Wallace Wittkoff, global product engineer for Wilden Pump & Engineering, discusses the benefits of air operated pumps for fluid and product transfer in the biopharmaceutical industry
The terms batch or continuous, cleaning validation, product containment, separation of process and mechanical equipment are all central issues surrounding modern biopharmaceutical processes. At the heart of these issues is how fluids get transferred in these processes. Air operated double diaphragm pumps offer new options and solutions to traditional methods.
Because of the inherent challenges of biopharmaceutical processes, fluid transfer solutions have lagged compared to other industrial and even hygienic processes. For example, manual container, gravity or nitrogen purge transfer systems are commonly found in critical product transfer process applications. These types of product transfer processes are becoming rarer everyday, however these types of applications are still prevalent in some industries. To see evidence of this look at the history of process facilities and note how they have tended to be multi-storey.
In a manual container transfer system, the products are produced and placed in a container that is transported to the next process. The benefits and drawbacks of this are well understood. In a gravity system, the product must flow down during the process. Vertical plant space in today's modern plants may not be available to accomplish this.
Inert gas purge systems generally use nitrogen to transfer fluid, accomplished by pressurising the source vessel so that the fluid is forced out to its intended destination. Inherent dangers of sparge pressurised vessels and difficulty of implementing CIP (clean in place) systems with the purge method are some drawbacks. However, both gravity and purge systems offer containment and delicate handling of the product, as well as other value added benefits.
The water for injection (WFI) loop is today the most common use of high purity pumps in the industry. Neither gravity nor nitrogen purge can meet the constant demand of process water throughout an entire plant. As this water must be in continuous circulation with no static areas, the solution here is to use sanitary centrifugal pumps modified to meet the demands of WFI by employing high purity stainless casing drains, high polish and double mechanical seals with flushing systems.
Manufacturers have also improved the design of positive displacement lobe-type pumps for applications requiring positive transfer of viscous and sometimes shear sensitive materials. While both centrifugal pumping technology and rotor/lobe type positive displacement pumps have been around for a century or more, the evolution of this pump to meet the biopharmaceutical industry has only occurred within the last 10 to 15 years. Upgrades in material purity, such as switching from castings to fabricated metals, improvements in seal technology, higher polish and hygienic standards have helped the evolution of this pump for a wider range of appropriate biopharmaceutical applications.
The air operated double diaphragm pump (AODDP) is a more recent solution in fluid transfer for the biopharmaceutical industry and has already established a key role. The technology was invented and patented by Jim Wilden, founder of Wilden Pump & Engineering.
There is a good reason for the rapid uptake of AODDP technology in high purity processes. This is best illustrated by the AODDP's close cousin, the diaphragm valve. The diaphragm valve has for a long time been the choice valve for high purity processes. The main issue is product containment. Both the diaphragm valve and diaphragm pump both share the common traits of a containment, low shear, sealess stem or shaft-free functional solutions. The AODDP option is becoming a more viable solution for many engineers in the biopharmaceutical industry.
In order to meet all biopharmaceutical needs, a design utilising the latest AODDP technology has been introduced. The Wilden UB pump, also known as the Biocor, is designed to meet critical process requirements 'out of the box'. These include high purity, high polish, traceable materials with 3-A and EHEDG certifications as well as certifiable elastomers with appropriate FDA and USP class VI approvals. These pumps have achieved the goal of being in the same class as other hygienic pumps that have biopharmaceutical certifications for CIP and SIP (steam in place) duty.
For some applications, the cleaning validation requirements may be impractical. For these applications, pumps are available that are ultra-pure and yet disposable, such as Wilden's UA series pumps. These pumps feature chemical resistance and purity from solid machined PTFE. Pumps such as the Wilden UA are suitable when change over is necessary, because they do not allow product cross-contamination. In some cases the cost of cleaning a traditional pump would exceed the cost of a new pump and therefore a reliable, yet disposable pump is the best option.
Examples of applications for AODD pumps in biopharmaceutical processes are as follows:
- Chemical Feed: This is the first and most traditional role for AODD pumps and results from the safe, sealess, contained and positive feed capability for volatile or potent chemicals, including solvents, buffers, acids, and bases.
- Sampling: Complex biological or chemical reaction processes under very strict conditions require frequent and multi-point sampling. The ability to extract these samples with a negative suction condition, the maintenance of a high degree of containment and avoidance of cross-contamination are key features.
- Product Transfer: The AODD pump removes current limitations of gas purge systems for continuous processes. A purge type transfer requires that a process is either filled or emptied at separate times. However, a pumped system would allow both processes to occur at the same time. Using an AODD pump would still keep the system contained and pure much like the purge systems.
- Chromatography, Separation, Purification and Filter feed/discharge: These processes frequently require shear sensitive transfer and constant pressure feed, attributes that are found in AODD pumps equipped with pulsation dampeners. As solvents or potent products are involved, high containment along with classified area configured pumps are required and AODD pumps fit this need.
- CIP Fluid and Joint CIP/ Product use: A product transfer process line and its respective CIP circuit often overlap, requiring a pump that accommodates both needs. Inert gas purge systems illustrate this challenge. The process reactors for these systems must be cleaned using tank spray ball devices. If the product residue and cleaning chemicals cannot be drained to a floor drain, a pump is required to recover and remove the CIP fluid return. For optimum cleaning of the reactor, the fluid level cannot rise during cleaning, otherwise a 'scum' line will form at the fluid surface and result in deficient cleaning. The self-priming and dry-running capabilities of the AODD pump make it ideal for this service.
- Product Recovery and Sludge Removal: The dry-running, self-priming, full containment product capabilities of AODD pumps make this an ideal application as product or waste extracted from many filtering or separation processes may be intermittent.
AODDP is the only pump technology that can be split so that the 'power side' is mostly located remotely in unclassified areas where the fluid end can be placed remotely as needed within the classified area. The only connection between the two is an air supply line. Electric motors, oil-filled gear cases and greased bearings for pumps no longer have to be located in the clean area.
While each application should be studied for the correct fluid transfer solution, the air operated double diaphragm pump, much like diaphragm valves, is the pump of choice for many applications. Pump suppliers and distributors can provide assistance, resolve challenges and offer practical solutions.