True Aseptic Design

True Aseptic Design

2017-02-24

Single use technologies are the currently focus for many in the Biopharm community. Estimates predict the yearly turnover for this market segment to grow into the Billions of dollars. The major players in single use technologies have invested heavily in acquisitions and development to bolster their offerings. The financial commitment alone will guarantee this outcome. However, when considering single use technologies the conversation should not be confined only to plastic components and flexible bags. Stainless steel can also be single use if you believe in yourself and try hard enough!

All kidding aside, the economies of scale of stainless steel systems are simply too great to ignore completely. Economics, coupled with the general risk of single use systems assure that stainless steel process systems will be with us for some time. After all, putting millions of dollars of product at stake in a plastic bag carries with it some amount of risk. With all of the advancements and research being poured into single use technologies is it any surprise that suppliers of stainless systems and major system components, such as valves, have for the most part settled upon decade’s old designs? With end users, the logic is that it’s validated,  this is the way we’ve always done it, and we don’t have any issues  has in many cases been a barrier to the introduction of technology advancements.

The soft parts in these systems – gaskets and valve diaphragms, play critical roles in control and maintaining a sterile barrier. Proper selection and maintenance of these soft parts contribute significantly to operation expenses.  However in many cases it is the dead legs and un-used portions created by T’s and the improper application of valves that create and add to the problem.

Industry groups ASME-BPE and BPOG estimates suggest the change-out programs of soft parts accounts for over 50% of all planned maintenance activities. In addition, issues with critical elastomeric components not compatible with today’s CIP and SIP operations are responsible for 20% of equipment related deviations and 10% of all corrective maintenance. In short, soft part issues represent the number one contamination risk in stainless steel systems.

These user focused Industry groups have recently spent considerable time and effort to evaluate valve diaphragm change outs.  They are rightly concerned with the excessive replacement costs and unpredictable failures.  Previously this work had been focused on gaskets. The result with gaskets was a clear performance criteria and ranking for the various EPDM elastomers designed for biopharma applications.  With regards to valve diaphragms the challenges are greater due to the dynamic properties required of the EPDM diaphragms.  Regardless if the diaphragm is in direct contact or employed as a support backing to a fluoropolymer diaphragm face, the elastomeric properties are critically important. The primary focus has naturally been on weir style valves that constitute the vast majority of hygienic valves in use.

The work being done today in developing and testing EPDM compounds suitable for long term use on bioprocessing systems is commendable.  However it is not clear how extending the life of single piece EPDM and two piece EPDM/PTFE/PFA diaphragms will affect long term contamination risks. It is therefore important to understand the role compression set plays in the performance of these EPDM elastomers.

Under compressive pressure and at elevated temperatures that are close to sterilization temperatures, many EPDM compounds will deform under this load and will eventually become brittle.  These changes will affect the body seal and dynamic performance of the diaphragm.  This change starts with the very first steam cycle. One typical example is these valves in vacuum conditions, it is widely known that the two piece diaphragms do not fare well when hot and put under vacuum.  While gaskets are by design a static seal, weir valve diaphragms do not have a static body seal, the small movements in this area can contribute to bypass, and in addition the diaphragms have to be supple enough to stretch. For this reason EPDM compounds for gaskets should be different than valve diaphragms.

Improving diaphragm performance is no doubt important but the key process design issue remains the continued use of weir valves and the introduction of dead-legs into critical piping systems.  In addition weir valves do not offer a true aseptic valve design. Some may argue that their systems need only be considered sanitary and not aseptic. But this is taking a narrow approach to the ideal of maintaining the highest level of product safety along the entire process chain by eliminating contamination whenever and wherever possible.

Important is the physics of the interface between the diaphragm and the valve body that introduce an asymptotic dead leg. This seemingly infinitely small area of little concern is in reality an incredibly large cavern of sorts to the average microbe. This small area is prone to low velocities and thus is an inherently difficult area to clean. Sterilizing kills any leftover product in this area, but actuation of the valve can also introduce the new batch to this same material and thus is a potential source of downstream cross contamination.

The significant point is that there are valves that offer a true aseptic design. With proper application these valves eliminate dead legs and can greatly reduce unused portions of piping. These valves have a single positive body seal which eliminates product bypass. The added bonus is the precision machined PTFE valve diaphragms operate reliability at cryogenic temperatures on the low side, to temperatures far in excess of normal sterilization temperatures. The valves as standard have two readily validated product contact materials, EN 1.4435-BN2 and PTFE USP Class VI-121°.  The valves are highly corrosion resistant and widely compatible with today’s biopharmaceutical fluids.

This wide performance range of a true aseptic valve should interest reliability and quality engineers. Additionally the ability to optimize process systems by eliminating dead legs and reduce piping should also interest design engineers and production managers.

Sensitive biopharmaceutical products and the systems in which they are produced need to be treated with special care. It may seem obvious but those working in the stainless segment of our industry must continue to expand their knowledge base and tool kit. There needs to be freedom to investigate new methods and opportunities to optimize their processes in order to keep stainless steel systems viable well into the future.

CAD valves are designed to properly address piping configurations upstream, around and downstream of process vessels. The family of CAD valves is also available in unique ready to use assemblies and offer a wide range of application solutions.  The CAD valves are engineered to easily able to deliver a compact design, free of dead legs, allowing the absolute minimum solution hold up.  The valves are constructed from two materials: EN 1.4435-BN2 and PTFE USP Class VI-121° which assures the widest range of material compatibility. Processing with CAD valves, will provide you an efficient process system, simple, reliable, and easy to validate.

 CAD valves benefits:
- Complaining CIP-SIP Cycles
- No unused portions
- Flush flow design
- Easy process Validation
- Wide range answering applications needs
- Extensive tech documentation for Validation

 CAD valves are the key tools able to help you that critical criteria are easily satisfied.

 

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