GB2300627A

GB2300627A - Bulk Storage Hoppers

Info

Publication number: GB2300627A
Application number: GB9609446A
Authority: GB
Inventors: Lyndon Bates
Original assignee: AJAX EQUIP Ltd
Current assignee: AJAX EQUIP Ltd
Priority date: 1995-05-06
Filing date: 1996-05-07
Publication date: 1996-11-13
Anticipated expiration: 2016-05-07
Also published as: GB2300627B; GB9609446D0

Abstract

A hopper for the bulk storage of particulate material, with inclined walls leading to an outlet, comprises a plurality of elongate insert members (36) spaced from one another within the walls, each member being secured by a support (29) along at least a portion of its length to the adjacent wall at an inclination steeper than that of the adjacent wall, whereby in use to promote a pattern of mass flow material in the hopper during discharge through the outlet. Preferably the inserts are mounted so as to be spaced from the walls, slope towards the outlet, are wider at the bottom than the top and are preferably curved. A bottom portion of the insets may be free so as to be cantilevered. Preferably a vibrator 37 is provided which may be arranged to vibrate the free portions of the inserts. The hopper may be conical or chisel shaped, have a steeply angled conical outlet section (Fig 14), have an inverted cone or cone and cylinder below the outlet (Figs 15 and 16) or have a bin activator (Fig 17) or an outlet screw or conveyor (Fig 18).

Description

Title: Bulk Storaae Hoovers Field of the invention This invention relates to bulk storage hoppers, and more particularly to improvements in hoppers which tend to induce so called "Mass Flow" in particulate bulk material during discharge thereof.

Background to the invention Bulk storage containers, variously referred te as hoppers, silos, bunkers and bins, are widely used for the temporary storage of quantities of loose particulate solids. For the purposes of the present application, the term "hopper" will be used to cover all such differing forms of storage containers for oati ulate material where the raterial is filled into the top of =e container and moves during the discharge process to an outlet situated In the lower regius of the container.

Referring to Figures 1 to 10 f the ccompanying drawings, the manner in which the material moves during the discharging process is essentially characterised by whether all the material is in motion, termed "Mass Flow" (as shown in Figure 1), or ether an internal channel of flow 2 develops within a bed of static material 3 termed "Funnel Flow" or "Core Flow", as shown in Figure 2.

As shown in Figure 3 storage containers are commonly made in the form of a cylindrical body section 4 fitted with a concentric conical converging section 5. Further common shapes are of rectangular or square cross sections 5, with either a pyramid-shaped base section 7 as shown in Figure 4, or a construction with a Vee section 8 converging to an outlet slot 9, as shown in Figure 5.

The Mass Flow form of movement of the hopper contents offers various operating advantages, but the converging wall surfaces of the container require to be much steeper than is the case with Funnel Flow type of hoppers. Mass Flow hoppers therefore have the disadvantage of either requiring greater headroom in order to store a particular volume of product, or of storing less volume within a limited headroom.

Mass Flow hoppers also require specialised design based upon measured properties of the material to be stored. The necessary expertise and bulk material testing produce tends to be expensive in relation to the manufacturing cost of many hoppers used in the process industries.

As a consequence, most hoppers in service are of the Funnel Flow type. Many of these hoppers experience problems associated with this form of material flow. Any segregation which takes place during filling is not corrected when the material is discharged. Flow stoppages can occur due to the materiaL 'bridging' as 3 stable mass over the outlet. The discharge may have e-rat z and/or limited flow rates. The density and sehaviou. of the product varies when filled into sacks, Reg, oins drums or other containers. 'Flushing', i.e.

uncontrolled discharge of the product in a fluid state, is also a performance hazard. There is always an indeterminate and extended storage period for some portion of the contents, because the order of discharge is not related to the sequence with which the differing regions of the hopper are filled.

This feature may lead to deterioration uf the product's condition, its flowability or other forms of adverse behaviour.

The Prior Art The angle of wall inclination required to promote Mass Flow of the hopper contents, is a function of the frictional characteristics of the bulk material on the contact surface of the container wall and of the internal angle of friction of the bulk material. The required angle of wall inclination to promote wall slip in containers of cone and wedge shape construction is described in a technical paper entitled "Gravity Flow of Bulk Solids" published by A.W. Jenike, Bull 126, University of Utah, 1965.

The mechanism by which bulk materials are held in a firm position against the wall of a container, whilst an internal flow channel develops in the body of the stored material during outflow, is the result cf a compound assembly of stresses. In the case of a conical hopper these comprise three components, respectively generated by:1. Wall Friction - Resistance to wall slip is mobilised by potential movement of the material relative to a wall, as shown in Figure 6 by arrow 10, giving rise to an opposing force il parallel to the contact surface 12 because of the friction of the material against the wall.

The magnitude of this resisting force is a function of the interfac characteristics between the bulk material ant the wall surface, and is proportional to the contact pressure 13 ,;nick is acting at 90" to the wall surface.

The required wall inclination for Mass Flow is closely related to the wall friction angle of the stored solid sliding on the contact surface of the container walls.

2. Radial Pressure - In the conical outlet section of a hopper as shown in Figure 7, the radially acting pressure from the flowing arterial in a central core region of the hopper contents acts against the supporting surface cf the static material at the flow boundary interface 15.

This pressure not only resists the boundary layers moving radially inwards, but also enhances the ultimate outward pressure against the container wall to result in an increase in the wall friction effect.

3. Circumferential Pressure - Resistance to a reduction in the circumferential dimension of material in an outer annular region of a cone shaped hopper as shown in Figure 8, is generated by virtue of the bulk material being subjected to a compressive hoop stress 16 as the material commences to move down within the converging section into a cross-section of reduce diameter. The presence of the outer container wall and of material occupying the central region of the cross-section provides a state of confinement of the annular bulk, to oppose deformation of tis material, and hence its ability to move to the towers region of the hopper with its smaller cross section.

These tree components can be considered in greater detail: 1. ali Friction Changes of the slic characteristics Df the bulk material on the wall intact surface influence the hopper geometry required to provide wall slip. Differing surface finish or materials of construction, wall ne materials and surface coatings are common used to improve way slip. In some cases the condition of the bulk material itself is modified to give better flow characte- sçics.

This approach has strict limitations, in that the range of suitable materials for construction cr lining the wail surfaces are limited by the friction values available, and also by cost and other criteria o. use. Surface frictional values are inherent properties of the interface characteristics between the bulk material and the contact surface, and lower values may not be achievable. Fixing methods for facing materials may also raise problems of flow, hygiene and the durability of the installed surface.

It is also found that differing materials used for hopper wall construction do not always exhibit similar relationships of frictional values with differing bulk materials. A surface which has a lower value of friction surface than another surface with one bulk material may have a higher frictional value when used with another bulk material, or even with the same material when it has a differing moisture content, temperature or other variant.

There is no ubiquitous low friction surface. Measured values of contact friction are needed to establish optimum contact surface materials for specifIc products.

2. Radial Pressure A proposal for stimulating mass flow in a hopper is disclosed in UK Patent No. 2,056,296 and consists of fitting an inner cone 17 to the hopper as shown in Figure 9. The inner cone has steep walls to stimulate mass flow of the inner contents 18 and its inner walls sustain the pressure acting radially outwards 19 from this central flowing region.Material in the outer annulus 20 is therefore able to deform more easily by virtue of containment or the active radial pressures of the central region ct flow. This material in the outer regions of the hopper diameter is thus able to flow and slip on the outer walls at lower (ie less steep) inclinations than if the inner cone were not fitted. A characteristic of this system is that the Inner and outer regions are essentially separate flow channels where the form of flow in each is dictated by their respective geometries and contact conditions.Each section requires its separate extraction conditions 21, 22 to be satis ied.

3. Ciroumferential Pressure An alternative approach developed earlier by the present applicant, is shown in Figure .0, and provides an inclined tubular form of insert 23 to shield the outlet region 24 and direct tne extractive flow channel from the outlet 25 to a position 26 behind the insert. Dilation of the flowing media underneath the insert provides a region of reduced pressure into which the remaining cross-section of material 27 may flow in order to reduce in diameter as it moves down within the hopper. This encourages the whole contents of the hopper to flow in a mass flow manner.The reduction in circumferential stress provided by this insert permits the material in the hopper cross-section to deform more easily, and enables slip to develop on the hopper walls at lower inclinations than if it were not fitted.

Drawbac:rs of the design methods described above are tat they are cumbersome and expensive to manufacture and they are relatively difficult to install, particularly when supplied as retrofits to improve flow in existing hoppers. The forms of insert above referred to also sustain high structural loads, due to their manner of offering support to the flowing contents.

It is en ,inject of the present invention to provide an improved hopper awing converging walls whose inclination is less steep than ctnventional, and in which the stored material moves in a Mass Flow manner during the discharge process.

With the foregoing and other objects hereinafter appearing in view, the features c- tis invention include the modification cf the stress pattern acting within the bulk material within the hopper to allow some local relief from the radially acting stress c- material in the central region of the whopper, also to provide relief for the circumferential or transverse stress of the material resting In the outer peripheral regions of the hopper contents and te support in part the stresses acting radially outwards from the flowing material in the central region cf the hopper, with corresponding reduction in wall frictional forces.

Summarv of the invention According to one aspect of the present invention there is provided a hopper for the bulk storage of particulate material, the hopper having inclined walls leading to an outlet, comprising a plurality of elongate insert members spaced from one another within the walls, each member being secured along at least a portion of its length to the adjacent wall at an inclination steeper than that of the adjacent wall, whereby in use to promote a pattern of mass flow of material in the hopper during discharge thereof through the outlet.

In the case of conical hoppers, the invention incorporates features to provide both radial and circumferential stress relief for the contents cf the hopper in the region of the walls and also cause a reduction of the friction forces opposing slip on the walls by reducing the wall contact pressures. For wedge and pyramid shaped hoppers the invention provides support for flow forces acting outward towards the wall and relief for horizontal forces in the flowing media acting parallel to the walls. Deformaticn and Mass Flow of the product takes place at less steep wall inclinations than with hoppers not fitted with these inserts.

The components described in the invention are more simple to manufacture and fit than the previously known ones, part;cularly for installation in existing storage hoppers.

They also allow more robust and simpler methods of support, by virtue cf their basIc design.

Where the hopper is of a conical form, the internal surface of each elongate member is preferably directed generally inwards towards the vertical centre line of the hopper.

The width of the internal surface of each member preferably increase from the top towards the bottom thereof.

The internal surface of the member may be curved, preferably about a radius centred cn the vertical centre line of the hopper.

The internal surface of each member preferably has a low friction characteristic, which may be imparted by surface treatment of the internal surface, or by applying a separate liner material to the surface.

The lowermost end of each member is preferably unsupported from the adjacent wall, so that it is overhung or cantilevered towards the outlet of the hopper.

Advantageously, means are provided for vibrating the elongated members. This may e achieved by one or more vibration means mounted eternally to the wall of the hopper and preferably parallel thereto.

Where the elongate members are overhung, the vibration means is preferably arranged to oscillate the overhung portions so that they oscillate in resonance.

A vlbrattry bin ac-ivator is preferably provided t the outlet in addltlon to, or Jn place of, the vibration means.

At the outlet there may be provided a conical extension piece having walls inclined at a relatively steep angle to accommodate convenrional mass flow.

An inverted cone may be provided beneath the elongate members at the cuties on the hopper. Extending from the inverted cone there may oe provided a cylindrical body directed downwards towards the hopper outlet.

Where the hopper is of a Vee form construction, the elongate members may be disposed on opposite sides of the hopper in an alternating or staggered configuration.

The staggered members may be arranged to overlap the discharge outlet, so that their ends extend beyond the outlet. Thereby, as material is extracted from the topside of the members at the outlet, it tends to draw further material from the underside of the members.

An elongate member may also be provided at each end wall of the Vee hopper, being secured to the respective end wall at an angle similar to that of the other members.

At the outlet of the Vee hopper there may be provided means for the transverse removal sf material discharged from the outlet.

The transverse removal means may be constituted by a screw feeder or by a belt or vibration feeder. The removal means preferably extracts material along the full length of the outlet.

According to another Aspect of the invention there is provided a inset system adapted for pssllloning within the chamber of a hopper having an inlet, a first wall and an outlet, said insert stem comprising a flow deflector having a top end and a bottom end, and a suppcrt surface; and a support member ata-- to said flow deflectcr, said support member being adapted to be attached to the first wall of the hopper to support said flow deflector in a spaced relation to the first wall Of the hopper such that said flow deflector forms a central flow region iocated inwardly from said support surface within the chamber of the hopper and an outlying flow region located between said flow deflector and the first wall of the hopper within the chamber of the hopper, said flow regions providing a mass flow pattern of the hopper contents.

Preferably said first wall of the hopper is inclined at an angle to the horizontal. and said top end of said flow deflector is spaced father from the first wall of the hopper than is said bottom end of said flow deflector such that said support surface of said flow deflector is inclined at an angle which is steeper than the angle at which the first wall of the hopper is inclined.

Brief description of the drawings Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figures 1 to 10 are grown hoppers of a design as described above; Figure 11 is a vertical section through a conical hopper embodying the invention; Figure 12 is a section similar to Figure 11 but showing a tapered insert members and a vibrator; Figure n is a perspective view of a Vee shaped hopper with insert members; Figure 3 A is R transverse cross-section of the hopper of Figure 13;; Figure 13 B is a lcngtldual section of tne hopper taken on the line XtII- XIII of Figure i3 A; Figure 3 C is à plan view torr. above of the hopper corresponding to Figure 13 B; Figure 14 shows a modified mass flow expansion whopper fitted to the outlet of a hopper in accordance it the invention; Figure 15 shows a modification with a inverted cone fitted below the insert members; Figure 16 shows a further modification with a cone and cylinder fitted below the insert members;; Figure 17 shows a "9in Activator" fitted below a hopper section with insert members; and Figure 18 shows a mass flow chisel section with a progressive extraction screw feeder fitted below a hopper section with insert members.

Detailed description of embodiments of the invention The vertical section of Figure 11 shows effectively front and side elevation views of three equi-spaced elongate inserts 28, the fourth insert not being visible in this sectional view.

The inserts are mounted at a relatively steep inclination on supports 29 secured te the wall of a conical form of hopper 30.

The lower portions of the inserts 31 project below the bottom edges of the supports 29 and into the "drawdown" region of the hopper outlet 32, ie the outlet region in which material is extracted during the discharge process.

The assembly of inclined inserts 23 is designed in relation to the geometry of the container, and having regard to the frictional properties of the bulk material on the contact surface of the hopper walls. These inserts form support surfaces internal to the hopper 33 on which the bulk material will siip during flow. The inner upwardly facing surface of each insert forms a d;sctinous support surface for material held in the central region of the hopper 34. These surfaces have the effect of providing a partial Mass Flow form of hopper on whIch the central contents of the hopper will slide.

The underside 35 of the inserts provide regions shielded from the outward acting pressure from the central section. The outlying material is separately extracted from the outlet by sliding down the local outer walls. The flow of material from under the inserts offers sections of reduced radial pressure for the outlying contents of the container cross-section. The adjacent outlying regions may then slide down the local converging faces of the hopper, because the relaxation of confining pressure at 90 to the direction of movement allows the bulk material to deform and flow more easily.

In hoppers of conical shape the invention provides the following advantages:a) The radial pressure acting on the wall is reduced by the shielding provided by fle inserts and the shear strength cf the bulk material transferring stress from the material in the central region of the hopper which is supported by tne inserts F-i C' optional forces between the stored material and the outer wall of the hopper are correspondingly reduced, both under the inserts and in the spaces between them by virtue of the reduced wall contact pressures.

b) Material in the outer regions of the hopper which is caused to move downwards in the hopper experiences regions of reduced circ mLerential pressure n the periphery due to the shielding of the inserts. This effect allows the material to reduce in diameter more easily bv relaxing regions of the hoop stress normally resisting flow in a converging channel.

c) The regions of reduced pressure under the inserts also provides an escape flcw route for the adjacent central disposed material to move cut and down the shielded flow path. The adjacent wall support cf the inserts for the central region transfers supporting stress to the adjacent regions between the inserts and so reduces the pressure acting outwards on the material in the outlyIng annulus of the hopper. This reduction of outward acting forces reduces the confining pressures and allows the material in the outer regions to deform more easily as it moves to a lower position in the hopper.

The contribution of these factors, to ease wall slip and deformation of the material in the hopper, permits Mass Flow to take place at less steep inclinations than if the inserts were not fitted.

Figure 12 shows a modified design in which the width of the inserts reduces from narrow at their top ends 36 to wider at their bottom ends 37 in the hopper. The increase in area under the inserts offers a progression in the degree of radial shielding to the regions nearest the wall at differing heights within the container. The number of inserts used in a hopper may also be varied according to the geometry of the installation.

By using differing materials of constructIon, coating of the inner surface of the inserts or facing the surface with a liner of low friction material (according to the properties of the bulk material being handled) the optimum designs can be achieved to suit applications at differing scales of installation.

Although the inner surface o= each insert is hcwz to be planar, in some cases it may be preferable for the surface to be curved about a radius centred at the vertical centre line of the hopper.

A further variant shown in Figure 12 is the provision of a vibrator 38 mounted on the outside of the hopper. This should preferably, but not essentially, be mounted in line with the support 29 to the insert. The construction cf the inserts is such that the extended tips 37 of the inserts which overhang the supForts are tuned to vibrate in natural synchronism with the frequency of the vibrator. As a consequence the tips 37 oscillate in resonance to provide a disturbing mechanism to counter the tendencv for the bulk material to form a flow obstructive arch cr 'bridge' across the small span of the flow opening between the inserts.

An additional effect of the vibration is to cause a lowering of the frictional forces resisting slip on both the inserts and on the container wall and also to assist the deformation of bulk material in contact with the surfaces which are influenced by the vibration by applying disturbing forces to the bulk.

Referring to Figure 13 and Figures 13 A to 13 C, there is shown how the invention may be applied to a Vee shaped hopper 39 in which two inserts 40 are fitted in a staggered arrangement to opposIte sides of the inclined hopper faces. The inserts 40 are secured to the hopper faces by support ribs 40A and overlap the discharge slot 41, being longtidually spaced apart to provIde a gap therebetween.End inserts 42 in the form of reduced width members are also fixed directly against the end faces of the Vee hoppers to provide side relaxation of deformation stresses arising from convergence of the flow change The ictn of the irserts sO again progressively increases towards the outlet slot 41, so that material is extracted preferentally from the uncercides of the inserts to provide local regions of reduced flow pressure within the bulk material. Such lower pressure regions allow adjacent bulk material to spread sideways and so deform more easily in flow between the inclined hopper surfaces.

Figure 14 shows ho the design of the basic conical or Vee shaped hopper may ce of a two stage form, with a ccnventional mass flow design for tne lower region 43 up to a diameter at which te flow channel has expanded sufficiently to draw from under the inserts.

Further options for expanding the flow from the hopper outlet region, to suit the drawdown characteristics of the invention, take the form of either an inverted cone 44 alone, as shown in Figure 15, or alternatively an inverted cone above a cylinder type member 5 of established form, as shown in Figure 16, each being secured beneath the inserts 28 to provide preferential extraction from thereunder.

Various forms of feeders and discharge devices may also be employed to provide a sufficiently large outsize to satisfy the hopper outlet flow channel requirements. One such device is a vibrated Bin Activator 46, as shown in Figure 17.

Alternatively, a chisel shaped Mass Flow hopper 47 and screw feeder 48 with continuous extracting characteristics over the length of the outlet slot, may be used. Suitably designed Belt Feeders or Vibratory Feeders may also be employed in conjunction with the inserts.

Such associated extraction devices serve te cause material to be extracted from the regions under the inserts, as described above.

Claims

1. A hopper for the pulk storage of particulate material, the hopper having inclined walls leading to an outlet, comprising a plurality of elongate insert members spaced from one another within the walls, each member being secured along at least a portion of its length to the adjacent wall, whereby in use to promote a pattern of mass flow of material in the hopper during discharge thereof through the outlet.

2. A hopper according to claim 1, in which the hopper is of a conical form, the internal surface of each elongate member being directed generally inwards towards the vertical centre line of the hopper.

3. A hopper according to claim 1 or claim 2, in which the width of the internal surface of each member increases from the top towards the bottom thereof.

4. A hopper according to any one of claims 1 to 3, in which the internal surface of the member is curved, preferably about a radius centred on the vertical centre line of the hopper.

5. A hopper according to any one of claims 1 to 4, in which the internal surface of each member has a low friction characteristic, which is imparted by surface treatment of the internal surface or by applying a separate liner material to the surface.

6. A hopper according to any one of claims 1 to 5, in which the lowermost end of each member is an overhung portion unsupported from the adjacent wall, so that it is cantilevered or overhung towards the outlet of the hopper.

7. A hopper according to any one of claims 1 to 6, in which means is provided for vibrating the elongated members.

8. A hopper according to claim 7, in which the vibration means is mounted externally to the wall of the hopper and parallel thereto.

9. A hopper according to claim 7 or claim 8, each as dependent on claim 6, in which the vibration means is arranged to oscillate the overhung portions of the members so that they oscillate in resonance.

10. A hopper according to any of claims 7 to 9, in which a vibratory bin activator is provided at the outlet in addition to, or in place of, the vibration means.

11. A hopper according to any one preceding claim, in which at the outlet there is provided a conical extension piece having walls inclined at a relatively steep angle relative to a horizontal plane, to accommodate conventional mass flow.

12. A hopper according to any one preceding claim, in which an inverted cone, having its apex uppermost, is provided beneath the elongate members at the outlet of the hopper.

13. A hopper according to claim 12, in which there is extending from the inverted cone a cylindrical body directed downwards at the outlet of the hopper.

14. A hopper according to any one preceding claim ,in which the hopper is of a V-form or triangular construction converging to a discharge outlet slot, and the elongate members are disposed on opposite sides of the hopper in an alternating or staggered configuration.

15. A hopper according to claim 14, in which the staggered members are arranged to overlap the discharge outlet, so that their ends extend beyond the outlet.

16. A hopper according to claim 14 or claim 15, in which an elongate member is also provided at each end wall of the V hopper, being secured to the respective end wall at an angle similar to that of the other members.

17. A hopper according to any one of claims 14 to 16, in which at the outlet of the V hopper there is provided means for the transverse removal of material discharged from the outlet.

18. A hopper according to claim 17, in which the transverse removal means is constituted by a screw feeder or by a belt or vibration feeder.

19. A hopper according to claim 17 or claim 18, in which the removal means extracts material along the full length of the outlet.

20. An insert system adapted for positioning within the chamber of a hopper having an inlet, a first wall and an outlet, said insert system comprising a flow deflector having a top end and a bottom end, and a support surface; and a support member attached to said flow deflector, said support member being adapted to be attached to the first wall of the hopper to support said flow deflector in a spaced relation to the first wall of the hopper such that said flow deflector forms a central flow region located inwardly from said support surface within the chamber of the hopper and an outlying flow region located between said flow deflector and the first wall of the hopper within the chamber of the hopper, said flow regions providing a mass flow pattern of the hopper contents.

21. A system according to claim 20, in which said first wall of the hopper is inclined at an angle to the horizontal, and said top end of said flow deflector is spaced farther from the first wall of the hopper than is said bottom end of said flow deflector such that said support surface of said flow deflector is inclined at an angle which is steeper than the angle at which the first wall of the hopper is inclined.

22. An insert system according to claim 20 or claim 21, in which said bottom end of said flow deflector is located generally vertically above the outlet of the hopper.

23. An insert system according to any one of claims 20 to 22, in which said support surface of said flow deflector has a first width at said top end and a second width at said bottom end, said second width being wider than said first wIdth.

24. An insert system according to claim 23, in which said support surface is generally V-shaped.

25. An insert system according to any one of claims 21 to 24, including a plurality of flow deflectors located within the chamber of the hopper.

26. An insert system according to claim 25, in which said bottom ends of said support surfaces are spaced apart from one another to create a gap therebetween adapted to allow the contents of the hopper to flow therethrough.

27. An insert system according to any one of claims 21 to 26, in which said flow deflector includes a low-friction liner which forms said support surface.

28. An insert system according to any one of claims 21 to 27, in which said bottom end of said flow deflector includes an overhung tip which extends in a cantilevered manner from said support member.

29. An insert system according to claim 28, including a vibrator associated with said flow deflector, said vibrator adapted to vibrate said overhung tip to apply a disturbing force to the contents of the hopper.

30. An insert system according to any one of claims 20 to 29, in which the hopper includes a second wall opposing the first wall, said insert system including a plurality of said flow deflectors, said flow deflectors being respectively alternately attached to the first wall and the second wall of the hopper.

31. A hopper for the bulk storage of particulate material substantially as herein described with reference to, and as tllustrated in, Figures 11 to 18 of the accompanying drawings.

32. An insert system for positioning within a hopper substantially as herein described with reference to, and as illustrated in, Figures 11 to 18 of the accompanying drawings.