Effect of bend orientation on life and puncture point location due to solid particle erosion of a high concentration flow in pneumatic conveyors

An investigation into predicting failure of pneumatic conveyor pipe bends due to hard solid particle impact erosion has been carried out on an industrial scale test rig. The bend puncture point locations may vary with many factors. However, bend orientation was suspected of being a main factor due to the biased particle distribution pattern of a high concentration flow. In this paper, puncture point locations have been studied with different pipe bend orientations and geometry (a solids loading ratio of 10 being used for the high concentration flow). Test results confirmed that the puncture point location is indeed most significantly influenced by the bend orientation (especially for a high concentration flow) due to the biased particle distribution and biased particle flux distribution.

Direct measurement of powder flavor adhesion onto crisp surface using a novel adhesion tester

A new experimental procedure has been implemented and a prototype of a novel adhesion tester has been designed and constructed using rapid prototyping technology. A tumbler mixer has been designed and constructed for coating powder material onto a crisp substrate. In the impact separation experiment, the amount of powder detached from one side of a crisp substrate by the effect of impact forces (48g, 77g, 102g) generated by the tester was measured. Salt particles with different size fractions (63-125, 125-180, and 180-250m) and several flavoring powders have been tested extensively. By plotting the detachment versus impact force, the difference obtained between adhesion strength of different flavoring powders (which is a strong function of particle size and surface oil content of the crisp) has been discussed. The detachment rate of salt particles increased (from 1% to 2%) with particle size (from 63 to 250m) in the presence of oil on the surface of the crisp substrate and decreased rapidly with the increase in the amount of oil applied (from 0 to 1%).

Divorce deals and bankruptcy

Discusses the rights and responsibilities of trustees and beneficiaries of co-owned land under the Trusts of Land and Appointment of Trustees Act 1996, in particular s.14 which allows the court to make an order declaring the extent and nature of a person's interest in the property. Refers to the Court of Appeal decision in Avis v Turner on whether the existence of an earlier court order postponing the sale of matrimonial property following the owners' divorce meant that an application could not be brought by a trustee in bankruptcy under s.14. Considers the "exceptional circumstances" which could allow the court to postpone the sale. [From Legal Journals Index]

What's exceptional?

Outlines the factors which the court needs to consider when deciding whether to grant an application for the sale of a property where the owner becomes bankrupt. Considers the different priorities to be given to the claims of trustees in bankruptcy and to secure lenders, with reference to the Trusts of Land and Appointment of Trustees Act 1996 ss.14 and 15, the Insolvency Act 1986 s.355A, and the exceptional circumstances in which claims will not be granted. Explores case law, in particular the Court of Appeal ruling in Avis v Turner, and the implications of the Human Rights Act 1998. [From Legal Journals Index]

Modelling of a dosator: an analytical approach based on measured powder flow properties

[No abstract is available for this article.]

Has cultural studies sounded the death-knell of classical sociology prematurely?: the view from Romani studies

The paper will argue that although Bryan S.Turner's recent defence of classical sociology was seen as apostacy by some, it points to real problems in the idealism and a-historicism of contemporary cultural studies. The paper will examine the importance of the classical sociological problematic in getting the field of Romani Studies started, and the continuing relevance of a sociological approach rooted in history and political economy. [From the Author]

The impact of powder flowing properties on dosator filling system operation

Purpose: To study the impact of powder flow properties on dosator filling systems, with particular focus on improvements in dose weight accuracy and repeatability. Method: This study evaluates a range of critical powder flow properties such as: flow function, cohesion, wall friction, adhesion to wall surfaces, density/compressibility data, stress ratio “K” and gas permeability. The characterisations of the powders considered in this study were undertaken using an annular shear cell using a sample size of 0.5 litres. This tester also incorporated the facility to measure bed expansion during shear in addition to contraction under consolidation forces. A modified Jenike type linear wall friction tester was used to develop the failure loci for the powder sample in conjunction with multiple wall samples (representing a variety of material types and surface finishes). Measurements of the ratio of applied normal stress versus lateral stress were determined using a piece of test equipment specifically designed for the purpose. Results: The correct characterisation of powders and the incorporation of this data into the design of process equipment are recognised as critical for reliable and accurate operation. An example of one aspect of this work is the stress ratio “K”. This characteristic is not well understood or correctly interpreted in many cases – despite its importance. Fig 1 [Omitted] (illustrates a sample of test data. The slope of the line gives the stress ratio in a uniaxial compaction system – indicating the behaviour of the material under compaction during dosing processes. Conclusions: A correct assessment of the bulk powder properties for a given formulation can allow prediction of: cavity filling behaviour (and hence dosage), efficiency of release from dosator, and strength and stability of extruded dose en route to capsule filling Influences over the effectiveness of dosator systems have been shown to be impacted upon by: bed pre-compaction history, gas permeability in the bed (with respect to local density effects), and friction effects for materials of construction for dosators

Modelling of dosator operation for improved manufacturing performance

Purpose: To develop an improved mathematical model for the prediction of dose accuracy of Dosators - based upon the geometry of the machine in conjunction with measured flow properties of the powder. Methods: A mathematical model has been created, based on a analytical method of differential slices - incorporating measured flow properties. The key flow properties of interest in this investigation were: flow function, effective angle of wall friction, wall adhesion, bulk density, stress ratio K and permeability. To simulate the real process and (very importantly) validate the model, a Dosator test-rig has been used to measure the forces acting on the Dosator during the filling stage, the force required to eject the dose and the dose weight. Results: Preliminary results were obtained from the Dosator test-rig. Figure 1 [Omitted] shows the dose weight for different depths to the bottom of the powder bed at the end of the stroke and different levels of pre-compaction of the powder bed. A strong influence over dose weight arising from the proximity between the Dosator and the bottom of the powder bed at the end of the stroke and the conditions of the powder bed has been established. Conclusions: The model will provide a useful tool to predict dosing accuracy and, thus, optimise the future design of Dosator based equipment technology – based on measured bulk properties of the powder to be handled. Another important factor (with a significant influence) on Dosator processes, is the condition of the powder bed and the clearance between the Dosator and the bottom of the powder bed.

Modelling dosator filling and discharge of powder

Dosators and other dosing mechanisms operating on generally similar principles are very widely used in the pharmaceutical industry for capsule filling, and for dosing products that are delivered to the customer in powder form such as inhalers. This is a trend that is set to increase. However a significant problem for this technology is being able to predict how accurately and reliably, new drug formulations will be dosed from these machines prior to manufacture. This paper presents a review of the literature relating to powder dosators which considers mathematical models for predicting dosator performance, the effects of the dosator geometry and machine settings on the accuracy of the dose weight. An overview of a model based on classical powder mechanics theory that has been developed at The University of Greenwich is presented. The model uses inputs from a range of powder characterisation tests including, wall friction, bulk density, stress ratio and permeability. To validate the model it is anticipated that it will be trialled for a range of powders alongside a single shot dosator test rig.

Review of models for predicting the discharge rates of bulk particulates from silos and bins

Various models for predicting discharge rates have been developed over the last four decades by many research workers (notably Beverloo [1], Johanson [2], Brown [3], Carleton [4], Crewdson [5], Nedderman [6], Gu [7].). In many cases these models offer comparable approaches to the prediction of discharge rates of bulk particulates from storage equipment when solely gravity is acting to initiate flow (since they invariably consider the use of mass-flow design equipment). The models that have been developed consider a wide range of bulk particulates (coarse, incompressible, fine, cohesive) and most contemporary works have incorporated validation against test programmes. Research currently underway at The Wolfson Centre for Bulk Solids Handling Technology, University of Greenwich, has considered the relative performance of these models with respect to a range of bulk properties and with particular focus upon the flexibility of the models to cater for different geometrical factors for vessels.

Effect of machine dependence on wall failure property measurements, Jenike versus an annular shear tester

Annular, ring or torsional shear testers are commonly used in bulk solids handling research for the purpose of powder characterisation or equipment design. This paper reports from a DEFRA sponsored project which aims to develop an industrial powder flow-ability tester, (based on the annular shear tester) that is economic to buy and quick and easy to use in trained but unskilled hands. This paper compares the wall failure loci measured with an annular shear cell with measurements obtained using the accepted standard wall friction tester, the Jenike shear cell. These wall failure loci have been measured for several bulk solids which range from fine cohesive powders to free-flowing granular materials, on a stainless steel 304 2B wall surface.

Start-up and running forces on bulk solids feeders: experimental findings versus available models

Many different models have been postulated over the years for sizing of feeder drives; these models have different bases, some rationally based and others more rule-of-thumb. Experience of Jenike & Johanson and likewise of The Wolfson Centre in trouble-shooting feeder drives has shown that drive powers are often poorly matched, so there is clearly still some way to go towards establishing a universally-used reliable approach. This paper presents an on-going programme of work designed to measure feeder forces experimentally on a purpose designed testing rig, and to compare these against some of the best known available models, and also against a full size installation. One aspect which is novel is the monitoring of the transition between the “filling stress field” load on the feeder and the “flowing stress field” load.

Measurement of pressure profiles in pneumatic conveying pipelines

Accurate design of two-phase air-solid pipelines requires data from flow and pressure measurements, requiring the appropriate positioning and selection of sensors as well as judicious processing of signals. This paper shows how detailed measurements of pressure profiles have been obtained for use in design of improved pneumatic conveying pipelines.

Caking strength of granulated clay under frozen conditions

Transport of particulate clay occurs during some extremely cold weather conditions typically in the winter in the far North area. During the transport and temporary storage time, the clay may cake inside a rail or road wagon or in a silo, and consequently be difficult to be discharged from the containers. This paper studied caking strength of a granulated clay powder with a certain water moisture content of 18% for influences of temperature, packing stress and freezing time. The temperature tested was -5 oC, -10 oC and -20 oC. Because the clay powder may be packed at different bed depth, the study was undertaken across the packing stress range at 8.3 kPa (1 m bed depth), 25.0 kPa (3 m) and 75.0 kPa (9 m). Freezing time varied between 4 hours (transport) and 18 hours (overnight). During the tests, failure of caked materials was measured using a QTS texture analyzer and the caking strength of frozen samples was calculated. Influences on freeze caking of granular clay in storage or transport are discussed briefly. Some conclusions are made at the end of the paper,including recommendations for practical methods for mitigating these problems.