The importance of diaphragm traceability

How much garden hosepipe have you installed in your biopharmaceutical processing plant recently? Hopefully none — the risk of contamination associated with such a reckless act would be catastrophic.

Of course, there is a certain amount of non-stainless steel material in every system, but have you ever stopped to think just how much? If you made the calculation, you might be horrified at the result. Recognising the potential risks, the R&D team at Crane Process Flow Technologies (CPFT) has developed a tool that calculates the total wetted surface area for a mix of valves and weirs. For a simple comparison – or as it turned out a frighteningly graphic picture of the magnitude of that risk – this tool illustrates the result as a length of hose.

Key component For example, a typical processing system incorporating 1,000 sanitary and aseptic valves of varying sizes would contain a total diaphragm wetted surface area of around 10.25m², which equates to 161m of 20mm nominal bore hose (see table on p32). It is not uncommon for a biopharma-ceutical processing plant to use hundreds, even thousands of diaphragm valves. The diaphragm itself is the key performance component within the valve, but it can be a potential source of process environment contamination. So if you consider the combined wetted surface area of these diaphragms, the issue of elastomer selection is seen in full perspective. The CPFT tool enables a visible demonstration of the importance of using fully traceable diaphragm material in hygienic applications. It also allows the user to visualise his total diaphragm wetted area and, hopefully, understand the implications and associated risks of not using fully traceable components.

Starting point It is important that elastomers employed in aseptic applications conform to the Food and Drug Administration (FDA) Code of Federal Regulations, chapter 1, title 21, part 177, para 2600 Rubber Articles Intended for Repeated Use and para 1550 Perfluoro-carbon resins, issue revised April 2002. However, FDA conformance is just the starting point in ensuring that the diaphragm supplied meets quality and performance characteristics. CPFT elastomeric diaphragms used in the Saunders HC4 range are manufactured from a formulation of raw materials that have been precisely weighed and combined into a compound by controlled intermixing and milling operations. The uncured or un-vulcanised compound is then "calendered" into continuous 100m sheets, forming the basis of the diaphragm's internal structure (see diagram, left). Physical properties of the elastomer are determined during the latter stages of the blending process, and a representative sample is subjected to a number of analyses, including rheometer (a measure of vulcanisation characteristics), tensile strength, hardness and elongation parameters. Unique identification numbers are moulded onto the finished diaphragm that trace its manufacturing history back to the initial blend. This historical information enables the product to be rigorously investigated right back to its source, which is a vital route in the event of a problem during use, and acts as a guarantee that it conforms to the supplier's specification. In addition, CPFT provides certification of the physical properties of each batch to ensure product consistency, supported by a complete documentation validation package for all diaphragms that make contact with bioprocess media. Elastomers are a complex mix of ingredients and are selected to provide the desired properties for both the functions of the component and its intended application. The ingredients will certainly include a base polymer, activators, fillers and curing agents, and may be augmented with process aids and accelerators. All can affect the properties of the elastomer.

Critical importance Unfortunately, some users underestimate or even overlook the critical importance of elastomeric components. The consequences of such oversights may lead to contamination of the line media or even plant stoppages, both of which will inveitably result in financial implications. All Saunders diaphragms are developed and manufactured in-house, allowing CPFT to take complete control of technological advancement and design. Saunders diaphragms have also been tested and certified in accordance with USP Class V and VI by an accredited independent test laboratory.

Full traceability For many years the bioprocessing industry has demanded that all stainless steel components are supplied with full traceability, but then relegated polymers to merely complying with FDA Drop Register. As valuable as FDA compliance is, it does not provide the customer with any physical characteristics or provide any indication of performance level within the process. Now, however, there is a shift in focus towards fully traceable polymer components and the industry is beginning to demand real vigilance in this key area. In conclusion, the role of elastomers in bioprocessing systems tends to be underestimated but can be critical. The technology is available to manufacture diaphragms to the traceability requirements of EN 10204.3 1b to complement the stainless steel content of processing systems. Choosing a diaphragm manufactured from an elastomer compound that complies with FDA regulations and is certified to USP 25 can mean ease of validation and confidence in product quality and purity. Fully traceable diaphragm valve materials offer a guarantee that the product quality conforms to the customer's specifications and significantly reduces the risk of contamination from unknown materials entering the process. The pharmaceutical industry increasingly regards traceability of materials as an important factor in avoiding contamination in sterile environments. When choosing a diaphragm valve it is paramount that the same standards should apply.