A. A. Cenna

Physical and mechanical properties of jute, bamboo and coir natural fiber

A systematic study has been carried out to investigate the mechanical and physical properties of jute, bamboo and coir (brown and white) single fibers. The tensile properties (tensile strength, Young’s modulus and strain to failure) were determined by varying span length. Scanning electron microscopic analysis was also carried out to determine the physical properties of fibers in order to correlate with its strength, Young’s modulus and strain to failure. The Young’s modulus and strain to failure were corrected using newly developed equations. The study revealed that with increasing test span length the Young’s modulus increased and tensile strength as well as strain to failure decreased. This is because no extensometer could be used in this test set-up and machine displacement (denoted by α) was used for the modulus determination. It is also attributed that larger span length helps to minimize the machine displacement compared to smaller ones due to the reduced relative effect of slippage in the clamps. Among all fibers, the Young’s modulus of bamboo fiber was the highest. Jute fiber had smoother surface compared to other three examined fibers.

A high-pressure shear cell for friction and abrasion measurements

This paper describes the design and operations of a high-pressure shear cell capable of pressing granular material against candidate wear surfaces at macroscopic pressures of up to 700MPa. The wear surface is then forced laterally yielding information about coefficient of friction and wear mechanics during slip at the surface. This pressure covers the range commonly experienced in many mining operations, including those involved in ore crushing. Recent results with the shear cell will be presented. This involves the crushing of quartz against test tiles of Ni-hard 4 steel. Results for coefficient of friction and 3-body abrasion are reported. Wear results are quantified and compared in terms of contact profilometry and non-contact profilometry involving reflected light confocal microscopy.

Flow Visualisation in Dense Phase Pneumatic Conveying of Alumina

Pipeline wear is a very complex problem and at present there is limited understanding of the wear mechanisms responsible for the reduction of pipe wall thickness in critical wear areas. The ability to determine the wear mechanisms in these areas holds the key in determining the service life of pneumatic conveying pipelines in industry. In this paper design and construction of a visualisation test rig is presented which enables better understanding of the flow process in pneumatic conveying pipelines. Results from the flow visualisation have been analysed and presented for an insight to the flow patterns in the critical wear areas of pneumatic conveying pipelines.

Analysis of Wear Mechanisms in Pneumatic Conveying Pipelines of Fly Ash

Pneumatic conveying is a frequently used method of material transport particularly for in-plant transport over relatively short distances. This is primarily to exploit the degree of flexibility it offers in terms of pipeline routing as well as dust minimization. Approximately 80 % of industrial systems are traditionally dilute phase system which uses relatively large amount of air to achieve high particle velocities to stay away from trouble, such as blocking the pipeline. However, for many applications higher velocities lead to excessive levels wear of pipelines, bends, and fittings. To combat these problems, many innovative bends have been designed. These designs have solved the problem of wear in the bends, but often introduce the wear problem in the area immediately after the bend due to the changed flow conditions. Wear in pneumatic conveying is a very complex problem and at present there is limited understanding of the wear mechanisms responsible for the severe wear in certain areas of a pneumatic conveying pipeline. The ability to determine the wear mechanisms in these areas holds the key for determining the service life of pneumatic conveying pipelines in industry. Even though the fly can be conveyed at low velocity dense phase mode, wear of pipeline conveying fly ash remained a critical issue for many power plant operators. In this paper the wear mechanisms in a fly ash conveying pipeline has been analyzed. Wear samples from fly ash conveying pipeline have been collected and analyzed for dominant wear mechanisms in the critical wear areas. Analysis of the worn pipeline showed continuous wear channels along the bottom of the pipeline consistent with the abrasive wear by larger particles. The other severe wear areas are the sections after the special bends used to reduce bend wear. Scanning electron microscope (SEM) analysis of the surfaces revealed that both erosive wear and abrasive wear mechanisms are present in these areas. Formation of a surface layer similar to transfer film in alumina conveying pipelines have been recognized in this analysis. These layers seem to be removed through brittle manners such as cracking and spalling. The wear mechanisms and the wear debris seen on the surface are consistent with wear by larger particles.

Wear Mechanisms in Pneumatic Conveying of Sand and Analysis of Predictive Model for Pipeline Thickness Loss

Pneumatic conveying is a process of transportation of powder and granular materials through pipelines using high pressure gas. It is a frequently used method of material transport particularly for in-plant transport over relatively short distances, although long distance pipelines are becoming more common with technological advancements in this area. The major advantages of the system are the degree of flexibility it offers in terms of pipeline routing, dust minimization within the factory environment as well as automation. A large percentage of industrial systems are traditionally dilute phase system, which use relatively large amounts of air that lead to high particle velocities. Dense phase systems are designed to operate at relatively low velocity regimes which reduced the wear to some extent. Yet the problem of wear remains a major issue with these conveying systems. Service life of a pneumatic conveying system is dictated primarily by the wear in pipelines and bends due to the interactions between the particles and the surfaces. Depending on the conveying conditions or modes of flow, wear mechanism can be abrasive or erosive or a combination of both. The locations of the high wear areas also varies, depending on the ratio of the solids mass flow rate and the air velocity along the pipeline. Wear tests have been conducted using sand through a 50 mm diameter, 25 m pipeline fitted with a short radius bend to study the wear mechanisms associated within the critical wear area of the pipeline. The pipeline thickness loss has also been monitored using an ultra sonic thickness gage to generate the wear profile inside the pipeline. Surface analysis has been conducted using a scanning electron microscope to determine the associated wear mechanisms in the area. Finally, experimental results have been compared with the output of an energy based predictive model and the associated variations have been discussed.

Micromechanics of wear and its application to predict the service life of pneumatic conveying pipelines

Pneumatic conveying involves the transportation of a wide variety of dry powdered and granular solids through pipeline and bends using high pressure gas. It is a frequently used method of material transport particularly for in-plant transport over relatively short distances. This is primarily to exploit the degree of flexibility it offers in terms of pipeline routing as well as dust minimization. Approximately 80% of industrial systems are traditionally dilute phase system which uses relatively large amount of air to achieve high particle velocities to stay away from trouble, such as blocking the pipeline. However, for many applications higher velocities lead to excessive levels of particle attrition or wear of pipelines, bends and fittings. To combat these problems, there are systems designed to operate at relatively low velocity regimes. Yet one problem remains as a major issue with these conveying systems which is wear. In pneumatic conveying, service life is dictated by wear in critical areas of the pipelines and bends due to higher interaction between the particles and the surface. Depending on the conveying conditions or modes of flow, wear mechanism can be abrasive or erosive or a combination of both. Recent developments in predictive models of wear of materials showed that by using the particles energy dissipated to the surface and the surface material properties, it is possible to predict the overall material loss from the surface. Material loss from the surface is then can be converted to determine the pipeline thickness loss that can be used to indicate the service life of the pipeline. In this paper wear mechanisms in the critical wear areas of pneumatic conveying pipeline have been analysed. Based on the wear mechanisms, predictive models have been selected from the literature. A number of factors have been incorporated to apply the model into pneumatic conveying processes. Conveying tests were performed in the laboratory to determine the time to failure as well as gradual thickness loss in the bend. Finally experimental results have been compared the model output and the variations have been analysed for further improvement of the models.

Experimental determination of cutting and deformation energy factors for wear prediction of pneumatic conveying pipeline

Pneumatic conveying has become a well established method of transporting materials in the resource and process industries. Erosion is a phenomenon that occurs in pneumatic conveying pipeline due to the inherent nature of conveying process. In pneumatic conveying, particulate material is transported by the motive of compressed gas with velocities usually less than 60 m/s. In the present investigation, erosion tests were performed in order to study the wear behaviour and determine specific energy factors of pipeline material for the predictive models of wear in dense phase mode of pneumatic conveying pipeline. These tests were performed on mild steel and aluminum surface with alumina and Ilmenite particles. Double disc method was used to measure the particle impact velocities with different powder mass flow rates at different compressed air pressures for erosion tests. Erosion rate and erosion behaviour were studied under the influence of solid particle erosion at dense phase conveying condition. Deformation and cutting energy factors were then determined for predicting wear based on the material removal mechanisms. These factors will then be incorporated in a generic software algorithm to predict the service life of pneumatic conveying pipeline.

Understanding Wear Mechanisms and Their Implication to Service Life of Pneumatic Conveying Pipelines

Pneumatic conveying is a process of transporting particulate material through pipelines using compressed gas. As material is conveyed through pipeline and bends, the pipeline especially after bends suffers severe wear due to particles’ interactions with the surfaces. Removal of material from solid surfaces by action of impinging particles is known as erosion. It is well known that particle velocity and impact angle play a major role in determining the material removal rate from the surface. In a recent study, it was demonstrated that materials’ response to deformation during impacts dictates how the material is removed from the surface. This paper presents the surface characteristics of ductile materials due to single-particle impacts as well as standard erosion using micro-sand blaster. Surface and subsurface damage characteristics with respect to the impact parameters as well as particles’ angularity have been presented. Aluminum and mild steel surfaces impacted by spherical zirconia and angular alumina particles have been analyzed using scanning electron microscope (SEM). Finally, the material removal mechanisms have been discussed with respect to the service life of pneumatic conveying pipelines.

Effects of Surface Modifications on Wear Mechanisms in Fly Ash Conveying Pipelines

Pneumatic conveying is a frequently used method of material transport particularly for in-plant transportation over relatively short distances. This is primarily to exploit the degree of flexibility it offers in terms of pipeline routing as well as dust minimization. Approximately 80 % of industrial systems are traditionally dilute phase system which uses relatively large amount of air to stay away from trouble, such as blocking the pipeline. Wear in pneumatic conveying is a very complex problem, and at present, there is limited understanding of the wear mechanisms responsible for the severe wear in certain areas of the pipeline. One of the recent studies [1] showed that the surface modifications by conveying materials can alter surface characteristics which change the wear mechanisms of the pipeline. Better understanding of the surface modifications and their effects on wear mechanisms can play a significant role in developing predictive models for the service life of pneumatic conveying pipelines. In this paper, wear surfaces from fly ash conveying pipeline have been studied for a better understanding of the surface modification and its effects of wear mechanisms. Wear samples were analyzed using SEM Energy Dispersive X-ray Spectroscopy (SEM-EDS). Analysis of surface elements discovered high level of silicon (Si) and aluminum (Al) present in the modified surface areas which apparently responsible for brittle failure of the surface layer. Although the actual form of the chemical compounds has not been analyzed, it is evident that the surface modification by the constituents of the conveying material is one of the major contributors to the severity of wear in fly ash conveying pipelines.

Investigation of Energy Consumption and Wear in Bypass Pneumatic Conveying of Alumina

Dense phase pneumatic conveying is critically dependent on the physical properties of the materials to be conveyed. However, many materials, such as alumina and coarse fly ash, which are highly abrasive, do not have dense phase conveying capacity. Bypass pneumatic conveying systems provide a dense phase capability to non-dense phase capable bulk materials. These systems also provide the capacity of lower the conveying velocity and therefore lower pipeline wear and lower power consumption occurs. The objectives of this work were to study the energy consumption and wear of bypass pneumatic transport systems. Pneumatic conveying of alumina experiments were carried out in a 79 mm diameter main pipe with a 27 mm inner diameter bypass pipe with orifice plate flute arrangement. High-speed camera visualizations were employed to present flow regimes in a horizontal pipe. The experimental result showed the conveying velocity of bypass system is much lower than that of conventional pipelines; thus, specific energy consumption in the conveying process is reduced. The service life of the bypass line has also been estimated.