Sanitary Diaphragm Pump for Critical Bioprocess Applications

Abstract

An easily cleaned and/or sterilized fluid pumping assembly including a first pump housing including a first inner chamber. The first pump housing includes a fluid access port adapted to provide fluid communication between an outside of the first pump housing and the first inner chamber. Also, included is a second pump housing having a first coupling flange securely mated to the first pump housing. The second pump housing includes a second coupling flange adapted to be removeably and securely mated to a third coupling flange on a piston housing. Additionally, a flexible diaphragm is provided disposed between the first and second pump housings. The diaphragm is in fluid communication with the first inner chamber. Also, the diaphragm is displaceable by a driven piston for expelling fluid from the first inner chamber. More than one such assembly is used in combination to provide a constant flow fluid delivery system.

Description

The present application claims priority to provisional patent Application Ser. No. 60/679,524, filed May 10, 2005. This earlier filed provisional application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Many fluid handling applications in biotechnology require a pump to move the fluid. Generally, when handling biological fluids it is important to ensure that an uncontaminated environment has been maintained throughout the process. Thus, the pumps are designed to be easily cleaned and sanitized before and after each use, thus controlling or reducing microbial contamination. In particular, contemporary biotechnological filtration and/or chromatography require equipment to be sanitized prior to use in order to ensure a fluid handling environment with minimal microbial contamination.

In some chromatography processes, one or several liquid solutions are pumped into a chromatography column filled with a resin which varies depending on the particular process. The liquid flow rate must be constant and accurately controlled, while maintaining a relatively high degree of pressure (several bars/atmospheres or more) in order to drive the liquid through the column. Similarly, in a filtration process a relatively high degree of pressure is used to drive a liquid through a filter (normal or direct flow) or across a filter (cross or tangential flow). The latter is commonly used when liquid is re-circulated across a filter membrane. In such cross flow applications a precise flow rate and high pressure is required to ensure that more than a minor percentage of fluid flows through the filter relative to the recirculation rate. The high pressure is required to help drive the liquid through certain filters (such as membrane or cross-flow ultra-filters) that resist or limit the passage of fluid. Thus, as in chromatography, the fluid flow rate in filtration must often be accurately controlled, while maintaining several bars/atmospheres or more of pressure.

Peristaltic pumps are commonly used in biotechnological applications because they do not contact the liquid stream but only the outside of the process tubing, only the inner diameter of the process tubing comes in contact with the liquid stream. They operate by means of a constriction that moves along the tubing, thus its parts avoid contact, and thus contamination, of the handled liquid. However, such tubing pumps are limited to lower pressure applications. A high pressure environment, such as several bars/atmospheres requires heavier gauge or reinforced tubing, which is no longer flexible enough to be pinched or squeezed. Thus, the peristaltic pumps are not suited for high pressure environments.

Sanitary rotary lobe pumps are commonly used in biotechnology processes. These pumps can operate at relatively high pressures but they contain numerous components, such as the pump rotors, that contact the liquid stream. The contaminated components must be cleaned and sanitized after each use and possibly disassembled. Such a process can have added costs and delays that are not desirable. Also, this process requires high quality components that can withstand the added wear, which can also increase costs. Additionally, the type of precision components generally used as well as the relatively large number that get contaminated with each use, makes those parts too valuable to throw away after a single or small number of uses.

It is therefore desirable to provide a fluid pumping system that is suitable for relatively high pressure environments, while preferably maintaining a constant and accurate fluid flow rate. Also, the system must be easily sterilized or uncontaminated between uses.

SUMMARY OF THE INVENTION

The present invention relates to an apparatus for pumping fluids that is easily cleaned and/or sterilized after each use. Preferably, any parts contaminated by fluid contact can be easily removed and replaced. Also, those contaminated parts should be easily sterilized or designed to be disposable and thus replaced with inexpensive replacements. Using the preferred diaphragm pump of the present invention, few elements ever come in contact with the handled fluid, while providing a low shear, efficient, low cost method and system of pumping biological fluids. Additionally, the invention provides an apparatus and system that provides a constant and accurate fluid flow rate, while able to operate in relatively high fluid pressure environments.

In one aspect of the present invention, a fluid pumping apparatus is provided that includes a first pump housing including a first inner chamber. The first pump housing includes a fluid access port adapted to provide fluid communication between an outside of the first pump housing and the first inner chamber. Also, included is a second pump housing having a first coupling flange securedly mated to the first pump housing. The second pump housing includes a second coupling flange adapted to be removeably and securedly mated to a third coupling flange on a piston housing. Additionally, a flexible diaphragm is provided disposed between the first and second pump housings. The diaphragm is in fluid communication with the first inner chamber. Also, the diaphragm is adapted to be displaced by a driven piston for expelling fluid from the first inner chamber.

In another aspect of the present invention a fluid pumping apparatus is provided that includes a first pump housing with a first inner chamber. The first pump housing includes a fluid access port adapted to provide fluid communication between an outside of the first pump housing and the first inner chamber. A second pump housing is provided that includes a second inner chamber. The second pump housing is secured to the first pump housing. Further provided is a flexible diaphragm disposed between the first and second pump housings. The diaphragm is in fluid communication with the first inner chamber. Yet further, a third pump housing is provided that is removeably secured to the second pump housing. The third pump housing includes a piston access port. Also, the first, second and third pump housings are adapted to form a continuous unitary outer pump shell. Additionally a driven piston is adapted to move the flexible diaphragm toward the fluid access port.

In yet another aspect of the current invention a chromatography pump assembly is provided that is adapted to deliver fluid at a constant flow rate. The pump assembly comprising a first conduit for receiving fluid, a second conduit for expelling fluid, a first and second diaphragm pump in fluid communication with the first and second conduits and a valve system. Each pump includes an inner fluid chamber, an inner flexible diaphragm, and a rigid drive mechanism adapted to push the diaphragm thereby expelling fluid from the inner fluid chamber. The valve system is adapted to block fluid flow from the first conduit to one of the first and second pumps, while simultaneously blocking fluid flow to the second conduit from the other of the first and second pumps.

In yet another aspect of the current invention a method for pumping a fluid is described comprising providing conduit adapted to communicate fluid from at least one source to at least one destination. Then, coupling a first disposable and/or sterilized diaphragm pump to an intermediate position of the conduit. The first diaphragm pump is adapted to expel fluid by activation of a driven piston. Additionally, securing a piston housing for the driven piston to the first pump. Thus, the piston housing and the first pump forming a unitary continuous outer pump shell. Then, initiating the driven piston thereby pumping fluid out of the diaphragm pump. Thereafter, removing and discarding the first diaphragm pump after a single use, and replacing the first diaphragm pump with a second diaphragm pump. The second diaphragm pump being disposable and/or sterilized prior to use as part of the assembly.

These and other objectives, features, and advantages of this invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an embodiment of a fluid pumping apparatus in accordance with the subject invention.

FIG. 2 is an exploded cross-sectional view of an upper pump housing, fluid conduit and valve assembly, in accordance with the subject invention.

FIG. 3 is a cross-sectional view of an alternate embodiment of the upper pump housing shown in FIG. 2, in accordance with the subject invention.

FIG. 4 is an exploded cross-sectional view of the upper pump housing shown in FIG. 2 with an alternate embodiment fluid conduit, in accordance with the subject invention

FIG. 5 is a cross-sectional view of a further embodiment of a fluid pumping apparatus in accordance with the subject invention.

FIG. 6 is a partial schematic and cross-sectional view of a fluid pumping system using two of the fluid pumping apparatus shown in FIG. 5.

FIGS. 7a-c are top, front and right-side views, respectively, of a fluid handling assembly, using two fluid pumping apparatus in accordance with the subject invention.

FIG. 8 is a cross-sectional view of an alternate embodiment of the upper pump housing shown in FIG. 2, in accordance with the subject invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the drawings, FIG. 1 shows a fluid pump head 100 adapted to be mounted and sealed with a piston assembly, in accordance with an embodiment of the invention. The diaphragm pump 100 is preferably formed by an upper pump housing 120 and a lower pump housing 160, that when sealed together form an outer pump casing. Both the upper and low pump housings 120, 160 include radially protruding flanges 128, 162 that when mated together secure the diaphragm 140 there between. This configuration forms a fluid chamber 125 between the upper pump housing 120 and the diaphragm 140. In this way, the inner surface of the upper pump housing 120 and the upper surface of the diaphragm 140 are the only portions of the pump 100 that should come in contact with the fluid. In contrast, a secondary chamber 165 is also formed between the lower pump housing 160 and the diaphragm 140. Preferably, the secondary chamber 165 does not ever come in contact with the fluid. Additionally, the lower pump housing 160 preferably is adapted to be secured to a piston and vacuum assembly. The lower housing 160 preferably includes a coupling flange 168 that is designed to removeably seal with a piston housing. Thus, lower chamber 165 contains piston and vacuum forces capable of driving the diaphragm, which in turn moves fluid.

FIG. 2 shows how the upper pump housing 120 is preferably installed as part of a fluid flow path in an intermediate location. A select fluid is input from a feed side 10 and pumped toward an outlet side 90. Between those two ends 10, 90 are the pump 100, valves 70 and other conduits and connectors, such as the T-connector 50 shown. FIG. 3 shows an alternate embodiment of upper pump housing 121, which provides more than one fluid port. Preferably, an inlet port 123 is coupled to the feed side and an outlet port 124 is coupled to the fluid destination. FIG. 4 shows an embodiment similar to that shown in FIG. 2, but with a Y-connector 51. FIG. 8 shows an alternate embodiment of the upper pump housing 122, with a variation of the coupling nozzle 116. The nozzle 116 includes a hose barb connector 117 with a stop 119 to assist in hose or tubing installation and a notch 118 for placement of a compression component to secure the hose/tubing (not shown) in place during pump operation at high pressures.

The diaphragm pump 100 cycles between drawing-in liquid and expelling liquid from its fluid chamber 125. The diaphragm 140 is adapted to extend back and forth between the upper and lower chambers 125, 165. As shown in FIG. 5, when secured to a piston assembly 200 that preferably includes a piston housing 220 with its own coupling flange 222, a driven piston rod 210 and piston 205, and one or more vacuum ports 164, 224, the diaphragm 140 can be forced to deflect toward or away from the fluid port 110. Preferably, at least one vacuum port 164, 224 is provided for depressurizing the lower chamber 165. The piston housing 220, along with the packed or sealed piston rod opening 225, closes-off the lower chamber 165 and helps maintain an appropriate reduced pressure therein. The reduced pressure biases the diaphragm 140 to deflect toward that lower chamber 165. The vacuum pressure, which is applied on the non-liquid side 165 of the pump, is preferably sufficient negative pressure to fill the upper housing chamber 125 with liquid fast enough to maintain the desired flow rate into the pump.

Preferably, the piston 205 is designed to mechanically push the diaphragm 140 toward the fluid port 110. When the pump assembly is coupled to fluid input and output lines through the upper coupling nozzle 115, as the piston 205 retracts, diaphragm 140 moves from the upper chamber 125 toward the lower chamber 165, biased by the vacuum forces, and preferably draws fluid into the upper chamber 125. FIGS. 1 and 5 shows the diaphragm 140 drawn toward the lower pump housing 160. After the upper chamber 125 is filled with a fluid, as the diaphragm 140 is caused to move upward, preferably by the piston 205, toward the fluid port 110, the fluid is expelled through the fluid port 110. For both drawing-in liquid to and expelling liquid from the pump 100, the rate of the liquid flow can be controlled to achieve the desired conditions.

In a preferred embodiment, the diaphragm pump 100 shown in FIG. 1 is designed as a disposable unit for single or very limited use. The pump 100 preferably only has two elements (the upper housing 120 and the diaphragm 140) that ever come in contact with the handled fluid. Thus, by providing an easily removable pump housing 120, 160 along with its diaphragm 140 as a single unit, the contaminated parts can be changed-out after a single use. This prevents having to disassemble the pump, with the associated potential human or environmental exposure to process constituents, which in some cases may be hazardous. Even further, before use, as a single unit the pump housing 120, 160 along with its diaphragm 140 can be delivered assembled and sterilized (by gamma, chemical or moist heat processing) ready for use without the need to expose the fluid path to environment where it can be subject to microbial contamination. Both the upper pump housing 120 and the lower pump housing 160 can be made from inexpensive plastic, ceramic or metal materials designed for single or limited use, such as those discussed in 1997 Association of the Advancement of Medical Instrumentation Technical Information Report designated—TIR17-1997 (hereinafter referred to as “AAMI 1997”). In this way, the pump 100 is preferably disposed or discarded after it has been contaminated during use as a fluid handling element. It should be noted that references herein to the term “disposable” are to elements that are designed to be thrown away or discarded after a very limited number of uses and preferably a single use. The housings 120, 160 can be made formed by machining, stamping, molding or other known techniques for forming such items.

Alternatively, only the upper housing 120 and the diaphragm 140 can be designed or intended for replacement, being the only contaminated parts in the pump 100. Replacing them provides a quick and easy way to replace the pump assembly without taking time for cleaning in critical applications. Also, more of the assembly is re-usable by discarding only the contaminated portions. The upper pump housing 120 and the diaphragm 140 could either be separate or provided in a preassembled state. Either these two disposable elements can be bonded together or temporarily secured using tape or a clamp to hold them together. In this way, these two disposable elements 120, 140 can be added to the rest of the assembly and then secured using a sturdy, reuse-able clamp. As in the embodiments discussed earlier, the clamp is preferably suited to hold the pump together under normal operating pressures and vibrations.

As mentioned above, the motion of the flexible diaphragm 140 draws-in and then expels the liquid in the upper pump chamber 125. The diaphragm 140 is sealed between the upper and lower housings 120, 160 at the diaphragm coupling 130. The flexible diaphragm 140 allows the pump to intake and expels liquid while maintaining a seal between two pump housings 120, 160. The diaphragm is preferably made of a durable, flexible material such as silicone or thermoplastic elastomers, such as those given in AAMI 1997. Preferably, the diaphragm 140 is provided with a bulbous radial flange 142 that acts as a sealing ring when sandwiched between the upper and lower housings 120, 160. Also, the diaphragm 140 can have a reinforced portion at its center 148, as well as other portions (not shown) as desired. In a further preferred alternative embodiment, the diaphragm 140 can be reinforced with fabric or other materials, either embedded or joined to one side (such as the non-fluid-contact side), as might be suited to a particular application.

The upper and lower coupling flanges 128, 162 can be secured using a contemporary sanitary clamp, tri-clamp or a locking collar (not shown). A clamp or collar can provide a simple mechanical means of securing and sealing the pump 100. Preferably, the clamp or collar is made from similar durable but inexpensive materials to those of the upper and lower pump housings 120, 160. Compatibility of materials for these different elements can ensure that all the parts of the pump 100 expand or contract in unison, as a result of temperature or pressure changes.

In a further alternative embodiment, the pump 100 can be made integral with the flexible diaphragm 140, providing a unitary element that is self-contained and easily added to or removed from a fluid handling assembly. To form such a unitary embodiment, the upper and lower sections of a pump housing 120, 160 could be ultrasonically bonded with the diaphragm 140 in place. Alternatively or additionally, the two flanges 128, 162 could be chemically bonded.

The use of inexpensive clamps, collars or bonding techniques is particularly suited for a disposable or single use pump in accordance with the present invention. Because inexpensive materials and assembly techniques can be used to manufacture these elements, economies of scale can make it more cost effective and time efficient to use a new diaphragm pump 100, than to clean and/or re-sterilize those parts for reuse. Cleaning, sanitizing or re-sterilizing a pump between uses involves significant down-time or delays between applications. In accordance with the present invention, the pump 100 is preferably pre-sterilized and delivered to the end user sterile and ready to use. Techniques such as gamma sterilization require large capital investments, and are not generally located on premises to the end-user. Thus, it is advantageous to perform the sterilization techniques during the assembly process and provide a relatively inexpensive product that can be disposed after a single or very small number of uses. With other pumps used in these processes such as rotary lobe pumps, product contact parts cannot be reasonably disposed of after used and some cannot be sterilized where sterilization creates a better quality process by eliminating microbial contamination from a fluid stream versus sanitization that only reduces microbial contamination.

As will be recognized by one of skill in the art, many variations are possible and within the scope of this invention. For example, the pump 100 can be made to any convenient size, from relatively small bench top type systems to large, industrial scale pumping systems. The valve systems, conduit, and vessels described herein throughout can likewise be increased in size and/or capacity to provide pumping systems of various sizes and performance capabilities.

When ready for use, the pump head 100 is preferably secured to the piston housing 200. As with the coupling 130 of pump housings 120, 160, the lower housing flange 168 can be secured to the piston housing flange 222 using a contemporary sanitary clamp, tri-clamp or a locking collar (not shown). Preferably, the piston housing securing mechanism is easily removable, so that pump 100 can be replaced when needed. Alternatively, in certain applications, it may be desired to sterilize the “piston” side of the diaphragm pump compartment. This could be done by autoclave, steam-in-place or other known techniques. This may be desirable if the pump used in a sterile process, such as a filtration process connected to a cell culture bioreactor, where an extra level of sterility assurance was desired.

As shown in FIGS. 6 and 7a-c, a fluid flow path is generally provided from a feed side 10 and pumped toward an outlet side 90. Between those two ends 10, 90 are one or more sets of fluid conduit 20, 80, valves 70 and possibly other connectors. In one alternative embodiment of the current invention, the pump 100 is integrated into a single use flow path, including select conduit, connectors and/or valves. This fully integrated flow path configuration would preferably be sold to customers, assembled and even gamma-irradiated or ready to be sterilized by steam. The flow path could contain a large variety of components such as single use process containers (plastic/polymeric containers/bags), conduit, sensors, filters, and connectors. Thus, as described above, even when assembled in a complete integrated flow path, the connection of the lower pump housing 160 can be made to the piston housing 200 and vacuum system when ready for use. Similarly, the pump head 100 and corresponding flow path conduits could be removed at the end of the process and disposed of without exposing users to the process fluid.

Numerous different valves 70 are available to suit particular applications. Automated valves, tubing pinch valves, or check valves (such as duck bill, ball, spring or flapper valves) can be used to allow liquid to flow into the pump head 100 from the feed side 10 during an intake cycle and prevent liquid from being drawn from the pump outlet 90. Also, the valves 70 preferably prevent liquid, during a pump 100 expelling cycle, from being pumped from the pump head 100 back to the feed side 10 of the pump and only allow it to go toward the pump outlet 90. The valves 70 could be integral to the pump head (not shown) or as shown in FIGS. 2 and 6, integrated into the conduit leading into 20 and out of 80 the pump head 100. Alternatively, separate intake and outlet valves could be integrated into a special upper pump housing (not shown). In the case of automated valves, timing can be controlled by the pump control system 300.

When drawing fluid into the pump 100, a feed side 10 valve is preferably open and an outlet side 90 valve is preferably closed. When expelling fluid from the pump, a feed side 10 valve is preferably closed and an outlet side 90 valve is preferably open. When such valves 70 are automated, in order to synchronize their timing, control equipment is generally employed. Preferably, the same control equipment 300 operating the pump process synchronizes the valves 70.

It should be noted that the upstream fluid conduit 20 (on the feed side of the pump 100) preferably does not need to withstand high pressures. In fact, it is preferred that the fluid flowing through the upstream conduit 20 only be at ambient pressure. While upstream pressure can be supplied to fill the pump head 100, such is not necessary when using a vacuum on the non-liquid contact side of the pump assembly. In other words, the vacuum draws the diaphragm and correspondingly the fluid at the rate set by the piston. However, in contrast, the downstream fluid conduit 80 is preferably designed to withstand higher pump outlet pressures necessary for select filtration and chromatography applications. Thus, the downstream conduit 80 is preferably either reinforced or heavy gauge tubing, hose or pipe. It should be noted that references herein to the term “fluid conduit” or simply “conduit” are generally to elements capable of communicating fluid, such as tubing, hoses, pipes, or channels. It is understood that particular choices of conduit size, materials and design can be made to suit the application.

As discussed above with regard to the materials used for the pump, container and connectors, it should be understood it is preferred that the couplings between the pump 100 should be inexpensive, reliable and easy to manipulate and secure.

As shown in FIGS. 6 and 7a-c, a preferred embodiment uses a pump system with at least two “heads” 100 to deliver continuous flow. A combination of the two synchronized pumps avoids the intermittent flow rate generated by a single pump process. Each pump head 100 preferably cycles from a phase drawing liquid into its pump head, to a cycle expelling liquid from the pump head. Synchronizing the cycles of the two pump heads, generates a liquid flow rate that is relatively constant. The speed of the pistons would control the flow rate of liquid. Also, optimized pump head 100 and piston 205 sizes can achieve a wide range of flow rates and flow rate accuracies. A single head version of the pump described could also be made but it would deliver intermittent flow.

As shown in FIGS. 7a-c, the pump requires a control system 300 to control the piston speed (flow rate) and to make sure the pump 100 is safe to use. The control system 300 may be a stand-alone, as part of the pump 100, or may be integrated as part of a larger control system. A pressure sensor placed downstream of the pump (not shown) may be used to shut down the pump if pressure builds above a user defined set-point. Preferably, valves 75, in combination with the control system 300, direct the choice of one or more liquid input lines 10 from which the pump will draw. Also, the valves 75 can be automated on/off valves, such as automated diaphragm valves, controlling the selection of input liquid. Additionally, because the conduit assembly upstream of the pump 100 is preferably not pressurized, disposable hoses or tubing can be used in combination with automated pinch valves. Pinch valves are preferred for the upstream control system valves because disposable hoses or tubing can be quickly and easily loaded and unloaded. However, it is understood that the valves 75 could alternatively be manually actuated valves.

It should be noted that the fluid can be a homogenous liquid, a composition of disparate fluids or one or more fluids combined with other solid matter. As mentioned above, the fluid is preferably drawn from one or more select feed/supply lines 10 into the diaphragm pump 100 and then expelled to one or more outlet lines 90 toward an intended destination.

While various embodiments of the present invention are specifically illustrated and/or described herein, it will be appreciated that modifications and variations of the present invention may be effected by those skilled in the art without departing from the spirit and intended scope of the invention.

Claims

1. A fluid pumping apparatus comprising:

a first pump housing including a first inner chamber, said first pump housing including a first fluid access port adapted to provide fluid communication between an outside of said first pump housing and said first inner chamber;

a second pump housing including a first coupling flange securedly mated to said first pump housing, said second pump housing including a second coupling flange adapted to be removeably and securedly mated to a third coupling flange on a piston housing; and

a flexible diaphragm disposed between said first and second pump housings, said diaphragm in fluid communication with said first inner chamber, said diaphragm adapted to be displaced by a driven piston for expelling fluid from said first inner chamber.

2. The apparatus of claim 1, wherein said first pump housing, said second pump housing and said flexible diaphragm are disposable.

3. The apparatus of claim 1, wherein said first pump housing, said second pump housing and said flexible diaphragm are sterilized at least one of before and after use as a fluid pumping apparatus.

4. The apparatus of claim 1, wherein said first pump housing, said second pump housing and said flexible diaphragm are permanently secured.

5. The apparatus of claim 1, wherein at least two of said first pump housing, said second pump housing and said flexible diaphragm are permanently secured.

6. The apparatus of claim 1, wherein said first pump housing includes at least one second fluid access port.

7. The apparatus of claim 1, wherein said second pump housing is in fluid communication with at least one vacuum port for depressurizing an inside of said second pump housing.

8. The apparatus of claim 1, further comprising:

a piston assembly including said piston housing and said driven piston, said piston housing removeably secured to said second pump housing, said piston housing including a piston access port for guiding said driven piston, said first pump housing, second pump housing and piston housing forming a continuous unitary outer pump shell.

9. The apparatus of claim 7, wherein said second pump housing and said piston housing are secured by at least one of a locking collar or clamp.

10. The apparatus of claim 7, wherein said piston access port includes at least one of a bearing and seal.

11. A fluid pumping apparatus comprising:

a) a first pump housing including a first inner chamber, said first pump housing including a fluid access port adapted to provide fluid communication between an outside of said first pump housing and said first inner chamber;

b) a second pump housing including a second inner chamber, said second pump housing secured to said first pump housing;

c) a flexible diaphragm disposed between said first and second pump housings, said diaphragm in fluid communication with said first inner chamber;

d) a third pump housing removeably secured to said second pump housing, said third pump housing including a piston access port, said first, second and third pump housings adapted to form a continuous unitary outer pump shell; and

e) a driven piston adapted to move said flexible diaphragm toward said fluid access port.

12. The apparatus of claim 11, wherein said first pump housing, said second pump housing and said flexible diaphragm are disposable.

13. The apparatus of claim 11, wherein said first pump housing, said second pump housing and said flexible diaphragm are sterilized at least one of before and after use as a fluid pumping apparatus.

14. The apparatus of claim 11, wherein at least two of said first, second and third pump housings are permanently secured.

15. The apparatus of claim 11, wherein said first pump housing includes at least one second fluid access port.

16. The apparatus of claim 11, wherein at least one of said second and third pump housings is in fluid communication with at least one vacuum port for depressurizing said second inside chamber.

17. A chromatography pump assembly adapted to deliver fluid at a constant flow rate, said pump assembly comprising:

(a) a first conduit for receiving fluid;

(b) a second conduit for expelling fluid;

(c) a first and second diaphragm pump in fluid communication with said first and second conduits, each pump including i) an inner fluid chamber, ii) an inner flexible diaphragm, and iii) a rigid drive mechanism adapted to push said diaphragm thereby expelling fluid from said inner fluid chamber; and

(d) a valve system adapted to block fluid flow from said first conduit to one of said first and second pumps, while simultaneously blocking fluid flow to said second conduit from the other of said first and second pumps.

18. The assembly of claim 17, wherein at least one of said first and second diaphragm pump is disposable and adapted to be easily removed from said assembly.

19. The assembly of claim 17, wherein at least one of said first and second diaphragm pumps is sterilized prior to use as a part of the assembly.

20. The assembly of claim 19, wherein said assembly is adapted to sustain a closed sterilized environment for fluid handling.

21. The assembly of claim 17, wherein each of said pumps further includes a vacuum coupling for depressurizing a portion of said pump, whereby said diaphragm draws fluid into said inner fluid chamber.

22. The assembly of claim 17, wherein said valve system is further adapted to alternatively block fluid flow from said second conduit to one of said first and second pumps, while simultaneously blocking fluid flow to said first conduit from the other of said first and second pumps.

23. A method for pumping a fluid comprising:

providing conduit adapted to communicate fluid from at least one source to at least one destination,

coupling a first disposable diaphragm pump to an intermediate position of said conduit, said first diaphragm pump adapted to expel fluid by activation of a driven piston,

securing a piston housing for said driven piston to said first pump thereby said piston housing and said first pump forming a unitary continuous outer pump shell,

initiating said driven piston thereby pumping fluid out of said diaphragm pump,

removing and discarding said first diaphragm pump after a single use, and

replacing said first diaphragm pump with a second diaphragm pump.

24. The method according to claim 23, wherein said diaphragm pump includes

a) a first pump housing including a first inner chamber, said first pump housing including a first fluid access port adapted to provide fluid communication between said first inner chamber and said conduit,

b) a second pump housing including a first coupling flange securedly mated to said first pump housing, and

c) a flexible diaphragm disposed between said first and second pump housings, said diaphragm in fluid communication with said first inner chamber.