However, it must be noted that the stress (pressure) in a silo However, extensive experience has shown that designing equipment without regard to the actual bulk materials being handled often leads to flow problems, such as arching, ratholing, erratic flow and even no flow. The flow rate on the hopper front wall should be slightly less than the flow rate on the back wall. Figure 1 : Sometimes temperature probes are needed too Approximate four active volumes with four rectangular prisms using the techniques mentioned previously. Figure 6 shows schematic diagrams for two common shear-cell testers. To calculate the slope of hopper wall: () = 2 + 60 To calculate the minimum outlet diameter for hopper, this equation is used: () = In Craven et al [1], there are six materials of powder tested and four types of wall material of hopper tested, but for this report, we picked only three materials of powder which are wood When using an adjustable gate, it is desired to be parallel to the hoppers front wall. Repeat the preshear and shear steps at the same consolidation level for a range of normal stresses. 3 Beds. Air balancing, when discharging a hopper, an especially when this This can lead to the calculation of 2 //-->, Follow us on Twitter Note that the way a powder is flowing is depending on its The physical properties and direct shear test data of the ten food powders served. Hoppers and Hopper Design for Reliable Flow of Powders and Bulk Solids. Stainless Steel are common materials, some silos are also in different wall friction angle and internal friction angle the If a rotary valve is used, a short vertical spool section should be installed between the hopper outlet and valve inlet. FIGURE 3. [2] George G. Chase, "Hopper design", volume 10, The Powder has a given ability to slide and fall when it is stored in a what happens with liquid. the powder below the hopper. Unfortunately, chemical engineers education and training on bulk solids are often insufficient for such tasks. actually required for the process). a proper flow of material (no dead zone), Make sure the feeder can take the powder in the whole section of Protect your facility from explosions with venting panels, flameless venting systems, and chemical suppression systems. If you are author or own the copyright of this book, please report to us by using this DMCA report form. This is accomplished by first testing the material to measure wall friction, and then calculating the minimum hopper angle that will allow mass flow. hoppers will be preferred, because of the easiness of cleaning. Principles of Shear Testing; Arching and Ratholes in Silos; Minimizing Dust Explosion Risks in . Hopper valley angle calculation Inputs Internal angle Wall "A" to vertical 1: Degrees Internal angle Wall "B" to vertical 2: Degrees Note - Type in respective value inside of coloured cell above, then click outside cell to enter. See Schulze [4] for a discussion of the challenges of accurately predicting the pressure gradient. properties. Mass Flow bin : all the mass of product will move at Figure 4 : The other point of intersection of this circle and the horizontal axis is the unconfined yield strength (fC). Note that these analyses assume continuous handling of the powder. ; Phone: 978-649-3300; Email: gmehos@jenike.com), and an adjunct professor at the University of Rhode Island. If the powder is to be stored at rest for a period of time, time tests should be conducted. The critical rathole diameter is calculated by first determining the major consolidating pressure, 1, on the powder. In the photograph, you can see a typical hopper from the side and from the top. Top 5 New Discharging powder is often overlooked, The rathole will then periodically fail as the base of the material falls above the screw. the wall friction angle as a function of the hopper angle. The feeder must not contact any adjacent structure, because it must be free to vibrate. Once a materials Flow Function has been determined, the minimum outlet width or diameter that will prevent cohesive arching can be calculated, using the hoppers flow factor (ff). NEW CONSTRUCTION. ensure a good flow. Funnel flow bins are subject to ratholes. -------------- Rubber pads, directly mounted on the inside of a hopper are Abascus for flow factor calculation [2], STEP 4 - Calculate the critical cohesive strength (fc_crit). (expressed in terms of throughput, cycle time or number of batches / Figure 3. The hopper rear wall angle must be steep enough to permit material flow. This relationship is commonly called the materials Flow Function. Hopper: A converging sloping wall section attached to the bottom of a silo. Take 3 degrees margin and select 20 degrees for the feeder outlet. Adding the hopper drag power requirement to the standard conveyor drive requirement of 1 HP yields a raw horsepower requirement of 21.5 HP. Finally, we presented a technique to calculate how to reduce hopper drag load by adding pressure relief to hopper bottoms. Stress profile in bulk solids silos. Equation 3 continuous mixing comparison Particularly when using Jenike's own Modify one hopper opening of 38 x 60 to four hopper openings, each at 19 wide x 30 long. Hopper shape, angle, and internal surface required for bin flow pattern Outlet size and shape engineered to avoid poor flow and ensure discharge rate Feeder selection and design to maintain reliable discharge from hopper outlet Unique design features for powder and bulk solids reliable handling, processing Experience Highlights Acceptable hopper design -Although a T/H of 0.6 is ideal, a T/H of 0.5 to 1.0 is acceptable. must be designed by using the face velocity of a material to filter. 3. Typical consequences of bad air balancing are : a reduction in flow The flow factor is constructed by drawing a line having a slope equal to 1/ff through the origin. that the forces pushing the product to flow are minimal : arching (powder is blocked in a stable : critical outlet diameter to avoid ratholing [2], Figure 6 : These recommendations pertain to handling free-flowing material. The resulting shear stress is measured as a function of the applied normal stress. He received his B.S. General powder properties, including flow properties, collapse can make a large amount of material fall, if the silo has 3. The cohesive strength is measured by shear-cell testing, as described in ASTM D-1628 [2] and D-6773 [3]. Measure the pressure and flowrate in two locations of the bed. 2 types of equations are usually found in the literature : the The critical rathole diameter is determined from the following (First In First Out). Figure 2 : be able to release air in the mixer to avoid overpressure. For hoppers and feeders that handle non-free-flowing material, contact your equipment supplier for advice about the design specifications. behavior observed. In order to avoid that, both feeder design and hopper design must accommodate material properties. This Then draw a second semicircle tangent to the yield locus through the origin. Cohesive strength Material with enough cohesive strength due to stickiness or sharp jagged edges can cause slow movement through a transition and possible bridging at the discharge.This may require a large opening or unique hopper design to allow for flow. How do we calculate the drag force which a hopper exerts on a conveyor belt? We can approximate two active volumes with two rectangular prisms in which L = L T. To conservatively simplify the calculation, ignore T. Therefore, each prisms volume may be calculated as follows, The active weight of 2 prisms may be calculated as follows, Total active weight = 2 prisms x volume of each prisms x material bulk density, Hopper drag load = 0.5 x total active weight. diameter of outlet that will manage to keep a constraint on They are To make the situation more difficult, critical solids flow properties are often unavailable and must be determined experimentally. In bulk solid storage discussions, the terms hopper, bin, and silo are often used interchangeably. On big ones, the Ft. 301 Crawford Pkwy, Clayton, NC 27520. How is it possible to relieve pressure from the conveyor belt beneath the hopper opening? The hopper front wall angle must be just big enough to permit material flow. In addition, a properly designed hopper produces a depth of discharged material that is slightly lower than the height of the hopper gate varying based upon the particle size and cohesion of the material. It's free to sign up and bid on jobs. 5. To find the effective angle of friction, draw a line through the origin that is tangent to the larger Mohrs circle. The plot of the unconfined yield strength (fC) against the major principal stress (1) is the flow function of a bulk solid, and describes the relationship between a bulk materials cohesive strength and its consolidation stress. To determine the permeability of a bulk solid, run a gas through a bed of powder contained in a cylinder. Dust explosions are a major hazard of unloading and conveying operations. there is a height of powder in the bin, the powder on top pushing on This plot shows the theoretical mass-flow hopper angles for hoppers with round or square outlets. characteristics can be determined thanks to a shear tester (see section on powder characteristics). He holds a B.Sc. The angle of wall friction () is the angle that is formed between the horizontal axis and a line drawn from the origin to a point on the wall yield locus. Different correction factors should be applied. to be determined (star valve difficult to fit to a wedge-shaped The critical discharge diameter is the diameter under or Airlock Parameters for Johanson equation. 1. outlet diameter to prevent arching. The next step in the data analysis is to determine the major principal stress (1), i.e., the maximum normal stress exerted on the bulk solid during the test, and the unconfined yield strength (fC), i.e., the cohesive strength of the bulk solid. A calculation by using the FEM in the SolidWorks Simulation has been carried out to determine the . The minimum length of the feeder is determined by projecting the angle of repose for the specific material from the gate point (see illustration titled Ideal Hopper Design) to the feeder pan, and adding 4 to 6 inches to prevent a free flow condition. Mixer capacity FIGURE 2. state) can thus happen at this level in the hopper. SAJJAD KHUDHUR ABBAS Ceo , Founder & Head of SHacademy Chemical Engineering , Al-Muthanna University, Iraq possibility exists to actually install a pipe in between the Greg Mehos is a senior project engineer with Jenike & Johanson, Inc. (400 Business Park Dr., Tyngsboro, Mass. Any combination of and that falls within the limiting mass flow region of the chart will provide mass flow. Dilute phase pneumatic conveying design and calculation This design has been done on the basis of considering only rice as a storage matter. If the The mass discharge rate is equal to the product of the velocity, outlet cross-sectional area, and the materials bulk density at the outlet. Question, remark ? can be the case with very bad flowing materials (for which the Otherwise, a small change in powder properties may cause the flow pattern inside the hopper to change from mass flow to funnel flow bringing its associated risk of flow problems. In food application, conical Mass flow silos This plot shows the recommended wall angles to ensure mass flow in a hopper with flat walls and a slotted outlet. are taken into account, it delivers a hopper design that can be guaranteed to work. As opportunity crude usage increases, unexpected corrosion has become a major issue in piping and process units. of internal friction, Knowing the characteristics of the product to discharge is the 1st Avoid and solve . enough, without getting over the maximum pressure authorized. | Diversity Inclusion & Equity, A portable conveying system for pharma and food products, Selection Guide for Solids-Drying Systems, Conveyor Selection for Bulk Solids Processes, Facts At Your Fingertips: Hopper Outlet Geometry and Arching, PEMA and Kansas St. University Bulk Solids Innovation Center form partnership, Test Your Knowledge: Focus on Jacketed Vessel Heating, Professional Engineer - Payne + Dolan, Inc. a Walbec Group Company - Appleton, WI, Survey Crew Chief - Payne + Dolan, Inc. - a Walbec Group Company - Appleton, WI, Professional Land Surveyor - Payne + Dolan, Inc. - Walbec Group Company - Appleton, WI, Concrete Project Manager - Zenith Tech Inc. a Walbec Group Company - Waukesha, WI, Senior Test Systems/Electrical and Instrumentation Engineer - Vital Materials Co., Limited - Bowling Green, OH. FIGURE 4. particles), A good hopper design is the 1st necessary conditions to have fluidization happen which is detrimental to the discharge rate Figure 2. on Next, the shear step is conducted. During this step, the vertical compacting load is replaced with a smaller load, and the sample is again sheared until it fails. Figure 4. the flow. are listed in this page : Powder It is important to note that, for fine Search for jobs related to Hopper design calculator or hire on the world's largest freelancing marketplace with 19m+ jobs. By continuing to browse our website, you agree to those policies. Improve energy efficiency A shoot of The kinematic angle of internal friction () and effective angle of internal friction () can also be determined, as shown in Figure 7. section of pipe between the hopper and the valve (2 diameter), As mentionned above, the flow of fine particles will be sensitive Bulk solids and powder flow properties testing, silo and hopper design, discharge and conveyor technology . Syntron Material Handling| A Kadant Company. The angle of wall friction () is the angle that is formed when a line is drawn from the origin of that graph to a point on the wall yield locus. feeder must be designed to draw out the solid on the entire section Additionally, skirts must run parallel to trough sides and must be reinforced to resist bulging outward against the trough. A Google search for cybersecurity wake-up call turns up more than 2 million hits; adding industrial controls systems narrows the search to a bit under 300,000 hits. You must be logged in to view this content. To accomplish this, both the hopper and the feeder need to work together. You must be an AIChE member to view this article. Feeder design considerations. To determine hopper drag load, simply calculate the weight of active material and apply a cutting force factor. the hopper, and can turn a mass flow bin into a funnel flow bin. Adding a hopper with an opening 38 wide and 60 long results in a hopper drag load of 6,769 lbs, as follows. For each of these bins type, the critical outlet diameter, From a design point of view, it is important to be able to determine the loads acting on feeders in hopper/feeder combinations and the corresponding power requirements. Sloping walls required for mass flow in wedge-shaped hoppers can be 1012-deg less steep than those required to ensure mass flow in conical hoppers. Notice that an inverted angle has been welded to the bottom of the hopper opening. Once the product flow characteristics and design parameters are established, the efficient design of a silo or can be undertaken. allowing to take more and more powder on the direction of the This lesson presents arching theory, how to calculate hopper drag load, how to design hopper pressure relief, and how to calculate the power required to overcome hopper feeder drag. equilibrate pressures : i.e. are sensitive to arching AND ratholing. The powder is consolidated in the top part due to pressure. For near-size material, the width should be at least 4 times the diameter of the largest particle. Join now. 3 Beds. The angle of wall friction () is obtained by following the method described in ASTM D-6128 [2]. This results in non-uniform flow. The first step to achieving mass flow is to ensure that the converging walls are steep enough, and have friction low enough, to allow the bulk materials to slide along them. The gate is acting as an adjustable front wall. document.write(document.title); To determine the yield locus, plot the failure shear stress against the normal stress (Figure 2). He developed testing methods, equipment, and design techniques and conducted experiments to confirm and refine his groundbreaking analysis [1]. Two primary flow patterns can occur in a bin or a silo: mass flow and funnel flow (Figure 1). 2. page : Because bulk solids are anisotropic, the stress on the sample varies with direction. 8. Pivotal work on the development of the theory of bulk solids flow began in earnest in the early 1950s, when Andrew Jenike applied a solids-mechanics-continuum concept to develop a logical, theoretical approach for understanding and managing solids flow. The first step in the design process is to determine the fundamental properties needed to predict the flow behavior of bulk solids: cohesive strength, internal friction, compressibility, wall friction, and permeability. REFERENCES [1] George G. Chase, "Hopper design", volume 10, The University of Akron, 13th July 2012, Page no. 4. Effective tension (Te) = 330 lbs. +91-9879950702 Monday - Friday 10:00 - 7:30 Rakhiyal, Ahmedabad, Gujarat . The discharge rate can then be 100 times less "lump" parameters are used. He served on the executive board of AIChEs Particle Technology Forum and is a past chair of the Boston AIChE section. flow happening in silos or hoppers. except for sand where it is 2.9. Transition Calculator is useful for Generating Flat Pattern Layout or Fabrication Layout of all types of transition shapes such as rectangular to round, square to round, round to rectangular, round to square, pyramid and truncated pyramid transitions. Nichols recommends a front wall angle of 55 2. Required power = 330 lbs x 100 fpm= 33,000 ft-lbs/min. Funnel Flow bin : the discharge of the product at the center The yield locus, determined by the shear cell tests, is used to calculate the major principal stress (1), unconfined yield strength (fC), effective angle of friction (), and kinematic angle of internal friction (). hopper surfaces and material used for construction of hopper. The outlet of the hopper section must be large enough to prevent cohesive arches or stable ratholes from developing. a good flow of product when discharging a hopper. Jenike, A.W., Storage and Flow of Solids, Bulletin 123, University of Utah Engineering Station, 1964 (revised, 1976). It also explains how to convert hopper drag load into required conveyor drive power. "About" page to know more about those cookies and technologies . Parsons, KS 67357 Phone: +1 620-423-3010 Fax: +1 620-423-3999 Sales: sales@tankconnection.com Knockers are usually powered by compressed air. stress, Make sure the pipe slopes are large and steep enough to ensure In our first tutorial, we presented the purposes of hoppers, standard conveyor belt loads, and special hopper loading. Use this video in conjunction with our growing library of tutorials on how to design and maintain bulk handling belt conveyors. have a funnel behavior. ASTM D-6773, Standard Shear Test Method for Bulk Solids Using the Schulze Ring Shear Tester, ASTM International, 2008. This tutorial has shown that arching theory may be used to approximate hopper surge loading on feeder belt conveyors. If material particles are nearly the same size (i.e., near size), T should be at least four times the size of the largest particle. Their common objective is the prediction of material behavior within a prescribed bin hopper system. ASTM D-6128, Standard Test Method for Shear Testing of Bulk Solids Using the Jenike Shear Cell, ASTM International, 2006. and powder will be taken out only on one side of the hopper The power to overcome this drag is calculated as follows. rotary Valve, Calculation As shown in Figure 13, this channel will draw material from the top surface into the flow channel until a stable rathole forms and the channel empties. One of the objections to the use of any rational hopper design method has historically been the high cost of undertaking the characterisation tests. Active Volume = 3.2 ft x 5 ft x 3(3.2 ft) = 150 ft3, Active Weight = 150 ft3 x 90 pcf = 13,538 lbs. A mass flow screw feeder, comprised of a tapered section followed by a section with increasing pitch, ensures that the capacity of the feeder increases in the direction of flow (see Figure 13). Lump breakers are positionned after a hopper, they will not 5. line to axi-symetric hoppers (cone), STEP 6 - Calculate the critical outlet diameter. FIGURE 5. This, in turn, reduced required conveyor drive power from 23.2 HP to 12.2 HP. Hopper Design.pdf Uploaded by: InunHazwaniKhairuddin December 2019 PDF Bookmark Download This document was uploaded by user and they confirmed that they have the permission to share it. Hopper Recommendations 1. The Powder Flow Function, the wall friction angle, the static angle The point where it crosses the flow function will give the It is the second of a two-part tutorial on designing hopper feeder conveyors. corresponding to crit=fccrit. A sample of powder is placed in a cell and then pre-sheared that is, the sample is consolidated by exerting a normal stress, and then sheared until the measured shear stress is steady. Hopper angle for mass flow Once the wall friction results are known, the recommended hopper angle to ensure mass flow can be readily calculated. product outside of a bin is its cohesive strength. Contact us at admin@powderprocess.net. A hopper with a rotary valve should have a spool section above the valve inlet (left); otherwise, preferential flow may occur on one side of the hopper (right). Syntron Material Handling Engineering Manager Brad Nichols recommends a rear wall angle of 60 2. The wall yield locus is constructed by plotting shear stress against normal stress. flow out of the silo. To find the kinematic angle of internal friction, draw one line tangent to the smaller Mohrs circle and another that is horizontal at its intersection with the yield locus; the angle between them is the kinematic angle of internal friction. silo must be determined also. generating the largest volume of air to release or admit must powder and the discharge of hoppers. can form archs In a bin, the powder is submitted to pressure, due to the fact that These pre-shear and shear steps are repeated at the same consolidation level for a number of reduced normal stresses, and the yield locus is then determined by plotting the failure shear stress against the normal stress (Figure 7). Only the active volume of material in the hopper, rather than the total volume, needs to be considered. After a number of values have been recorded, the wall yield locus is identified by plotting shear stress against normal stress (Figure 3). Mohrs circles can be used to determine the major consolidation stress and cohesive strength from the yield locus. The relationships obtained were used together with other relevant expressions to develop an add-in tool for the determination of the pertinent hopper design parameters (exit size, mass flow. Ideal hopper design -A properly designed hopper produces uniform material flow to the feeder trough, with material at the front of the hopper moving slightly slower than at the rear of the hopper. It is essential to minimize the hopper opening as much as possible without restricting material flow. David S. Morgan is a senior consultant at Jenike & Johanson (3485 Empresa Dr., San Luis Obispo, CA 93401; Phone: 805-541-0901; Email: dmorgan@ jenike.com). to the flow of air returning from the discharge point and opposing As shown below, a conveyor with a length of 20 ft, a handling rate of 500 tph, and a belt speed of 100 fpm has been preloaded, showing that it requires approximately 1 HP to carry the load. wedge-shaped hopper can be used. The active zone is defined by the length and width of the hopper opening, called L and W. We can conservatively approximate the active volume with a rectangular prism, rather than a parabolic shape. naturally. FIGURE 10. flow bin, which, when designed properly will ensure a reliable Note: a minimum safety factor of 3 deg should be used. To be noted that these Mass flow (a) ensures a more-uniform discharge of bulk solids than funnel flow (b) or expanded flow (c). Placement of the feeder in the processing line must include enough space around the feeder to allow its elevation to be decreased by approximately 2 inches to accommodate material load while the feeder is not operating. We supply Motorized Pulley belt conveyor drives, serving equipment manufacturers directly and end users through a network of independent distributors & local service providers throughout the United States and Latin America. k=f(particle shape, hopper angle) and is in the range 1