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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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Glucose Feed Lines

Addressing the cleanability of glucose feed lines is a key maintenance issue for many process engineers working with large-scale fed-batch processes with Escherichia coli (E-Coli) fermentation systems.  The following solution was developed in response to a client who has on-going cleaning as well as maintenance issues with their systems.  The client supplied the following P&ID diagram and provided the following details:

Existing glucose feed system
Glucose Feed Initial PID

“The glucose is fed from a 2″ header and the actual take-off lines are 3/4″.  From the header there is a 4″ dead leg to the shut-off valve.  The process requires steaming this line prior to take-off all the way to the trap and waste line.  The diagram shows quarter turn ball valves which are an on-going cleaning and maintenance issue.  Sugar build-up in the valves prevents sealing as well as leaking through the valve bodies on three piece valves.”

The client has used weir style valves without success.  Like the ball valves the weir valves suffer with sugar build-up on the weir.  The other issue is that the client reports that the nuts on the weir valves “back-off” after steaming.  I will get to that in a moment.

To better understand the “as built” system the original P&ID was sketched out in its real life orientation.

Glucose Feed Proper orientation

Glucose Feed Proper Orientation

In the sketch above it is easier to visualize the multiple dead legs in the system and the unused portions that trap the glucose prior to steaming.

The following sketch imagines how the same system could be designed using the Rattiinox CAD valves which would eliminate the dead legs in the process.

CAD valve PID
Glucose Feed CAD Valve Sketch

Pictured below is the proposed Rattiinox engineered solution that would eliminate the problem with sugar build-up from the steaming operation as well as improve cleaning and sterilization by eliminating the dead legs.  Note: The system could be further optimized by using CAD valves at the steam and PW drops.

Glucose Feed System using CAD valves
Glucose feed system engineered using CAD valves

A few things to point out with the Rattiinox engineered system.  One important change is the addition of a purified water feed for flushing the system prior to steaming.  This will address the cooking of the glucose during steaming.  The CAD valves are a better choice in this case because the turbulence in the valves results in better flushing with no chance of glucose building up as in the crevices of the ball valves or at the diaphragm body interface with the weir valves.  The image below shows one possibility of the Rattiinox CAD valve take off solution that combines the valve on pipe as well as the rinsing and steam valve machined from one piece.  There of course are other options that includes the satellite valve as a stand alone valve.

Rattiinox CAD valve on pipe
Rattiinox CAD valve on pipe

The image below shows the Rattiinox low point drain assembly.  With the pT 100 located at the lowest point, sterilization of all the upstream piping can be easily and quickly validated.

CAD Valve Bottom Drain Assembly
CAD Valve Bottom Drain Assembly

 

Bottom Drain Assembly
Rattiinox low point drain assembly. Designed to plug in to existing systems in a compact design.

 

Regarding the customer’s comments about the nuts on the weir valves backing off after steaming, this is likely not the case.  It has been well documented that many EPDM elastomer compounds used in our industry are not well suited for steaming applications.  What we have seen in many cases is that EPDM compounds that have a high compression set will readily deform under load.  So under the pressure of the bolt torque in combination with high temperatures the EPDM backer is becoming thinner which gives the appearance of the nuts backing off when in fact they are losing torque because the diaphragm has failed.  Repeated torquing accelerates the process.  The Rattiinox CAD valves with the solid PTFE diaphragms do not encounter this problem and can be steamed repeatedly without losing compression which results in lower overall costs associated with valve maintenance.

 

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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.

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Double Position Sensor

Double Position Sensor for Aseptic Valves

Today’s biopharmaceutical processes are highly automated in order to maintain strict control over each process step and operation.  Many of the sensor packages available today are very large, heavy and require technicians to open each device in order to wire and calibrate it for the valve.  There is a better and faster way.

SEND – The Double Position Sensor from Rattiinox provides an indication on the state of the pneumatic valve and on the extended 90° manual actuator, giving the possibility to record the opening and closing position of the valve.  The sensor is easy to program using the CAD Hand Held Programmer (YACT-SENP-0XC0-X0000) or automatically via PLC.  The same sensor is used for all sizes of CAD valves from 1/2″ to 4″ thanks to the already included adapters.  There are no calibration adjustments to be made inside the sensor making set-up and calibration of one or 1000 valves very fast.

 

Like all of the normally open or normally closed pneumatic actuators for the CAD valve, the double position sensor is manufactured from stainless steel.  The smooth finish makes it easy to wipe down if necessary.  The three color LED indicating light allows for 360° viewing and has an IP67 rating.  Via a set screw, the sensor housing can be rotated 360° so that the communications cable is located in the optimal stress free position.  The sensor module mounts to the top of the actuator with a simple threaded connection.

Double Position Sensor
CAD Double Position Sensor

Clean and Aseptic Valves of CAD Product Line have simple and safe design, with their full drainability, without asymptotic seal and dead leg, are offering fast cleanability and sterilization practices. They are designed to fulfill the stringent demands of CIP-SIP and Production Cycles on Aseptic Processing.

Double Position Sensors
Double Position Sensors on automated CAD aseptic valves
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Low Point Drain Assembly

Typical bottom point drains in pharmaceutical installations for aseptic processing are composed of a large CIP drain valve and a smaller valve for the condensate drain. These valves may have a common inlet, but the two outlets have to be separated and work alternately according to the upper running process: CIP or SIP. An additional connection has to be added and this connection should be as close as possible to the closure areas of the two valves in order to connect the temperature transmitter. This close coupling allows accurate detection of the temperature level on the lower part of the installation to be sure that during SIP cycles, the entire system is running at the required temperature. Welding of all the components of this system together require repetitive and sometimes complex work due to the fact that the height available is often very limited.

Bottom Drain Assembly
Rattiinox Bottom Drain Assembly

Rattiinox CAD Bottom Point Assemblies are the answer to this need. Two different designs are available according to the requested steam trap. Both types are available in two main sizes: 3/4” valve for CIP drain valve + 1/2” for condensate drain valve or 1” CIP drain +1/2” condensate drain. Both systems have all required Tri-Clamp connections and can be connected to the installation in few minutes, saving hours of on-site work and speeding the finishing of the installation. The CAD Bottom Point assembly will result in a very compact design with a final quality not possible when compared to the same work done with typical tools available during on-site or skid fabrication.  The desing is also flexible.  The product inlet and temperature sensor connections are reversible.

When coupled with an aseptic diverting valve instead of the common “sterile access point” valve, a true zero dead-leg can be achieved on the process side resulting in greater product recovery as well as better and faster cleaning and sterilization.  The two valves work together to provide a block and bleed system.

The design temperature range of -80 to 200 ºC (-112 to 392 ºF) and design pressure of the valve body from -1 to 10 bar (-14.5 to 145 psi) allows these assemblies to be safely specified for all common process applications.  As always the applied actuator and diaphragm may have different design temperature and/or pressure limits. The weakest component determines the maximum design temperature and pressure limits, when they are assembled.  The low point drain assemblies come standard with a internal surface (manually polished) of Ra ≤ 0.3μm (16μin) and an external surface polish of Ra ≤ 0.5μm (20μin).  Electropolishing  is also available.  Each valve body is labeled for full LOT traceability with Certificate of Conformity and Materials Certification 3.1.  Rattiinox maintains a strict Quality Assurance System which guarantees the control and traceability of the product.  CAD valve are classified for PED Directive 97/23/EC and fulfill ASME BPE Standards.

The low point drain assembly from Rattinox is precision engineered for the most stringent aseptic process requirements.

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Improving Hygienic Design

What do you consider to be the most important benefit of Single-Use solutions?  

According to Aspen Alert’s 7th Annual Single Use Market Survey the leading answer is Reduced Cleaning at 39% followed by Ease of Use at 31% and Quick Turnaround at 23%.  Coming in a distant fourth in the survey was Cost Savings at 7%.  Since our initial involvement with the introduction of the first wide scale implementation of single-use technology in both the upstream and downstream process, single use technologies of all types have gained the vast majority of press coverage and one could argue, overall interest from the customers we serve.  Some market analysis predict this trend to continue but will eventually reach some type of equilibrium with stainless steel systems.  It is interesting that in the face of formidable competition from single-use systems, the design of hard piped stainless steel process systems has changed very little.  The industry group ASME-BPE has moved in several areas to implement adaption of standardization in specifications and dimensions but overall system piping design has changed little.  Independent research and indeed practical knowledge point to several key areas where hygienic piping systems can be improved.

The standard piping  “T” with the leg in either the “up” or “down” position has been shown to contribute significantly to a reduced ability to clean and sterilize.  Many times the “T” in a process system, is created with a weir style diaphragm valve.  Due to the inherent design of the weir valves, a dead-leg is built in to the valve and subsequently the piping system.  Weir valves also present issues with reliable “fine” cleaning at the point where the diaphragm meets the valve body.  The last piping component which has been widely overlooked is sanitary clamp gasket seals.

The standard “T” presents problems for cleaning do the creation of areas of low turbulence and in the case of the inverted “T”, an air pocket which affects both cleaning and steam sterilization.  Of course having the “T” with the down leg presents challenges in flushing the area with enough turbulent flow to clean and then with enough steam over time to heat the collected condensate.

In the real world, the standard “T” and the associated dead-legs can be reduced but not eliminated when using the industry standard kit of weir valves.  And while the radial right angle valve design greatly improves on the weir valve, there are several versions that create problems because of a dual body seal and bellows design of the diaphragm.  Weir valves also suffer from the problem of the body seal having to act as both a static and dynamic seal.  This movement invariably has the effect of pumping product between the valve body and the diaphragm.  This design also creates an asymptotic or infinite angle dead-leg which is very difficult to clean and takes time.

The preferred material for sanitary piping systems is the EPDM based rubber compound.  However recent independent testing proves not all elastomers are the same.  For years, bioprocess engineers have struggled with poor performing EPDM sanitary gasket and O-ring seals.  The market has viewed all EPDM elastomers as a commodity and so looked predominantly at price as a deciding factor.  The prerequisite for an EPDM gasket to be suitable for service was based on the elastomers ability to pass various laboratory tests against cyto-toxicity as well as leachables and extractables.  Unfortunately, passing the USP Class VI tests has no bearing at all on how an elastomer will perform in today’s demanding CIP/SIP bioprocess systems.  One key aspect of an elastomers performance is known as compression set.  This is the amount of permanent movement an elastomeric article will have under load (pressure and temperature).  The smaller the number the better.  Gaskets with a high compression set will squeeze into the inner pipe diameter, acting as an orifice plate of sorts.  This in turn creates a number of problems that must be addressed.  Once protruding into the ID of the pipe the gaskets create small dams that prevent complete draining.  This can adversely affect an entire CIP system or flow rates for critical systems such as column packing.  In addition chemical and flow erosion is accelerated on the exposed gasket material.  And with more material inside the pipe ID there is less material inside the ferrules.  This can be identified by loose clamps after a steam cycle.  The direct result of leachables and extractables is evident with gaskets and O-rings that adhere to the ferrules, in some case literally gluing themselves in place.  Damage to piping and instrumentation can take place while maintenance technicians struggle to take these connections apart.

Getting back to single-use technologies, there is a clear justification for their implementation.  However many of the perceived benefits of single-use over stainless systems can be greatly mitigated once the industry moves away from the old and on to the new.

There is a better way

A greater use of zero dead-leg connections on vessels as well as in-line instrument ports can have a big effect on cleaning and sterilization by eliminating the unused pipe segments and shadow areas that “T’s” and inline valves create.  In repeated tank sterilization studies performed by a large pharmaceutical customer, connections that employed a zero dead-leg flange came up to temperature in line with the side wall of the tank.   Other connections using even short sanitary clamp ferrules lagged behind the rest of the tank as much as 10°C.  In order to get these points up to temperature both the steam pressure and time had to be increased.  In connections where a standard weir valve was installed onto a zero dead–leg flange the result of the increased pipe length resulted in the same increased time, pressure and temperature to effectively sterilize.  The use of a radial diaphragm valve such as the Rattiinox CAD valve with an extended diaphragm puts the sealing point of the valve virtually in-line with the tank wall, positively affecting both cleaning and sterilization cycles.

In the case of instruments that need to be connected in-line or on process vessels, the zero dead-leg instrument port, which we also helped introduce, reduces the effective dead-leg to one pipe diameter or less.  There has also been recent advancements from instrument suppliers such as WIKA to supply integrated temperature and pressure solutions with a completely smooth product flow path.

The CAD radial diaphragm from Rattiinox addresses all the issues with poor system design related to weir valves as well as the poor design of other radial valves with regards to dual seals and bellows.

The James Walker EPDM compound EP75B has been tested both independently and by customers to be the highest performing EPDM compound.  This particular EPDM compound has a 4% compression set and very low extractables and leachables.  Even after repeated exposure to CIP 100 and CIP 200 and steaming, does not extrude into the product flow path or adhere to stainless ferrules.

 

 

 

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Basics of Hygienic Design

Hygienic-design-PharmAseptic

In view of the increasing requirements on safety and cleanability and regardless if for sanitary or sterile production,the quality requirements for valves and measuring instruments are also increasing. Thus, when choosing the correct valve or measuring instrument, the choice of material and the required surface finish quality is a decisive factor. Continue reading Basics of Hygienic Design