AU2015376856B2

AU2015376856B2 - Centrifugal scroll screen apparatus

Info

Publication number: AU2015376856B2
Application number: AU2015376856A
Authority: AU
Inventors: Michael Trench
Original assignee: Weir Minerals Australia Ltd
Current assignee: Weir Minerals Australia Ltd
Priority date: 2015-01-15
Filing date: 2015-12-27
Publication date: 2021-03-11
Anticipated expiration: 2035-12-27
Also published as: WO2016112428A1; AU2015376856A1

Abstract

A centrifugal scroll screen apparatus has a housing (10) and a rotating screen assembly including a base-of-spoke piece (13) cooperating with the housing (10) to substantially divide the housing into housing portions receiving filtrate and product passing through the base-of-spoke piece (13) respectively. The base of spoke piece (13) and housing (10) including respective labyrinth portions (81, 82), each comprising a replaceable service item. The labyrinth portions collectively comprise a plurality of complementary annular ridges (83) interleaved to create a labyrinth selected to substantially resist filtrate contamination of the product. The housing (10) is selectively separable substantially in the plane of the base-of-spoke piece (13).

Description

CENTRIFUGAL SCROLL SCREEN APPARATUS

Technical Field

[0001] This disclosure relates in general to a centrifugal scroll screen apparatus and, in

particular, to an improved fine coal centrifugal scroll screen machine.

Background of the Disclosure

[0002] Pulverized coal is washed by forming a water slurry and dewatering the slurry by

passage through a fine coal centrifugal scroll screen machine. A typical machine is known as

a vertical fine coal centrifugal scroll screen machine and includes a housing, a screen assembly

mounted for rotation on a vertical axis in the housing and comprising a base-of-spoke piece

supporting the lower, wider end of a frustoconical screen member, the base of spoke piece

cooperating with a dividing wall in the housing to form housing portions receiving filtrate

passing through the screen member and product passing through the base-of-spoke piece

respectively.

[0003] The screened coal product is actively stripped from the screening surface of the screen

member by a scroll assembly of helical scroll vanes mounted for differential rotation within the

screen member, the edges of which scrape the deposited fine coal and urge it through apertures

in the base-of-spoke piece. A drive assembly generally comprising an electric motor and

gearbox differentially drives the rotation of the screen assembly and scroll assembly mounted

on concentric drive shafts. Incoming fine coal slurry passes down vertically under a gravity

head into an inlet assembly supported on said housing and feeding in to the upper, narrow end

of the screen member.

[0004] The commercially important features of a fine coal centrifuge are throughput, ease of

maintenance and reduction of downtime. Prior art fine coal centrifuges may require significant

difficult disassembly for maintenance.

Summary

[0005] In a first aspect, the present invention resides broadly in a centrifugal scroll screen

apparatus including:

a housing;

a screen assembly mounted for rotation in said housing and comprising a base-of-spoke

piece and a substantially frustoconical screen member having an inner screening surface and

removably secured by its base to the base-of-spoke piece, the base of spoke piece cooperating

with the housing to substantially divide the housing into housing portions receiving filtrate

respectively, the base of spoke piece and housing including respective labyrinth portions, any

one or both labyrinth portions comprising a replaceable service item, the labyrinth portions

collectively comprising a plurality of complementary annular ridges interleaved to create a

labyrinth selected to substantially resist filtrate contamination of said product, said housing

portions being selectively separable substantially in the plane of the join between the base-of

spoke piece and screen member;

a scroll assembly having a plurality of substantially helical scroll vanes and mounted

for rotation within said screen member with an edge of each said vane lying in selected

proximity to said screening surface;

drive means selected to differentially drive the rotation of said screen assembly and said

scroll assembly about a machine axis; and an inlet assembly supported on said housing and cooperating with an open apical end of said screen member to deliver material to be screened to said screening surface.

[0006] In certain embodiments, the housing portions may include a fixed inner portion

associated with the drive means and a moveable outer portion associated with the inlet

assembly, said inner and outer portions having complementary peripheral mating flanges

secured with selectively releasable fixing means. By this means the join is accessible for

maintenance when the housing portions are separated.

[0007] In certain embodiments, the selectively releasable fixing means may include a plurality

of circumferentially spaced key slots associated with the peripheral mating flange of the inner

portion and each supporting a blind stud, corresponding stud holes associated with the

peripheral mating flange of the outer portion, and securing means selected to engage the studs

to clamp said peripheral mating flanges together. Typically the studs and securing means are

complementary threaded components.

[0008] In certain embodiments, the key slots are formed in slot bodies welded outward of the

peripheral mating flange of the inner portion, each slot body and blind stud being retained in

assembly by a resilient retainer adapted to pass over the stud and substantially encapsulate the

slot body. By this means the blind stud is retained to the housing inner portion by means that

protects the arrangement from the aggressive erosive and corrosive environment. This provides

an inexpensive and easily replaceable fixing system that addresses both wear and corrosion

problems of alternative fixing methods. The welded slot bodies may be formed of stainless

steel.

[0009] The resilient retainer may comprise a cap having a cylindrical side wall adapted to

engage the slot body and substantially closed at one end by an end wall having an aperture

adapted to pass over and engage the stud. The resilient retainer may be secured in position by any suitable means. For example, the resilient retainer may be threaded on one or both of the inner cylindrical side wall to engage a complementary threaded side surface of the slot body.

The end wall aperture may be internally threaded to engage the corresponding threaded stud.

Alternatively, the resilient retainer may be a tight fit on the stud and have a complementary

profile to the slot body whereby the retainer may resiliently snap onto the slot body. The

resilient retainer may suitably be moulded of a chemically and abrasion resistant elastomeric

material such as polyurethane elastomer.

[0010] In its simplest embodiment, the blind stud includes a bolt and the securing means

includes corresponding nut. The bolt and nut are preferably of stainless steel or a like resistant

alloy such as MONEL©.

[0011] In certain embodiments, the housing portions may relatively conjoined by one or more

hinge portions. This is especially the case where the machine orientation is horizontal, where

a vertically hinged outer housing portion provides access for ground-level maintenance. The

selected configuration of the hinge portions may be geometrically selected to cooperate with a

hinged inlet assembly as described above to allow the assembly of the outer housing portion

and inlet assembly to be opened with ample clearance of the wet-end parts, to provide

maintenance access to the entire wet side of the apparatus. This access is achievable without

the use of cranes, in the case of horizontal machines at least.

[0012] In the aggressive environment anticipated for screen machines, the hinge portion or

portions may be lubricated by a positive pressure lubricator. For example, the positive pressure

lubricator may include a grease reservoir pressurized by a spring loaded piston and having a

delivery outlet spigot screwed into the bore of a hinge to lubricate the pin-to-bore surfaces

thereof Positive grease pressure resists the ingress of abrasive fines, thus prolonging the

service life of the hinge portion.

[0013] In certain embodiments, a filtrate or effluent outlet may be integrally formed with the

outer housing portion.

[0014] In certain embodiments, at least the housing portion receiving filtrate passing through

the screen member may be formed of moulded polymer or polymer composite. As the effluent

chamber and the wet end of the housing per se is exposed to an abrasive environment in use,

an integral outer housing and effluent chamber may be unitarily formed on an engineering

polymer material such as ultra-high molecular weight polyethylene (UHMWPE).

Alternatively, the outer housing may be formed more conventional such as of wear resistance

lined steel, and having attached thereto a polymer or composite effluent chamber portion.

[0015] The machine is preferably a horizontal machine.

[0016] The inlet assembly supported on the housing may include an inlet body defining a

substantially annular inlet space substantially coaxial with and opening in to an open apical end

of the screen member and a material supply conduit delivering the material to be screened to

the annular space, the material supply conduit being aligned in a tangent to the annular space

selected to deliver the material to the screening surface substantially in the direction of rotation

of the screen assembly.

[0017] Apparatus having the foregoing inlet features has an advantage over prior art scroll

centrifuge machines in that the material supply conduit being aligned in a tangent to the annular

space rotates the incoming material substantially in the direction of rotation of the screen

assembly. The material needs less acceleration by the screen to reach centrifugally effective

speeds, increasing throughput and reducing screen wear. The annular space effectively confines

the feed to adjacent the screen surface. This permits the use of product supply gravity head in

a substantially self-regulating manner, generally not requiring choke regulation of supply by

velocity arrestors or the like. The present invention is readily adapted to a horizontal machine with a vertical gravity feed finding a ready tangent to the horizontal machine axis, with additional advantages accruing as described hereinafter.

[0018] In certain embodiments, the inlet assembly may include an inlet body forming the

annular inlet space and including an integral spigot to the supply conduit. The inlet space and

spigot may be lined with a wear resistant material. The wear resistant material may for example

be selected from refractory materials such as sintered ceramic materials and fired ceramic

materials.

[0019] In certain embodiments, the inlet body may be selected from fabricated or cast metal,

moulded engineering polymer and composites. Simpler forms may be readily fabricated from

steel. More complex inlet body shapes may be formed by molding as described hereinafter.

[0020] In certain other embodiments, the wear resistant lining may selected from wear resistant

elements bonded into the inlet body to form the lining and a wear resistant ceramic liner about

which the inlet body is formed. The wear resistant elements may be sintered ceramic tiles. For

example, the tiles may comprise sintered alumina, other refractory metal oxides or sintered

carbides.

[0021] In certain other embodiments, the wear resistant lining may be an integral hot sintered

ceramic liner having a spigot portion merging with a substantially involute annular inlet space

portion. The inlet body may be formed thereabout by molding or, for example, an engineering

polymer or composite material.

[0022] The wear resistant lining including an involute annular inlet space portion may be

produced by, for example, repetitively dipping a wax plug into ceramic powder slurry and

drying between dips, to form a green liner. The green liner may be further dehydrated and the

wax plug removed by heating, followed by calcining to form a hard ceramic material.

[0023] The inlet axis may be inclined to the machine axis. In certain embodiments, the axis of

the tangential material supply conduit may lie in a plane that intersects the machine axis by an

angle of from 0° to about 10 from the perpendicular, measured away from the screen assembly.

[0024] In certain embodiments, the material to be screened may be delivered to the annular

inlet space by pressure head means selected from gravity and pump. For example, the head

may be provided by the usual gravity head commonly used to supply conventional vertical fine

coal centrifuges of the prior art. In most applications, the gravity feed may be supplied without

the use of velocity arrestors. In the case of pump feeds, this may include a pump which either

replaces or supplements a gravity head. The pump make be selected from all classes of pumps

known in the art for moving the particular slurry be screened. For example the pump may be

selected from centrifugal pumps.

[0025] In certain embodiments, the machine axis may be substantially horizontal. This has

several advantages. The use of a horizontal machine with an inlet assembly according to the

above does not suffer from the disadvantage of the few prior art horizontal machines of the feed

extending the floor plan, since the feed in the present apparatus is tangential to the inlet and

machine axis.

[0026] The inlet assembly of a horizontal machine may be formed separately from and be

hinged to the housing. The inlet assembly may extend its annulus forming outer cylindrical

wall into the housing to confine the feed to the annular space defined by the screening surface

and the scroll vanes. The portion of the annulus forming outer cylindrical wall extending into

the housing may include part of the housing or may include an integral part of the hinged inlet

assembly.

[0027] Where the portion of the annulus forming outer cylindrical wall extending into the

housing includes an integral part of the hinged inlet assembly, the hinge arrangement may be positioned and configured to allow the inlet assembly, including the wall extending into the housing, to clear an aperture in the housing to enable maintenance access. When the inlet assembly is in its closed up position in the housing, there may be provided a gasket arrangement.

The gasket arrangement may be compressed by any suitable means. For example the inlet

assembly may be secured in the closed position with closure bolts.

[0028] In certain embodiments the drive means may include a motor and a power-dividing

gearbox providing the differential drive through concentric shafts as per the prior art, wherein

the gearbox may have a pressurized-circulation lubrication system including at least one

lubricant pump delivering lubricant from a reservoir and at least two filters in parallel, each

being associated with isolation valve means selected to allow filter maintenance without shut

down of the gearbox.

[0029] A conventional gear or other positive-displacement lubrication pump may pressure

supply the gearbox with lubricant from an atmospheric reservoir. Circulated lubricant may be

returned to the reservoir via a low pressure return line. The parallel filters may be located in

either the supply line or the return line. The filters may be selected from single use or

serviceable filter assemblies. For example, each filter may be a disposable spin-on filter

cartridge.

[0030] The isolation valve means may take any suitable form including, but not limited to

electrically selected or manually operated isolation valve means. The respective isolation

functions may be integrated into a single action changeover valve and non-return valves. For

example, the filters may be supplied by an inlet line from pump by a filter-selecting Y-valve,

each filter having a respective non-return valve on its delivery line.

[0031] The issue of reducing cross contamination of the product and effluent or filtrate streams

is specifically addressed with reference to the labyrinth. Preferably, at least the labyrinth portion of the housing is a replaceable component. More preferably, both labyrinth portions are replaceable components.

[0032] The labyrinth may be pressurized via a manifold associated with the housing. The

manifold may comprise an annular passage formed on the housing portion surrounding the

periphery of the base of spoke piece and feeding a pressurized fluid into the labyrinth. The

pressurized fluid may be air, since air is not a contaminant for either product or effluent streams.

[0033] As an alternative to or in addition to a labyrinth, cross contamination may be addressed

by the rotating base of spoke piece cooperates with the static housing by means of a slinger

portion associated with the base of spoke piece and selected to substantially resist filtrate

contamination of said product. The slinger portion may include an axially directed annular wall

secured to the base of spoke piece and adapted to run in proximity to the aperture between the

housing portions receiving filtrate passing through the screen member and product passing

through the base-of-spoke piece respectively, and a plurality of circumferentially spaced slinger

vanes inclined to the machine axis and located radially outward of and adjacent to the annular

wall.

[0034] In certain embodiments, the slinger portion may include a slinger member including the

annular wall and slinger vanes formed on a mounting flange adapted to be secured to the base

of spoke piece. The slinger member is thus a replaceable service item which operates in a high

wear region, and additionally serves to protect that portion of the base-of-spoke piece in a

sacrificial manner.

[0035] The prior art of scroll machines includes methods of adjustment of the clearance

between the scroll vane edges and the screening surface to account for running in and relative

wear. In every case of disassembly and reassembly the clearance between these items is necessary to fine tune for efficiency. Excess clearance results in material pick up in the machine.

[0036] In the past, adjustment of the clearance has required removal of the outer housing

portion, attempting to measure the actual clearance by generally-obstructed visual means,

estimating the adjustment required, removal of the screening member by crane from the base

of-spoke piece, releasing of the scroll from the shaft by removal of its pattern of bolts while

supporting by crane, insertion or removal of a calculated thickness of shim, and reassembling.

[0037] In certain embodiments of the present apparatus, the drive means may include the

respective concentric drive shaft portions extending axially substantially through the screen

assembly, wherein the scroll assembly drive shaft may be connected to the scroll assembly by

an axial adjuster operable to adjust the selected proximity. The axial adjuster may include a

shaft portion and a scroll portion each having a respective camming surface whereby relative

rotation of the scroll portion and the shaft portion axially adjusts the selected proximity, and

locking means selectively operable to rotationally secure the scroll portion and the shaft portion.

[0038] The locking means may include splines, axially directed locating pins or the like. The

locking means is preferably selected to resist malfunction or jamming through the ingress of

fines. In any case, the axial adjuster is preferably protected in use by a cover such as a polymer

cap. For example, the mechanism of the axial adjuster may be protected by a polyurethane

elastomer cap.

[0039] The locking means may comprise a multi-pin staking device and axial bolt and plate.

Such an arrangement provides stepwise adjustment. However, stepless adjustment may be

achieved by an expanding coupling between the shaft and the scroll such as that provided by a

RINGFEDER'locking means. A scalar indication of adjustment may be provided by inscribed

scale marks on outer end faces of the scroll portion and the shaft portion.

[0040] In use, the hinged inlet assembly only (if used) or the housing outer portion is removed

or swung away (in a horizontal embodiment) whereupon the axial adjuster may be exposed.

Without removing the screen member and the scroll member (as required by the prior art) the

locking means may be released and the scroll member rotated on the shaft to effect adjustment

of the clearance between the scroll vanes and the screening surface of the screen member.

Thereafter the locking means may be engaged, the protection installed and the housing portions

closed together. The initial condition need not be measured at all; the adjustment is dynamic

in that the parts are in situ while the adjustment is made. The adjustment can be measured in

real time or the clearance fully closed up by one direction of relative rotation of the scroll on

the shaft rotation and backed off to create a selected working clearance.

[0041] One or both of the shaft portion and the scroll portion may include a replaceable service

part secured to its respective shaft or scroll.

[0042] In certain embodiments, the fixed inner portion may support a hoist assembly selected

to enable maintenance removal and replacement of the wet side components of the apparatus,

such as one or more of the scroll assembly and the screen assembly. Where the machine axis

is substantially horizontal, the hoist assembly may include a rail supported by the fixed inner

housing portion and extending overhead of the outer portion, a hoist mounted for movement

along the rail, and hoist adapters connecting a lifting terminus of the hoist to one or more of the

scroll assembly and the screen assembly.

[0043] The rail may comprise a monorail extending far enough to deliver components to a

trolley, with may be customized to receive a components in its in-use orientation. The hoist

may be a cable hoist or a chain hoist. The hoist adapters may be generic hooks or grabs. It is

preferred that the hoist adapters be custom configured to lift each component substantially

though its centre of gravity.

[0044] Whereas the prior art requires an external crane, certain embodiments herein are capable

of change out of components without additional overhead lifting gear. Whereas prior art

overhead lifting gear is generally multipurpose and must be rated accordingly, the present

embodiments are rating matched to the actual machine components. The relative short cable

or chain length to the component reduces the risk of load swing.

[0045] The scroll assembly includes structure to support the scroll vanes relative to the scroll

drive shaft. To a greater or lesser extent, the geometry of scroll members of the prior art has

tended to allow hang-up of product internally of the scroll member, which can lead to increasing

rotating mass and out-of-balance operation. In certain embodiments the present scroll assembly

includes a substantially frustoconical liner substantially interconnecting inner edges of the

vanes and spaced from the screening surface, said liner extending substantially to the base-of

spoke piece.

[0046] The liner may also extend substantially to the outer ends of the vanes. The liner may be

integrated into a collar portion that cooperates with the inlet assembly to confine the infeed of

material to the annulus containing the vanes.

[0047] In the event that the conical included angle of the liner is such that product hang-up still

occurs, the liner may be associated with an inner conical wall portion creating an enclosed

annulus within the liner and presenting a flatter conical included angle. By this means any

material passing into the space is discouraged from hanging up since the centrifugal component

of the forces acting through the flatter conical surface will direct the product toward the base

of-spoke piece.

[0048] Sampling of product quality is an important control element. The existing inspection

doors on centrifuges (which in previous days were used to take samples) comprises a manual

unrestrained sampling scoop inserted into a moving stream with rotating parts nearby. It is desirable that a sampler should have repeatability so that the sample should be consistent enough to see small changes in product output moistures.

[0049] A centrifugal scroll screen machine according to the foregoing description may include

a product sampler. For example, a product sampler may comprise a tubular body mounted by

a first open end to a corresponding aperture though a wall of the product housing portion, the

tubular body having its tubular axis substantially perpendicular to a product flow in said housing

portion. A sample shuttle may comprise a tubular receptacle selectively and captively movable

in the tubular body between a sampling position where a sampling portion extends into the

product flow and a sample delivery position with a delivery portion extended out of a second

open end of the tubular body, the sampling portion having side wall opening which faces

substantially upstream of the product flow and the delivery portion having a delivery opening.

A piston assembly may be captively slidable in the sample shuttle and may have a piston portion

and a control rod portion extending out of the second open end, the rod portion being operable

to selectively move the piston portion from a position located adjacent a terminal end of the

sampling portion to a position adjacent an outer end of the delivery opening.

[0050] The sampler may have a tubular body and sample shuttle which are each substantially

cylindrical in section.

[0051] The sample shuttle may be made captively moveable in the tubular body by an operating

handle attached to the sample shuttle extending out of and movable along an axial slot formed

in the cylindrical side wall portion of the tubular body.

[0052] The scroll vanes may be rendered more wear resistant than the base metal by laminating

the metal faces with adhesively bonded ceramic elements.

[0053] Other aspects, features, and advantages will become apparent from the following

detailed description when taken in conjunction with the accompanying drawings, which are a

part of this disclosure and which illustrate, by way of example, principles of the inventions

disclosed.

Description of the Figures

[0054] The accompanying drawings facilitate an understanding of the various embodiments.

[0055] FIG. 1 is a vertical section through centrifugal screening apparatus in accordance with

this disclosure;

[0056] FIG. 2 is a cut-away isometric view of the apparatus of FIG. 1;

[0057] FIG. 3 is a cut-away, isometric wire frame view of the apparatus of FIG. 1, showing

product and effluent flow paths therethrough;

[0058] FIGS. 4 and 5 are exploded isometric views of a scroll assembly for use in the

apparatus of FIG. 1;

[0059] FIG. 6 is a detail view of the hub of the scroll member portion of FIGS. 4 and 5;

[0060] FIG. 7 is a section though the scroll assembly of FIGS. 4 and 5;

[0061] FIG. 8 is a detail sectional view of the hub of the scroll assembly of FIGS. 4 and 5;

[0062] FIG. 9 is an isometric view of the shaft portion of the scroll assembly of FIGS. 4 and 5;

[0063] FIGS. 10 to 12 are a progression of side views showing maintenance disassembly of

apparatus according to FIG. 1;

[0064] FIG. 13 is a detail isometric view of the securing means between housing portions of

the apparatus of FIG. 1;

[0065] FIG. 14 is detail section of the securing means of FIG. 13;

[0066] FIG. 15 is an isometric view of a gearbox lubrication system as used in the apparatus

of FIG. 1;

[0067] FIG. 16 is a section though components of a pressurized labyrinth for use in the

apparatus of FIG. 1;

[0068] FIG. 17 is a cutaway isometric view of the labyrinth arrangement of FIG. 16;

[0069] FIG. 18 is a cutaway isometric view of the labyrinth arrangement of FIG. 16 in the

context of the apparatus of FIG. 1;

[0070] FIG. 19 is an isometric view of a slinger member as an alternative to a labyrinth and

usable in apparatus of the type illustrated in FIG. 1;

[0071] FIG. 20 is a section through the slinger member of FIG. 19;

[0072] FIG. 21 is an elevation of the slinger member of FIG. 19;

[0073] FIG. 22 is a cut-away isometric view of a simple labyrinth alternative to the labyrinth

of FIGS. 16 to 18;

[0074] FIG. 23 is a section of the labyrinth of FIG. 22; and

[0075] FIG. 24 is an elevation of the labyrinth of FIG. 22;

[0076] Fig. 25 is an isometric view of a sampler for use with the apparatus of Fig. 1, operatively

closed;

[0077] Fig. 26 is an isometric view of the sampler of Fig. 25, operatively open; and

[0078] Fig. 27 is a longitudinal section of the sampler of Figs. 25 and 26, operatively

discharged.

Detailed Description

[0079] In the FIGS. 1 to 3 there is provided generally a centrifugal screening apparatus

including an inner "dry side" housing portion 10 and an outer "wet side" housing portion 11.

A screen assembly 12 is mounted for rotation in the wet side housing portion 11 and includes a

base-of-spoke piece 13 and a frustoconical screen member 14 having a wedge-wire formed

inner screening surface 15 and removably secured by its base to the base-of-spoke piece 13.

The base of spoke piece 13 cooperates with the housing 10 to substantially divide the housing

10, the wet side housing portion 11 receiving filtrate passing through the screen member 14 to

an effluent chamber 16 and the dry side housing portion 12 receiving product passing through

the base-of-spoke piece 13 to a product delivery chamber 17. The filtrate or effluent chamber

16 is integrally formed with the outer wet side housing portion 11.

[0080] A scroll assembly 20 has a plurality of substantially helical scroll vanes 21 supported

on a conical liner 22 fabricated to a drive plate 23. The drive plate 23 has a hub 24 secured to

an inner drive shaft 25 whereby the scroll assembly 20 is mounted for rotation within the screen

member 14 with an edge of each said vane 21 lying in selected proximity to the screening

surface 15. The inner drive shaft 25 forms part of a drive assembly including an outer shaft 26

mounting the base-of-spoke piece 13 by a drive cone 27, the inner 25 and outer 26 drive shafts

being differentially driven to rotate the screen assembly 12 and the scroll assembly 20 about

the machine axis at different speeds in use.

[0081] An inlet assembly 30 is supported on the wet side housing portion 11 and includes an

inlet body 31 defining a substantially annular inlet space 32 with an axial occluding plug portion

33, the annular inlet space 32 being substantially coaxial with and opening in to an open apical

end 34 of the screen member 14. A material supply conduit 35 delivers the material to be

screened under gravity head to the annular inlet space 32, the material supply conduit 35 being

aligned in a tangent to the annular inlet space 32 to deliver said material to the screening surface

15 substantially in the direction of rotation of the screen assembly 12, as shown in the flow path

36 of FIG. 3.

[0082] The inlet body 31 includes an integral spigot 37 connected to the supply conduit 35 via

sleeve coupling 40, permitting decoupling of the inlet assembly 30 from the supply conduit 35

for maintenance.

[0083] The annular inlet space 32 and spigot 37 are lined with a wear resistant tiles 41 formed

of sintered alumina. The inlet body 31 is fabricated from steel. The wear resistant tiles 41 are

bonded to the steel with epoxy based adhesive grouting composition.

[0084] The inlet assembly 30 is hinged to the wet side housing portion 11. The inlet assembly

30 extends an outer cylindrical wall portion 42 into the wet side housing portion 11 to confine

the feed to an annular space 43 defined by the screening surface 15 and the scroll vanes 21.

The hinge arrangement (not shown) hinging the inlet assembly 30 to the wet side housing

portion 11 is positioned and configured to allow the inlet assembly 30, including the wall

portion 42 extending into the housing portion 11, to clear the housing portion 11 to enable

maintenance access. The inlet assembly 30 is sealed to the housing portion 11 by a gasketed

flange 44 compressed to the housing portion 11 closure bolts installed through holes 45.

[0085] The fixed, inner portion dry side housing portion 10 is associated with and supports the

drive means and the outer, wet side housing portion 11 associated with the inlet assembly 30 each have complementary peripheral mating flanges 46, 47 secured with selectively releasable fixing means 50 as detailed in FIGS. 15 and 16. The housing portions 10, 11 are selectively separable substantially in the plane of the join between the base-of-spoke piece 13 and the screen member 14.

[0086] The selectively releasable fixing means 50 includes a plurality of circumferentially

spaced key slots 51 associated with the peripheral mating flange 46 of the inner dry side housing

portion 10 and each supporting a blind stud 52, in this embodiment a stainless steel bolt.

Corresponding stud holes 53 associated with the peripheral mating flange 47 of the outer, wet

side housing portion 11 cooperate with nut 54 and washer 55 securing means selected to engage

the studs 52 to clamp the peripheral mating flanges together.

[0087] The key slots 51 are formed in slot bodies 56 welded at 57 outward of a gasketed sealing

flange portion 60 of the inner dry side housing portion 10, each slot body 56 and blind stud

being retained in assembly by a polyurethane elastomer resilient retainer 61 adapted to pass

over the stud 52 and substantially encapsulate the slot body 56. The welded slot bodies 56 are

formed of stainless steel.

[0088] The resilient retainer 61 comprises a cap having a cylindrical side wall 62 adapted to

engage the slot body 56 and substantially closed at one end by an end wall 63 having an aperture

64 adapted to pass over and engage the stud 52. The resilient retainer 61 may be threaded on

both of the inner cylindrical side wall 62 to engage a complementary threaded side surface 65

of the slot body 56. The end wall aperture 64 is internally threaded to engage the corresponding

threaded stud 52.

[0089] The housing portions 10, 11 are hinged together about a substantially vertical hinge (not

shown) to provide access to the wet side components for ground-level maintenance. The hinge

portions are geometrically selected to cooperate with the hinged inlet assembly 30 as described above to allow the assembly of the outer housing portion 11 and inlet assembly 30 to be opened with ample clearance of the wet-end parts, to provide maintenance access to the entire wet side of the apparatus. In the aggressive environment anticipated for screen machines, the hinge portion or portions are lubricated by a positive pressure lubricator (not shown), in this embodiment comprising a grease reservoir pressurized by a spring loaded piston and having a delivery outlet spigot screwed into the bore of each hinge to lubricate the pin-to-bore surfaces thereof.

[0090] The drive for the respective shafts 25, 26 includes a motor driven transmission belt 66

driving a power-dividing gearbox 67 providing the differential drive through the concentric

shafts 25, 26. A pressurized-circulation lubrication system 70 as illustrated in detail in FIG. 15

includes a lubricant positive displacement impeller pump 71 delivering lubricant from a

reservoir 72 to two disposable spin-on filter cartridges 73 mounted in parallel on a selector

assembly 74. Circulated lubricant is returned to the reservoir 72 via a low pressure return line

75. The selector assembly 74 delivers lubricant oil to the gearbox 67 via a supply line 76.

[0091] The selector assembly 74 includes a manual, lever single action, filter selecting

changeover valve 77 and respective non-return valves for each filter 73.

[0092] Cross contamination of the product and effluent or filtrate streams in the embodiment

of FIGS I to 3 is specifically addressed in the detail of FIGS. 16 to 18 in a first embodiment,

FIGS. 19 to 21 in a second embodiment, and FIGS. 22 to 24 in a third embodiment of

exclusionary methods.

[0093] In the embodiments of FIGS. 16 to 18, and 22 to 24 (where like components are

numbered alike) the exclusionary principle is one of a labyrinth, wherein the rotating base of

spoke piece 13 cooperates with the inner housing 10 via a labyrinth 80 selected to substantially

resist filtrate contamination of the product. The labyrinth 80 include cooperating labyrinth members 81, 82 machine screwed to a respective one of the base of spoke piece 13 and a portion of the inner housing 10 surrounding its periphery. The passive labyrinth members 81, 82 of

FIGS. 22 to 24 have two cooperating pairs of closely-running annular ridges 83 interleaved to

create the labyrinth.

[0094] The labyrinth of FIGS. 16 to 18 is pressurized with air via a manifold 84 comprising an

annular passage feeding a pressurized fluid into the labyrinth via a plurality of ports 85. The

pressurized air supply 86 is not a contaminant for either of the product or effluent streams.

[0095] As an alternative embodiment to or in addition to a labyrinth, cross contamination may

be addressed as per the embodiment of FIGS. 19 to 21 by the rotating base of spoke piece 13

cooperating with the static housing portion 10 by means of a slinger member 87 machine

screwed to the base of spoke piece 13. The slinger member 87 includes an axially directed

annular wall 90 and adapted to run in proximity to the aperture between the housing portions

10, 11 receiving filtrate (effluent) passing through the screen member 14 and product passing

through the base-of-spoke piece 13 respectively, and a plurality of circumferentially spaced

slinger vanes 91 inclined to the machine axis and located radially outward of and adjacent to

the annular wall 90.

[0096] FIGS 4 to 9 illustrate particular features of the scroll assembly 20 as embodied. As

stated the drive means includes the concentric drive shaft portions including a scroll assembly

drive shaft 25. The present embodiment includes an axial adjuster located at the mounting hub

24 to drive shaft 25 connection and operable to adjust the selected proximity of the scroll vanes

21 and the screen surface 15.

[0097] The axial adjuster includes a shaft portion 92 and a scroll portion 93 each having a

respective camming surface 94 whereby relative rotation of the scroll portion 93 and the shaft

portion 92 axially adjusts the selected proximity. The shaft 25 end portion 95 and the scroll hub 24 bore 96 are both plain and are adapted to be locked together by RINGFEDER© stepless locking means 97. The axial adjuster is protected in use by a polyurethane elastomer cap 100.

[0098] In use, the hinged inlet assembly 30 and the housing outer portion 11 is swung away

and the cap 100 removed, whereupon the axial adjuster is exposed. The RINGFEDER@

stepless locking means 97 is released and the scroll member 20 is rotated on the shaft 25 to

effect adjustment of the clearance between the scroll vanes 21 and the screening surface 15 of

the screen member 14. Thereafter the locking means 97 may be engaged, the protection 10

installed and the housing portions closed together.

[0099] A hoist assembly 101 (best illustrated in FIGS. 10 to 12) includes a monorail 102

supported by the fixed inner housing portion 10 and extending overhead of the outer housing

portion 11. A chain hoist 103 is mounted for movement along the monorail 102. Custom hoist

adapters 104, 105 and 106 connect a lifting terminus 107 of the hoist 103 to the screen member

14, the scroll member 20 and the base-of-spoke piece 13 respectively. The respective hoist

adapters 104, 105 and 106 are configured to lift the respective component 14, 20 and 13

substantially though its centre of gravity.

[00100] The scroll assembly 20 includes a substantially frustoconical liner 22 as described,

substantially interconnecting the inner edges of the vanes 21 and spaced from the screening

surface 15, the liner extending substantially to the base-of-spoke piece 13 and to the outer ends

of the vanes 21. The liner 22 is integrated into the collar portion 34 that cooperates with the

inlet assembly 30 to confine the infeed of material to the annulus 43 containing the vanes 21.

The conical included angle of the liner 22 is such that product hang-up may occurs. An inner

conical wall portion 110 creates an enclosed annulus 111 within the liner 22 and presenting a

flatter conical included angle. By this means any material passing into the space is discouraged from hanging up since the centrifugal component of the forces acting through the flatter conical surface will direct the product toward the base-of-spoke piece 13.

[00101] A product sampler assembly 112 is located at an aperture in a side wall 113 of the

product delivery chamber 17, and is illustrated in detail in Figs. 25 to 27. The product sampler

112 comprises a cylindrical body 114 mounted to the side wall 113 by a flange 115. The

cylindrical body 114 has its cylindrical axis substantially perpendicular to a product flow in

product delivery chamber 17.

[00102] A cylindrical sample shuttle 116 has an open inner end 117 and a substantially closed

outer end 120 including an integral rod guide 121. The cylindrical sample shuttle 116 has a

pair of inner sampling cut outs 122 which are facing generally upward into the product flow in

the product chamber 17 in use. A sample delivery cut out 123 faces generally downward in use

to gravitationally aid sample recovery from the sampler 112 in use.

[00103] A piston 126 is secured to a rod 127 passing through the rod guide 121 and is made

captive by a locking collar 130 adjacent a push/pull handle 131. The piston 126 is movable in

the shuttle 116 between the position illustrated in Figs. 25 and 26 and the position as illustrated

in Fig. 27.

[00104] The sample shuttle 116 is made captively movable in the cylindrical body 114

between a sampling position (as in Fig. 26) and a sample delivery position (as in Fig. 27) by an

operating handle 124 attached to the sample shuttle 116 and extending out of and movable along

an axial slot 125 formed in the cylindrical body 114.

[00105] In use, in normal, non-sampling operation of the centrifuge (Fig. 25), the piston 126

is advanced in the shuttle 116 and the shuttle 116 is withdrawn by the operating handle 124

until the face of the piston 126 and the open inner end 117 are essentially flush with the flange

115. To sample, as in Fig. 26, the operating handle 124 is used to insert the open outer end 117

(occluded by the piston 126) into the product chamber 17, exposing the inner sampling cut outs

122 to the flow of product in the product chamber and filling the shuttle 116 with sample. The

filled shuttle 116 is then withdrawn with handle 124.

[00106] Thereafter withdrawal of the push/pull handle 131 draws the rod 127 and piston 126

assembly to discharge the sample through the cutout 123 into a collection cup (not shown).

[00107] Apparatus according to the embodiment has specific advantages over prior art scroll

the feed to adjacent the screen surface. The apparatus does not require velocity arrestors or the

like.

[00108] The use of a horizontal machine with an inlet assembly according to the above does

not suffer from the disadvantage of the few prior art horizontal machines of the feed extending

the floor plan, since the feed in the present apparatus is tangential to the inlet and machine axis.

[00109] The housing portions 10, 11 being selectively separable substantially in the plane of

the join between the base-of-spoke piece 13 and the screen member 14 means that the join is

accessible for maintenance when the housing portions are separated.

[00110] The blind stud 52 being retained by the polyurethane cap 61 to the housing inner

portion 10 by means that the arrangement is protected from the aggressive erosive and corrosive

environment. This provides an inexpensive and easily replaceable fixing system that addresses

both wear and corrosion problems of alternative fixing methods.

[00111] The respective labyrinth portions members are a replaceable service item which

operates in a high-wear region and additionally serves to protect that portion of the base-of

spoke piece in a sacrificial manner.

[00112] The slinger member is a replaceable service item which operates in a high-wear

region, and additionally serves to protect that portion of the base-of-spoke piece in a sacrificial

manner.

[00113] The axial adjuster according the embodiment allows adjustment substantially without

disassembly. Initial condition need not be measured at all; the adjustment is dynamic in that

the parts are in situ while the adjustment is made. The adjustment can be measured in real time

or the clearance fully closed up by one direction of relative rotation of the scroll on the shaft

rotation and backed off to create a selected working clearance.

[00114] Whereas the prior art requires an external crane, certain embodiments herein are

capable of change out of components without additional overhead lifting gear. Whereas prior

art overhead lifting gear is generally multipurpose and must be rated accordingly, the present

or chain length to the component reduces the risk of load swing.

[00115] In the foregoing description of certain embodiments, specific terminology has been

resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the

specific terms so selected, and it is to be understood that each specific term includes other

technical equivalents which operate in a similar manner to accomplish a similar technical

purpose. Terms such as "left" and right", "front" and "rear", "above" and "below" and the like

are used as words of convenience to provide reference points and are not to be construed as

limiting terms.

[00116] In this specification, the word "comprising" is to be understood in its "open" sense,

that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense

of "consisting only of'. A corresponding meaning is to be attributed to the corresponding words

"comprise", "comprised" and "comprises" where they appear.

[00117] In addition, the foregoing describes only some embodiments of the invention(s), and

alterations, modifications, additions and/or changes can be made thereto without departing from

the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not

restrictive.

[00118] Furthermore, invention(s) have described in connection with what are presently

considered to be the most practical and preferred embodiments, it is to be understood that the

invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to

cover various modifications and equivalent arrangements included within the spirit and scope

of the invention(s). Also, the various embodiments described above may be implemented in

conjunction with other embodiments, e.g., aspects of one embodiment may be combined with

aspects of another embodiment to realize yet other embodiments. Further, each independent

feature or component of any given assembly may constitute an additional embodiment.

Claims

WHAT IS CLAIMED IS:

1 A centrifugal scroll screen apparatus including:

a housing;

a screen assembly mounted for rotation in said housing and comprising a base-of-spoke

piece and a substantially frustoconical screen member having an inner screening surface and

removably secured by its base to the base-of-spoke piece, the base of spoke piece cooperating

with the housing to substantially divide the housing into housing portions receiving filtrate

passing through the screen member and product passing through the base-of-spoke piece

respectively, the base of spoke piece and housing including respective labyrinth portions, any

one or both labyrinth portions comprising a replaceable service item, the labyrinth portions

collectively comprising a plurality of complementary annular ridges interleaved to create a

labyrinth selected to substantially resist filtrate contamination of said product, said housing

portions being selectively separable substantially in the plane of the join between the base-of

spoke piece and screen member;

a scroll assembly having a plurality of substantially helical scroll vanes and mounted

for rotation within said screen member with an edge of each said vane lying in selected

proximity to said screening surface;

drive means selected to differentially drive the rotation of said screen assembly and said

scroll assembly about a machine axis; and

an inlet assembly supported on said housing and cooperating with an open apical end of

said screen member to deliver material to be screened to said screening surface.
2. A centrifugal scroll screen apparatus according to Claims 1, wherein said housing

portions include a fixed inner portion associated with said drive means and a moveable outer portion associated with said inlet assembly, said inner and outer portions having complementary peripheral mating flanges secured with selectively releasable fixing means.
3. A centrifugal scroll screen apparatus according to Claim 1 or Claim 2, wherein said

selectively releasable fixing means comprises a plurality of circumferentially spaced key slots

associated with the peripheral mating flange of said inner portion and each supporting a blind

stud, corresponding stud holes associated with the peripheral mating flange of said outer

portion, and securing means selected to engage said studs to clamp said peripheral mating

flanges together.
4. A centrifugal scroll screen apparatus according to Claim 3, wherein said key slots are

formed in slot bodies welded inward of the peripheral mating flange of said inner portion, each

said slot body and blind stud being retained in assembly by a resilient retainer adapted to pass

over said stud and encapsulate said slot body.
5. A centrifugal scroll screen apparatus according to Claim 3 or Claim 4, wherein said

blind stud comprises a bolt and said securing means comprises a nut.
6. A centrifugal scroll screen apparatus according to any one of Claims 1 to 5, wherein

said housing portions are relatively conjoined by one or more hinge portions.
7. A centrifugal scroll screen apparatus according to Claim 6, wherein each said hinge

portion is lubricated by a positive pressure lubricator.
8. A centrifugal scroll screen apparatus according to any one of the preceding Claims,

wherein at least the housing portion receiving filtrate passing through the screen member is

formed of moulded polymer or polymer composite.
9. A centrifugal scroll screen apparatus according to any one of Claims 1 to 8, wherein

said machine axis is substantially horizontal.
10. A centrifugal scroll screen apparatus according to any one of the preceding Claims,

wherein said inlet assembly includes an inlet body defining a substantially annular inlet space

substantially coaxial with and opening in to an open apical end of said screen member and a

material supply conduit delivering said material to be screened to said annular space, said

material supply conduit being aligned in a tangent to said annular space selected to deliver said

material to said screening surface substantially in the direction of rotation of the screen

assembly.
11. A centrifugal scroll screen apparatus according to Claim 10, wherein said inlet assembly

includes an inlet body forming said annular inlet space and including an integral spigot to said

supply conduit, said inlet space and spigot being lined with a wear resistant material.
12. A centrifugal scroll screen apparatus according to claim 11, wherein the inlet body is

selected from fabricated or cast metal, moulded engineering polymer and composites.
13. A centrifugal scroll screen apparatus according to Claim 11 or claim 12, wherein said

wear resistant lining is selected from wear resistant elements bonded into the inlet body to form

the lining and a wear resistant ceramic liner about which the inlet body is formed.
14. A centrifugal scroll screen apparatus according to Claim 13, wherein the wear resistant

elements are sintered ceramic tiles.
15. A centrifugal scroll screen apparatus according to Claim 13, wherein said wear resistant

lining is an integral hot sintered ceramic liner having a spigot portion merging with a

substantially involute annular inlet space portion.
16. A centrifugal scroll screen apparatus according to any one of Claims 10 to 15, wherein

the axis of the tangential material supply conduit lies in a plane that intersects the machine axis

by an angle of from 0° to about 10 from the perpendicular, measured away from the screen

assembly.
17. A centrifugal scroll screen apparatus according to any one of Claims 10 to 16, wherein

the material to be screened is delivered to said annular inlet space by pressure head means

selected from gravity and pump.
18. A centrifugal scroll screen apparatus according to any one of the preceding Claims,

wherein said drive means includes a motor and a power-dividing gearbox providing said

differential drive through concentric shafts, said gearbox having a pressurized-circulation

lubrication system comprising at least one lubricant pump delivering lubricant from a reservoir

and at least two filters in parallel, each being associated with isolation valve means selected to

allow filter maintenance without shut-down of said gearbox.
19. A centrifugal scroll screen apparatus according to Claim 18, wherein each said filter is

a disposable spin-on filter cartridge.
20. A centrifugal scroll screen apparatus according to Claim 18 or Claim 19, wherein said

filters are supplied by an inlet line from said pump by a filter-selecting Y-valve, each filter

having a respective non-return valve on its delivery line.
21. A centrifugal scroll screen apparatus according to Claim 1, wherein at least the labyrinth

portion of the housing is a replaceable component..
22. A centrifugal scroll screen apparatus according to any one of Claim 21, wherein said

labyrinth is pressurized by a manifold comprising an annular passage formed on a housing

portion surrounding the periphery of the base of spoke piece and feeding a pressurized fluid

into the labyrinth via a plurality of ports communicating the passage with the interior of the

labyrinth.
23. A centrifugal scroll screen apparatus according to any one of Claims 1 to 22, wherein

the rotating base of spoke piece cooperates with the static housing by means of a slinger portion

associated with said base of spoke piece and selected to substantially resist filtrate

contamination of said product.
24. A centrifugal scroll screen apparatus according to Claim 23, wherein the slinger portion

comprises an axially directed annular wall secured to said base of spoke piece and adapted to

run in proximity to an aperture between the housing portions receiving filtrate passing through

the screen member and product passing through the base-of-spoke piece respectively, and a plurality of circumferentially spaced slinger vanes inclined to the machine axis and located radially outward of and adjacent to said annular wall.
25. A centrifugal scroll screen apparatus according to Claim 23 or Claim 24, wherein the

slinger portion comprises a slinger member including said annular wall and said slinger vanes

formed on a mounting flange adapted to be secured to said base of spoke piece.
26. A centrifugal scroll screen apparatus according to any one of the preceding Claims,

wherein the drive means includes respective concentric drive shaft portions extending axially

substantially through said screen assembly, the scroll assembly drive shaft being connected to

the scroll assembly by an axial adjuster operable to adjust said selected proximity.
27. A centrifugal scroll screen apparatus according to Claim 26, wherein said axial adjuster

comprises a shaft portion and a scroll portion each having a respective camming surface

whereby relative rotation of said scroll portion and said shaft portion axially adjusts said

selected proximity, and locking means selectively operable to rotationally secure said scroll

portion and said shaft portion.
28. A centrifugal scroll screen apparatus according to Claim 27, wherein said locking means

comprises a Ringfeder-type locking means.
29. A centrifugal scroll screen apparatus according to Claim 27 or Claim 28, wherein one

or both of said shaft portion and said scroll portion comprises a replaceable service part.
30. A centrifugal scroll screen apparatus according to any one of Claims 10 to 29, wherein

said fixed inner portion supports a hoist assembly selected to enable maintenance removal and

replacement of one or more of said scroll assembly and said screen assembly.
31. A centrifugal scroll screen apparatus according to Claim 30, wherein said machine axis

is substantially horizontal and said hoist assembly comprises a rail supported by said fixed inner

portion and extending overhead of said outer portion, a hoist mounted for movement along said

rail, and hoist adapters connecting a lifting terminus of said hoist to one or more of said scroll

assembly and said screen assembly.
32. A centrifugal scroll screen apparatus according to any one of the preceding Claims,

wherein the scroll assembly includes a substantially frustoconical liner substantially

interconnecting inner edges of said vanes and spaced from said screening surface, said liner

extending substantially to said base-of-spoke piece.
33. A centrifugal scroll screen apparatus according to any one of the preceding claims,

wherein metal faces of the scroll vanes are laminated with adhesively bonded ceramic elements.
34. A centrifugal scroll screen apparatus according to any one of the preceding claims,

wherein the housing portion receiving product passing through the base-of-spoke piece includes

a product sampler comprising:

a tubular body mounted by a first open end to a corresponding aperture though a wall

of said housing portion, said tubular body having its tubular axis substantially perpendicular to

a product flow in said housing portion;

a sample shuttle comprising a tubular receptacle selectively and captively movable in

said tubular body between a sampling position where a sampling portion extends into said product flow and a sample delivery position with a delivery portion extended out of a second open end of said tubular body, said sampling portion having side wall opening which faces substantially upstream of the product flow and said delivery portion having a delivery opening; and a piston assembly captively slidable in said sample shuttle and having a piston portion and a control rod portion extending out of said second open end, the rod portion being operable to selectively move said piston portion from a position located adjacent a terminal end of said sampling portion to a position adjacent an outer end of said delivery opening.
35. A centrifugal scroll screen apparatus according to Claim 34, wherein said tubular body

and sample shuttle are each substantially cylindrical in section.
36. A centrifugal scroll screen apparatus according to Claim 34 or Claim 35, wherein said

sample shuttle is made captively moveable in said tubular body by an operating handle attached

to said sample shuttle extending out of and movable along an axial slot formed in the cylindrical

side wall portion of said tubular body.