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Radial Diaphragm Tank-Bottom Outlet Valves

The Rattiinox CAD aseptic radial diaphragm tank-bottom outlet valve represents the latest advancements in both radial diaphragm valve and tank-bottom outlet valve design.  Rattiinox CAD (Clean and Aseptic Design) radial diaphragm valves have been engineered for use in the most demanding process applications.  The description varies but whether you describe your process as sanitary, high-purity, sterile or aseptic, your valves must be cleanable in place, sterilizable in place, reliable as well as easy and fast to service. Some of the typical applications for the CAD valves are in media preparation, fermentation, harvest, filtration including critical separation, concentration and purification steps.  Additional applications where the CAD valves are also ideal is high-purity water distribution loops, water and product sampling and of course tank-bottom outlet service.

Rattiinox CAD Tank-Bottom Outlet Valves
Rattiinox CAD Tank-Bottom Valve

The Rattiinox CAD radial diaphragm valves have a single body seal and are self-draining with no entrapment areas. Other valves are characterized by multiple body seals that risk the entrapment of stagnant product between the various seals.  Valves that have multiple seals increases the risk of process cross contamination and should be avoided at all costs.  The Rattiinox CAD valves have seals that are at 90° and fully open for easy, fast and perfect cleaning.  Other sanitary valves are designed with body closure as well as product path seals that have asymptotic angles that are hard to clean because of the reduced velocity in the ever decreasing angle.

Membrane Valve Asymptotic Seals
Membrane Valve Asymptotic Seals

The Rattiinox CAD valves fitted with the precision machined solid PTFE diaphragm have shown excellent service life, which in most cases is rated in years.  The unique design also allows removal of the diaphragm from the valve for inspection and re-installation without negative effects.  The CAD valve diaphragms can be changed very quickly and the reduced need to change diaphragms in the first place represents real maintenance cost savings!

Rattiinox CAD Tank-Bottom Outlet Valves
Rattiinox CAD Tank-Bottom Outlet Valve

It is well known that the clamping force for TC connections is not uniform. Unlike valves that use a clamp connection, the stainless steel seal ring on the Rattiinox CAD valve provides complete 360° pressure on the entire diaphragm. The Rattiinox CAD valves save maintenance down time as it can take less than a minute or two to change a diaphragm.  The valves feature a unique stop feature that prevents over tightening of the diaphragm.  The CAD valve is the first diaphragm valve (radial or membrane) to be engineered to use a solid PTFE diaphragm as the primary option.  Rattiinox CAD valves fitted with the standard PTFE diaphragm seal against pressures that far exceed standard bioprocess applications which increases your reliability safety margin.  Independent testing has purposefully stressed the CAD valves to pressures upwards of 90 bar and 0.92 bar vacuum with no leaks or ill-effects on the diaphragm.  This level of safety and reliability is simply not available from elastomeric based valves.

Rattiinox CAD Tank-Bottom Outlet Valves with Satalite valve with tangential outlet
Rattiinox CAD Tank-Bottom Outlet Valve with Satalite valve with tangential outlet

The Rattiinox CAD valves have been tested at temperatures above 160°C (320°F) for extended periods of time without damage.  Testing was performed with cycle times counted in seconds instead of minutes and the duration of testing lasting months instead of days.  In all cases the valve body and process seals hold 6 bar (90 psi).  Real word clients commonly report service life of the diaphragms in many cases over two years in high cycle process applications.  The Rattiinox CAD valve is a true flush bottom design and is highly adaptable to many challenging requirements.  The valves do not have a pocket or double body seals and are fully drainable.  As you would expect, the CAD tank-bottom outlet valve is generally welded flush to the bottom of the vessel. In other configurations the CAD tank-bottom valves can be flange mounted, welded into the knuckle of the tank or machined directly into the bottom dish.  And as you might also expect the Rattiinox CAD tank-bottom outlet valves can be ordered with a closed fitting satellite valve for cleaning and steaming behind the main diaphragm. These valves can have an eccentric outlet that eliminates the standard downward elbow for applications where the vessel bottom has limited clearance.

Rattiinox CAD Tank-Bottom Outlet Valves
Rattiinox CAD Tank-Bottom Outlet Valve

No matter your applications, the Rattiinox CAD valve has the ideal valve configuration to allow you to concentrate on other process issues instead of managing the maintenance of your valves.  Which is why we say the CAD valve is one valve with many solutions.

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Valve reliability in aseptic process systems

Rattiinox CAD valves

Aseptic Process Systems

Over the last couple of decades aseptic process systems in the pharmaceutical industry have evolved from small molecule, chemical based systems to large molecule biological processes.  With this evolution has come a change in process designs that includes but is not limited to clean in place and sterilize in place systems as well as an increasing regulatory burden.  Not to mention the increase in use of disposable systems.  It has been suggested that valves, system dead legs and unused piping as well as poor performing elastomers used in gaskets and seals are key areas for improvement in aseptic bioprocess systems.  In as much as the industry still relies on stainless steel based systems, it is important to note that some of the key equipment, most notably, membrane valves, commonly referred to as weir valves and their installation into the process have not changed much in this time.

The following compares today’s membrane valves to the latest generation of aseptic radial diaphragm valve manufactured by Rattiinox S.r.l.  The radial diaphragm valve is a design approaching its 25th anniversary.  One key difference from membrane valves is that it is based upon a right angle flow path.  In this way the sealing point is at the outside limits of the valve.  The Rattiinox CAD valve is the latest generation of radial valve and the first engineered around a solid PTFE diaphragm.

An old adage states that the devil is in the details.  Another adage states, that if you want to clean it, don’t hide it.  In the case of membrane valves, the devil is in the small areas of the valve that are very difficult to clean quickly and reliably.  The reason is that all membrane valve designs result in several areas that include an asymptotic “dead leg”.  This has been known for some time. The asymptotic angle is such that it approaches zero the closer it is to the seal point.  This creates an area of low velocity and low turbulence.  Both conditions inhibit quick and thorough cleaning.  Another feature of membrane valves is that the valve design incorporates a dead leg into the body.  This is unavoidable because of where the valve seals.  By contrast the Rattiinox CAD valve incorporates stationary, open seal points that facilitate cleaning.  There is no place for product entrapment.  The turbulence created in the valve also helps reduce the possibility of biofilm formation.

The CAD valve diaphragms are precision machined from solid virgin PTFE block.  This material is well known for its broad chemical and heat resistance and very low E&L profile that is well understood.  The diaphragms are internally supported by a mirror polished stainless steel armature that also acts as a pressure contrast system, providing support against high pressure and vacuum.   The CAD valve diaphragms also have a much longer life compared to flat membranes.  Testing above one million cycles at temperatures above 150°C has been achieved with no discernable wear.  At the same time sealing to pressures at 6 bar at -60°C is standard.

There are literally hundreds if not thousands of valve styles available however this number shrinks dramatically when discussing valves suitable for today’s sanitary and aseptic processes.  Almost by default, membrane valves constitute the vast majority of valves currently used in sanitary process design for pharmaceutical systems.  It is suggested that this tool kit is outdated because of the new demands placed on these systems.  Some will argue that today’s process systems do not need to be aseptic because of final terminal sterilization steps.  However, this line of reasoning does not take into account the costs due to lost product and additional work as well as the costs involved with repeated occurrences of membrane failures and elastomer material breakdown due to chemical attack from CIP and SIP steps.  It seems it would make at least as much sense to strive to reduce or eliminate these occurrences and the resulting deviations as much as possible.

Because most every valve in a system can be considered unique simply because of where it is placed, Rattiinox has developed over 100 different versions of the CAD valve across the various sizes from ½” to 4”.  This allows system engineers flexibility to select the correct valve for every location to insure there are no dead legs and to achieve the ultimate goal of full drainability and product recovery.  Tank bottom outlet valves and take off valves on high purity water systems are well known applications for radial valves.  However there really are no aseptic process applications were the CAD valves’ superior geometry and drain-ability are not improving the overall process.  It is interesting to note that skid systems designed with CAD valves tend to have a smaller foot print and overall lower system volume which is certainly a benefit when dealing with today’s high value drug products.

Forward thinking engineers should realize that problems, especially those that are repeat offenders are opportunities for improvement and should be catalyst for change.  Valves with poor performing diaphragms, and to a large extent gaskets that deform and stick, are often considered normal conditions because of the frequency that these issues occur.  However there are solutions to these issues and it involves using the correct materials and designs.  Our industry will continue to rely on stainless steel systems for large scale GMP production.  It only makes sense to improve these systems to be easier and faster to clean and more reliable to sterilize, operate and importantly, validate.  There is a new right way to a better end result which can be achieved by paying attention to the details.