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Here you can find articles with technical expertise and background information on powder and bulk solids handling and processing.
Magnetic separator or metal detector? About magnetic filtering, magnetic separation, several ways to remove metal foreign bodies from your product streams.
Magnetic separator or metal detector?
About magnetic filtering, magnetic separation, several ways to remove metal foreign bodies from your product streams. Magnetic separators remove metal foreign bodies from your product streams. Metal foreign bodies ’contaminate’ your product, and they can also cause severe damage to your machinery. Rejection of batches is costly, but it can be even more costly if the foreign bodies are not removed, making it necessary to conduct a product recall. You will then be faced with huge costs and reputation damage. Examples of metal contaminants / foreign bodies: staples, nails and screws, bolts and nuts that have vibrated loose, wear of the moving steel and stainless steel machine parts and rust particles (corrosion). Magnetic separators filter and remove metal contaminations from your product streams, in order to guarantee high product quality and prevent damage to machines. Magnetic separator or metal detector? A magnetic separator filters/traps (and later removes) or immediately removes the metal contaminants from the product flow. Magnetic separators cause practically no product
20.09.2021  |  276x  |   | 
Segregation mechanisms: the basics of de-mixing Segregation or de-mixing is the difference in  composition of several samples of one bulk material. This article gives insight in the general influences and aspects of segregation.
Segregation mechanisms: the basics of de-mixing
Segregation or de-mixing is the difference in composition of several samples of one bulk material. This article gives insight in the general influences and aspects of segregation. If samples taken from one batch have a different composition, this is called segregation or de-mixing. The samples may differ on the basis of the components present (different products) or the fractions present (different particle sizes). Segregation means that the properties of a batch of bulk material are no longer constant at every location, resulting in a loss of quality. Combating segregation involves many aspects. by: ir. P.J. van der Kooi This article deals with general influences and aspects of segregation. The second article in this series deals with the aspects specifically related to storage and flow in the silo. Product properties and segregation Global distinction In mixtures of identical particles, by definition, no segregation can occur. De-mixing is a consequence of the difference in properties of the various components or fractions in a mixture. It can be caused by various mechanisms, in which the process also plays an important role.
02.09.2021  |  094x  | 
About the gully angle of pyramid shaped hoppers Recommendations for proper flow from rectangular or pyramid shaped hoppers, in view of the corners of the hopper that are less steep.
About the gully angle of pyramid shaped hoppers
Recommendations for proper flow from rectangular or pyramid shaped hoppers, in view of the corners of the hopper that are less steep. Rectangular hoppers are widely used to store bulk solids. Although convenient to fabricate they have process drawbacks in that large flat sides are prone to deflection, so often require stiffening, and the converging faces form gully angles that offer poor flow and self-clearing properties. Some small compensation is given by the rectangular outlets being somewhat easier to fit with slide valves. ​​ The gully angle of a symmetrical, pyramid shaped hopper is roughly 10 degrees less steep than sides and is prone to retention of product unless it is radiused. For Mass Flow design purposes, the inclination of the gullies should be considered as a cone. For Funnel Flow hoppers the gully angle should exceed the wall friction angle by at least 10 degrees. Some product retention in the corners is almost inevitable unless the corner is radiused or significantly increased in inclination. Mass flow is much more practical and residue much less likely if the end walls
01.09.2021  |  065x  | 
Why contract manufacturing is both critical and crucial The outsourcing of production and the division of labour are key factors for seizing market opportunities and growth in the post-industrial age.
Why contract manufacturing is both critical and crucial
The outsourcing of production and the division of labour are key factors for seizing market opportunities and growth in the post-industrial age. For decades, large companies have outsourced production capabilities, thus driving globalisation –but also contributing to the decline of domestic industries. Digitalization, however, means it makes sense for more and more well-known global players to relocate production back to Europe. Contract manufacturing, for example, gives an idea of where this journey can take us. For a long time, the outsourcing of certain manufacturing tasks promised potentially large cost-savings for companies, with personnel-intensive business areas reduced in size or even closed completely and processes – from toy production to the manning of telephones – relocated in order to save time and money. At the same time, service providers who were not only able to cope with special projects, but were also increasingly able to build up technological know-how, found an increasing demand for their services. The reason for this was – and still is – the continued and growing need for tailor-made
27.08.2021  |  058x  | 
Hopper Design Process
Hopper Design Process
The first stage of the hopper design process commences with establishing the form of flow regime that should be generated when discharging. . Basic choices 1. Mass Flow. For products that deteriorate in some way over time and are to be held in hoppers that may be re- filled before fully emptying. 2. Expanded Flow. For products with poor flow properties that either do not deteriorate in extended storage or the non-mass flow contents will be discharged before the hopper is re- filled. 3. Funnel Flow. For free flowing products that do not deteriorate during extended storage time. Geometric form The second stage is to choose a geometric form for the storage container, usually either circular, with conical hopper section or rectangular, with pyramid or slot outlet. The outlet region may be transformed to a chisel shape to exploit the flow benefits of plane flow and slot outlets. Eccentric shapes and multiple outlets are normally best avoided. This choice tends
11.08.2021  |  044x  | 
VdS-certified fire protection concept for belt dryers For the first time, T&B is preparing a certified protection concept in cooperation with VdS
VdS-certified fire protection concept for belt dryers
For the first time, T&B is preparing a certified protection concept in cooperation with VdS The drying of materials is often the prerequisite for their further processing. The drying process, i.e. the thermal removal of water and other liquids, makes the dried goods durable, mixable, grindable or otherwise usable for further process steps. Drying processes have been industrial standard for many decades already. The first belt dryer in Europe, for example, went into operation as long ago as 1907. These days, belt dryers are used in a wide range of different branches. Examples include belt dryers for timber, pharmaceuticals, food, plastics, wastewater sludge and many other organic substances. All these substances have one thing in common: they are combustible and, in combination with a belt dryer, result in a high fire load. The importance of belt dryers in industrial applications has increased significantly over the past few years. Generally, standard series belt dryers have a modular design. They are made up of a product feeding module, a drying module
11.08.2021  |  544x  | 
When to select a ‘Bullet’ or ‘Cone-in-Cone’ insert
When to select a ‘Bullet’ or ‘Cone-in-Cone’ insert
Flow inserts can be used for many different reasons, such as improving flow, reducing overpressures on feeders, rectifying segregation and inhibiting ‘Flushing’. They are often installed as retrofits to overcome operating problems, but require experienced design to secure optimum benefits without introducing other problems. The ‘Cone-in-Cone’ and ‘Bullet’ Types are amongst methods used to improve flow by converting a flow regime from Funnel to Mass flow. The question is : -which type is most appropriate for a given application? The ‘Bullet’ insert is a central fitting of a diverging and converging cone that forms an annular flow channel in the hopper. The degree of cone convergence is chosen to ensure the material will mass flow when discharging. A drawback of this device is that the hopper capacity is reduced by the volume of the fitting. This may be compared with the Cone-in-Cone insert, where a steeper cone is installed in the center of the
04.08.2021  |  029x  | 
Spray (micro) encapsulation of sensitive substances in matrix form An overview of essential oil and vitamin case studies
Spray (micro) encapsulation of sensitive substances in matrix form
An overview of essential oil and vitamin case studies Phytochemicals are increasingly found in many food, chemical and agricultural items. Product and process optimization is becoming ever-more important in all of these industries, with a focus on quality, manufacturing efficiency, stability and formulation costs. Essential oils are volatile substances with a relatively high vapor pressure; they are susceptible to oxidation and light and may change or may even lose their properties when directly exposed to stressors. Like other sensitive, volatile, odor- or taste-intensive liquid active ingredients, they must therefore be protected from the environment or vice versa. For this protection and to simplify handling — as well as for better dosage and targeted release — these substances are therefore progressively offered and used in encapsulated and/or free-flowing forms. Various processes can be used to deliver products with a compact structure. During process development, the most suitable procedures and equipment
21.07.2021  |  584x  | 
More efficiency and profit by accurate  weighing  Preventing waste by more accurate weighing and dosing. A summary of where weighing can assist your process and save you money.
More efficiency and profit by accurate weighing
Preventing waste by more accurate weighing and dosing. A summary of where weighing can assist your process and save you money. Given the constantly rising prices of raw materials, the investment in accurate weighing and precise filling is worthwhile more than ever. In this article, we give some examples of how to achieve optimum efficiency with proven technology. Intake with ship unloader When discharging vessels or transporting via conveyor belts, a throughput weigher can be used to weigh the continuous bulk flow in batches. A built-in bunker weigher allows the individual weights to be totalised and the product flow to be recorded accurately. It becomes even more efficient if this can be done via a mobile installation. Incoming and outgoing control with weighbridge To keep a good eye on the global product flow of your company, all goods that enter or leave your plant should be weighed. The weighbridge can be linked to access control systems such as number plate cameras, barriers, badge systems, etc., making it impossible to enter or leave the site without being weighed. Logging in
07.07.2021  |  566x  | 
The importance of uniform drawdown by feeders
The importance of uniform drawdown by feeders
Whenever a bulk material is stored the contents are required to flow reliably and under control during both the filling and emptying processes. Few problems become apparent during filling, although some may be caused that show later. The regime of flow generated during the discharge process depends on the storage vessel construction and properties of the bulk material being handling, but essentially follows a mass or funnel flow form, depending whether the total stored contents move during discharge. The two major benefits of Mass Flow are the securement of reliable flow without arching or ‘ratholing’ and the elimination of indeterminate residence time due to static regions of storage during discharge. Other benefits are secured are that the risk of ’flushing’ is reduced and that segregation that may have occurred during filling is redressed. It is essential for mass flow that extractions takes place over the entire area of the hopper outlet. However, to secure
04.07.2021  |  032x  | 
Vacuum conveying of sticky product at Campine Belgium TBMA België has supplied Campine with a bag dump cabinet with blow-through rotary valve, piping and Piab unit for the conveying of sticky products.
Vacuum conveying of sticky product at Campine Belgium
TBMA België has supplied Campine with a bag dump cabinet with blow-through rotary valve, piping and Piab unit for the conveying of sticky products. Pre-testing in the TBMA test room showed that these products can be easily processed with vacuum conveying. Also, a smart solution was invented to prevent cross-contamination. Alternative for bag handling Campine in Beerse (Belgium) recycles industrial waste streams to make new raw materials. The company dismantles lead-based car batteries and is engaged in the recovery of metals. They also produce high-quality antimony trioxide as flame retardant synergist, raw material for pigments or catalyst for PET production. This makes the company a prominent player in the circular economy. Specifically for the plastic market, Campine produces masterbatches in which powdered additives are mixed in a carrier polymer. In this way, they relieve their customers when it comes to safe processing of dusty and ATEX-sensitive powders. To optimise their production process, Campine sought an alternative to pouring bags of additives directly into a gravimetric feeder. This refilling
28.06.2021  |  242x  | 
Clever design of Big-Bag filling units for Van Delft Biscuits The TBMA Big-Bag filling units play a key role in the internal handling during the spice nut production, and in coating these traditional delicacies with chocolate.
Clever design of Big-Bag filling units for Van Delft Biscuits
The TBMA Big-Bag filling units play a key role in the internal handling during the spice nut production, and in coating these traditional delicacies with chocolate. Billions of ‘pepernoten’ (spice nuts) roll out of the ovens of Van Delft Biscuits every year. New is the in-house process line for coating traditional delicacies with chocolate. The TBMA Big-Bag filling units play a key role in the internal handling during the spice nut production. Engineering to the millimeter For Van Delft Biscuits, TBMA has supplied two Big-Bag filling units for handling spice nuts. The challenge was to fit the Big-Bag filling installation into the reasonably compact factory hall where a new coating machine is located. The available height was 4400 mm. Ultimately, TBMA managed to engineer a filling machine in which the two-meter-high big bag can be filled and weighed suspended, while there is also room for the more than one-meter high metal detector and an elevator belt. Above it is even a 30 cm space left for the operator to clean the installation. Filling the Big-Bag suspended has the advantage that the bag can be stretched and is filled
28.06.2021  |  099x  | 
Optimising functional ingredients for enhanced nutrition  Fluidised bed and spouted bed processes offer manufacturers almost unlimited possibilities in terms of optimised particle design and the functionalisation of ingredients, the properties of which can be fine-tuned
Optimising functional ingredients for enhanced nutrition
Fluidised bed and spouted bed processes offer manufacturers almost unlimited possibilities in terms of optimised particle design and the functionalisation of ingredients, the properties of which can be fine-tuned Fluidised bed and spouted bed processes by Glatt offer manufacturers almost unlimited possibilities in terms of optimised particle design and the functionalisation of ingredients, the properties of which can be fine-tuned using spray granulation, agglomeration, microencapsulation and coating. The consumer demand for fortified products is constantly growing and has been well received by end users. The form in which health-promoting probiotics, dietary fibres or antioxidants are consumed depends on both the preferences and everyday habits of the individual: some prefer sports drinks, protein bars or enriched iced tea, whereas others favour more direct dosage forms, such as effervescent tablets, sachets or capsules. However, although the manufacturing processes associated with these products present numerous challenges, a universal requirement is that functional ingredients must be stable during storage, precisely dosed, dissolve quickly or have a depot effect. Key
12.05.2021  |  930x  |   | 
Explosion-Proof vs. Intrinsically Safe Equipment There are two characteristic electronic safety standards: intrinsically safe and explosion-proof. Which one do you need?
Explosion-Proof vs. Intrinsically Safe Equipment
There are two characteristic electronic safety standards: intrinsically safe and explosion-proof. Which one do you need? In regard to electronic safety standards, there are two characteristics that are often referred to in manufacturing: Intrinsically safe and explosion-proof. Sometimes the term “explosion proof” is also used to describe the environment of operations and both means of protection, environment or equipment, are acceptable for safe manufacturing processes. Intrinsically Safe Intrinsically safety equipment combats hazards because it is incapable of causing sparks or combustion. This means that intrinsically safe equipment must limit electrical current, voltage and heat. This reduces the risk of explosion in hazardous and combustible environments such as distilleries, chemical plants, fuel refineries or textile manufacturers. Intrinsically safe equipment may be more critical in areas impacted by system breakdown, vapors and gases, combustible dust or a combination of all three. Explosion-Proof Utilizing explosion-proof or flame-proof equipment is a method of protection
30.04.2021  |  172x  | 
Increasing demand for used machines Circular economy specialist Surplus Select is seeing an increasing demand for used machines, for the food, cosmetics or animal feed industries.
Increasing demand for used machines
Circular economy specialist Surplus Select is seeing an increasing demand for used machines, for the food, cosmetics or animal feed industries. What started out as a social mission to bring together suppliers and customers of used machines, has now grown into a circular economy mindset within the process industry. The Surplus Select circular economy initiative, founded in 2001, gives start-ups, R&D departments and pilot plants the opportunity to achieve limited-budget production by using pre-owned processing machines. "We started by offering very basic services, but now we have become a serious market player, and are being approached by large multinationals for the acquisition of high-quality, sustainable solutions”, says Rick Soepenberg, founder and owner of Surplus Select. Whether it’s machinery for the food, cosmetics or animal feed industries, Surplus Select has over 400 eye-catching machines at their 1500 m2 warehouse and 4000 m2 outdoor site in the Dutch village of Swifterbant; all waiting for new owners. According to Soepenberg, buying up large stocks of surplus machinery is a risky but nevertheless
24.04.2021  |  2025x  | 
Improved performance for crop protection products Plant protection products, be they herbicides or fungicides, must be dust-free, free-flowing, stable, safe to handle + provide good redispersibility properties.
Improved performance for crop protection products
Plant protection products, be they herbicides or fungicides, must be dust-free, free-flowing, stable, safe to handle + provide good redispersibility properties. Product development usually focuses on the optimization of successful products: That means improved effectiveness and storage, safer handling and easier dosing. As well as these long-standing challenges, however, farmers and manufacturers of crop protection products are facing an increasingly fragmented market with regionally specific requirements. Due to globalisation and imbalances in the ecosystem, it is becoming increasingly necessary to control pests in a targeted manner and protect plants from previously unknown threats. Yet a growing market for organic farming means an increase in demand for biological or biodegradable crop protection agents which are obtained, for example, by fermentation processes. Industrial processing means these intermediate products are not temperature-stable and require gentle treatment at low temperatures. A further challenge is climate change: Cultivated areas in normally temperate climate regions are now exposed to weather events such
11.03.2021  |  294x  |   | 
Handling Bulk Materials; What’s the Big Deal? Process technologies have advanced enormously the past decades. But  flow problems have persisted. This article will discuss some of the more common causes. 
by R.J. Farnish
Handling Bulk Materials; What’s the Big Deal?
Process technologies have advanced enormously the past decades. But flow problems have persisted. This article will discuss some of the more common causes. by R.J. Farnish The movement and storage of bulk materials within processes has been a fundamental activity for many plants since the event of the industrial revolution in the 18th century. Process technologies have advanced enormously in their sophistication and efficiency over the intervening period to the current day. If it were possible to bring an engineer from the early days of industrialisation to see what is available today they almost certainly would not believe their eyes at the sheer diversity of plant equipment tailored for specific process requirements and end products. Sadly, what they probably would be able to relate to are the silos, bunkers and hoppers that function poorly and are often on the receiving end of the not so tender attentions of plant operators. This article will discuss some of the more common causes of processing/flow problems that have persisted over the decades. Fundamentals The discharge problems that are experienced when handling bulk
05.03.2021  |  242x  | 
Hopper inserts, an approach to solving poor flow Enhanced hopper performance through sustained examination of  materials, hopper geometries and influence of insert design.
Hopper inserts, an approach to solving poor flow
Enhanced hopper performance through sustained examination of materials, hopper geometries and influence of insert design. The enormous volume of bulk materials handled every year means solids must be stored in hoppers, intermediate bulk containers, silos and other storage devices, often several times before being processed. However, storage can result in a number of handling issues including erratic surges, arching, ratholes, packing, flushing, dead regions, feed upsets, and in some cases can reduce the suitability of the product for the next process stage [IMG02**R45] Although it is seemingly counterintuitive to introduce an obstacle into the storage container as a solution to these problems, the use of inserts can enhance storage container performance. An insert is usually a static fitting on the inside of a bulk storage container, including liners and other modifications that alter the internal space of a vessel. Flow regimes are determined by how the individual particles in a bulk solid respond to local forces at contact points. An insert alters the flow regime of a material
02.02.2021  |  261x  | 
Improving flow in hoppers with Sigma2-relaxation Plane flow is less troublesome as axisymmetric flow. Sigma2-relaxation will show even less flow problems. By: Lyn Bates
Improving flow in hoppers with Sigma2-relaxation
Plane flow is less troublesome as axisymmetric flow. Sigma2-relaxation will show even less flow problems. By: Lyn Bates Stresses on bulk materials can be applied as compressive, tensile or in shear. Whatever combination is applied can be resolved into principle stresses by means of Mohr’s circles. i.e, stresses acting normal to surfaces at right angles to each other without shear stresses. Stresses applied on a sample in one principle plane induce a deformation, creating a reduced stress at 90° according to the Poisson’s ratio of the material (See fig. 2a). That is the change in the width per unit width of a material relative to its change in its length as a result of strain. Bulk material flowing down a conical converging channel has to deform in two planes under the compressive stresses of reducing diameter. Product in a plane flow channel only converges is one plane so, despite being confined, it will flow down walls about 10° less steep that in a cone. A plane flow channel that widens slightly at 90° to the converging plane will allow a larger degree of relaxation to
28.01.2021  |  202x  | 
CenTrax for RWE Eemshaven power plant Downtime of the conveyor belts caused delays in supply and additional costs. Within a month CenTrax tracker rollers proved to be the solution.
CenTrax for RWE Eemshaven power plant
Downtime of the conveyor belts caused delays in supply and additional costs. Within a month CenTrax tracker rollers proved to be the solution. The constant downtime of the conveyor belts caused delays in supply and additional costs. RWE consulted TBK Group, after which it was decided to install our CenTrax tracker rollers for a trial period. Within a month, it was already clear that CenTrax was the solution to their misalignment problem. Large coal and biomass power plant RWE Generation’s Eemshaven power plant is the largest coal and biomass power plant in the Netherlands. Covered conveyor belts ensure dust-free transport of the coal from ships to the power plant or the storage yard. This process was always accompanied by jerks and jolts due to frequent belt misalignment. The constant downtime of the conveyor belts caused delays in supply and additional costs. RWE consulted TBK Group, after which it was decided to install our CenTrax tracker rollers for a trial period. Within a month, it was already clear that CenTrax was the solution to their misalignment problem. [IMG03**R45**] Misalignment due to
18.12.2020  |  213x  |   | 
The importance of the Tensile Strength of powders Tensile Strength is the prime component of cohesion, which has many adverse consequences, especially in small scale, as in pharmaceutical applications
The importance of the Tensile Strength of powders
Tensile Strength is the prime component of cohesion, which has many adverse consequences, especially in small scale, as in pharmaceutical applications Great emphasis is directed to securement of measured values of the flow properties of bulk materials because of the need to design storage, process and handling equipment that provides reliable performance. Until the 1960’s the design of bulk storage equipment depended largely on empirical experience because of the lack of a scientific understanding of the behaviour in bulk of particulate materials. From a background in soil mechanics, [1], hopper design parameters were established in the 1960’s based on the measurement of bulk density, wall friction and shear strength values. [2]. This initiated industrial, academic and Government interest in the benefits that industry may gain from a scientific approach to the subject of bulk technology with seminars, conferences, exhibitions, magazines and specialised courses springing up all over the world. Shear plane length limitations of the Jenike call were overcome by annular cells, [3], [4], [5]. Interest in the dynamic
17.12.2020  |  200x  | 
How to increase capacity of an inclined screw conveyor When the axis of a screw conveyor is inclined, the capacity falls off progressively. Changing the arrangement of the casing can help.
How to increase capacity of an inclined screw conveyor
When the axis of a screw conveyor is inclined, the capacity falls off progressively. Changing the arrangement of the casing can help. The capacity of a screw conveyor falls off progressively as the axis of the casing is inclined. This is mainly because the dynamic repose slope surface of the material is unchanged and is limited by material carrying over the centre shaft by its rotation to fall back into the prior pitch space so the inclination of the screw flight cuts off an underside section of the material in transit. There is also a small degree of back leakage from the upper region, where the radius of the screw separates from the vertical wall of the casing above the centre shaft level. This effect increases with inclination as gravity supplements the force of the friction of the casing wall restraining the contact layer of the material. Moreover, when the axis of the conveyor is inclined, not only is the geometry of the screw affected, but the sliding angle of material on the flight surface is reduced. The inner region of a screw flight face has a much coarser inclination than at the tip
14.12.2020  |  377x  | 
Pressure reduction in silos: intermediate cones a reliable solution Higher silos may show problems such as quaking or honking, or too high stresses on the product stored.  Intermediate cones are a reliable and well designable solution.
Pressure reduction in silos: intermediate cones a reliable solution
Higher silos may show problems such as quaking or honking, or too high stresses on the product stored. Intermediate cones are a reliable and well designable solution. If, for whatever reason, a company invests in larger silos, one must be aware of problems. The bulk material experiences greater pressure in a larger silo. This means that the properties of the bulk material change in a negative way. It is therefore very important to keep that pressure under control. An important instrument is the wall of the silo. One can apply rings or coat the wall. This article deals with the application of intermediate cones. With a well-designed intermediate cone one can reduce the pressure, the product flows again, and shocks will be a thing of the past. Bigger silos, bigger problems Increasing capacities or shorter lead times sometimes require larger stocks of raw materials. For companies that store their raw materials in silos, this means an investment in higher or wider silos. This may lead to problems not experienced before, because the bulk solid experiences greater pressure in a larger silo. This changes the properties of the bulk solid,
11.12.2020  |  235x  | 
Matching feeder extraction pattern with hoppers Hopper design is primarily based on the nature and physical properties of the material to be stored, but the feeder is also very important.
Matching feeder extraction pattern with hoppers
Hopper design is primarily based on the nature and physical properties of the material to be stored, but the feeder is also very important. The criteria for hopper design are primarily based on the nature and physical properties of the material to be stored. The first decision is to choose an appropriate flow regime, Generally - mass flow is selected for products that deteriorate over time, funnel flow for inert, free flowing materials and expanded flow for poor flow, inert contents. [1]. This step determines the slope of the hopper walls in relation to the wall friction value. The minimum hopper outlet size depends on the shear strength of the material and outlet shape. [2]. Consideration has to be given to products that segregate of fluidise to ensure that their discharged condition is suitable for further processing and ultimate use. Plane flow from ’V’ shape of hopper sections offers benefits for flow and capacity over radial flow in conical shaped hoppers, but requires a feeder to extract from an outlet slot. Feeders play a crucial role in the performance of a hopper and form an integral
09.12.2020  |  291x  | 
Silo design: avoiding flow problems through adequate design Avoid silo problems, such as bridging, funnel flow, ratholing, arching, segregation and product decay. Silo design for gravity flow; most economic.
Silo design: avoiding flow problems through adequate design
Avoid silo problems, such as bridging, funnel flow, ratholing, arching, segregation and product decay. Silo design for gravity flow; most economic. To avoid problems in silos concerning flow, product ageing or decay, silo design is necessary. The design of a silo is based on the most economical case: gravity flow. Wall friction, internal friction and bridging properties determine the applicable hopper angle and opening diameter. In some cases through the design procedure it is found that a "simple" silo is not possible. This however saves a lot of work and costs. [IMG01**R45**] INTRODUCTION To prevent flow problems in a silo, proper silo design is necessary. The most obvious (and the most economical) way of storing bulk solids is in a silo with gravity flow. In this case the silo consists of a cylindrical or rectangular part with a hopper. The hopper lets the product converge to the opening. This simple fact is the direct cause of most problems, such as: unsteady flow, segregation, remaining product, ageing or decay of the product, shaking or quaking of the silo, flooding, or: flow does not occur at
27.11.2020  |  1047x  | 
Screw feeder design for hassle-free feeding Proper feeding through well designed pitch profile and core diameter variation
Screw feeder design for hassle-free feeding
Proper feeding through well designed pitch profile and core diameter variation In solids handling processes screws are often used to feed powders from silos. This has a number of advantages: contamination of powder is avoided, as well as pollution of the surroundings. A proper feed rate can be achieved in a large range of feed capacity. When using a screw feeder, the hopper of the silo can be wedge shaped. This offers an additional advantage with regard tp flow. However, if a screw feeder is not designed properly, core flow and bridging can occur. Also the risk of flooding (uncontrollable flow) or excessive wear is present. A proper design, where pitch and core diameter are adjusted to the properties of the product, prevents these problems. Introduction In a production process solids will be handled at one point or another. Raw materials are often in the form of solids, and also at processes with mainly liquids or gasses, there usually are steps where powders are used. The feeding of these components is of great importance. Too much or too
27.11.2020  |  698x  | 
The gentle processing of highly volatile oils by fluid bed technology Sensitive raw materials, especially those that are volatile or of natural origin, require particularly gentle process conditions.
The gentle processing of highly volatile oils by fluid bed technology
Sensitive raw materials, especially those that are volatile or of natural origin, require particularly gentle process conditions. Spray granulation, spray coating and (micro)encapsulation procedures have proven to be methods of choice, as they enable high yields, low temperatures and bespoke properties. When it comes to cosmetics, product development often focuses on proven, multifunctional ingredients. This is in addition to the ongoing demand for natural ingredients, as consumers increasingly look for effective cosmetic products that neither harm their health nor the environment. Glatt Ingenieurtechnik, the German expert in particle design, process development and plant engineering, offers unique particle processing solutions based on fluidised bed and spouted bed technologies for essential oils, collagens, active substances, stabilizers, enzymes, fragrances, aromas, vitamins and controlled release products, all of which can be optimally produced, protected and refined. Efficient fluidised and spouted bed processes Unique flow, mechanical and thermodynamic properties make fluid bed technology
03.11.2020  |  677x  | 
Vibration screening machines: Round vs. Rectangular When a Round Vibro Screen Would be a Better Bet
Vibration screening machines: Round vs. Rectangular
When a Round Vibro Screen Would be a Better Bet Vibration screening machines are among the most popular screening machines on the market. No wonder, as this type of screening can be used for almost any product, with the exception of easily breakable bulk solids. It is particularly effective as the screening movement for vibration screening machines is, unlike with linear screening machines, vertical as well as horizontal, meaning even small vibration screening machines can achieve large levels of output. Vibration screening machines are available in a variety of different sizes and designs, meaning that the shape of the screen – which influences many different aspects of the screening process – probably plays the biggest role when it comes to selecting an appropriate machine. Round vibration screening machines which have specific benefits, and are even the better choice for some applications. Round screening machines Small space, large screening surface area – the low amount of space required per
19.10.2020  |  1982x  | 
Process Technologies to Optimize Detergent Manufacturing Cleaning agents and detergents can be produced environmentally friendly and effective, using fluid bed and spouted bed technologies. Experts from Glatt Ingenieurtechnik explain.
Process Technologies to Optimize Detergent Manufacturing
Cleaning agents and detergents can be produced environmentally friendly and effective, using fluid bed and spouted bed technologies. Experts from Glatt Ingenieurtechnik explain. As a manufacturer of consumer goods, the detergent industry must respond to megatrends like no other. One of these drivers is sustainability; eco-friendly biosurfactants have been available since 2009 and, now, alternative complexing agents such as α-ADA or MGDA-Na3 can be produced from renewable raw materials and used to replace phosphates. According to the German Zukunftsinstitut (Future Institute), the neo-ecology megatrend is causing a reorientation of the values of global society, culture and politics and will have a defining impact on the 2020s [1]. Consumers and business partners alike are asking about transparent value creation and whether social aspects are being considered. As an example, seamless traceability has long been standard practice. Yet, the ongoing microplastics debate calls for a rethink when it comes to encapsulated fragrances or when the fibres of functional clothing have to be fished out of wastewater. Solutions for all these requirements can
02.10.2020  |  5912x  | 
Why you shouldn`t do without protective screening This articles gives reasons why you shouldn’t do without protective screening in industrial manufacturing processes.
Why you shouldn`t do without protective screening
This articles gives reasons why you shouldn’t do without protective screening in industrial manufacturing processes. Protective screening is probably one of the most common screening procedures in industrial manufacturing processes. You will learn why you shouldn’t do without protective screening, and what makes a good protective screen using the example of the reworked Engelsmann screening machine JEL Fix II. Why protective screening? Protective screens are used to eliminate disruptive foreign objects and impurities from bulk goods. These foreign objects can be plastic residues, for example, or metal parts such as screws which end up in the product by accident and can cause contamination. Lost knives for cutting bagged goods or protective gloves have also been found in products. To ensure a consistently high quality in the end product, these foreign objects must be separated before the product is put into its sales packaging. If this doesn’t happen, the worst-case scenario for the manufacturer is product recalls and a damaged public image. Contamination doesn’t just
15.07.2020  |  2475x  | 
The selection of screw feeders
Screw feeders are used for dispensing loose solids at a controlled rate from a bulk storage container, such as a silo, hopper, bin, IBC or big bag. These are normally chosen to satisfy one of two principle functions: - 1. To discharge the product from storage in a controlled manner, whilst generating an extraction pattern from the container outlet that generates the required flow regime in the stored material. 2. To meter the feed at a suitable rate, uniformity and condition to meet the demands of the receiving point. In either case, certain basic criteria must be met. - Deliver the design flow rate as and when required, reliably. - Deliver the material in a suitable condition. - Deliver to the required receiving point. - Fit into the available space. In Case 1, the feeder should be designed as an integral member of the storage container to optimise the geometry and performance and provide an extraction area that ensures reliable flow at an adequate
01.01.2020  |  023x
Guide to the design of hoppers
The performance of Bulk storage hoppers and silos is sensitive to the nature of their contents so consideration must first be given to the physical properties with respect to the operational requirements of the system. See the I.Mech.E publication: - ‘Guide to the specification of bulk solids for storage and handling applications’. A primary feature of design is choosing a flow regime that is compatible with the product(s). This dictates the zone order of discharge of the contents. If the equipment includes a feeder or discharge device to promote or control the flow, it must be considered as an integral feature with the storage section in determining the extraction pattern. Flow Regime. The basic choice rests with between a ‘Mass Flow’ pattern, where the total contents are in motion during discharge and a form of ‘Funnel Flow’, where the flow is confined to a narrow flow channel from the outlet to the surface of the material, or a combination of
01.01.2020  |  025x
Violent Vibrating of Screw Elevator due to ‘Epicyclic Rolling’ of the
A screw elevator can, in relatively rare cases, vibrate so violently that it is completely impractical to continue working. This phenomena can develop with the machine runs empty of product and/ or when conveying material. The stiffness of an elevator screw is relatively low by virtue of their essential slender construction to move bulk material to a height many times the diameter of their centre shaft, so the auger tube can be deflected relatively easily. The screw fabrication also entails significant welding of the flights to the centre tube such that weld distortion and flight stresses tend to build-in out of balance stresses. Whilst good practice dictates that screws are straightened after manufacturer, they are rarely stress relieved or dynamically balanced. This form of vibration is initiated if the screw shaft is deformed such that the tips of the screw flights contacts the casing and develops sufficient frictional grip to commence the screw ‘whirling’,
01.01.2020  |  024x
Screw Feeder Extraction for Uniform Flow
Despite the wide use of screw feeders for discharging hoppers, with a notable exception, (1), there is little published describing the flow patterns they generate. There can be some difficulty of compensating for the initial flight transfer capacity and basing the extraction on swept volume takes no account of the inefficiency of long screw pitches. Users are therefore rarely aware of the potential improvements in performance that they are missing. The benefits of Mass Flow are well known, but less widely understood are the significant difference between mass flow and uniform flow and the radical difference in extraction pattern needed when extracting from a rectangular or a circular hopper. Uneven drawdown can have serious structural and performance consequences, ranging from complete physical​ collapse to large density variations, ‘flushing’, segregated discharge and extended residence times that raise flow or product quality problems. However, whilst uniform
01.01.2020  |  020x
Hopper Blending of Large Batches
The blending and homogenising of large quantities, say of 10 to 500 Te, of bulk materials that requires all regions of the material to be mixed with all other regions, is generally impractical to undertake by ‘working’ the total mass. However, the result can be achieved recirculating the bulk in two streams utilising the loading, storage and discharge facilities that are used to handle the product. This process exploits the loading and discharge equipment of the system to recirculate the contents, during which time the mixing takes place. The essential components are: - Two Mass Flow storage hoppers that will each hold 50% of the required batch load. - Two screw feeders that provide a uniform draw from plane flow hopper sections. - Two ‘diffusion devices’, fitted at the hopper inlets. - One reversing conveyor to deliver to the hopper inlets. - One elevator to load the hoppers. - Variable speed drives on the screw feeders, or variable control of the supply
01.01.2020  |  022x
Benefits of plane flow hoppers.
The selection of a hopper construction may focus on capital cost, leading to the choice of a conical construction, rather than a plane flow outlet section. Plane flow, however, offers many advantages that can outweigh the additional expense in a complete assessment. A comparison between a plane flow channel compared with that developed in a conical hopper must take account of the need for a feeder to collect from an extended length of hopper outlet slot, whereas gravity flow may be adequate for discharge from a conical outlet. However, a feeder will provide discharge rate control and so are often fitted to conical outlets. Many benefits of a plane flow hopper can be secured, features marked in bold may dominate their selection criteria: 1. Fine control of the discharge rate by a feeder 2. Discharging in a more stable condition of bulk density. 3. The potential for higher discharge rates. 4. Increased holding capacity. 5. Saving of headroom. 6. More
01.01.2020  |  021x
Recommended Construction Features for hopper discharge screws
➢ Apart from small hoppers and feeders that are less than around 100mm diameter, it is good practice to make the feeder as a separate, bolt-on unit to the hopper outlet flange. This facilitates removal for repairs, replacement, modifications and access through the hopper outlet should any ever be required. ➢ Progressive extraction along the total hopper outlet length is essential for mass flow, minimising powder needs and attrition. Uniform pitch construction feed screws should only be used where: - the length of outlet is less than one and a half time the screw diameter, or the zone order of discharge of the hopper contents is unimportant and power requirements are not significant. ➢ The inlet width to the screw must exceed the ‘critical arching span’ for a gravity feed type machine. Excess width, especially liable with multi-screw feeders, will increase the shear force, and hence power needs, of extraction ➢ Do not use any screw section with
01.01.2020  |  021x
How to Assess Loads on Feeders, (a Practical Approach).
Feeders are widely used for metering bulk solids and discharging the contents of hoppers and silos. At the smaller scale power requirements may not be economically significant, but for larger units become very important, as an underassessment can have expensive consequences. It can also be difficult to determine what power is necessary, on what to allow a safety factor and gross over-assessments incur excess capital costs and long term inefficiencies. The topic has commanded considerable interest in recent years, as attached references, but the subject is complex and general conclusions and formula have been derived from results that may only be valid in similar circumstances to the experimental conditions. The first task in an investigation is to define the conditions of interest. In the case of feeder loads the main objective is usually to determine the maximum drive power that has to be provided. The worst case scenario is that of starting with a full bin after
01.01.2020  |  024x
Avoiding common caking problems
Powder that ‘cake’ present serious problems in bulk storage and handling systems. The most common cause is moisture migration due to temperature changes with materials that are soluble. Caking creates resistance to flow in bins, hoppers and silos and can result is build-up of residue on walls and the surfaces of equipment. Not all materials are affected, and some are much more vulnerable than others, but steps can usually be taken to avoid conditions that develop caking processes or disturb the effects. Several mechanisms cause bulk materials to ‘cake’ by forming strong bonds between the constituent particles. The phenomenon should not be confused with cohesive, electrostatic, surface tension forces and interlocking characteristics that may develop strong bulk strength, but are not rigid or brittle. Caking is essentially related to the nature of the contact surfaces involved and how these develop firm continuity between the constituent particles. The basic
01.01.2020  |  024x
Bulk Material Tests for Project Performance Evaluation
Quantitative tests can be performed on single particles, (for resistance to breakage), or on a sample of the bulk material. Various standards, (British Standard, ASME, ISO, DIN etc.), have been developed for specific objectives. Key values for flow in storage and handling are bulk density, shear strength and wall friction. Attrition and Segregation are separate, but related, issues. None of these properties are single value measurements and a degree of expertise is necessary in their conduction and interpretation. Selection Criteria: * Understand the purpose of the test. The data required for design must be more complete, as compared to quality control testing during operation. * Understand and emulate the underlying mechanism in the process or unit operation. * Consider the requirement for frequency of testing with complexity of test. * Evaluate the product stability, sample size requirements and hazards associate with handling. * Check if a
01.01.2020  |  025x
Breakthrough in Reversing Screw Feeder Design
The many benefits given by the ability of a screw feeder to extract progressively from a long outlet slot have been previously denied when the separate benefit of massive headroom saving was adopted to deliver to two alternative receiving points by reversing the direction of discharge. Various screw forms are used to serve long hopper outlet, but screws that generate progressive extraction would cause undue compaction if reversed in discharge direction. Screws that are of uniform geometry can be reversed, but currently these will only generate ‘live flow’ from short outlet lengths. They can be used on longer outlets, but this negates the flow benefits of a long outlet slot and leaves ‘dead’ regions of material in storage that will not discharge until the hopper content reduce to empty the original flow channel. A conventional screw feeder can only secure live extraction from a slot length equivalent to around one and a half pitches. Even this length is only practical
01.01.2020  |  021x
A Pauper’s Powder Testing Kit
Measuring the physical properties of bulk materials for flow characterisation is generally thought to be an expensive process involving skilled technicians, specialised equipment and demanding an expert evaluation of the results. As a rigorous process, this is true and no one should decry the work and effectiveness of experts in this field. However, there is little to stop anyone with a rudimentary knowledge of mechanics and stress conditions from deriving rough values of key design parameters that will serve as an indication of the degree of difficulty than may be expected in handling a product and securing measured values that can be used in a conservative design for non-critical applications. The sizes and material of construction the items listed for this kit are not ‘cast in stone’, but are suggested as typical to show the principles involved and their practicality for bench scale testing. The main features of interest are: * Bulk density, in stated conditions
01.01.2020  |  021x
Screw Feeder Types
Industry handles particulate solids in prodigious quantities, at massive differences in scale, in a vast range of conditions, and not always very well. This is not because the standard of engineering in industry is low or the process technology is poor. One has only to compare the performance of plants that handle liquids and gasses with those handling solids, (1), to appreciate that there is a fundamental difference in the ability of bulk solid projects to achieve anywhere like a similar degree of operating efficiency as these industries handling liquids and gasses. Even industries that use small quantities of bulk materials, such as pharmaceuticals, pigments, metallic powders and ceramics, face difficulties that tend to increase with the decreasing scale of application. These industries may be small bulk users compared with the food, chemical, detergent and mineral industries, but each is of major importance in their own right. In fact all sections of industry that
01.01.2020  |  019x
10 Common Questions about Storage Hoppers
Q - Most of the hoppers I come across suffer ‘Hammer Rash’ or have other problems. Is it true that a hopper should always be of Mass Flow design to work best? A - No. A Mass Flow hopper has certain benefits, but it also has drawbacks. The choice of flow pattern is the first and most important decision to make in hopper selection therefore it is vital to base it on the correct reasons. The key feature of Mass Flow is that all the contents are in motion towards the outlet during the discharge process. This pattern carries three, separate advantages. One, the absence of static regions of material during out-flow means that there are no pockets of stagnant storage that may deteriorate in condition because they remains undisturbed for an indefinite period. This is a particularly serious hazard if the hopper is re-filled before it completely empties. The second major benefit of Mass Flow is that bulk materials flow better and more consistently in a Mass Flow hopper.
01.01.2020  |  018x
Active and Passive Stress States – Relevance to Bulk Material Behavior
A grasp of the difference between active and passive stresses is necessary to understand how bulk materials behave in storage hoppers, silos and mechanical equipment, such as feeders and mixers. An active stress is one that presses onto a contact surface due to the forces generated within the body of the material. If the surface were to be slightly moved away from the material, such stresses will follow and continue to act with virtually the same pressure. A passive stress is caused by the resistance offered to a bulk material against any force trying to compact the mass of product. If the surface is withdrawn slightly, this pressure ceases. A simple case to illustrate the difference is that of retaining walls for a hopper or stockpile. Product piled against the walls exerts a force caused by the horizontal stresses generated within the bulk material. If the wall is withdrawn slightly, the material will normally collapse and form a new shape pressing with a similar force.
01.01.2020  |  022x
Angle of Repose
The ‘angle of repose’ of a bulk material is often quoted as a specific value and sometimes cited as a measure of the materials flow prospects. In practice, the inclination adopted by an unconfined surface of a bulk material depends to a greater or lesser extent on the manner of its formation and its relevance to the way in which the bulk material flows is limited to unconfined behaviour. The ‘loose poured’ angle of repose normally forms a conical pile from a single point fill with the loose material sliding down a diverging surface. This separation of the particles on a moving layer of reducing thickness allows the finer fractions to be deposited, whilst the larger components roll further down the slope. This is the most common form a segregation in bulk products that has a wide particle size distribution. The main value of this angle of repose it that it determines the ‘Ullage’ of a hopper, that is, the space above the surface of the material that cannot
01.01.2020  |  023x
Regimes of Flow in Storage Hoppers
General Flow Patterns in Bulk Storage Hoppers Various terms are used to describe the differing flow patterns by which bulk material fills and empties from hoppers. The expressions ’Mass flow’, and ’Core’ or ’Funnel Flow’, are widely used to describe the main two patterns of flow behavior. These terms, however, lack the precision to differentiate between significant variations of local or overall behavior in bulk storage systems. More detailed definitions of flow patterns in hoppers are set out in ISO/DIS 11697; however, these do not clearly distinguish between differing combinations of regional modes of behavior in compound flow systems, or unambiguously relate to the nature of stress systems set up within the bulk material and on the container walls. To describe the material behavior more accurately, definitions of flow regimes components are prescribed which form the basis of a structured classification to define differing flow patterns, as characterised
01.01.2020  |  027x
The Evolution of Powder Technology
Powder Technology developed from the union of civil engineers, concerned about the desirable stability of soils, and the industrial engineers concern with the undesirable stability of bulk solids in order to obtain reliable flow. Structural engineers joined this coalition, by needing to design storage economic containers to contain the stresses of bulk material in static and flow conditions. Flow problems with coal and iron ore in the US steel industry stimulated a study of the parameters that influence the tendency for bulk materials to arch in storage bins. From this single work flowed a torrent of further research on other topics of associated industrial interest. The implied deliverance of industry from the scourge of bulk handling problems was found embryonic. Both the human and application backlog was formidable and never thoroughly tackled. The testing and design process was also demanding in skill and experience. Consequently, some disillusionment set in and
01.01.2020  |  027x
Guidelines to Prevent Particle Jamming or Structural Blockages
With this article, we would like to draw attention towards an important, yet often ignored concept of mechanical jamming of particles.. Flow blockages can occur for cohesionless bulk solids when the ratio of particle diameter to discharge orifice diameter exceeds a critical value. When the particles in the flow stream converge towards the discharge outlet, jamming can occur if the size of the particles is large enough to sustain a stable interlocking arch. Jamming phenomenon or structural blockage cannot be predicted from current theories (Jenike and others) for cohesive materials. Jamming is statistical in nature. The probability of jamming to occur at the outlet depends on the random nature of packing as the particles move towards the discharge outlet. The jamming probability increases with particle size. The problem is further complicated if the bulk material has a wide particle size distribution or multi-modal size distribution and the particles are non-spherical.
01.01.2020  |  023x
Challenges in Handling Fine Powders: Flooding, Flushing and De-aeratio
Fine powders with low permeability will exhibit fluid like behaviour due to high degree of aeration and subsequent low de-aeration rates. Uncontrolled and unpredictable discharge of fine powders out of process vessels is called flooding or flushing. Fine powders can flow uncontrollably through belt feeders, vibratory feeders or screw feeders since they rely on cohesion and angle of repose to contain the bulk solid. Fine powders also leak through the clearances of a rotary feeder under a surcharge pressure. These features pose major problems in handling fine powders for industrial applications. Excess gas in the interstitial voids partially supports compacting loads and opposes the development of shear strength, allowing the mass to behave similar to a liquid of very low viscosity. In contrast, the same material in a settled condition exhibits extreme flow difficulties due to its poor permeability which inhibits the expansion of the bulk solids. The flooding tendency
01.01.2020  |  021x
Ten Key Steps to Prevent Dust Explosions
1. Ensure that the entire flow route is enclosed within a coherent, professionally designed system of containment, inert atmosphere, suppression or venting. 2. Verify that all electrical equipment, drives, cabling, lighting, fitting, instruments and control panels within the zoned area, conform to relevant standards and regulations. 3. Incorporate positive seal breaks between defined zones of isolation. 4. Employ substantial earth connections between all relevant sections of plant and periodically check their integrity. 5. Review the flow route and employ best design methods to minimise particle attrition, dust generation and dispersion. 6. Use only flameproof inspection lamps, spark-proof spanners and approved tools for working in rated areas. 7. Allow site work to be undertaken only through work permits and method statement procedures on plant that is certified clean and vented by way of a vetted program. Hot work, including burning,
01.01.2020  |  023x
Ten Key Steps for the Un-enlightened Purchaser of Solids Handling Equi
1. Do not give the supplier any information about the bulk material. Show him a sample that you have obtained from the floor or nearest rejection bin. This will test his ability to find out what the material is really like in practice, and he should be a clairvoyant anyway. The real benefit though, is that you cannot be held responsible when the plant doesn’t work. 2. NEVER call in a consultant. People might come to think that you do not know your job. He will cost you hard cash now. Any lost production and increased manufacturing costs will fall some time in the future, and can be blamed on others, if your still around. 3. Do not compromise the bin holding capacity with minor details, such as steep wall angles for slip or large outlet size for reliable flow. Any fool knows that most materials will slide down a 45 degree inclined surface and the hole must be bigger than the largest lump. And after all, it is the operator’s job to get the material out, so
01.01.2020  |  020x
Ten Key Steps to Ensure Sound Solids Handling Contracts
1. The crucial factor is to secure plant that works well. The cost of inadequate performance and ’teething troubles’ can far outweigh superficial initial cost ’savings’ between offers by different vendors. Prepare a ’Cost/Liability assessment for production delays, rectification provision and performance shortfall. Read the Rand Report and a follow up investigation, (1, 2), on the performance of Solids Handling Plants if you like horror stories, and then make a judgement that includes optimum exposure costs. Do not let the contract price dominate the buying decision. 2. Do not depend on Penalty clauses or Litigation for insulation against problems. (a) No contractor can economically meet realistic consequential damages for almost unlimited liability on a full production facility. (b) The root causes of operating problems are almost invariably due to behavior characteristics of the bulk material as a result of product conditions not accommodated
01.01.2020  |  022x
Ten Key Steps to Secure Safe and Reliable Powder Test Results
1. Identify and record the true source and history of a powder samples for testing. Secure an authorised and dated signature that verifies that the samples reflect the full range of conditions that are to be accommodated in relevant bulk handling equipment 2. Have a complete data sheet for handling hazards of the material to be tested.Read, heed and respect the details. 3. Have clear reasons for conduction of the tests, to make sure that the tests conducted are necessary and relevant to the purpose of interest. 4. Have full control, and record, the measured value of the test conditions. Relative humidity, temperature, date and time of testing and the presence of witnesses. Use a standard data sheet that has a prepared form to record the above details with an identifying reference, as well as the test measurements. 5. Have adequate safety protection close to hand, and support facilities available or well identified, as appropriate. Use the protective
01.01.2020  |  022x
Ten Key Steps to Minimise Particle Attrition during Handling
Ultimately, the formation of fresh product surfaces is proportional to the energy expended in its creation. Therefore, to reduce the total energy absorbed by a storage and handling system by way of good initial design, certain basic principles stand out as means to reduce the degree of particle attrition that a bulk material will suffer. 1. Establish the threshold strength at which the particles can sustain an applied load without breaking. Relate to the following: 2. Minimise or reduce free fall. Employ spirals or cascades to loose height with low contact forces. Use broad, deep and slow feed streams on chutes. If large drops are inevitable, disperse the flow stream as much as practical. 3. Minimise impact frequency and magnitude as practical. Try to ensure contact velocities are low, oblique to contact surfaces and employ resilient contact materials to reduce sharp, concentrated loads. 4. Avoid slip on rough surfaces, past flow obstructions
01.01.2020  |  023x
Ten Key Steps for Reliable Lean Phase Pneumatic Conveying
1. Do not use sloping pipe runs between 200 and 800 inclination. Re-fluxation, (run-back and re-conveying of the same material), will require the pipe to re-transfer the product slipping back on top of its normal load and the effect is accumulative. This significantly increases the conveying burden and will tend to accumulate to block the lower bend. 2. Allow a ‘reasonable’ horizontal conveying length, (15 to 20 pipe diameters), before the first bend, to allow the bulk material to accelerate to a stable conveying speed and reduce the sectional loading of the conveying pipe. Material slowed by the bend occupies a greater proportion of the cross sectional area of the pipe and thereby offers more obstruction to the air flow, which increases the pressure drop along the system. 3. Do not fit bends close together on the pipe run for reasons similar to the above. 4. Consider stepping the pipeline on long runs. Air expands with pressure drop, so velocities inevitably
01.01.2020  |  020x
The Flow Commandments
From the second book of Jenike, according to the house of Ajax 1. Thou shalt not follow in the ways of the Hitites, to smite or cast heavy blows upon the surface of storage vessels, nor even use minor beatings, lest the plague of Hammerash be upon you and your feed be denied forever. 2. Thou shalt not poke, prod nor enter staves or poles into the contents of a bin, from the outlet, nor the top surface, nor any manner of opening to the vessel. For masses of high walls are not sound and collapsing solids may fall upon you and your land. 3. Thou shalt not gaze upon the open outlet from a bin from whence flow has ceased or not commenced, for thine eyes may be filled with great unpleasantness, and there will be much weeping, wailing and gnashing of teeth, and thy cup of woe will overflow. 4. Thou shalt not inject air without end into a stored material, under the penalty of a great flood, who’s power to spread across the land is mighty to behold. 5. Thou
01.01.2020  |  022x
Ten Key Steps for Reliable Screw Conveyor Performance
1. Make sure that the discharge ports cannot block, or if they can, that the equipment is fail safe by means of an interlocked pressure switch, level detector, a safety coupling, robust stall condition or an emergency overflow. A screw can develop extremely high direct compacting forces, but bulk material is not be easily pushed around corners unless in a saturated condition. 2. Do not overload the casing cross section, particularly if hanger bearings are fitted. If the supply feed can surge, as with dust collectors, plate filters, and some process equipment, then incorporate a reduced capacity inlet section, such as reduced pitch or diameter flights, or a separate feeder to prevent the in-feed overfilling the screw section. 3. If the bulk material can trap in the flight tip clearance, use a larger casing or smaller screw to give more working clearance. Take special care with products such as wood chips, paper, and hard, flat, flakes that can laminate to form a
01.01.2020  |  021x
Ten Key Steps for avoiding Screw Feeder Discharge Problems
There is no difference in operating principle between Screw Feeders used to discharge large storage containers and those whose prime function is to to control the dispensation of material to processes. In practice the main function of the former is to provide reliable and complete discharge of the stored contents, with reasonable feed rate control and, in some cases, control of the zone order of discharge. By contrast, Metering Screw Feeders have the prime function of providing an even and accurate rate of feed, and often the secondary function of providing verification and record of performance. The accuracy required varies according to the application. By nature Screw Feeders are volumetric devices, therefore the amount dispensed at a given screw speed depends upon the condition of density of the product. Good design can usually secure consistent density condition, but cannot provide verification or alarm should allowable tolerances by exceeded. For this reason, gravimetric
01.01.2020  |  022x
Ten Key Steps to Counter Segregation in Bulk Solids Handling
1. Avoid long repose slopes when filling hoppers. Use dispersing plates or ’overflow’ pots with a small ’drain’ to avoid ‘single point’ fill. However, take great care that any distributing device fitted has no feed or extraction bias, otherwise the situation can be exacerbated by eccentric flow. 2. A Mass Flow discharge pattern is a good re-mixing process for products segregated during filling a storage container. However, it is not a ’cure-all’. When the level of material in the storage system falls to transformation point at which the walls commence to converge, the velocity of flow in the centre of the cross section is higher than that at the walls. Consequently, the last portion of the contents of a batch to discharge comprises material originally local to the wall. With most repose fill situations from a single inlet feed point, this region comprises mainly coarse fractions. A central insert, (not necessarily circular), can help by distending
01.01.2020  |  022x
Tips to reduce high starting loads on feeders
It is essential for reliable performance that the outlet of a hopper is large enough to ensure the material to flow out so a design margin is necessary above the minimum needed. Slot outlets secure flow benefits and extra capacity but the width of these are often tapered to give progressive extraction by belt feeders. As the minimum size has to be greater than the ‘critical arching span’ to ensure reliable flow, the larger widths allow heavier loads to act on the feeder. Excessive loads can arise on feeders with outlets that are significantly larger than the ‘critical arching span’ so it is important to base the design on measured properties of the material to be handled and avoid excessive overdesign. Even so, feeders can experience much higher starting loads than those of sustained running. The culprit is often not high compacting stresses, although those generated during filling a hopper may contribute to the state of packing and confinement, but often
01.01.2020  |  021x
Ten Key Steps for Achieving Reliable Flow from Hoppers
1. Make sure that you know the full range of conditions of the material to be stored. Secure an officially verified, ’fully representative’, sample and check that it is of consistent supply, from a homogeneous stock and stable in time and under the relevant operating conditions, - or know the reason why. Check what will be ‘worst’ condition. 2. Measure wall friction every time with options of the wall contact material. There is no ubiquitous ’Low Friction’ material, it depends upon both the product and the contact surface. Also, wall slip depends almost entirely on wall friction. It is easier to promote flow than generate wall slip if the slope of the hopper wall is inadequately steep. Getting the wall angle right is a most important design feature. 3. Establish, and allow for, any extended periods of storage. Not just in normal use, but for reasons of production campaigns, holidays, breakdowns, or irregular stoppages. 4. Check whether the ambient
01.01.2020  |  018x
Rules and Tools for modifications to bulk solids equipment
Modifications to existing equipment for bulk solids can be a challenging activity, placing demands on commercial, psychological and technical experience. This article provides considerations for successful intervention. Bulk solids applications provide many situations where modifications are needed to secure acceptable performance on newly installed or recently altered plant. The reason is almost invariably because the physical properties of the bulk material to be handled were not properly taken into account in the original design. The experienced bulk solids practitioner has many resources at his disposal to rectify the situation, but must also be aware of the immutable conditions that apply when undertaking a retrofit operation. Contract circumstances are totally different from original supply contracts, as are constraints and commercial factors. The search for solutions is also more demanding than an original design because the situation is compromised by the existing plant, pressure to achieve production and commercial and human factors. However, a combination of broad and specialised experience, state of art technology, innovative techniques and proprietary equipment, backed by
01.01.2020  |  018x
Overcome poor flow in hoppers with Lynflow™ ‘Tuned Reeds’.
Stimulating the flow of bulk materials in hoppers by the use of vibrators is greatly handicapped by the difficulty of applying the vibration to where it is most needed. A force is required to overcome the unconfined failure strength of the bulk material where an ‘arch’ forms over the outlet or to break down the wall of a ‘rathole’ that has developed through the central region of the stored material. Vibration applied to a confined loose solid usually results in the bulk gaining strength and then being more difficult to handle. This is particularly true if the material is not able to flow. Apart from this, problems of noise, fatigue, failure of welds and possible resonance or vibration affecting other local plant, a consequence of crudely applied vibration, is that flow is often generated at the expense of flow consistency. This is because a bulk mass in a firm condition tends to break down erratically from unstable arches or flake away in surges from the inner
01.01.2020  |  018x
How does the capacitive measuring principle work? The function of a moisture sensors using a capacitive measuring principle is explained.
How does the capacitive measuring principle work?
The function of a moisture sensors using a capacitive measuring principle is explained. There are plenty of different measuring methods to determine the residual moisture of material such as bulk solids. Now we are focusing on the capacitive functional principle. Inter alia it finds its use in in-line moisture measurement (directly integrated within a working process). It can be classified into two methods of moisture measurement, direct and indirect. Direct measurement Direct measuring procedures are e.g. the Karl-Fischer-Tritation or drying out material (loss of water by using a drying cabinet, probably the most often used method). Indirect measurement Moisture sensors and systems belong to the indirect moisture measuring techniques as they allow conclusion concerning the water content by using for example the capacitive moisture measuring principle. Further possible measurements work with microwave, infrared or conductance methods. The main criteria is that these procedures do not detect the residual moisture of the bulk solids directly. Rather
23.08.2018  |  18078x  | 
De-mixing behavior and segregation problems in silos  Segregation in silos can occur during filling, storage or discharge. In all three stages, measures can be taken to combat this phenomenon.
De-mixing behavior and segregation problems in silos
Segregation in silos can occur during filling, storage or discharge. In all three stages, measures can be taken to combat this phenomenon. In silos segregation of bulk solids that consist of different fractions or component scan be a problem. De-mixing will result in a unsteady composition of product flowing out. At one stage this may be too coarse, at another to fine. Or the percentage of a components is too high or too low. Segregation can occur during filling, during storage and during discharge of the silo. However, in all three stages, measures can be taken to combat this phenomenon. by: ir. P.J. van der Kooi [INTERMEZZO**M99****The previous article looked at the general aspects of segregation. This article deals with the aspects specifically related to storage and flow in the silo.**] Segregation in silos As mentioned in the previous article, segregation (de-mixing) is a result of the difference in properties of the different components or fractions in a mixture. Segregation can be caused by various mechanisms and occur at different places in the production process. A well-known problem
..  |  024x  | 
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