calculation of knife refining machines together with the supporting structure. The design of refiners and supporting structures is carried out by various organizations. The knife refining machine and the supporting structure are a single dynamic system and, therefore, they must be calculated together. The forces exciting the oscillations of the refiners are investigated. Dynamic and mathematical models of the system are developed. The proposed method of dynamic calculation has been successfully tested on TF-52 and TWIN-66 refiners by OJSC "Solikamskbumprom". The developed method of dynamic calculation can be used in other industries, such as metallurgical and mining. © Published under licence by IOP Publishing Ltd

Features of the rotor dynamics of knife refining machines

The paper researches the features of the rotor dynamics of knife refining machines. The rotor of these machines turns in the pulp. The total imbalance of the refiner rotor consists of mechanical, hydraulic and hydrodynamic components. The mechanical imbalance of the refiner rotor changes due to the plate wear. In the knife refining machines, it is advisable to use automatic balancing devices to compensate for the imbalance of the rotor during operation of the refiner without stopping it. The methodology for calculating the beats of the rotor plate has been developed and tested. The operational cross-knife gaps of the knife refining machines are comparable to the beats obtained. It is recommended to eliminate gaps in the design of the rotor assembly, i.e. use bearings with tensioner and use a stator to make refiner adjustment. The developed methodology for calculating beats can be used in other similar machines, for example, in centrifugal pumps. © Published under licence by IOP Publishing Ltd

Reliability of plate of knife refiners

The subject of the researches is reliability of plate of knife refiners. Mathematical model of reliability connecting technical resource of plate with the major factors influencing reliability is offered. Influence of regime, operational, efficiency and protective factors is considered. Recommendations about increase in reliability of plate are developed. Offered technique of reliability research can be used in other machines, for example, in centrifugal pumps. © 2020 Published under licence by IOP Publishing Ltd