CENTRIFUGAL SEPARATOR HAVING AN IMPROVED FLOW AND SYSTEM COMPRISING SUCH A CENTRIFUGAL SEPARATOR

Abstract

A centrifuge (1) for separating intermixed particulate material of different specific gravity. The centrifuge (1) comprising a centrifuge bowl (10) having a plurality of annular recesses (19), a housing (30), an inlet (17), and means for rotating the centrifuge bowl (10) about the central axis (15). An annular cavity (31) is defined between the housing (30) and the centrifuge bowl (10). The annular cavity (31) is fluidly connected to the plurality of annular recesses (19) on the inner surface of the centrifuge bowl by a number of perforations in the centrifuge bowl wall (12). The annular cavity (19) has a fluid inlet to provide fluid into the annular cavity. The annular cavity (19) has an accumulated cross-sectional flow area (Allow) at two different heights in the annular cavity that differs by at least a factor 10.

Claims

1-15. (canceled)

16. A centrifuge bowl (10) having a base, a circumferential wall surrounding a central axis and an open end substantially opposite of the base, said central axis passing through the base, the circumferential wall having an inner and outer surface, the inner surface (23) of the centrifuge bowl comprising a plurality of annular recesses (19) at axially spaced positions; wherein a first portion of the inner surface of the centrifuge bowl comprising one or more recesses has an angle with respect to the central axis (15) which is different than the angle of a second portion of the inner surface of the centrifuge bowl comprising one of more recesses.

17. The centrifuge bowl (10) according to claim 16, wherein the second portion of the inner surface is located closer to the centrifuge bowl base (11) than the first portion of the inner surface and that the angle of the second portion of the inner surface is greater than the angle of the first portion of the inner surface.

18. The centrifuge bowl (10) according to claim 16, wherein the centrifuge bowl wall may substantially be shaped as a half sphere or a paraboloid.

19. The centrifuge bowl (10) according to claim 16, wherein the difference in inclination between the angles of the first portion of the inner surface and the second portion of the inner surface is at least 3 degrees to 5 degrees.

20. The centrifuge bowl (10) according to claim 16, wherein the difference in angles of the first portion of the inner surface and the second portion of the inner surface is between 5 degrees and 15 degrees.

21. The centrifuge bowl (10) according to claim 16, wherein the recess distance between recesses, measured from an upper edge of an annular recess to a lower edge of the next recess, varies.

22. The centrifuge bowl (10) according to claim 16, wherein the recess distance is varied by having different sized spacings between the recesses.

23. The centrifuge bowl (10) according to claim 16, wherein a first lower portion of the inner surface comprises recesses that is more spaced than recesses in a second portion of the inner surface.

24. A centrifuge (1) for separating intermixed particulate material of different specific gravity comprising: a centrifuge bowl (10) having a base (11), a circumferential bowl wall (12) surrounding a central axis (15) and an open end substantially opposite of the base (11), said central axis (15) passing through the base (11), the circumferential bowl wall (12) having an inner and outer surface, said inner surface comprising a plurality of annular recesses (19); a housing (30) for accommodating the centrifuge bowl (10), said housing (30) having a base (34) located in the central axis (15) and a circumferential housing wall (33) surrounding the central axis (15); an inlet (17) configured to allow entry of a slurry into the centrifuge bowl (10), preferably arranged substantially in parallel with the central axis (15); means for rotating the centrifuge bowl (10) about the central axis (15); an upper portion of the housing wall (33) is connected to an upper portion of the bowl wall (46), and the base (11) of the centrifuge bowl is connected to the base (34) of the housing thereby defining an annular cavity (31) between the bowl wall (12) and the housing wall (33); the annular cavity (31) being fluidly connected to the plurality of annular recesses (19) on the inner surface of the centrifuge bowl by a number of perforations in the bowl wall (12); a fluid inlet fluidly connected to the annular cavity (31), wherein a first portion of the inner surface of the centrifuge bowl comprising one or more recesses has an angle with respect to the central axis (15) which is different than the angle of a second portion of the inner surface of the centrifuge bowl comprising one of more recesses.

25. The centrifuge according to claim 24, wherein the second portion of the inner surface of the centrifuge bowl is located closer to the centrifuge bowl base (11) than the first portion of the inner surface of the centrifuge bowl and that the angle of the second portion of the inner surface is greater than the angle of the first portion of the inner surface.

26. The centrifuge according to claim 24, wherein the difference in inclination between the angles of the first portion of the inner surface and the second portion of the inner surface is at least 3 degrees to 5 degrees.

27. The centrifuge according to claim 24, wherein the difference in angles of the first portion of the inner surface and the second portion of the inner surface is between 5 degrees and 15 degrees.

28. A centrifuge (1) for separating intermixed particulate material of different specific gravity comprising: a centrifuge bowl (10) having a base (11), a circumferential bowl wall (12) surrounding a central axis (15) and an open end substantially opposite of the base (11), said central axis (15) passing through the base (11), the circumferential bowl wall (12) having an inner and outer surface, said inner surface comprising a plurality of annular recesses (19); a housing (30) for accommodating the centrifuge bowl (10), said housing (30) having a base (34) located in the central axis (15) and a circumferential housing wall (33) surrounding the central axis (15); an inlet (17) configured to allow entry of a slurry into the centrifuge bowl (10), preferably arranged substantially in parallel with the central axis (15); means for rotating the centrifuge bowl (10) about the central axis (15); an upper portion of the housing wall (33) is connected to an upper portion of the bowl wall (46), and the base (11) of the centrifuge bowl is connected to the base (34) of the housing thereby defining an annular cavity (31) between the bowl wall (12) and the housing wall (33); the annular cavity (31) being fluidly connected to the plurality of annular recesses (19) on the inner surface of the centrifuge bowl by a number of perforations in the bowl wall (12); a fluid inlet fluidly connected to the annular cavity (31), wherein an accumulated cross-sectional flow area (A.sub.flow) at two different heights in the annular cavity (31) differs by at least a factor 10, such that a first section of the annular cavity (52) is at least partially separated from a second section of the annular cavity (53).

29. The centrifuge (1) for separating intermixed particulate material according to claim 28, wherein A.sub.flow at two different heights in the annular cavity (31) differs by at least a factor 100.

30. The centrifuge (1) for separating intermixed particulate material according to claim 28, wherein the annular cavity (31) comprises at least one barrier member (50) adapted to at least partially separate the annular cavity (31) into at least a first and second section (52,53).

31. The centrifuge (1) for separating intermixed particulate material according to claim 28, wherein the at least one barrier member (50) is integrated in the bowl wall (12) and/or the housing wall (33).

32. The centrifuge (1) for separating intermixed particulate material according to claim 31, wherein the barrier member (50) comprising an orifice member (201).

33. The centrifuge (1) for separating intermixed particulate material according to claim 28, wherein the centrifuge (1) is configured to have a pressure gradient in the annular cavity (31) along the outer surface of the centrifuge bowl wall that has a positive and a negative value.

34. The centrifuge (1) for separating intermixed particulate material according to claim 28, wherein a top flange (56) of the centrifuge bowl and a top flange (55) of the housing comprising at least partially overlapping openings, configured for de-silting the annular cavity (31) and allowing the annular cavity (31) to be in fluid communication with the surroundings, preferably wherein the centrifuge bowl top flange opening and/or the housing top flange opening comprise a de-silting nozzle (72).

35. A method of separating intermixed particulate material of different specific gravity using the centrifuge according to claim 24, comprising: providing slurry comprising said intermixed particular material of different specific gravity therein, into the inlet (17); allowing entry of the slurry to the centrifuge bowl (10); rotating the centrifuge bowl (10) about the central axis (15) using said means for rotating the centrifuge bowl (10) about the central axis (15); and separating said intermixed particulate material of different specific gravity by virtue of centrifugation.

36. The method of claim 35, further comprising the step of collecting the intermixed particulate material in the plurality of annular recesses (19) in the inner surface of the centrifuge bowl (10).

37. The method of claim 35, further comprising the step of fluidizing the intermixed particulate material in said plurality of annular recesses (19) via the number of perforations in the bowl wall (12).

38. The method of claim 35, further comprising the step of allowing at least some of said intermixed particulate material pass said recess having an angle with respect to the central axis (15) which is different than the angle of a second portion of the inner surface of the centrifuge bowl (10) comprising one of more recesses.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The invention will be described in more details below by means of non-limiting examples of presently preferred embodiments and with reference to the schematic drawings, in which:

[0069] FIG. 1 shows a schematic cross-sectional view of a centrifuge according to an embodiment of the invention;

[0070] FIG. 2 shows a schematic cross-sectional view of a centrifuge bowl and a housing according to an embodiment of the invention;

[0071] FIG. 3 shows a schematic cross-sectional view of a centrifuge bowl and a housing according to another embodiment of the invention;

[0072] FIG. 4 shows a schematic cross-sectional view of a centrifuge bowl and a housing according to yet another embodiment of the invention;

[0073] FIG. 5 shows a schematic cross-sectional view of a centrifuge bowl and a housing according to yet another embodiment of the invention;

[0074] FIG. 6a to FIG. 6c show a top view of a variety of different barrier members according to an embodiment of the invention;

[0075] FIG. 7 shows a schematic perspective view of a section of a centrifuge bowl according to an embodiment of the invention;

[0076] FIG. 8 shows a schematic cross-sectional view of an upper portion of a centrifuge bowl and housing according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0077] FIG. 1 shows a schematic view of a centrifuge 1 according to one embodiment of the invention. The centrifuge 1 comprises a centrifuge bowl 10 having a base generally indicated at 11 and a peripheral centrifuge bowl wall 12 standing upwardly from the base 11 to an open mouth 13. The centrifuge bowl 10 is attached to a support shaft 16 which enables the centrifuge bowl 10 to rotate around a central axis 15. In the specific embodiment shown the shaft 16 is supported by bearings and the means for rotating the centrifuge bowl 10 is in the form a motor 2. The motor 2 drives the shaft 16 through a belt and a pulley arrangement. The rotation means and the bearings are mounted on a support frame 3. A feed duct 17 is arranged through the open mouth 13 and configured to provide a feed preferably in the form of a mixture of heavier and lighter particulate materials in a water slurry. The inlet of the feed duct is preferably located at a position near the base 11. In the particular embodiment shown, the feed is provided along the central axis 15 and deposited onto a guide plate 18 at the base 11. The feed is then deflected in a radial directed with regards to the central axis 15. The feed then moves onto the peripheral wall 12 for separation of the heavier materials into a plurality of annular recesses 19 on the peripheral wall 12 while the lighter materials in the feed pass over the centrifuge bowl wall 12 to the open mouth 13 for discharge. Material exiting from the open mouth 13 is collected by a launder 20.

[0078] The inner surface 23 of the peripheral wall of the centrifuge bowl 10 is generally formed by molding a liner material onto a metal shell or skeleton frame. Thus, the recesses are formed directly by the liner material while the bowl is structurally formed from metal. The liner material is generally a resilient polymer material such as urethane which is resistant to wear.

[0079] The overall angle of the centrifuge bowl wall 12 relative the central axis 15 may vary or be constant. In the embodiment shown in FIG. 2 the centrifuge wall 12 has a first lower portion 45 which has a larger angle relative to the central axis 15 than a second upper portion 46 of the centrifuge wall 12. Alternatively, the centrifuge wall 12 may have a first, second, and third portion, each having a different angle smaller than the previous section relative to the central axis 15. It is clear that the number of sections having a different angle may be increased further. As the number of sections is increased the shape becomes rounder and ultimately the shape of the centrifugal wall 12 in a cross-sectional view may be circular, i.e. the centrifuge bowl wall 10 may have a shape similar to a half sphere or a paraboloid.

[0080] The annular recesses 19 are axially spaced along an inner surface 23 of the centrifuge bowl wall 12. The centrifuge bowl wall 12 is substantially frusto-conical so that the diameter of the annular recesses 19 increases from a first recess at the base 34 to a last recess at the open mouth 13. By diameter is meant the distance from one point on the base 40 of an annular recess through the central axis 15 to a point on the base 40 of the same annular recess 19 on the opposite site of the centrifuge bowl 10. The annular recesses 19 include side walls 41 which converge towards a base 40 of the recess 19.

[0081] Material that passes over the centrifuge bowl wall 12 through the open mouth 13 is collected by a launder 20 for discharge. Around the centrifuge bowl 10 is provided a housing 30 defining an enclosure around the centrifuge bowl 10. The housing 30 has a housing wall 33 and a base 34. The base 34 is connected to the base 11, and the housing wall 33 is connected to the centrifuge bowl wall 10 near the open mouth 13. The centrifuge bowl wall 10 and the housing 33 thereby defines an annular cavity 31. Openings 32 fluidly connect the annular cavity 31 with the base of the annular recesses 19. The annular cavity 31 has a fluid inlet (not shown), preferably located near the base 34 and adapted to provide pressurized fluid into the annular cavity 31. Preferably the fluid may be supplied by a duct through the shaft. The fluid may be a liquid such as water or a pressurized gas such as air. The fluid distributes in the annular cavity 31, and may flow through the openings 32 in the centrifuge bowl wall 12 into the annular recesses 19. The openings 32 may be a plurality of small perforations or a single opening comprising a changeable orifice. The orifices may then comprise perforations in different numbers and sizes. The pressurized fluid, fluidizes material collected in the annular recess 19 and results in that a fluidized bed is defined in the annular recesses 19. The fluidized beds acts to separate heavier material which tends to collect in the recesses from lighter material which tends to be flushed out of the recesses and out of the open mouth 13 of the centrifuge bowl 10.

[0082] The separation and collection process is a batch process so that the heavier material is collected in the recesses for subsequent wash down and collection. Lighter material flows upwards and is discharged through the open mouth 13. After separation the collected material is washed down to the base 11 and passed through a discharge opening 26 and through the concentrate outlet 27. The feed duct 17 comprises a cylindrical tube carried on a cover 28 of the launder 20. Thus, the tube forming the feed duct 17 is in fixed position and remains stationary as the centrifuge bowl 10 rotates around the axis 15. As the centrifuge bowl 10 and housing 30 is rotated, feed material in the centrifuge bowl 10, but also fluid in the annular cavity 31 is subject to centrifugal acceleration. While the centrifuge 1 is rotating the fluid in the annular cavity 31 exhibits a pressure distribution that largely increases with distance from the central axis 15, while to a lesser extent decreasing with elevation. The centrifuge of the present invention is configured with means to change this pressure distribution to a more beneficial pressure distribution which allows greater control over the fluid flow supplied to the individual annular recesses 19.

[0083] Turning now to FIG. 2 showing the centrifuge bowl 10 in greater detail. The annular cavity 31 is configured with means for changing the pressure distribution. This is achieved by separating the annular cavity into at least a first lower section 52 and a second upper section 53 separated by a barrier member 50. The barrier member 50 is in this embodiment shown in the form of an annular ring 200 mounted between the housing wall 33 and centrifuge bowl wall 12. The first section 52 and second section 53 are fluidly connected by means of barrier openings 51 in which orifices are mounted. The barrier openings 51 are spaced around the barrier member 50 to provide the desired flow. In the cross-sectional view presented in FIG. 2 only two barrier openings 51 can be seen, but 16 barrier openings are distributed around the barrier member 50. Alternatively, the barrier member 50 may comprise 4 to 30 barrier openings, preferably 10 to 20 barrier openings.

[0084] Two different planes through the centrifuge bowl at a height 400 and a height 401 is indicated by dotted lines. The height is measured from the base and any height between the base and top of the centrifuge bowl 10 may be selected. At height 401 the dotted line passes through the second section 53 of the annular cavity. The area of the annular cavity in this plane is referred to as the accumulated cross-sectional flow area (A.sub.flow). At height 400, the dotted line passes through the barrier member 50 and the barrier opening 51. The A.sub.flow at this height is substantially smaller than the A.sub.flow at height 401, since fluid is allowed only to flow through the sixteen barrier openings 51. The difference between A.sub.flow at height 400 and A.sub.flow at height 401 is around a factor 100.

[0085] The barrier member 50 may comprise a number of openings allowing passage of fluid. Some of these openings may have an orifice installed therein and other openings may have a plug installed therein. Both the orifices and plugs are removably attached, so that they can be replaced. By configuring the barrier member 50 with a desired number of orifices or plugs, it is possible to increase or decrease the flow between the first section and second section. The orifice allows the channel through the opening to be modified. However, it is also possible not to install any plug or orifice in the opening. This configuration provides the largest flow through the opening. It is therefore possible to vary the factor of the two A.sub.flow's for this shown embodiment to between 20 to 1000 by installing orifices or plugs in the barrier openings 51. A variety of barrier members 50 will be discussed later with regards to FIG. 6.

[0086] In the present embodiment the annular cavity 31 is provided with a fluid inlet near the base 34 in the first lower section 52. Once the centrifuge bowl 10 rotates, the fluid pressure will increase up through the annular cavity because of the sloped peripheral wall of the housing and centrifuge bowl and hence an increasing distance from the center axis 15. The pressure in the first section 52 will therefore increase towards the barrier member 50. Because the flow through the barrier member 50 is restricted, the fluid pressure will decrease across the barrier member 50. The pressure in the second upper section 53 adjacent the barrier member 50 is therefore lower than a pressure adjacent the barrier member 50 in the first section 52. The maximum pressure in the first section 52 is therefore higher than the lowest pressure in the second section 53.

[0087] Particulate materials may be present in the annular cavity 31, due to for example an impure water supply, and will be subject to centrifugal forces, causing them to settle outwards and upwards on the sloped peripheral housing wall 33. The centrifuge bowl wall 12 comprises a plurality of openings 71 around the periphery of the top flange 56 to expel and prevent the accumulation of this particulate material. This is shown in more detail in FIG. 8 which show a cross-sectional view an upper portion of the centrifuge comprising the top flange 56 and the de-silting means 70. A de-silting nozzle 72 is located in each of the openings 71 to control the discharge rate and improving maintainability due to their easy replacement. In the present embodiment the top flange 56 of the centrifuge bowl has been expanded to envelope these openings, with the de-silting nozzle inserts being held down by the centrifuge bowl 12. An opening 73 is located in the housing top flange 55 to fluidly connect the annular cavity 31 to the surroundings. The housing 30 and the centrifuge bowl 10 are removably attached to each other in the flanges (55, 56) by fastening means 74 in the form of a shredded bolt and a corresponding shredded hole in the flanges. By having the de-silting means located in the flange 56 of the centrifuge bowl, compared to in the housing flange 55, allows for the diameter of the centrifuge bowl 10 to be larger. This increase the distance from the center axis 15 of the centrifuge 1 and thereby increase the centrifugal force.

[0088] Whereas in the prior art the desilting openings were located outside the radius of the top flange 56 of the centrifuge bowl 10, in the present embodiment the desilting openings pass through both the bowl top flange 56 as well as the housing top flange 55, allowing for an increase in the centrifuge bowl diameter as well as an optimization of the fastener configuration attaching the bowl to the housing. De-silting nozzle inserts may be installed in the de-silting openings 71 as before, or in an alternative arrangement the de-silting nozzle may be incorporated into the housing flange 55 or the centrifuge bowl flange 56

[0089] Turning now to FIG. 3, FIG. 4, and FIG. 5 showing different embodiments of the centrifuge bowl 10 and housing 30 comprising different barrier members 50. In FIG. 3 the barrier member 50 is a solid ring 100. The ring 100 do not comprise any openings between the first section 52 and the second section 53. Instead the first section 52 and second section 53 are in fluid communication by means of a set of by-pass conduits 60.

[0090] The by-pass conduits 60 acts as a fluid outlet in the first section 52 and a fluid inlet in the second section 53. The location of the inlet and outlet may in this way be modified. The set of by-pass conduits 60 are distributed around the outer wall of the housing 30. The solid ring 100 is in this embodiment integrated with the housing wall. The ring 100 are in contact with a sealing portion 48 of the centrifuge bowl in the form of a flange. A gasket may be provided between the ring 100 and the flange to form a tight seal.

[0091] The annular cavity 31 may also be divided into a plurality of sections such as more than two sections. An embodiment of the invention having this configuration is shown in FIG. 4. The annular cavity 31 is separated into three sections by means of two barrier members 50 in form of two solid rings 100. The first section 52 is in fluid communication with the second section 53 and the third section 54 by means of a set of by-pass conduits 60. Alternative to this configuration, the first section 52 and second section 53 may be connected by a first set of by-pass conduits 60, and the second section 53 and third section 54 may be connected by a second set of by-pass conduits 60. Alternatively, each of the first section 52, second section 53, and optionally the third section 54 are supplied by an individual fluid inlet. This provides the option to supply the same or different fluid pressure in each of the sections. The more the annular cavity 31 is divided into sections, the more the pressure profile may be controlled. A plurality of sections may naturally also be fluidly connected by the barrier members shown in FIG. 2.

[0092] Turning now to FIG. 5 showing another embodiment of the invention, in which the annular cavity comprises a plurality of barrier members 50 in the form of barrier inserts 110 and 115. A number of barrier inserts 110 are removably attached along the circumference of the housing wall 33 to provide a restriction of the flow between a first section 52 and a second section 53. The barrier inserts 110 and the housing wall 33 are provided with mutual corresponding fastening means. As an example, the barrier inserts 110 may be provided with a threaded pin and the housing wall 33 a corresponding threaded hole. The barrier inserts 110 may vary in size. The distance between the barrier inserts 110 can be changed by providing barrier inserts 110 which are narrower or wider. Similarly, the length of the barrier inserts 110 can be varied to provide a desired gap between the barrier inserts 110 and the outer surface of the centrifuge bowl wall 24. A number of sets of barrier inserts 115 may be removably attached along the circumference of the housing wall 33 and the outer surface of the centrifuge bowl wall 24. This provides a gap between the barrier inserts 115. The barrier inserts 115 may also be varied in size to provide a larger or smaller gap. In the embodiment shown, the difference in A.sub.flow at height 400 and A.sub.flow at height 401 is a factor 6 whereas the difference in A.sub.flow at height 400 and 402 is a factor 9. The barrier inserts 115 therefore provides a larger pressure reduction than barrier inserts 110 provided the loss coefficient is similar.

[0093] Turning now to FIG. 6a, FIG. 6b and FIG. 6c which show different barrier members 50 in the form of annular barrier members. Annular barrier member 200 comprises eight evenly distributed openings 202 in the form of drilled holes. When the annular barrier member 200 is installed in an annular cavity 31, the openings 202 fluidly connects different sections of the annular cavity 31. The openings may have an orifice 201 or a plug 203 installed therein, to increase the restriction in flow of fluid between sections. The barrier member 200 may provide a difference in A.sub.flow of at least a factor 40 to 60 with all openings 202 open. If orifices of plugs are installed the difference in A.sub.flow may be even higher.

[0094] The annular barrier member 240 comprises openings in the form of four radial openings 241. The openings 241 may be fully opened or may be covered by a perforated or solid plate to limit flow through the barrier member 240. The plate may be welded or screwed onto the barrier member 240.

[0095] The annular barrier member 220 comprise an annular opening 221 along the inner periphery. The annular opening might alternatively be located along the outer periphery.

[0096] Turning to FIG. 7 which show a perspective view of a portion of a centrifuge bowl 10. It can be seen that the recesses 19 are wider and more spaced in the lower portion of the centrifuge bowl 10 than in the upper portion of the centrifuge bowl 10. The tips 22 of the annular recess, in the lower portion of the centrifuge bowl, are thicker and hence have relatively more wear material where higher wear is observed.

LIST OF REFERENCE NUMBERS

[0097] Centrifuge 1 [0098] Rotation means 2 [0099] Support frame 3 [0100] Centrifuge bowl 10 [0101] Base 11 [0102] Centrifuge bowl wall 12 [0103] Open mouth 13 [0104] Central axis 15 [0105] Support shaft 16 [0106] Feed duct 17 [0107] Guide plate 18 [0108] Annular recess 19 [0109] Launder 20 [0110] Ring Tip 22 [0111] Inner wall of centrifuge bowl 23 [0112] Outer wall of centrifuge bowl 24 [0113] Discharge opening 26 [0114] Concentrate outlet 27 [0115] Cover 28 [0116] Housing 30 [0117] Annular cavity 31 [0118] Centrifuge bowl wall openings 32 [0119] Housing wall 33 [0120] Housing base 34 [0121] Recess base 40 [0122] Side walls of recess 41 [0123] Lower portion of bowl wall 45 [0124] Upper portion of bowl wall 46 [0125] Sealing portion 48 [0126] Barrier opening 51 [0127] First section 52 [0128] Second section 53 [0129] Third section 54 [0130] Housing top flange 55 [0131] Centrifuge bowl top flange 56 [0132] By-pass conduit 60 [0133] De-silting means 70 [0134] Opening in top flange 71 [0135] De-silting nozzle 72 [0136] Housing flange opening 73 [0137] Fastening means 74 [0138] Solid annular ring 100 [0139] Barrier insert 110 [0140] Barrier inserts 115 [0141] Annular barrier member 200 [0142] Orifice 201 [0143] Opening 202 [0144] Plug 203 [0145] Annular barrier member 220 [0146] Annular opening 221 [0147] Annular barrier member 240 [0148] Radial opening 241 [0149] Height 400 [0150] Height 401