A separator module for a stormwater gully chamber is disclosed, the separator module comprising: a partition arrangement which, in use, divides the chamber into an upper region and a lower region, the partition arrangement comprising: an inlet chute having an opening which, in use, provides an inlet to the lower region from the upper region; an outlet chute having an opening which, in use, provides an outlet from the lower region to the upper region; and a weir separating the outlet chute from the inlet chute; wherein at least a portion of the partition arrangement is flexible so as to allow an external diameter of the partition arrangement to be adjusted to fit different sized chambers.

BACKGROUND 
     This invention relates to a separator module for a stormwater gully chamber. 
     Conventional gullies under roadways and other paved areas comprise a chamber having inlet and outlet pipes which open into the chamber at a position above the bottom of the chamber. There may also be a top inlet, which provides access to the interior of the chamber through a grating provided at the roadway surface, for example in a gutter. In use, solids entering the chamber, whether from the inlet pipe or through the grating, collect under gravity in the base of the chamber and can be extracted at intervals by means of a suction pipe introduced into the chamber after removing the grating. Such gullies have a low separation efficiency. Furthermore, in the event of heavy storm flows, collected solids in the base of the chamber, and solids floating on the surface tend to be stirred up, and can pass into the outlet pipe. 
     A hydrodynamic vortex separator may be used to improve the separation efficiency of the gully. Such separators are suitable for removing sediment, litter and oil from surface water runoff. 
       FIG. 1  shows an example of a hydrodynamic vortex separator used in a stormwater gully, as disclosed in U.S. Pat. No. 7,344,636. The separator comprises an inlet compartment  3  and an outlet compartment  5  installed within a chamber  7 . The inlet compartment  3  is connected to an inlet duct and the outlet compartment  5  is connected to an outlet duct. The inlet compartment  3  and the outlet compartment  5  are offset from one another around the circumference of the chamber  7  and are fluidically connected by a bypass duct  9 . 
     An opening  11  is provided at the bottom of the inlet compartment  3  which serves as an inlet to the interior of the gully chamber  7 . The inlet opening  11  is oriented so that inflowing liquid creates a circulating flow within the chamber  7  which assists in causing any solids within the incoming flow to accumulate and fall to the bottom of the chamber  7  or rise to the fluid surface depending upon their density. Similarly, the outlet compartment  5  has an opening which serves as an outlet from the interior of the chamber  7 . The outlet opening is oriented so that outflowing liquid passes through the outlet opening in a direction opposite that of the circulating flow. The relative orientations of the inlet and outlet openings means that, even under conditions of heavy flow, solids will be swept past the outlet opening rather than leave the chamber. 
     A weir is provided between the inlet compartment  3  and the bypass duct  9  so that, in periods of heavy flow, only some of the flow entering the inlet compartment  3  will pass through the inlet opening  11 , and the remainder will pass over the weir and through the bypass duct  9  directly to the outlet compartment  5 . 
     Although the bypass duct  9  may be cut to an appropriate length so that the inlet and outlet compartments  3 ,  5  align with the inlet and outlet ducts, the bypass duct  9  must be made available in different radii of curvature to conform to chambers having different diameters. Further, the size, number and position of the ducts is restricted somewhat by this arrangement. 
     In addition, the inlet and outlet compartments  3 ,  5  and the bypass duct  9  limit the bypass capacity of the separator. 
     It is therefore desired to provide a separator module which addresses or alleviates some or all of these issues. 
     SUMMARY 
     In accordance with an aspect of the invention, there is provided a separator module for a stormwater gully chamber, the separator module comprising: a partition arrangement which, in use, divides the chamber into an upper region and a lower region, the partition arrangement comprising: an inlet chute having an opening which, in use, provides an inlet to the lower region from the upper region; an outlet chute having an opening which, in use, provides an outlet from the lower region to the upper region; and a weir separating the outlet chute from the inlet chute. At least a portion of the partition arrangement is flexible so as to allow an external diameter of the partition arrangement to be adjusted to fit different sized chambers. 
     The separator module may be particularly beneficial in the US and UK markets, where chambers are sized based on metric and imperial measurements respectively. The flexible nature of the partition arrangement may also provide an improved seal against the chamber. 
     The partition arrangement may comprise a partition plate and a separate ledger component which, in use, connects to an inner wall of the chamber. The ledger component supports the partition plate within the chamber such that the partition plate does not directly contact the chamber, the ledger component defining the external diameter of the partition arrangement. The ledger component comprises a discontinuous flexible annular ring having a gap which allows the ledger component to expand or contract so as to alter the external diameter of the partition arrangement. 
     The ledger component may be resiliently deformed when inserted into the chamber. 
     The partition plate and the ledger component may comprise complementary structures which interlock with one another. The complementary structures can fix the relative orientations of the partition plate and the ledger component. The complementary structures may, in particular, be formed by the weir plates described below. 
     The partition arrangement may comprise a partition plate and separate inlet and outlet chute components forming the inlet and outlet chutes respectively, the partition plate having first and second openings for receiving the inlet and outlet chute components and an axially extending central standpipe portion disposed between the first and second openings. The central portion comprises first and second slots extending axially from the first and second openings. The width of the first and second slots and thus the width of the first and second openings is adjustable so as to alter the external diameter of the partition arrangement. 
     The inlet and outlet chute components may each comprise a backing plate which is received within the central standpipe portion, the backing plates covering the first and second slots. The backing plates may therefore seal against the slots to prevent water from passing through them. 
     The inlet and outlet chute components may each comprise a pair of circumferentially extending flanges which abut the partition plate. The circumferentially extending flanges allow the width of the first and second openings to be adjusted and abut with the partition plate over the full range of movement. 
     The central standpipe portion may comprise a bypass port, a top edge of which is positioned at or below a top edge of the weir. As the top edge of the bypass port is positioned at or below the top edge of the weirs, any accumulated floatable material in the upper region is able to pass into the lower region before the water level reaches the upper edge of the weir and so does not pass to the outlet chute. 
     The partition arrangement may further comprise an annular bypass channel fluidically coupling the inlet chute and the outlet chute via the weir. The annular bypass channel may be formed between the central standpipe portion and the surrounding wall of the chamber. The annular nature of the bypass channel maximizes its length and so increases the bypass capacity of the module. The bypass channel may prevent washout of material captured in the lower region during heavy flow conditions. 
     The annular bypass channel may be open at its top so as to avoid placing any limitation on the bypass capacity of the module. The head room over the weir is thus limited only by the height of the chamber. 
     The annular bypass channel may be inclined from the inlet chute to the outlet chute. This may prevent material from accumulating on the surface of the partition plate. 
     The annular bypass channel may be inclined at an angle of 30 to 40 degrees from horizontal. 
     The weir may comprise a pair of weir plates disposed either side of the outlet chute. Locating the weir plates either side of the outlet chute allows an inlet duct into the chamber to be located at any position about the remainder of the circumference. Accordingly, the separator module can be installed in a wide variety of chambers with different inlet and outlet duct configurations. Moreover, the separator module can support a plurality of inlet ducts and/or inlet ducts of a larger diameter. 
     The separator module may be installed in a chamber to form a separator. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: 
         FIG. 1  is a sectional view of a prior art separator; 
         FIG. 2  is a top perspective view of a separator in which a separator module according to an embodiment of the invention is installed in a gully chamber; 
         FIG. 3  is a perspective view of the separator module of  FIG. 2  alone; 
         FIG. 4  is another perspective view of the separator module; 
         FIG. 5  is a perspective view of a ledger component of the separator module; 
         FIG. 6  is an exploded view of a separator module according to another embodiment of the invention; and 
         FIG. 7  shows the separator module of  FIG. 6  assembled. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 2  shows a separator which comprises a gully chamber  2  having a cylindrical surrounding wall  4  and top and bottom end walls (not shown for clarity). An inlet duct  6  and an outlet duct  8  open into the surrounding wall  4 . An inlet may also be provided in the top wall in a region which is close to the surrounding wall  4  and at a circumferential position which is near to the inlet duct  6 . Such an inlet may be positioned in a roadway passing over the separator and covered by a grating. 
     A separator module  10  according to an embodiment of the invention is installed in the gully chamber  2 . As shown in  FIGS. 3 and 4 , the separator module  10  comprises a partition arrangement having a partition plate  12  and a separate ledger component  14 . 
     The partition plate  12  divides the chamber  2  into an upper region above the partition plate  12  and a lower region below the partition plate  12 . 
     The partition plate  12  comprises an inlet chute  16  and an outlet chute  18 . The inlet chute  16  comprises an opening  20  which provides an inlet to the lower region from the upper region. Similarly, the outlet chute  18  comprises an opening (not shown) which provides an outlet from the lower region to the upper region. 
     The inlet chute  16  has an arcuate shape which is contoured to conform to the curvature of the inner surface of the surrounding wall  4 . The inlet opening  20  is situated close to the internal surface of the surrounding wall  4 , and is oriented to direct incoming flow tangentially of the chamber  2 . That is, it lies in a plane extending radially with respect to the central axis of the chamber  2 . 
     Likewise, the outlet chute  18  has an arcuate shape which is contoured to conform to the curvature of the inner surface of the surrounding wall  4 . The outlet opening is situated close to the internal surface of the surrounding wall  4 . The outlet opening is oriented in the same direction as the inlet opening  20  with respect to the circumferential direction around the central axis of the chamber  2 . 
     The inlet chute  16  and outlet chute  18  are positioned in the partition plate  12  so that they are diametrically opposed from one another, with a central standpipe portion  24  disposed therebetween. The central standpipe portion  24  provides access to the lower region of the chamber  2  to allow the chamber  2  to be cleaned out using a standard vacuum tanker, for example. The central standpipe portion  24  also allows air to escape from the lower region as the latter fills with liquid. The central standpipe portion  24  may be cut to suit the headroom available within the chamber  2 . The central standpipe portion  24  may be closed at its upper end, for example, by a removable cover. 
     The partition plate  12  comprises an annular bypass channel  26  defined between the central standpipe portion  24  and the inner surface of the surrounding wall  4 . The annular bypass channel  26  fluidically couples the inlet chute  16  and the outlet chute  18  in the upper region. 
     The inlet chute  16  and the outlet chute  18  are arranged so that the exit from the outlet chute  18  in the upper region of the chamber is located above the entrance to the inlet chute  16 . Accordingly, the annular bypass channel  26  is angled and slopes upwards from the inlet chute  16  to the outlet chute  18 . The annular bypass channel  26  is inclined at an angle of between 30 and 40 degrees from horizontal. 
     The annular bypass channel  26  projects upwards either side of the outlet chute  18  to form a pair of weirs  28  which extend radially from the central standpipe portion  24 . As shown in  FIG. 2 , positioning the weirs  28  either side of the outlet chute  18  allows the inlet duct  6  to be disposed at any position about the remainder of the surrounding wall  4 . Indeed, this arrangement allows a plurality of inlet ducts and/or larger inlet ducts to be used. 
     The central standpipe portion  24  is provided with a bypass port  30  which opens into lower region. The top edge of the bypass port is positioned at or below the top edge of the weirs  28 . The bypass port  30  may allow air to escape from the lower region where the upper end of the central standpipe portion  24  is closed and sealed. 
     Referring now to  FIG. 5 , the ledger component  14  comprises an annular ring which is configured to be affixed to the inner surface of the surrounding wall  4 . The ledger component  14  is designed to support the partition plate  12  within the chamber  2  such that the partition plate  12  does not directly contact the inner surface of the surrounding wall  4 . 
     Accordingly, the ledger component  14  is shaped to conform to the profile of the underside of the partition plate  12 . Notably, the ledger component  14  comprises an inlet recess  32  which corresponds to the inlet chute  16  and an outlet recess  34  which corresponds to the outlet chute  18 . Between the inlet recess  32  and the outlet recess  34 , the ledger component  14  is inclined at the angle of the annular bypass channel  26 . The ledger component  14  further comprises a pair of projections  35  which correspond to the weirs  28 . 
     The ledger component  14  has a gap  36  positioned midway across the outlet recess  34 . Together with the flexibility of the material used to form the ledger component  14 , this discontinuity allows the ledger component  14  to contract so as to reduce its external diameter. 
     The complementary features of the partition plate  12  and the ledger component  14  interlock the two components so as to prevent rotation of the partition plate  12  relative to the ledger component  14 . There is, however, sufficient laxity between the complementary features so as to permit the ledger component  14  to contract by closing the gap  36 . 
     To install the separator module  10 , the ledger component  14  is inserted into the chamber  2 . Depending on the diameter of the surrounding wall  4 , the ledger component  14  may need to be deformed from its rest position to correspond to the inner diameter of the surrounding wall  4  by closing the gap  36 . The ledger component  14  is then affixed to the surrounding wall  4  before locating the partition plate  12  thereon. 
     The gap may also allow the ledger component  14  to expand so as to increase its external diameter. 
     In use, under low or moderate flow, incoming water flows into the chamber  2  from the inlet duct  6  and enters the inlet chute  16  either directly or having been directed to the inlet chute  16  by the angled annular bypass channel  26 . The water passes through the inlet chute  16  and enters the lower region via the inlet opening  20 . The flow enters the lower region in a tangential direction and so circulates around the lower region. The flow from the inlet opening  20  will also induce a circulating flow in the water accumulated in the lower region of the chamber  2 . This relatively low-energy circulating flow will assist in causing any solids within the incoming flow to accumulate and fall to the bottom of the chamber  2  or rise to the fluid surface depending upon their density. Furthermore, by sweeping past the outlet opening of the outlet chute  18 , solids will be less likely to enter the outlet chute  18 . The outlet chute  18 , and consequently the outlet duct  8 , will thus receive substantially clean water. 
     If the incoming flow rate from the inlet duct  6  increases to a rate above that which can pass through the inlet opening  20 , the level in the upper region will rise. 
     Eventually, it will reach the level of the upper edge of the weirs  28 , and will overflow into the outlet chute  18  and the outlet duct  8 . Much of the solids material entering the upper region through the inlet duct  6  will pass through the inlet chute  16  and emerge from the inlet opening  20 , and so, as before, will tend to fall to the bottom of the chamber  2  or rise to the fluid surface. Nevertheless, under heavy flow conditions, some solid material will pass, with the water, over the weirs  28  into the outlet chute  18 , and thence to the outlet duct  8 . However, since the main flow within the chamber  2  does not receive the surplus flow passing over the weirs  28 , there is less likelihood that the high flow throughput will stir up solids from the bottom of the chamber  2  or from the fluid surface and cause them to enter the outlet chute  18 . Moreover, since the top edge of the bypass port  30  in the central standpipe portion  24  is positioned at or below the top edge of the weirs  28 , any accumulated floatable material in the upper region is able to pass into the lower region before the water level reaches the upper edge of the weirs  28  and so does not pass over the weirs  28  to the outlet duct  8 . 
     The inclined annular bypass channel  26  prevents material from accumulating on the surface of the partition plate  12 . Initial tests have shown that an inclined annular bypass channel provides approximately a 80 to 90% reduction in accumulated solids on the floor of the bypass channel  26 , compared to the equivalent level channel. 
       FIGS. 6 and 7  show a separator module  110  according to another embodiment of the invention. Although not shown, the separator module  110  may be installed in the chamber  2  described in relation to the previous embodiment. 
     The separator module  110  comprises a partition arrangement having a partition plate  112 . The partition plate  112  divides the chamber  2  into an upper region above the partition plate  112  and a lower region below the partition plate  112 . 
     The partition arrangement further comprises an inlet chute  116  and an outlet chute  118  which are formed as separate components from the partition plate  112 . 
     The inlet chute  116  comprises an opening  120  which provides an inlet to the lower region from the upper region. Similarly, the outlet chute  118  comprises an opening (not shown) which provides an outlet from the lower region to the upper region. 
     The inlet chute  116  has an arcuate shape which is contoured to conform to the curvature of the inner surface of the surrounding wall  4 . The inlet opening  120  is situated close to the internal surface of the surrounding wall  4 , and is oriented to direct incoming flow tangentially of the chamber  2 . That is, it lies in a plane extending radially with respect to the central axis X of the chamber  2 . 
     Likewise, the outlet chute  118  has an arcuate shape which is contoured to conform to the curvature of the inner surface of the surrounding wall  4 . The outlet opening is situated close to the internal surface of the surrounding wall  4 . The outlet opening is oriented in the same direction as the inlet opening  120  with respect to the circumferential direction around the central axis X of the chamber  2 . 
     The inlet and outlet chutes components each further comprise a backing plate  138  and first and second circumferential flanges  140   a ,  140   b , which will be described in more detail below. 
     The partition plate  112  comprises an inlet recess  142  and an outlet recess (not shown) which are diametrically opposed from one another with a central standpipe portion  124  disposed therebetween. The inlet and outlet recesses are configured to receive the inlet and outlet chute components, respectively. 
     A keyhole slot  146  opens at the centre of each of the inlet and outlet recesses and extends partway up the central standpipe portion  124 . As per the inlet and outlet recesses, the keyhole slots  146  are diametrically opposed from one another and so divide the partition plate  112  into two halves which are joined to one another by the central standpipe portion  124  above the keyhole slots  146 . 
     As shown in  FIG. 7 , the inlet and outlet chute components are received by the inlet and outlet recesses of the partition plate  112  so that the inlet and outlet chutes  116 ,  118  are positioned centrally in the inlet and outlet recesses. The inlet and outlet chute components are received from below the partition plate  112 , with the backing plates  138  being inserted into the interior of the central standpipe portion  124  so that they cover the keyhole slots  146  formed in the central standpipe portion  124 . The circumferential flanges  140   a ,  140   b  abut with and seal against the underside of the partition plate  112 . The partition plate  112  comprises an annular bypass channel  126  defined between the central standpipe portion  124  and the inner surface of the surrounding wall  4 . The annular bypass channel  126  fluidically couples the inlet chute  116  and the outlet chute  118  in the upper region. 
     The annular bypass channel  126  projects upwards either side of the outlet chute  118  to form a pair of weirs  128  which extend radially from the central standpipe portion  124 . As described previously with respect to the separator module  10 , positioning the weirs  128  either side of the outlet chute  118  allows the inlet duct  6  to be disposed at any position about the remainder of the surrounding wall  4 . Indeed, this arrangement allows a plurality of inlet ducts and/or larger inlet ducts to be used. 
     Although not shown, the annular bypass channel  126  may be inclined as per the annular bypass channel  26  of the previous embodiment. 
     The partition plate  112  may comprise a number of tabs  144  which can be used to affix the separator module  110  to the surrounding wall  4  of the chamber  2 . If the (at rest) external diameter of the partition plate  112  is smaller than the internal diameter of the surrounding wall  4 , the keyhole slots  146  allow the two halves of the partition plate  112  to be splayed apart in order to increase the external diameter of the partition plate  112  to conform to the diameter of the surrounding wall  4 . 
     The connection of the tabs  144  to the surrounding wall  4  may maintain the two halves of the partition plate in this expanded position. Alternatively, the introduction or connection of the inlet and outlet chute components in or to the inlet and outlet recesses may maintain the partition plate  112  in the expanded position. 
     The backing plates  138  are of sufficient size so that they cover the keyhole slots  146  even when the partition plate  112  is in the expanded position. 
     To a lesser extent, the keyhole slots  146  may also allow the two halves of the partition plate  112  to be compressed together in order to decrease the external diameter of the partition plate  112 . 
     As described above, both the separator module  10  and the separator module  110  have mechanisms by which the external diameter of the module can be adjusted so as to conform to chambers having different diameters. This is particularly important where such modules are supplied to both the UK and US markets, with chambers being typically sized based on metric and imperial measurements respectively. The arrangements also provide an improved seal between the precast chamber and the components of the separator module.