A method and system for recovering filtered fluid from a product line between a filter device and a filtered fluid receiving device

Abstract

A system for transporting a filtered fluid from a filter into a filtered fluid sink, wherein the system comprises a source of a fluid, the filter having a housing, a porous filter medium comprised in the housing, an inlet, and an outlet, a filtered fluid sink, a feeding line fluidly connecting the source with the inlet of the filter, a product line fluidly connecting the outlet of the filter with the filtered fluid sink, a first pump positioned at the feeding line, a second pump positioned at the product line, and a source of gas connected to the feeding line, wherein the product line extends to the same height as or higher than the outlet of the filter with respect to the direction of the gravitational force.

Description

[0001] A Method and System for Recovering Filtered Fluid from a Product Line between a Filter Device and a Filtered Fluid Receiving Device

[0002] Technical Field of the Invention

[0003] The present invention is concerned with a method for filtering a fluid thereby yielding a filtered fluid. Furthermore, the present invention is concerned with a system for filtering a fluid. More specifically, the present invention is concerned with such a method or system, wherein the filtered fluid receiving container or device is positioned higher than the outlet of the filter device.

[0004] Background of the Invention

[0005] After using a filter device to filter fluid in a closed system, e.g. after filtration, a residual volume of filtered fluid can be retained between the downstream side of the filter medium and the filtered fluid receiving container for the filtered fluid, in particular in the product line in between. This can in particular be a problem if the filtered fluid receiving container or device is positioned higher than the outlet of the filter device.

[0006] For instance, sterile filtered fluids, as inter alia used in the pharmaceutical industry, can be very expensive, and thus, the loss of this fluid volume (for example, during the manufacture of biological therapeutics) can be costly. Further, during clinical trials, non- recoverable product may prevent manufacturers from preparing an adequate quantity of product, adversely impacting the ability to generate critical data that could lead to beneficial treatment. Cumulatively, the loss of even a few milliliters of fluid per filtration can represent a significant amount of money.

[0007] US 11 ,660,553 B2 and US 11 , 148,083 B2 disclose a system and a method, respectively, for recovering filtered fluid retained in a filter system using fluid flow paths having coaxially positioned hollow conduits. However, while this system or this method is able to recover filter fluid from the filter, it does not provide a solution to the present problem. Furthermore, the coaxially positioned hollow conduits introduce complexity and limit the flexibility of the position of the filtered fluid receiving container.

[0008] US 11 ,498,023 B2 and US 11 ,498,024 B2 are also concerned with a system and a method, respectively, for removing filtered fluid from a volume in the filter housing downstream of the filter membrane by passive replacement with gas. However, this prior art document is also not able to provide a solution to the problem as set out above, i.e. recovering filtered fluid from a product line if the filtered fluid receiving container or device is positioned higher than the outlet of the filter device. Summary of the Invention

[0009] Hence, there is the need for improved methods and systems for recovering retained filtered fluid from the product line between the filter device and the filtered fluid receiving container or device in particular if the filtered fluid receiving container or device is positioned higher than the outlet of the filter device.

[0010] It has now surprisingly found that above-mentioned object can be achieved by a system for transporting a filtered fluid from a filter into a filtered fluid sink, wherein the system comprises a source of a fluid, the filter having a housing, a porous filter medium comprised in the housing, an inlet, and an outlet, a filtered fluid sink, a feeding line fluidly connecting the source with the inlet of the filter, a product line fluidly connecting the outlet of the filter with the filtered fluid sink, a first pump positioned at the feeding line, a second pump positioned at the product line, and a source of gas connected to the feeding line, wherein the product line extends to the same height as or higher than the outlet of the filter with respect to the direction of the gravitational force.

[0011] It has further surprisingly found that above-mentioned object can be achieved by a method for transporting a filtered fluid from a filter having a housing, a porous filter medium, an inlet, and an outlet into a filtered fluid sink having an inlet, wherein the outlet of the filter is fluidly connected with the inlet of the filtered fluid sink by a product line, wherein the product line extends to the same height as or higher than the outlet of the filter with respect to the direction of the gravitational force, the method comprising the steps of filtering in a filtering step a fluid using the filter into the filtered fluid sink, whereby after the filtering step has finished a part of the filtered fluid remains as a remaining filtered fluid in the product line, and moving in a pump moving step the surge line filtered fluid from the product line into the filtered fluid sink by means of a pump and a source of gas fluidly connected to the product line.

[0012] The present invention has the advantage that the hydrostatic pressure, which is created by the product line and / or filtered fluid sink, i.e. a filtered fluid receiving container, being positioned higher than the outlet of the filter, can be overcome by the combined means of a pump and a source of gas. As the pump creates a pressure gradient, the source of gas allows for compensation of a reduced pressure created upstream of the pump. This method or system allows for recovering filtered fluid in the product line even in demanding setups, where the product line exceeds the height of the outlet of the filter or the filtered fluid sink is positioned higher than the outlet of the filter.

[0013] Brief Description of the Drawings Figure 1 is a schematic drawing of a system according to the most general embodiment of the present invention.

[0014] Figure 2 is a schematic drawing of the system according to a preferred embodiment of the present invention including a bag comprising gas and a source of pressurized gas connected to the feeding line.

[0015] Figure 3 is a schematic drawing of a peristaltic pump.

[0016] Reference Signs

[0017] 1 source of a fluid

[0018] 2 filter having a housing

[0019] 3 porous filter medium of the filter

[0020] 4 inlet of the filter

[0021] 5 outlet of the filter

[0022] 6 filtered fluid sink or filtered fluid container

[0023] 7 feeding line

[0024] 8 product line

[0025] 9 first pump

[0026] 10 second pump

[0027] 11 source of gas or bag filled with gas

[0028] 12 inlet of the filtered fluid sink or filtered fluid container

[0029] 13 source of pressurized gas

[0030] Definitions

[0031] The term ‘sterile’ as used herein denotes the status of an object having a significantly reduced number of bacteria and / or viruses on its surface to reduce the risk of an infection. In particular, the term ‘sterile’ denotes an object or substance, which has a bioburden load of lower than 10-6. The bioburden load can be measured i.e., according to ISO 11737-1 :2018.

[0032] The term ‘sterilization’ as used herein denotes a method to destroy all forms of living microorganisms from a substance. As there is always a certain probability of at least one microorganism to survive such procedure, the aim of sterilization is the reduction of initially present microorganisms or other potential pathogens. Generally, sterilization is accepted to be achieved if the bioburden load of the substance of object to be sterilized is lower than 10'6. The bioburden load can be measured i.e., according to ISO 11737-1 :2018. Sterilization can be achieved using several methods. In one sterilization process the object is heated up to at least 105 °C to achieve a sterile object. Thereby, the object should not be deformed by the elevated temperature. Preferably, the heating step is performed in an autoclave. In another sterilization process, the object is brought into contact with toxic gases such as a mixture of ethylene oxide and carbon dioxide. Filtration methods are also used to sterilize liquids, i.e., by using membrane filters, Seitz filters, and / or candle filters. Finally, sterilization can be achieved by indirect energy import into or onto the object, e.g., by ultrasonic waves, ultraviolet light, as well as by high energy particles (such as electrons, gamma- or X-rays).

[0033] The term ‘sterile air as used herein denotes air, which has been subjected to a sterilization process or which has been filtered by a sterile filter. The terms ‘sterile gas’ and ‘sterile ai can be used equivalently, e.g., embodiments referred to sterile gas also encompass the use of sterile air, and vice versa.

[0034] The term ‘aseptically transporting’ as used herein denotes the transport of a sterile substance, preferably a sterile liquid, in a closed system, wherein the sterility of the substance is not decreased.

[0035] The term ‘positive displacement pump’ as used herein denotes a pump, which moves a fluid by trapping a fixed volume of the fluid on a suction side and forcing the trapped volume into a discharge side. Some positive-displacement pumps operate in a mode, where on the volume of the cavity decreases while traveling to the discharge side. Generally, a positive displacement pump creates a pressure gradient between the suction side and the discharge side in that the pressure on the suction side is lower than the pressure on the discharge side. Typical positive displacement pumps are rotary-type positive displacement pumps, such as internal and external gear pumps, screw pumps, lobe pumps, shuttle block, flexible vane and sliding vane, circumferential piston, flexible impeller, helical twisted roots, and liquid-ring pumps. Other typical positive displacement pumps are reciprocating-type positive displacement pumps, such as piston pumps, plunger pumps, and diaphragm pumps. Finally, also linear-type positive displacement pumps are known such as rope pumps and chain pumps. A common feature of positive displacement pumps is that they form a barrier for the liquid against the intended pumping direction of the positive displacement pump. Hence, once a fluid volume has been moved from the suction side to the discharge side, the positive displacement pump does not allow a flow back of said fluid volume. This also holds true in case the pump stopped working.

[0036] The term ‘peristaltic pump’ as used herein denotes a specific embodiment of a positive displacement pump, in particular a specific embodiment of a rotary-type positive displacement pump. Reference is made to Figure 3. Thereby, it is a specific feature of the peristaltic pump that the fluid to be pumped is contained in a flexible tube (a). The flexible tube (a) runs through the housing (b) of the circular peristaltic pump. The peristaltic pump comprises a rotor (c), which comprises means to put pressure (d) on the flexible tube (a), such as wipers (d) or rollers (d) attached to the external circumference of the rotor (c). Thereby, the means to put pressure (d) on the flexible tube (a) compress the flexible tube (a) as they rotate by, whereby the flexible tube (a) is closed under compression. The closing of the flexible tube (a) forces the fluid to move through the flexible tube (a) during rotating of the rotor (c). Furthermore, the closing of the flexible tube (a) prevents the fluid from flowing back. As the flexible tube (a) opens to its natural state after the wipers (d) or rollers (d) have passed, more fluid is drawn into the flexible tube (a). This process is called peristalsis. Preferably, the peristaltic pump comprises two or more rollers (d) for compressing the flexible tube (a), thereby trapping a volume of fluid between them.

[0037] The term ‘source of gas’ as used herein denotes a device which provides gas continuously or up to a certain volume. Usually, the gas in the source of gas is present at a pressurized state in comparison to the pressure of the system it is connected to. Sources of gas might be gas pumps. Other embodiments comprise flexible containers filled with gas, which exerts pressure on the contained gas. The pressure exerted can be provided by means for putting pressure on the container or by using flexible container material and filling the container with pressurized gas. Most preferably the source of gas is a flexible bag comprising pressurized gas. Thereby, the flexible bag is preferably made from an gas-tight film comprising a polymer, preferably from a multilayer polymer film.

[0038] The term ‘filtered fluid sink’ as used herein denotes any device or container, which is intended to receive the filtered fluid. Usually, the filtered fluid is collected after filtering either to be further processed, packaged and sold or to be directly used i.e. in medical applications or in research. Hence, the type of the filtered fluid sink depends on the use case the system or method is intended to serve the filtered fluid for. In one embodiment, the filtered fluid sink is a filtered fluid container, which simply collects the filtered fluid. In another embodiment, the filtered fluid sink is a manifold, which distributes the filtered fluid to many containers or other devices such as syringes. Hence, in even another embodiment, the filtered fluid sink could be a syringe either for being packaged and sold or for being used in a subsequent treatment or method. Other filtered fluid sinks may be vials, ampoules, bottles, bioprocessing containers, and carboys.

[0039] The term ‘closed system’ as used herein denotes a system that allows the collection and processing (including filtration, and, if desired, the manipulation, e.g., separation of portions, separation into components, storage, and preservation) of fluid, without exposing the contents of the system to the environment in which it is being used. In particular, a closed system is suitable for aseptically processing sterile fluids and components by shielding them from influences by the environment.

[0040] The use of the terms ‘a’ and ‘an’ and ‘the’ and ‘at least one’ and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context.

[0041] The use of the term ‘at least one’ followed by a list of one or more items (for example, ‘at least one of A and B’) s is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context.

[0042] The terms ‘comprising’ , ‘having’, ‘including’, and ‘containing’ are to be construed as open-ended terms (i.e., meaning ‘including, but not limited to’) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., ‘such as’) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any nonclaimed element as essential to the practice of the invention.

[0043] Detailed Description

[0044] The present invention is concerned with a system for transporting, preferably aseptically transporting, a filtered fluid from a filter into a filtered fluid sink and a method for transporting, preferably aseptically transporting, a filtered fluid from a filter into a filtered fluid sink. The system and the method are described in more detail in the following with reference to Figures 1 and 2 using the reference signs as set out above.

[0045] System

[0046] The herein described system is a system for transporting a filtered fluid from a filter into a filtered fluid sink, wherein the system comprises: a source of a fluid (1), the filter (2) having a housing, a porous filter medium (3) comprised in the housing, an inlet (4), and an outlet (5), a filtered fluid sink (6), a feeding line (7) fluidly connecting the source of a fluid (1) with the inlet (4) of the filter (2), a product line (8) fluidly connecting the outlet (5) of the filter (2) with the filtered fluid sink (6), a first pump (9) positioned at the feeding line (7), a second pump (10) positioned at the product line (8), a source of gas (11) connected to the product line (8) wherein the product line (8) extends to the same height as or higher than the outlet (5) of the filter (2) with respect to the direction of the gravitational force.

[0047] Preferably, the system for transporting a filtered fluid from a filter into a filtered fluid sink is a system for aseptically transporting a filtered fluid from a filter into a filtered fluid sink. Hence, preferably, the source of gas (11) is a source of sterile gas, more preferably a source of sterile air.

[0048] The source of a fluid (1) is placed in communication with feeding line (7). The source of a fluid (1) can be a source container comprising the fluid to be filtered but can also be a production process for a fluid. Hence the source of a fluid (1) could also be e.g. a bioreactor producing the fluid to be filtered.

[0049] Typically, the system includes a connector such that the source of a fluid (1) and the filter (2) can both be placed in communication with the feeding line (7).

[0050] In a preferred embodiment, the first pump is a positive displacement pump and / or the second pump is a positive displacement pump. This has the advantage that fluid, which has passed the pump cannot flow back into the upstream part of the system. Hence, the pump has a barrier effect on back flow.

[0051] Furthermore, more preferably, the first pump is a peristaltic pump and / or wherein the second pump is a peristaltic pump. This has the advantage that the pump can be attached to the feeding line (7) and / or product line (8) without having an influence on the integrity of the lines. Hence, system integrity is enhanced, and risk of quality impact is reduced.

[0052] Preferably, the second pump (10) is positioned at the product line (8) in the herein described system. Preferably, the second pump (10) is positioned at the lowermost position of the surge line (8) with reference to the direction of the gravitational force. This has the advantage that the entirety of the remaining filtered fluid in the product line (8) can be recovered. In another preferred embodiment, the second pump (10) is positioned at the uppermost position of the product line (8), usually shortly before the inlet (12) of the filtered fluid sink (6). This facilitates moving any fluid, which has passed the pump (10) already, into the filtered fluid sink (6). In an even more preferable embodiment, the product line (8) comprises more than one pump.

[0053] In a preferred embodiment, the filter (2) is a sterile filter, more preferably a membrane filter. Generally, the filter (2) comprises a housing having an inlet (4) and an outlet (5) defining a filtration flow path between the inlet (4) and the outlet (5), and a porous filtration medium (3) having an upstream side and a downstream side across the filtration flow path. The filter (2) typically has at least a porous filtration medium. The filtration medium can have a variety of configurations, including planar, pleated and / or hollow cylindrical. Typically, the filter (2) is vented during the initial filtration of liquid so that the maximum available filter medium surface is used, and to prevent build-up of gas in the system. After the filter housing is filled with liquid, the vent can be closed. Preferably, the filter (2) includes a vent, or vents can be arranged upstream and / or downstream of the filter (2), so that gas can be vented.

[0054] Preferably, the filter (2) is not suitable for passing pressurized gas therethrough subsequent to passing a liquid therethrough.

[0055] Preferably, in the system as described herein, the source of gas (11) is a bag suitable for being filled with gas (11) and suitable for exerting a pressure on said gas filled therein. Hence, preferably, the walls of the bag are made from a flexible material, which can extend to a certain amount during filling with pressurized gas and which can therefore preserve the pressure of the pressurized gas.

[0056] Preferably, the source of gas (11) is connected to the product line (8) via a vent. This has the advantage that the pressurized gas can be isolated from the remaining system. Such a configuration is in particular advantageous during filtration, as otherwise liquid may enter the source of gas (11).

[0057] In another preferred embodiment of the system as described herein, the filtered fluid sink (6) is a filtered fluid container (6) having an inlet (12) and the product line (8) is connected to the inlet (12) of the filtered fluid container (6). Preferably, the inlet (12) or the product line comprise a back flow barrier. This can assure that the liquid stays in the filtered fluid container (6) once the filtered fluid container (6) is removed to transport the collected fluid elsewhere.

[0058] As stated above, the product line (8) extends to the same height as or higher than the outlet (5) of the filter (2) with respect to the direction of the gravitational force. Likewise, the inlet (12) of the filtered fluid container (6) is positioned higher than the height of the outlet (5) of the filter (2) with respect to the direction of the gravitational force. There are several reasons why it is advantageous to position the filtered fluid sink (6) as described. The main reason is that the hydrostatic pressure produced by the filtered fluid in such positioned filtered fluid sink (6) can be used to transport itself into downstream equipment removing the need for further transporting measures such as pumps or pressurized gas.

[0059] In another preferred embodiment of the herein described system the system further comprises a source of pressurized gas (13) connected to the feeding line (7). Such a source of pressurized gas (13) is in particular advantageous as it can be used to flush the system with gas prior to filtration. Furthermore, the source of pressurized gas (13) can be used to fill the source of gas (11) or the bag suitable for being filled with gas (11) with pressurized gas prior to filtration. Even more preferable, the source of gas (11) is connected to the product line (8) via a vent as described above, which can be closed after filling the source of gas (11) or the bag suitable for being filled with gas (11) with pressurized gas prior to filtration.

[0060] As noted above, the system may include additional optional components, including an optional upstream filter device, as well as further pumps, connectors, conduits, e.g., for connection to the next stage in processing, as well as flow control devices (such as clamps or valves). Some embodiments of the system do not require the presence or use of flow control devices. However, in some other embodiments, flow control devices are associated with various conduits to allow or prevent flow through the conduits. Initially, the various flow control devices are closed to prevent flow through the conduits.

[0061] Preferably, the herein described system is compatible with processes involving integrity testing of filter devices and filter systems.

[0062] Also preferably, the herein described system is suitable for use in a variety of systems, including closed systems, particularly bioprocessing systems.

[0063] The herein described system is preferably suitable for use with a variety of fluids to be filtered, for example, cell culture (e.g., including batch and fed-batch operations of suspension and adherent cell lines), preparing sterile or low bioburden fluids for the pharmaceutical and / or biopharmaceutical industries, including drugs, vaccines, and intravenous fluids, antibody- and / or protein-containing fluids, and / or fluids for the food and beverage industry. A variety of filter devices and containers, typically flexible (e.g., plastic) containers and conduits, including commercially available filter devices, are suitable for use in embodiments of the herein described system, and are known in the art. Suitable connectors, e.g., conduit connectors; molded tubing, and flow control devices such as clamps, seals, valves, transfer leg closures, and the like, are known in the art. In a preferred embodiment, the filter (2) is a membrane filter. Generally, the filter (2) comprises a housing having an inlet (4) and an outlet (5) defining a filtration flow path between the inlet (4) and the outlet (5), and a porous filtration medium (3) having an upstream side and a downstream side across the filtration flow path. The filter (2) typically has porous filtration medium. The filtration medium can have a variety of configurations, including planar, pleated and / or hollow cylindrical. Typically, the filter (2) is vented during the initial filtration of liquid so that the maximum available filter medium surface is used, and to prevent build-up of gas in the system. After the filter housing is filled with liquid, the vent can be closed. Preferably, the filter (2) includes a vent, or vents can be arranged upstream and / or downstream of the filter (2), so that gas can be vented.

[0064] Method

[0065] The herein described method is a method for transporting a filtered fluid from a filter (2) having a housing, a porous filter medium (3), an inlet (4), and an outlet (5) into a filtered fluid sink (6) having an inlet (12), wherein the outlet (5) of the filter (2) is fluidly connected with the inlet (12) of the filtered fluid sink (6) by a product line (8), wherein the product line (8) extends to the same height as or higher than the outlet (5) of the filter (2) with respect to the direction of the gravitational force, the method comprising the steps of

[0066] Filtering in a filtering step a fluid using the filter (2) into the filtered fluid sink (6), whereby after the filtering step has finished a part of the filtered fluid remains as a remaining filtered fluid in the product line (8), and moving in a pump moving step the product line filtered fluid from the product line (8) into the filtered fluid sink (6) by means of a pump (10) and a source of gas (11) fluidly connected to the product line (8).

[0067] In a preferred embodiment, the pump (10) used in the pump moving step is a positive displacement pump. This has the advantage that fluid, which has passed the pump (10) used in the pump moving step cannot flow back into the upstream part of the system. Hence, the pump (10) used in the pump moving step has a barrier effect on back flow.

[0068] Preferably, the method for transporting a filtered fluid is a method for aseptically transporting a filtered fluid. Hence, preferably, the source of gas (11) is a source of sterile gas, more preferably a source of sterile air.

[0069] Furthermore, more preferably, the pump (10) used in the pump moving step is a peristaltic pump. This has the advantage that the pump (10) used in the pump moving step can be attached to the product line (8) without having an influence on the integrity of the line. Hence, system integrity is enhanced, and risk of quality alterations is reduced.

[0070] Preferably, the pump (10) is positioned in the pump moving step at the product line (8) in the herein described method. Preferably, the pump (10) is positioned in the pump moving step at the lowermost position of the product line (8) with reference to the direction of the gravitational force. This has the advantage that the entirety of the remaining filtered fluid in the product line (8) can be recovered. In another preferred embodiment, the pump (10) is positioned in the pump moving step at the uppermost position of the product line (8), usually shortly before the inlet (12) of the filtered fluid sink (6). This facilitates moving any fluid, which has passed the pump (10) already, into the filtered fluid sink (6). In an even more preferable embodiment, the pump moving step comprises the use of more than one pump.

[0071] In a preferred embodiment, the filter (2) used in the filtering step is a membrane filter. Generally, the filter (2) used in the filtering step comprises a housing having an inlet (4) and an outlet (5) defining a filtration flow path between the inlet (4) and the outlet (5), and a porous filtration medium (3) having an upstream side and a downstream side across the filtration flow path. The filter (2) used in the filtering step typically has porous filtration medium. The filtration medium of the filter (23) used in the filtering step can have a variety of configurations, including planar, pleated and / or hollow cylindrical. Typically, the filter (2) used in the filtering step is vented during the initial filtration of liquid so that the maximum available filter medium surface is used, and to prevent buildup of gas in the system. After the filter housing is filled with liquid, the vent can be closed. Preferably, the filter (2) used in the filtering step includes a vent, or vents can be arranged upstream and / or downstream of the filter (2), so that gas can be vented.

[0072] More preferably, the filter (2) used in the filtering step is not suitable for passing pressurized gas therethrough subsequent to the filtering step.

[0073] Hence, in the herein described method, the pump moving step produces low pressure in the system located upstream of the pump. To compensate for such low pressure, the source of gas (11) is placed downstream of the filter (2) and upstream of the pump (10) in the product line (8) and is fluidly connected during the pump moving step. Hence, the ratio of the volume of gas, which can be provided by the source of gas (11) and the volume of the remaining filtered fluid in the product line (10) should be larger than or equal to 1 .

[0074] Preferably, in the herein described method, the source of gas (11) is a gas bag comprising pressurized gas, wherein the bag is fluidly connected with the product line (8). Hence, in case the source of gas (11) is a gas bag comprising pressurized gas, the ratio of the volume of the gas bag comprising pressurized gas to the volume of the remaining filtered fluid in the line (8) is larger than or equal to 1. This ensures that the remaining filtered fluid in the product line (8) can be completely recovered.

[0075] Preferably, in the filtering step of the herein described method, the fluid connection between the product line (8) and the source of gas (11) is closed, and wherein in the pump moving step the fluid connection between the product line (8) and the source of gas (11) is opened. This ensured that no fluid entrains the source of gas (11).

[0076] The fluid is filtered as it passes along the filtration flow path in the filter (2) through the porous medium (3). Preferably, the system is flushed with gas prior to filtration to increase sterility of the system. Hence, since gas can be present in the system, the filtered fluid displaces gas ahead of it, and the displaced gas, and filtered fluid, pass along the product line (8) into the filtered fluid sink (6). After filtration is completed, filtered fluid is retained in the product line (8). Hence, preferably, the herein described method comprises prior to the filtering step the step of filling in a gas filling step the gas bag (11) with pressurized gas.

[0077] Preferably, the gas filling step is carried out prior to a filter integrity testing or during filter integrity testing using forward flow or bubble point test methods or is carried out as part of any system leak test procedures.

Claims

Claims:

1. A system for transporting a filtered fluid from a filter into a filtered fluid sink, wherein the system comprises: a source of a fluid (1), the filter (2) having a housing, a porous filter medium (3) comprised in the housing, an inlet (4), and an outlet (5), a filtered fluid sink (6), a feeding line (7) fluidly connecting the source of a fluid (1) with the inlet (4) of the filter (2), a product line (8) fluidly connecting the outlet (5) of the filter (2) with the filtered fluid sink (6), a first pump (9) positioned at the feeding line (7), a second pump (10) positioned at the product line (8), a source of gas (11) connected to the product line (8) wherein the product line (8) extends to the same height as or higher than the outlet (5) of the filter (2) with respect to the direction of the gravitational force.

2. The system according to claim 1 , wherein the source of gas is a bag suitable for being filled with gas.

3. The system according to claims 1 or 2, wherein the first pump is a positive displacement pump, preferably a peristaltic pump, and / or wherein the second pump is a positive displacement pump, preferably a peristaltic pump.

4. The system according to any of the preceding claims 1 to 3, wherein the system for transporting a filtered fluid from a filter into a filtered fluid sink is a system for aseptically transporting a filtered fluid from a filter into a filtered fluid sink and / or wherein the source of gas (11) is a source of sterile gas, more preferably a source of sterile air.

5. The system according to any of the preceding claims 1 to 4, wherein the filter (2) is not suitable for passing pressurized gas therethrough subsequent to passing a liquid therethrough.

6. The system according to any of the preceding claims 1 to 5, wherein the filtered fluid sink (6) is a filtered fluid container (6) having an inlet (12) and wherein the product line (8) is connected to the inlet (12) of the filtered fluid container (6).

7. The system according to any of the preceding claims 1 to 6, wherein the inlet (12) of the filtered fluid container (6) is positioned higher than the height of the outlet (5) of the filter (2) with respect to the direction of the gravitational force.

8. The system according to any of the preceding claims 1 to 7, wherein the system further comprises a source of pressurized gas (13) connected to the feeding line(7).

9. A method for transporting a filtered fluid from a filter (2) having a housing, a porous filter medium (3), an inlet (4), and an outlet (5) into a filtered fluid sink (6) having an inlet (12), wherein the outlet (5) of the filter (2) is fluidly connected with the inlet (12) of the filtered fluid sink (6) by a product line (8), wherein the product line(8) extends to the same height as or higher than the outlet (5) of the filter (2) with respect to the direction of the gravitational force, the method comprising the steps ofFiltering in a filtering step a fluid using the filter (2) into the filtered fluid sink (6), whereby after the filtering step has finished a part of the filtered fluid remains as a remaining filtered fluid in the product line (8), and moving in a pump moving step the surge line filtered fluid from the product line (8) into the filtered fluid sink (6) by means of a pump (10) and a source of gas (11) fluidly connected to the product line (8).

10. The method according to claim 9, wherein the pump (10) is positioned at the product line (8) and / or wherein the pump (10) is a positive displacement pump, preferably a peristaltic pump.

11. The method according to claims 9 or 10, wherein the method for transporting a filtered fluid is a method for aseptically transporting a filtered fluid and / or wherein the source of gas (11) is a source of sterile gas, more preferably a source of sterile air.

12. The method according to any of the preceding claims 9 to 11 , wherein the filter (2) is not suitable for passing pressurized gas therethrough subsequent to the filtering step.

13. The method according to any of the preceding claims 9 to 12, wherein the source of gas (11) is a gas bag comprising pressurized gas, wherein the bag is fluidly connected with the product line (8).

14. The method of any of the preceding claims 9 to 13, wherein in the filtering step the fluid connection between the product line (8) and the source of gas (11) isclosed, and wherein in the pump moving step the fluid connection between the product line (8) and the source of gas (11) is opened.

15. The method according claims 13 or 14, wherein the method comprises prior to the filtering step. - filling in a gas filling step the gas bag (11) with pressurized gas.15

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