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This work aims to determine the root cause of unexpected failures of felt guide roll shafts of a paper machine. This was executed by performing finite element analysis (FEA) and metallurgical failure analysis. For the FEA, computer simulations were performed to assess load-bearing behavior of the shafts during operation. For the failure analysis, various techniques were employed including visual inspection, chemical composition analysis by emission spectroscopy, fracture surface analysis, and microstructural analysis by optical microscopy (OM) and scanning electron microscopy (SEM). The FEA results show that the effective stress values in the shaft cracking regions are far less than the fatigue limit but cracking still occurred. This suggests that the material's mechanical properties deteriorated due to corrosion. From the failure analysis results, it was found that corrosion fatigue was likely to be the root cause of the shaft failure incidents. [ABSTRACT FROM AUTHOR]

The reliability and performance of technological equipment largely depends on timely and reliable diagnostics of less durable assembly units, which include rolling bearings. An effective tool for determining state of the mechanical rotational systems on rolling bearings is vibration diagnostics. The variety vibration diagnostic method which are used on practise is due to the complexity extracting an informative component for estimation and predicting the state of rolling bearings from the general vibration signal of the study unit. The article is dedicated information content study of narrow frequency ranges of the vibration signal operation bearing assemblies paper machines and their use as diagnostic parameters for vibration diagnostics of rolling bearings. The paper presents the analysis results of vibration diagnostics existing methods of bearing assemblies of the technological equipment and establishes the determination defects in rolling bearings by changing the vibration level on the characteristic frequencies components of the vibration spectrum and the bypass spectrum provides more specific information about the nature damage of the bearing and its operation. On the processing experimental data base i.e. the average vibration velocity spectra signal taken from the bearing assembly paper machine, we offer a relative indicator for current state bearing estimation and its state prediction progress, which helps to make a decision on the suitability or unsuitability bearing.

Most paper mills in the Russian Federation consume around 40 % more electrical power than they actually require. The reasons are a low level of technical, scientific, and proficient assistance. Moreover, the produced goods have non-competitive consumption characteristics. The urgent current measures in this matter contain constructional and technological optimization, including drying temperature modes. The drying section of a paper machine is the most energy-consuming, while it significantly affects the mechanical strength and supplementary properties of the resulting paper goods with their structural and dimensional characteristics. Drying the paper web takes 72–77 % of the total energy of the paper machine. Therefore, the purpose of this study is to analyze the influence of the temperatures of the drying process on the strength and structural-dimensional properties of the paper, with the perspective for further application of the results in the practice of industrial companies and additional scientific investigation. The presented results show the influence of pulp type, beating degree, mass of 1 m2, and drying temperature on the strength and structural-dimensional properties of laboratory samples. Within the investigational process, laboratory samples from sulphate-bleached softwood and hardwood pulp were created and tested. The weights of the samples varied from 60 to 120 g/m2, and the beating degrees ranged from 20 to 50 °SR. The drying temperature extended from 80 to 140 °C. The analysis of the acquired paper samples revealed that the drying temperatures had a considerable impact on the strength, structure, and dimensional qualities of the material. Namely, while sulfate-bleached softwood and hardwood pulp types were used as a raw material, increasing the drying temperature from 80 to 140 °C had the greatest effect on the structural-dimensional properties of the paper made from a pulp with a higher beating degree and the greatest effect on the strength properties of the paper made from a pulp with a lower beating degree. For citation: Prokhorov D.A., Dubovy V.K. Influence of Drying Temperature on Paper Properties Made of Sulfate-Bleached Softwood and Hardwood Pulps. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 3, pp. 173–184. (In Russ.). https://doi.org/10.37482/0536-1036-2023-3-173-184

Foam forming technology has attracted much attention during the past few years in the paper industry. Its advantages compared to conventional water forming are a new product portfolio and increased process efficiency. To support the paper industry in pushing foam forming technology forward, process simulation is needed to provide supporting data for strategic decision-making and as a basis for equipment dimensioning. This study examined the conversion of an existing wallpaper machine from water to foam forming technology using process simulation. To determine the required process configuration and parameter changes in the existing process, both published and unpublished data on the foam forming process were collected. This paper also describes modeling of the foam phase in the selected simulation software. The suitability of existing paper process equipment for foam was analyzed. Simulations revealed that undisturbed operation with foam requires some equipment modifications and re-arrangements in water circuits. With foam forming, the water balance in both short and long circulation changes remarkably compared to conventional water forming, leading to a large increase in the long circulation volume flows. [ABSTRACT FROM AUTHOR]

The energy efficiency of the drying section of paper machine is determined by the technology of heat flows arrangements in it. Paper drying is the most energy-consuming stage of paper production. The thermal mode of the drying section is provided by the steam condensate system which is a part of it. Analysis of exergy increments shows that almost all elements of the drying thermal process are characterized by low exergy efficiency. The main ways for increasing the degree of thermodynamic perfection of the processes occurring in the drying section of the paper machine are identified based on the exergy analysis. It is assumed that the deep internal heat recovery of the steam-air mixture for heating the source air will increase the exergy efficiency of the heat recovery plant and reduce heat removal to the environment. The effectiveness of development and implementation of a closed cycle use of steam-air mixture in the drying section was examined. Building a closed cycle provides that the air mainly has a process duty, that is, it is a transport agent for the transfer of moisture and heat along a closed circuit. The calculations show that the exergy efficiency of the processes in the recovery unit of the drying section of the paper machine of the existing production is 28.6% against 66.29% for the proposed method.

This article describes a method of dewatering press felts using a blow-through device. The essence of this method is pressing out free water contained in the felt with unheated air at a slight overpressure. The usefulness of this method for various types of felt used in tissue machines was tested. The results showed that the effectiveness of this process depends mainly on the proper selection of the pressure difference on both sides of the dewatering felt and of the blow-through time (dwell time). The increase in the dryness of felts dewatered by means of the air blow-through method is closely related to the structure and contamination of the felt. In the second part of the study, the felts were additionally dewatered using a suction chamber with a vacuum of 20 kPa. Unfortunately, the increase in the dryness of the felts by means of a vacuum was not very high, only up to 2.8%. [ABSTRACT FROM AUTHOR]

This paper presents a statistical process control (SPC) chart for variables in a new feature for the paper machine in the paper industry. The traditional control charts like X-bar and R charts may be inadequate sometimes when the process exhibits abnormal situations which could lead to false decisions. When we are interested in detecting small shifts, Exponentially Weighted Moving average (EWMA) control chart provides the correct picture to make right decisions without affecting the process unnecessarily. This study is aimed at designing EWMA control chart in paper manufacturing process.

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The final quality of tissue paper depends on the parameters of the continuous transformation process and maintenance of rolls of a tissue paper machine. For a better quality, outer surfaces of the rolls must always be clean, and their roughness should be maintained in the same way. A Doctor Blade provides for such requirements. Our work is focused on the development of a pneumatic oscillator that moves a Doctor Blade in order to scrape the outer surfaces of the rolls. It is based on a low-friction double-effect cylinder with a through-rod. The integration of two limit switch valves, one for each head of the cylinder, and a smart pneumatic circuit to obtain a very low speed of the piston at constant load, represents the novelty of the proposed device. The piston of the cylinder allows for alternatively switching the limit switches that command the 5/2 air-operated pilot valve of the cylinder. The oscillator’s design, pneumatic circuit, and working principle are detailed. Experimental tests on the conceived limit switch and on the first prototype of the pneumatic oscillator validated the effectiveness of the proposed solution, the technical feasibility of the device, and the absence of stick-slip during the oscillatory motion at low speed.

This paper reviews key advances in understanding the hydrodynamics of the forming section of papermaking during the years 1950 to 2000. Over this period papermaking advanced from rather slow-speed Fourdrinier machines to modern high-speed twin-wire formers. The advances are described in the context of technical problems faced at the time to increase machine speeds and improve paper properties. The scientific work and advances in machine design contributed greatly to the marvel of modern papermaking, which now includes machines 10 m wide operating at speeds over 100 km/h.

Abstract We propose a maximum likelihood estimation approach for the identification of symmetric noncausal models. Such models are used to represent the cross-directional dynamic response of many industrial processes that are generally modeled with a high-dimensional gain matrix. Reducing the number of parameters in a noncausal model can significantly reduce the uncertainty associated with parameter estimates. We adapt the maximum likelihood method to treat symmetric noncausal models by showing that every symmetric noncausal process admits a spectrally equivalent causal model. It is then proved that the maximum likelihood estimate of this causal model converges to that of the original noncausal model. We present an iterative identification algorithm to efficiently estimate the parameters in noncausal models. Finally, we show that the parameter covariance estimate obtained from the causal model also converges to that of the noncausal model, which lays a foundation for optimal input design in noncausal processes. Several numerical examples illustrate the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Highlights • scanner path utilized as a manipulatable variable in paper machine cross-directional control. • faster response to load disturbances. • estimation of process noise and basis weight estimate uncertainty based on web-wide transmittance measurement. • adaptive model between transmittance and basis weight. ABSTRACT The cross-directional (CD) basis weight control on paper machines is improved by optimizing the path of the scanning measurement. The optimal path results from an LQG problem and depends on how the uncertainty of the present estimate of the basis weight and the intensity of process noise vary in CD. These factors are assessed by how accurately the CD basis weight estimate predicts the measured optical transmittance with a linear adaptive model on synchronized basis weight and transmittance data. Simulations on optimized scanner path in disturbance scenarios are presented, and the practical implementation of scanner control is discussed. [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)