Abstract:
Rotary shaft ( 220 ), housing ( 250 ) and packaging type seal ( 230 ) together form seal cavity ( 260 ). Seal cavity throat protector ( 200 ) in cavity ( 260 ) protects seal ( 230 ) against damaging materials from the region of impeller ( 210 ). Such material is directed away from seal ( 230 ) along spiral groove(s) ( 280 ) on inner surface of protector ( 200 ) with the assistance of flushing fluid entering cavity ( 260 ) via bore ( 270 ) and passing to inner surface of protector ( 200 ) via radial bores therethrough.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates to seal cavity throat protectors for use with rotary fluid equipment.  
         BACKGROUND OF THE INVENTION  
         [0002]    In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date:  
           [0003]    (i) part of common general knowledge; or  
           [0004]    (ii) known to be relevant to an attempt to solve any problem with which this specification is concerned.  
           [0005]    Rotary fluid equipment usually includes an operative portion such as an impeller which is driven by a prime mover such as a motor. The operative portion usually has a rotating shaft which connects the prime mover to the operative portion. Typically the operative portion is within a housing and the shaft extends through the back of the housing and through a shaft housing. Usually the shaft will be supported by bearings which are between the prime mover and the operative portion.  
           [0006]    In use, fluid being moved by the operative portion leaks into the cavity around the shaft. Such fluid may contain various contaminants which arise from erosion of the surfaces of the equipment and which may be abrasive. Therefore it is important to protect the bearings from the damaging effects of material in the fluid.  
           [0007]    Seals are used to engage the shaft and prevent fluid which enters the shaft housing from reaching the bearings. The seals are also susceptible to damage by contaminants in the fluid. The seals, shaft housing and shaft define a seal cavity which opens towards the housing containing the operative portion. During operation, the motion of the shaft causes fluid within the seal cavity to rotate and thus impact a centrifugal force on any contaminant material therein. The contaminants are thus directed radially outwardly towards the wall of the seal cavity.  
           [0008]    Previous attempts to protect seals in the seal cavity have included attachment of a plate or other member to the rotor at the entrance to the seal cavity, Such a plate assists in elimination of air and assists to prevent fluid from entering the seal cavity as the equipment comes to a halt. In addition, labyrinth-type seals have previously been devised to increase the difficulty of penetration by contaminants into the seal cavity.  
           [0009]    Prior U.S. Pat. No. 4,872,690 discloses a seal cavity protector with vent passages through the protector. The reference to this document is by way of illustration of one particular approach to the problem and is not to be construed as an admission that the document is common general knowledge in Australia or was known to persons in Australia at the priority date.  
           [0010]    According to U.S. Pat. No. 4,872,690, a pressure differential arises across the vent passages due to rotational flow of the fluid past the vent passages at the entrance to the seal cavity. The pressure differential decreases accumulation of contaminants within the seal cavity due to continuous flow of fluid through the vents. However, it has been found that such protectors tend to create too great a difference in pressure which in turn increases fluid flow into the seal cavity, as well as increasing wear on the shaft and components of the device.  
           [0011]    The next step in the protection of seals was the development of grooves or channels on the interior of the seal. Such advances were disclosed in U.S. Pat. Nos. 4,301,893, 4,084,825, 4,301,863 and Australian patent 688,977. While these patents disclosed the use of grooves and seals, there was a problem whereby the contaminants sought to be removed would still affect the seal. The prior art does not disclose a suitable means whereby the contaminants can be expelled from the seal cavity effectively. The prior art does not disclose an effective method of flushing fluid and thus any contaminants through the opening and hence away from the seal.  
         SUMMARY OF THE INVENTION  
         [0012]    According to a first aspect of the invention, there is provided a throat protector for throat of a seal cavity for rotary equipment, the seal cavity being defined by a rotary shaft with an axis of rotation and a shaft housing surrounding at least a portion of the rotary shaft, said seal cavity being located between seal means and said throat, said throat protector including:  
           [0013]    a first part arranged in use to surround a first region of said rotary shaft located at or adjacent said throat, said first part defining with said rotary shaft a passageway for ingress and egress of material through said throat;  
           [0014]    a second part arranged in use to surround a second region of said rotary shaft spaced axially from said first region towards said seal means; and  
           [0015]    an inner surface of said throat protector having a groove formed therein to direct flow of material through the throat protector towards the throat of said seal cavity, said inner surface having a first part region having the same or greater relative distance from the axis of rotation of the rotary shaft as that of a second part region of said inner surface, and said inner surface further having an enlarged diameter region relative to the first part region of the inner surface located intermediate said first and second parts.  
           [0016]    Providing a second part acting as a seal portion in one preferred embodiment capable of engaging the seal means and a groove to direct the flow of material through the throat protector enables material in the fluid to be directed down the groove and back out the opening in the throat protector through the throat of the seal cavity. This in turn decreases the abrasive damage of the seal means by material in the fluid and thereby prolongs the life of the seal means.  
           [0017]    According to one preferred embodiment, the seal cavity throat protector is a replaceable bushing. Various bushings according to this embodiment may be used in the same machinery depending on the requirements of the particular application. In addition, worn bushings can be replaced. Preferably a bushing according to the present invention has an outer surface which is adapted to fit in the housing. Preferably it has a complimentary surface. According to another preferred embodiment, the seal cavity throat protector may be integrally formed with the seal housing.  
           [0018]    According to a particularly preferred embodiment, there is further provided a bore which passes from the outer surface to the inner surface to allow passage of flushing fluid to flush material back through the open portion of the throat protector. The bore according to this embodiment may be of any suitable type and dimensions. The bore may be at any convenient entry angle relative to the inner and outer surfaces.  
           [0019]    According to another preferred embodiment, there may be more than one bore, and these bores may be at any convenient entry angle relative to each other. Where there is more than one bore, then preferably the angle of entry shall be at right angles relative to the other bores.  
           [0020]    According to another preferred embodiment, there is an indentation in the outer surface of the throat protector which connects with the bore. Such an indentation defines a cavity to provide a reservoir of flushing fluid to pass through the bore to the inner surface. Preferably the indentation extends along the outer surface. Where the outer surface defines one or more concentric cylinders about the axis of the shaft, then preferably the indentation runs around the circumference of the outer surface. Where there is more than one bore, then preferably they each start in the indentation in the outer surface.  
           [0021]    According to another preferred embodiment, where there is an indentation in the outer surface, then preferably the region of enlarged diameter in the inner surface is adjacent to the indentation in the outer surface. Preferably the indentation in the outer surface extends axially along the outer surface. Preferably the region of enlarged diameter in the inner surface runs around the circumference of the inner surface. Where there is more than one bore, then preferably they each enter the inner surface at the indentation in the region of enlarged diameter.  
           [0022]    According to a particularly preferred embodiment, the second part of the throat protector is adapted for sealing engagement with the seal. Preferably the second part has an axial end surface with a series of ridges and troughs to assist with sealing engagement with the seal or with packing material. Preferably the ridges and troughs run in concentric circles on the second part which engages with the seal or packing material. According to another preferred embodiment, the seal portion has at least one lip in the inner surface of the throat protector to further increase the sealing effect with the shaft. Preferably there are plurality of lips.  
           [0023]    According to another preferred embodiment, the groove defines a spiral along the inner surface of the throat protector. Preferably the spiral of the spiral groove is configured in the same direction as the intended rotation of the shaft. By forming a spiral in the same direction as the shaft, it is possible to maximise the effect of the centrifugal motion of the material in the fluid and thereby force the material towards the open portion of the throat protector and therefrom through the throat. The groove according to the present invention may be continuous along the inner surface of the throat protector. In addition, there may be multiple grooves. Where there are multiple grooves, the grooves start adjacent one end of the throat protector. However, the grooves may start intermediate the ends of the of the throat protector.  
           [0024]    According to another preferred embodiment, the groove starts adjacent the seal portion of the throat protector. According to another preferred embodiment, the groove exits the throat protector at an axial end of the first part adjacent to the throat.  
           [0025]    According to another preferred embodiment, the volume of groove per unit length of the throat protector varies with distance from the exit end of the throat protector. By varying the volume of groove per unit length of the throat protector, it is possible to vary the amount of pressure applied to the material to force it towards the open portion and therefore vary the flow rate of the material through the throat protector. Such variation is useful in catering for different characteristics of the fluid and contaminants. For example, fluids of different viscosity or temperature, and contaminants of different sizes or densities,  
           [0026]    According to one preferred embodiment, the volume of groove per unit length of the throat protector increases with distance from the exit end of the throat protector.  
           [0027]    According to another preferred embodiment the volume of groove per unit length of the throat protector decreases with distance from the exit end of the throat protector.  
           [0028]    According to another preferred embodiment, the pitch of the spiral groove varies. The volume of groove per unit length of throat protector may also be altered by altering the width of the groove. According to a still further embodiment, the volume of groove per unit length of throat protector is altered by altering the depth of the groove.  
           [0029]    According to another preferred embodiment, there is further provided a bore extending through the throat protector between the outer surface and the inner surface to allow egress of air.  
           [0030]    In accordance with a second aspect of this invention, there is provided a throat protector for a throat of a seal cavity for rotary equipment, the seal cavity being defined by a rotary shaft with an axis of rotation and a shaft housing surrounding at least a portion of the rotary shaft, said seal cavity being located between seal means and said throat, said throat protector including:  
           [0031]    a first part arranged in use to surround a first region of said rotary shaft located at or adjacent said throat, said first part defining with said rotary shaft a passageway for ingress and egress of material through said throat;  
           [0032]    a second part arranged in use to surround a second region of said rotary shaft spaced axially from said first region towards said seal means; and  
           [0033]    an inner surface of said throat protector having a groove formed therein to direct flow of material through the throat protector towards the throat of said seal cavity, said inner surface having an enlarged diameter region relative to the first part region of the inner surface located intermediate said first and second parts.  
           [0034]    Conveniently, the throat protector is replaceable having an outer surface which is adapted to fit into the shaft housing, the throat protector having fluid delivery means for supply of fluid to said enlarged diameter region. Preferably, the fluid delivery means includes at least one bore passing from the outer surface to the inner surface of the throat protector within the enlarged diameter region. The bore or at least one of said bores may have an entry point located within an indentation in the outer surface of the throat protector, said indentation in the outer surface extending around the circumference of the outer surface.  
           [0035]    In accordance with a third aspect of this invention, rotary equipment is provided including a rotary shaft having an operative portion rotated by said rotary shaft, said rotary shaft and said operative portion rotating, in use, about an axis of rotation, at least one seal cavity including seal means provided to protect bearing means for said rotary shaft from fluids acted upon by said operative portion, said seal cavity in part being defined by said rotary shaft, a shaft housing surrounding at least a portion of said rotary shaft, a throat leading from a region adjacent said operative portion, and said seal means, said rotary equipment further including a throat protector including a first part surrounding a first region of the rotary shaft located at or adjacent said throat, said first part defining with said rotary shaft a passageway for ingress and egress of material through said throat;  
           [0036]    a second part arranged to surround a second region of said rotary shaft spaced axially from said first region towards said seal means; and  
           [0037]    an inner surface of said throat protector having a groove formed therein to direct flow of material through the throat protector towards the throat of said seal cavity, said inner surface having an enlarged diameter region relative to the first part region of the inner surface located intermediate said first and second parts, and fluid delivery means for supply of flushing fluid through said shaft housing and into said enlarged diameter region.  
           [0038]    Conveniently, the fluid delivery means includes at least one passage through said shaft housing leading into said seal cavity. Preferably, said fluid delivery means includes at least one bore leading from an outer surface of said throat protector to said inner surface within said enlarged diameter region, the or each said bore in said throat protector having an entry in communication with a said passage for flushing fluid delivery provided through said shaft housing. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0039]    The invention will now be further explained and illustrated by reference to the accompanying drawings showing several preferred embodiments of the present invention, in which:  
         [0040]    [0040]FIG. 1 is a cross sectional view of the seal cavity schematically showing a bushing according to the present invention.  
         [0041]    [0041]FIG. 2 is a side view of a seal cavity throat bushing according to the present invention.  
         [0042]    [0042]FIG. 3 is a cross sectional view of a seal cavity throat protector according to the present invention depicting the inner surface.  
         [0043]    [0043]FIG. 4 is an end view of the seal portion of the sectioned throat protector of FIG. 3.  
         [0044]    [0044]FIG. 5 is a cross sectional view of the seal cavity showing the bushing in use in pump packing.  
         [0045]    [0045]FIG. 6 is a cross sectional view of the seal cavity showing the bushing in use in a mechanical seal.  
     
    
     DESCRIPTION OF PREFERRED EMBODIMENT  
       [0046]    [0046]FIG. 1 depicts a typical environment for a seal cavity throat protector in the form of a bushing according to the present invention which is shown generally at  100 . The environment includes an operative portion such as an impeller  20 , which is connected to a shaft  30 , the shaft  30  being connected to a prime mover such as a motor  40  (not shown). Seals  40  protect bearings which support the shaft which would be further along the shaft in the direction of arrow  50 . Shaft  30  together with shaft housing  60  and seals  40  form a seal cavity shown generally at  70 .  
         [0047]    Bushing  100  has a seal portion  104  adapted to surround the shaft and to engage a seal  40 , and an open portion  108  adapted to surround the shaft and to define with the shaft a passageway for ingress and egress of material. Bushing  100  has an outer surface  110  with a circumferential indentation  120 , into which a bore  65  through shaft housing  60  empties. Bushing  100  further has a bore  130  which runs from outer surface  110  to inner surface  140 . Bore  130  opens into indentation  150  in inner surface  140 .  
         [0048]    [0048]FIGS. 1 and 3 demonstrate inner surface  140  having several spiral grooves, shown generally at  160 . The hand of each spiral groove is in the same direction as the rotation of the shaft. The first spiral groove,  164  starts inside the bushing in the seal portion and ends at indentation  150 . The second spiral groove,  165  runs along indentation  150  in inner surface  140 . The third spiral groove, starts at indentation  150  and continues out of the end of the open portion  108 .  
         [0049]    Seal portion  104  has a series of ridges and troughs  105  which run in concentric circles on the part  106  of the seal portion  104  which engages with the adjacent seal  40 , in use.  
         [0050]    [0050]FIG. 2 demonstrates the features of the outer surface  110  of bushing  100 . Outer surface  110  has a circumferential indentation  120 . There is a bore  130  which runs from outer surface  110  to the inner surface  140 . Seal portion  104  has a series of ridges and troughs  105  which run in concentric circles on the part  106  of the seal portion  104  which engages with the seal  40 .  
         [0051]    [0051]FIG. 4 demonstrates an end view of the series of ridges and troughs  105  which run in concentric circles on the part  106  of the seal portion  104  which engages with the seal  40 .  
         [0052]    In use, shaft  30  and impeller  20  rotate and thereby cause fluid surrounding the impeller to be moved in the desired direction. Fluid being moved by the operative portion leaks into seal cavity  70 . Such fluid may contain various contaminants which arise from erosion of the surfaces of the equipment and which may be abrasive.  
         [0053]    Seals  40  protect the bearings on which shaft  30  sits. The seals are themselves protected by bushing  100  which, in the embodiment shown in FIGS.  1  to  5 , engages with and forms a seal with a seal  40  by virtue of the ridges and troughs  105  on the axially facing end portion  106  of the seal portion  104 .  
         [0054]    The rotational action of shaft  30  imparts a rotational movement to the fluid surrounding shaft  30  in seal cavity  70 . Material in the fluid is forced by the rotational movement of shaft  30  along grooves  164 , 165  and  166  towards open portion  108  and out of the opening surrounding the shaft  30  at the axial end of the bushing  100  adjacent to the impeller  20 .  
         [0055]    Additionally, flushing fluid enters circumferential indentation  120  on outer surface  110  via bore  65 . Flushing fluid builds in indentation  120  and then runs down bore  130  from outer surface  110  to the inner surface  140 . Material in the fluid in seal cavity  70  is thereby flushed down grooves  165  and  166  towards open portion  108  and out the opening.  
         [0056]    Inner surface  140  has an indentation  150  and a spiral groove  160  which starts inside the bushing in the seal portion  164 , but continues out of the end of the open portion  165 .  
         [0057]    [0057]FIG. 5 depicts a typical further environment for a seal cavity throat bushing  200  according to a further preferred embodiment of the present invention for use as a pump packing. The operative portion of the environment for this embodiment is a pump impeller  220 , which is connected to a shaft  230 . Packing or seals  240  protect the bearings which support the shaft  220  which would be further along the shaft in the direction of arrow  250 . Shaft  230  together with shaft housing  275  and packing  240  form a seal cavity shown generally at  270 .  
         [0058]    Flushing fluid enters the cavity  270  through a bore  265 , outer bushing surface indentation or cavity  225 , bore  235  in the bushing  200  and inner bushing surface indentation or cavity  255  and thereafter moves through the throat protector bushing  200  along the spiral grooves  260  and ultimately exits the cavity at a throat  290  leading from the shaft housing  270 .  
         [0059]    As shown in FIG. 5, the bore  235  in the bushing  200  is off set as it enters the intermediate cavity  255  in the bushing  200  so as to provide a fluid flow direction component as indicated by the arrows in FIG. 5 towards the throat  290 .  
         [0060]    [0060]FIG. 6 depicts a typical environment for a further preferred embodiment of a seal cavity throat protector in the form of a bushing according to the present invention for use in a mechanical seal which is shown at  300 . The operative portion is an impeller  320 , which is connected to a rotational shaft  330 . A seal  340  rotational with shaft  330  and cooperable mechanically with a second stationary seal member is, in a known manner provided to protected bearings which support the shaft  330  which would be further along the shaft in the direction of arrow  350 . Shaft  330  together with shaft housing  375  and seals  340  form a seal cavity shown generally at  370 . Flushing fluid enters the cavity through the bore at  365  in the shaft housing  375  and moves between seals  340  and the face  306  of the bushing  300  as indicated by the arrows, the flushing fluid then moves axially into the cavity  355  intermediate the axial ends of the bushing and along the bushing  300  via the spiral groves  360  and ultimately exits the seal cavity  370  at the throat  390 .  
         [0061]    The word ‘comprising’ and forms of the word ‘comprising’ as used in this description do not limit the invention claimed to exclude any variants or additions.  
         [0062]    Modifications and improvements to the invention will be readily apparent to those skilled in the art. Such modifications and improvements are intended to be within the scope of this invention.  
       BENEFITS OF THE INVENTION  
       [0063]    This invention reduces flush by 50 to 80%. It also increases packing life by 2 to 3 times. The invention requires less packing. The invention reduces shaft wear and sleeve wear and requires fewer gland adjustments.