Filtration systems

Abstract

A filtration system comprising a plurality of filters. Each filter defines a respective filter flowpath extending adjacent a respective filtration medium for tangential filtration by the filtration medium of fluid passing through the filter flowpath. The system also comprises a manifold connected to each filter, the system being selectively operable in a first state in which the manifold and the filter flowpaths form part of a first continuous flowpath around which fluid circulates passing in parallel through the filter flowpaths and a second state in which fluid circulates around a second continuous flowpath including the filter flowpath of at least one but not all of the filters, the second continuous flowpath having a lower volume than the first continuous flowpath and fluid passing into the second continuous flowpath from the manifold responsive to tangential filtration in the second state.

1 . A filtration system comprising:
 a first continuous flowpath for circulation of fluid therearound and a second continuous flowpath for circulation of fluid therearound after said circulation around said first continuous flowpath, fluid circulating around each continuous flowpath being filtered so that, for each continuous flowpath, fluid being filtered leaves said each continuous flowpath on filtration, wherein a portion of the first continuous flowpath is not included in the second continuous flowpath and wherein the second continuous flowpath has a lower volume than the first continuous flowpath;   a first feeding means for feeding fluid to the first continuous flowpath in response to fluid leaving the first continuous flowpath on said filtration of fluid circulating around the first continuous flowpath; and   a second feeding means for feeding fluid to the second continuous flowpath from said portion of the first continuous flowpath which is not included in the second continuous flowpath in response to fluid leaving the second continuous flowpath on said filtration of fluid circulating around the second continuous flowpath.   
   
   
       2 . A filtration system according to  claim 1 , wherein the filtration of fluid circulating around the first continuous flowpath comprises tangential filtration and the filtration of fluid circulating around the second continuous flowpath comprises tangential filtration. 
   
   
       3 . A filtration system according to  claim 1 , wherein said filtration of fluid circulating around each continuous flowpath is performed by filtration means associated with both the first and second continuous flowpaths. 
   
   
       4 . A filtration system according to  claim 3 , wherein the first continuous flowpath is associated with further filtration means that filters fluid circulating around the first continuous flowpath so that fluid leaves the first continuous flowpath on filtration. 
   
   
       5 . A filtration system according to  claim 4 , wherein the system comprises a plurality of filters, each filter defining a respective filter flowpath and having a respective filter medium disposed adjacent the corresponding filter flowpath for filtration of fluid passing through the corresponding filter flowpath, the first-mentioned filtration means comprising at least one but not all of the filters and the or each filter flowpath of said at least one filter being included in each continuous flowpath, and the further filtration means comprising the or each filter other than said at least one filter and the or each filter flowpath of said the or each other filter being included in the first but not the second continuous flowpath. 
   
   
       6 . A filtration system according to  claim 5 , wherein the fluid circulating around the first continuous flowpath passes in parallel through the filter flowpaths. 
   
   
       7 . A filtration system according to  claim 6 , wherein the system comprises a manifold connected to each filter and included in the first continuous flowpath, the portion comprising at least part of the manifold. 
   
   
       8 . A filtration system according to  claim 7 , wherein the second continuous flowpath includes at least one bypass that allows fluid to bypass said at least part of the manifold during circulation of fluid around the second continuous flowpath. 
   
   
       9 . A filtration system according to  claim 1 , wherein the means for passing fluid to the first continuous flowpath comprises a reservoir. 
   
   
       10 . A filtration system comprising a plurality of filters, each filter defining a respective filter flowpath extending adjacent a respective filtration medium for tangential filtration by the filtration medium of fluid passing through the filter flowpath, and a manifold connected to each filter, the system being selectively operable in a first state in which the manifold and the filter flowpaths of the plurality of filters form part of a first continuous flowpath around which fluid circulates passing in parallel through the filter flowpaths and in a second state in which fluid circulates around a second continuous flowpath having a lower volume than the first continuous flowpath, wherein the second continuous flowpath includes the filter flowpath of at least one but not all of the filters and wherein fluid is fed into the second continuous flowpath from the manifold in response to fluid leaving the second continuous flowpath on tangential filtration in the second state. 
   
   
       11 . A filtration system according to  claim 10 , wherein the second continuous flowpath includes at least one bypass that allows fluid to bypass at least part of the manifold during circulation of fluid around the second continuous flowpath. 
   
   
       12 . A filtration system according to  claim 10 , wherein the manifold is located below the filters for drainage of fluid from the or each filter flowpath not included in the second continuous flowpath into the manifold during circulation of fluid around the second continuous flowpath. 
   
   
       13 . A filtration system according to  claim 10 , including means for selectively restricting flow from the or each filter flowpath of said at least one filter. 
   
   
       14 . A filtration system according to  claim 11 , wherein the system includes a further manifold connected to each filter and included in the first continuous flowpath, one of the manifolds providing fluid to the filters and the other one of the manifolds receiving fluid from the filters during circulation of fluid around the first continuous flowpath, the second continuous flowpath including at least one bypass that allows fluid to bypass at least part of the further manifold during circulation of fluid around the second continuous flowpath. 
   
   
       15 . A filtration system according to  claim 10 , wherein the system includes a pump for circulating fluid around the first continuous flowpath, the pump being inactive during circulation of fluid around the second continuous flowpath, and fluid from the pump passing into the second continuous flowpath in response to said filtration of fluid circulating around the second continuous flowpath. 
   
   
       16 . A filtration system according to  claim 15 , wherein the system includes a further pump for pumping fluid around the second continuous flowpath. 
   
   
       17 . A filtration system according to  claim 16 , wherein the further pump has a lower throughput than the first-mentioned pump. 
   
   
       18 . A filtration system according to  claim 16 , wherein the further pump holds a lower volume of fluid than the first-mentioned pump. 
   
   
       19 . A filtration system comprising:
 a plurality of filters, each filter having an unfiltered fluid inlet, an unfiltered fluid outlet, a filtered fluid outlet, and a filtration medium and defining a filter flowpath between the unfiltered fluid inlet and the unfiltered fluid outlet for tangential filtration by the filtration medium of fluid passing along the filter flowpath;   a first continuous flowpath comprising the filter flowpaths of the plurality of filters and a fluid circuit coupled to the filter flowpaths of the plurality of filters;   a second continuous flowpath comprising each filter flowpath of at least one but not all of the plurality of filters and a fluid circuit coupled to each filter flowpath of said at least one filter, wherein the second continuous flowpath has a lower volume than the first continuous flowpath;   a valve arrangement coupled to the first and second continuous flowpaths; and   a pump arrangement, the valve arrangement and the pump arrangement being selectively operable in a first state to circulate fluid around the first continuous flowpath through the fluid circuit and in parallel through the filter flowpaths of the plurality of filters and in a second state to circulate fluid around the second continuous flowpath through the fluid circuit and through each filter flowpath of said at least one filter and pass fluid from at least part of the first continuous flowpath into the second continuous flowpath in response to tangential filtration in said at least one filter.   
   
   
       20 . A filtration system according to  claim 19 , wherein the pumping arrangement comprises first and second pumps. 
   
   
       21 . A filtration system according to  claim 20  wherein the second pump has a lower volume than the first pump. 
   
   
       22 . A filtration system according to  claim 19  further comprising a manifold coupled to the plurality of filters, wherein the first continuous flowpath includes the manifold and the second continuous flowpath includes a bypass that allows fluid to bypass at least part of the manifold during circulation of fluid around the second continuous flowpath.