News

The global supply chain is in crisis because of the COVID pandemic. The world is facing supply shortages caused by reduced labor availability and increased (albeit, necessarily increased) regulatory actions. Issues persisted throughout 2021 and despite best efforts from raw material suppliers, manufacturers, and logistics companies, as we go into 2022, everything from supermarket shelves to car showrooms continues to face shortages.

Supply chain issues are complex and widespread. Many industries still face challenges more than two years after the pandemic initially disrupted logistics.

Prior to the pandemic shipping and logistics operated on a “just-in-time” basis. That is, parts and material were moved to the manufacturing process only when they were needed. This strategy brought about greater efficiency and created leaner logistics. Cash balances realized by lower in-house inventories allowed investment in other areas of business.

Just-in-time logistics work great when the supply chain is not faced with challenges. However, when the supply chain is disrupted as it has been, suppliers can no longer provide manufacturers with materials in a timely manner. Suddenly, part availability drops. Demand vastly outstrips supply. Priority is given to certain products—like consumer electronics—over others. Manufacturers who have no available inventory sitting around must now wait until their orders are filled.

Just like that, the supply chain crumbles.

Shipments slow considerably.

Of course, the problem is more complicated than a simple lack of materials. Shipping itself hit a bump. The speed at which trucks, ships, trains, and planes manage to deliver goods slowed. Even as materials shipped, scheduling and labor shortage issues at major ports all around the world meant that goods sat in the port and moved to their destination at slower rates. Air freight capacities were severely impacted as passenger flights were dramatically cut back. In some situations, products in route to their destination can sit on a plane or ship for weeks on end. And shipping logistic experts have no answer as to why or as to when the product is expected to move.

Labor shortages cause issues.

Lack of labor has also impacted the supply chain. COVID disrupted the workforce and resulted in soaring unemployment rates in the U.S. during early 2020. The unemployment rate has since rebounded. In January 2021, the U.S. unemployment rate stood at 6.4%. By January 2022, it had fallen to 4%.

Beyond the effects caused by the pandemic, labor shortages have been brought on by increased competition. Demand for goods has gone up. Suppliers all over the world need more labor to help meet demand. As the need for labor has gone up, so has cost as companies compete for staff from the available labor pool.

Chip shortages cause major problems.

Shortage of microchips have halted manufacturing across many industries. Materials needed for chip manufacturing became unavailable for months at the start of the pandemic as producers of these materials shut down. At the same time demand for consumer electronics skyrocketed. Orders piled up, but without enough supply, manufacturers struggled to create the chips needed to meet demand. This has caused production delays and prices have risen as supply has become limited.

Other sectors that rely on microchips are affected by the demand for consumer electronics. In general, the market has given preference to consumer goods. Where possible, chips are first put towards the manufacturing of TVs, phones, computers, and the like. Manufacturers outside of the consumer electronics industry must wait even longer for goods as their needs are considered lower priority.

Adding to that is the fact that producing these chips, or semiconductors, is a long process. It can take up to three months to process raw materials into chips. As mentioned, in the early stages of the pandemic, some countries shut down their chip manufacturing plants. In Fall 2020, 83% of respondents told the Semiconductor Industry Association that they experienced disrupted operations due to lack of chips.

Virtually all manufacturers who produce something electronic have hit a snag (and so many of the goods we buy nowadays have chips built in). The industry most visibly affected is the auto industry. Car companies like Ford cancelled their orders for semiconductors at the start of the pandemic, thinking that demand had evaporated. But the auto industry soon realized that the demand was there. The problem: they could no longer produce enough cars to keep up. This has thrown the car market out-of-whack—new car inventory is low and used car prices are high. Similar market pressures have been felt across different industries.

Industrial manufacturers have been impacted by supply chain troubles.

Consumer goods are one thing, but what about business-to-business products—the items that make consumer product manufacture possible? Like consumer goods, industrial equipment manufacturers have hit the same problem; lack of availability of raw materials and components and supply chain logistics holdups.

It starts at the top. Again, the chips that are available have been routed for consumer goods. The more sophisticated the product, the longer the delay. Deliveries on some goods that industrial manufactures need are delayed up to a year or more. Shipping logistics have caused further issues. Even when goods are on their way, shipments themselves face delays.

Faced with these ongoing issues, manufacturers look to speed up production.

At this stage it is clear that product delays are inevitable. Out of necessity, companies like Rheonik and Kemtrak, manufacturers who provide various industries with meters and probes, have looked at ways of speeding product delivery. Let’s examine their efforts in greater detail.

So-called “blind” units, without display readouts, keeps the product moving.

Rheonik is a manufacturer of mass flow meters. These meters are microprocessor based. Some models of their mass flow meters have an LCD-readout screen. But the chips, and the LCD screen itself, are now hard to come by. Rheonik have begun shipping “blind” mass flow meters without the screen. Fortunately, the devices can be connected to a computer system via USB. No information is lost, and updates can still be completed. This strategy has helped Rheonik produce and ship flow meters much more quickly.

Spot buying can help ease the burden, but it comes with risks.

Several manufactures have turned to spot buying, or spot purchasing. This method is used when sourcing goods ahead of time is not possible. These types of purchases are usually unplanned and made up of small orders.

In some respects, spot buying is unavoidable. If manufacturers like Rheonik find an opportunity to procure a good, they have no choice but to act. Purchasing ahead of time is much more difficult now. This has helped fulfil orders in a timelier fashion. But it comes with risks. For one, because demand is high, costs go up. In addition, when spot buying, questions linger—is the product fake? is it new? is it the wrong spec?

If a good that is procured is not new, problems can persist. Manufacturers will not be certain of the component’s reliability. This means more overhead is necessary to ensure quality, a fact that has led to further delays. Reclaimed components—if they are available—are not as consistent as new ones, so failure rates go up.

Stockpiling goods helps—in the short term, at least.

There is no doubt that stockpiling goods can provide some insulation against ongoing logistic nightmares. Kemtrak has employed this method to some success. They have stockpiled components and materials to reduce some of the pressure faced and limit the need to spot buy. However, that has had an impact on cash flow and some development projects have been idled as result, so it has not proven to be the ultimate solution either.

The supply chain shortage has affected industries across all sectors and consumers all over the globe. And economists say that issues can last well into 2022, with no immediate solution in sight. The chaos has forced manufacturers to find new ways to deliver their products. Rheonik, for example, have removed non-essential components to speed up delivery times. Spot buying has occurred more often, an effort that costs more, but that has helped ease the problem.

At South Fork Instruments, we continue to do out best to procure and supply products to those industries that need it most. Get in touch with our experts today to learn more.

We all experience foam every day. Foam forms when squeezing a bath sponge, shaking a can of soda, or whipping a cup of coffee.

Foam also arises in many industrial processes. It can be produced biologically—due to anaerobic digestion or brewing—during wastewater cleanup, while cleaning and preparing starchy vegetables, or even when drilling oil and gas. In these applications, the formation of foam can pose a real problem.

Foam buildup is an unstable mixture, a two-phase medium of gas and liquid. A typical foam structure consists of gas pockets trapped in a network of liquid films.

Industrial foam looks like a simple formation of bubbles, but the reality is that foam is a complex and unstable material.

A foam structure consists of a two-phase medium of gas and liquid. Gas pockets become trapped within the liquid film. Foam that is non-destructive will eventually dissipate. The bubbles in a bubble bath, for example, lose their structure after just a short time. Why? Liquid always flows from top to bottom. The foam at the top collapses as the film becomes too thin to support the weight of the bubbles. This process limits the height that a foam column can attain.

This is not true of industrial foam, which can persist for hours or even days and continue to form upward rising columns. Industrial foam has high surface tension caused by mixing, stirring, or sparging. This type of mechanical agitation is common in many industrial manufacturing processes. In addition, in some processes, foam stabilizing agents are added to the process. These stabilizers include soaps, detergents, and/or proteins. These agents reduce drainage, allowing the column to continue growing.

Foam buildup can cause production delays, damage machinery, and reduce yields, which is why engineers have worked for years to find ways to mitigate foam formation.

Foam that does not dissolve—and, in some cases, continues to grow—is a real problem. These bubbles can occupy a lot of space, limiting the volume available for manufacturing a product. Foam coats everything it touches. In dirty water applications, the solids in the water are also in the foam. As the foam bubbles burst and drain, these solids are often left on the surfaces the foam touched, creating, in some cases, a thick, sticky mess that takes a great deal of effort to clean off. This coating can also clog pipes and valves and interfere with monitoring instrumentation, creating maintenance needs that can lead to long production delays.

Foam buildup must be carefully monitored to prevent problems. But monitoring foam is a full-time job and doing so manually comes with mixed results. The “eye test” is fallible. It is easy to miss the existence of foam and even easier to add the wrong amount of antifoam additives, which can potentially result in even worse foam conditions.

Most manufacturers have moved to measurement tools to help them control foam. Three of the most common instrument types utilized for foam measurement are:

Radar: Radar systems are typically mounted looking down at the surface of the liquid to be measured. Designed to measure level, there are two radar technology types – through air and guided wave. A microwave pulse is directed at the liquid. When it reaches the liquid, a proportion of the emitted signal is reflected back to the instrument. Water is a strong reflector, so an aqueous foam layer can reflect back a signal strong enough for a radar system to “lock on to”. However, radar systems can be easily fooled if the foam layer becomes lighter or denser, or its surface becomes more uneven. For very consistent applications, radar can work reasonably well although foam problems are rarely consistent!

Capacitance: Capacitance probes have been successful in detecting the presence of foam in some cases and have been used widely across industries. These probes work by detecting the dielectric properties of the foam as it builds up. However, capacitance probes overall are not an ideal solution for foam detection. Designed to measure 100% liquid, adjusting them to detect foam (1% liquid) means that when set, they are operating at the very end of their measurement capabilities. Furthermore, they cannot distinguish between foam and liquid and give a false positive if they become coated with material – fouling essentially renders capacitance probes useless.

Ultrasonic: In a similar way to radar systems, ultrasonic sensors emit a soundwave that is used to detect foam. Sound is reflected from the foam layer back to the sensor where it is used to give an indication of distance from the sensor and therefore foam height. Ultrasonic sensors can be highly unreliable when measuring foam. A foam layer can cause the transmitted signal to become scattered and lost and as the foam layer becomes lighter, the sensor can lock onto the signal being returned from the liquid layer below, ignoring the foam altogether.

The probes listed above are often used, but none offer an ideal solution for controlling foam.

Here is why Hycontrol’s SureSense foam control technology is better than the rest.

Hycontrol has developed a versatile range of foam detection and control systems to meet the challenges of foam in all industries. The technology behind these systems originated directly from foam control research, meaning that these highly specialized devices were designed specifically for foam control applications. They are not simply modified liquid level sensors—these are tools that have been created specifically for this challenging task.

To be reliable in use, Hycontrol probes use IMA technology, a patented method of ignoring coating and fouling on their active surfaces so they remain reliable, even when heavily soiled. Hycontrol SureSense and SmartFoam instrumentation uses probes that are based on this enhanced conductivity measurement technology.

The SmartFoam probe is a single point switch that provides an output when foam is detected. The SureSense system is a fully featured foam detection and control unit. It can be used as a standalone or in conjunction with a supervisory control system to automatically add defoamer chemicals on demand as foam is detected.

A typical SureSense system comprises of a sensor and a controller connected via special cables. The probe is installed in the process with its tip above the liquid level. When foam reaches the probe, the controller begins dosing chemicals using a configured strategy until the foam level subsides. Hycontrol SmartFoam and SureSense instruments:

Generate significant cost savings by reducing antifoam use and protecting equipment
Reduce downtime and labor costs
Increase productivity and quality of product

Hycontrol’s foam detection technology is the best available solution for controlling foam and preventing major foam disasters. Contact South Fork Instruments today to learn how we can help you prevent foam and maintain production efficiency.

I’m often asked whether Coriolis meters can measure mixed gas/liquid streams accurately. Unfortunately, the answer is not a simple yes or no. This is due to the volume of published material that offers information regarding (varying levels of) success in mixed stream measurements, but the limits of measurement are often vague and results specific.

Rheonik meters are tolerant of entrained bubbles, but issues with accuracy can still arise.

I can only speak to Rheonik meter performance, but from my experience, Rheonik meters are fairly tolerant of entrained bubbles, provided they are evenly distributed (e.g. foams are measurable because they are homogenous). However, accuracy will suffer—gas is compressible, and the movement of the tubes oscillating side to side will serve to compress the bubbles ever so slightly, so measurement will be affected (and potentially “noisy”) as they compress and decompress. The more gas, the more likely inaccurate readings will occur. It is difficult to quantify what that change in accuracy will be in a given application, because different applications react in different ways.

The good news is that density measurement will drop when bubbles are present. This drop is a strong indicator of their presence; it tells us what’s happening and indicates when accuracy may be suffering. Keep in mind that bubble regimes in a pipe can vary dramatically, from light bubbles all the way through slug flow and at some point, pretty much all Coriolis meters will fail to measure flow with any degree of reliability and usually end up in a fault condition.

Why are Rheonik Coriolis meters better at handling flows with entrained bubbles?

It really comes down to the unique mechanical construction of Rheonik meters. The mechanical construction uses a design that provides support for the measurement tubes rather than just letting them “dangle.” This alone improves performance when internal (pulsing/aeration) and external (vibration) disturbances are present. The drive method is torsional (rather than the solenoid style “bang-bang” drive in meters with unsupported tubing) and this ensures that there is positive drive force on the mechanism while it’s oscillating all of the time. The torsional nature of the drive along with the structured support for the measurement element means that Rheonik meters are typically better than most when measuring flow with entrained bubbles and therefore tend to go into fault less than other brands.

Some meters use electronic means to improve performance in mixed stream flows. Those electronic means range from masking meter fault condition by holding current value when it all gets to be too much to tweaking drive power and frequency in an attempt to keep up with the changing meter conditions. These work to end users satisfaction in many cases, but it is important to bear in mind that no one can handle erratic or slug flow situations in a Coriolis meter to the same accuracy as seen with single phase flows.

Rheonik transmitters have a feature called PFPM (partially filled pipe management) that can help when the flow regime gets too difficult.

The PFPM feature watches the reported density value (as one input while in operation) and should it drop below a preset threshold value or should the meter go into fault, the meter can be set to hold its current reading until it either reestablishes density above the threshold or times out. If bubble events are transitory, or even if there is a baseline aeration that worsens from time to time, PFPM can help mitigate bubble effects on the meter and therefore plant operation. Bubble events can often show up at the beginning or end of a process operation, when flows are lower, so the overall impact on accuracy is small. For operations where aeration is consistent, calibration factor adjustment can be used to correct for ongoing errors.

PFPM is a standard feature on all Rheonik meters with live density measurement capability and can certainly provide improved performance in difficult applications. It is also useful in detecting and reporting deteriorating measurement conditions—for instance, when reaching empty in a feed vessel—so action can be taken by operators or control systems before they become a problem. Coriolis meters equipped with advanced diagnostics capability such as Assurance Factor® diagnostics can be used in this way. With Assurance Factor®, it’s also possible to get a continuous readout of measurement quality so that events like increasing aeration are spotted and resolved before they become an issue.

A few other ways to try to improve bubble interference issues in Coriolis meter installations are:

Increase back pressure on the meter if possible. This helps keep gases dissolved in the stream so they aren’t such a problem.
If possible, install meters upstream of pumps or other equipment that might be causing the gas bubbles to form or be present in the flow.
Change the meter orientation so it is in “flag” mode—inlet at the bottom, outlet at the top. Doing so can help prevent bubbles gathering at the high spot when entering the meter and creating slugs. This is not applicable in all situations.

Finally, thinner liquids with gas bubbles are tougher to measure than thick liquids. Highly viscous flows, if aerated, tend to stay in the same state because the bubbles can’t “escape” through buoyancy or coalesce together to form larger bubbles as easily. Provided bubbles are not slug-like in these situations, it shouldn’t be a problem to measure flow to reasonable accuracy.

Choice of meter is important. Always check out the available bubble effect mitigation features as part of the process of choosing a flow measurement solution for your process. Please feel free to contact us if you have any questions about the applicability of Rheonik Coriolis meters for your operations.

Machines for mixing and delivering two-part (or more) chemicals for paint and adhesive coatings in industrial manufacturing plants must be accurate and reliable if the quality of the final product is to be maintained. High performance pumps are used to combine various chemicals in a predetermined mix ratio that are then delivered directly to the production line. Any unintended or unnoticed change in the proportioning of these chemicals being mixed can have a large impact and be very expensive in terms of rejected or off-spec product that often cannot be reworked.

Manufacturing plants have limited space, resulting in the installation of gear meters with small footprints which quickly lose accuracy due to wear and tear.

Painting machine equipped with Coriolis flow meter — Painting machine equipped with compact Rheonik Coriolis flow meter system.

While metering pumps are generally very reliable—and their throughput is well correlated to their speed of operation—it is common practice to fit a flow meter in line with them to provide flow rate feedback. This is done to confirm that the desired amount of material is delivered, as over time pumps will wear and their delivery versus speed will change slightly. The flow meter also provides an independent indication should there be an issue, such as blockage or leakage, in the flow line.

In any manufacturing facility, factory floor real estate must be maximized in terms of the final product(s) output potential. To meet this goal, machinery is designed to be compact, and paint and adhesive preparation machines are no exception. Often purchased in skid form from specialist suppliers, a great deal of piping and components are crammed into a small space and when it comes to flow meters, those that are small, handle high viscosity liquids and do not require long upstream/downstream straight runs are greatly preferred. Gear meters have been the meter of choice for many of these machines in part because of their ability to handle high pressures, but also because they meet these requirements while having reasonable accuracy. The downside of using gear meters is that they are mechanical devices and as such, are affected by the same issues as metering pumps. Blockage, leakage and mechanical wear will, over time, cause measurement drift.

Gear meters give good performance when new, but they must be maintained if they are to continue to provide that same performance over long periods.

Unfortunately, maintenance is typically reactive rather than proactive and only happens after a problem has occurred. When problems occur with a gear meter, the most likely cause is debris or foreign particles in the process line. Foreign particles become enmeshed in meters’ tight tolerance gears, causing wear and increasing resistance to flow.

Large pieces of debris can cause the meter to seize and stop working altogether. Foreign material can be introduced into a meter in a variety of ways: a quality issue from the fluid supplier, an upstream component—such as another pump—failing, or as a result of an unrelated repair task in upstream piping. Whatever the source of the foreign material, whenever such a problem occurs, the meter must be disassembled, and its internals inspected for damage.

Should “chips and dings” or score marks in the gearing be observed, then the rotors must be replaced to ensure integrity and accuracy. Also important is to ensure that the measuring chamber walls have not been damaged as this may further contribute to operation issues. In almost all instances, damage to the measuring chamber will require replacement of the flow meter. While the meter is being repaired, the production line is down.

Even when gear meters are not exposed to foreign material, over time, bearings can fail and rotors potentially crack. Unless the failure is catastrophic, the only indicator of a problem would be a change in tone or an increase in noise level when the meter is operating.

Compact Coriolis meters are a superior modern alternative to gear meters in applications where space is at a premium.

Like gear meters, Coriolis meters require no upstream/downstream straight pipe run, but have the distinct advantage of having no moving mechanical parts and being immune to the effects of foreign material passing through them. Furthermore, the availability of advanced diagnostic information from Coriolis meters allows maintenance to be proactive. Diagnostic messages can alert users to deteriorating performance in the process before failure actually occurs.

But the adoption of Coriolis meters by fluid handling and mixing equipment manufacturers has been limited, in part, by their pressure handling capabilities and perceptions that they are high cost.

Newer Coriolis models, like the Rheonik L series sensors feature high pressure (up to 20,000psi) and high temperature (up to 350°C) variants, greatly increasing the applicability of the technology in industrial applications. Machine and skid builders can use these high-performance, low-maintenance units with their multi-functional performance to enhance value to their customers. For corrosive material measurement applications, Rheonik Coriolis meters can be configured with a wide variety of exotic wetted materials more cost effectively than gear meters, and Coriolis meters have the distinct advantage of being able to measure both viscous and non-viscous materials to the same accuracy.

With the availability of smaller, more compact Coriolis flow meter bodies and small remote electronic units suitable for DIN rail mounting, the advantages of using Coriolis meters as an embedded component in paint and adhesive mixing equipment can be easily realized. Coriolis meters provide increased value to produced goods through increased quality and consistency while saving cost through higher machinery uptime and lower maintenance requirements while their incredibly small footprint allows for even more compact process skids, maximizing the use of available factory floor space.

One of the most labor intensive maintenance efforts in a plant relates to the figurative care and feeding of pH and ORP probes and other electrochemical sensors. While many such probes are touted as “rugged,” they are actually quite delicate. Advertisements tout their rugged build quality, often suggesting that they have been “beefed up” by wrapping a “tougher” pH measurement element in a strong, protective housing.

While this may help with handling in transit and on site, the measurement method is still identical, but the supposedly tougher pH measurement elements often result in reduced sensitivity and slower response to parameter changes.

Toughness aside, no electrochemical sensor can report accurate measurements if it is covered in gunk and grime, but traditional cleaning approaches are time intensive and costly.

It’s a common task to remove and clean probes in industrial installations. This may be done on a preventative schedule basis, or only when the measurement is “acting up,” but the cleaning process is largely the same.

First, the plant control room must be informed that the measurement point is going offline. The process flow, or sample line from the main flow, is then shut off and isolated so the technician can physically remove the probe and carefully clean it.

In hazardous applications, protective clothing is needed, often including disposable gloves. Once cleaned, the probe is reinstalled and the measurement brought back on line by reinsertion into the process. But this takes time, and the process of uninstallation, cleaning and reinstallation can cause damage to the probe itself.

A safer and more efficient method of keeping the measurement on line is to install an automatic retractor and cleaning system.

Retracting and cleaning a probe by hand must be performed as infrequently as possible, due to downtime and the potential for equipment damage. However, a retractor can operate frequently—as often as every 15 minutes, if necessary!—to keep the probe clean and in operating condition.

Automatic retraction systems can work in conjunction with a probe’s electronic unit to provide seamless measurement to a remote control system. In addition to providing a more reliable measurement, the useful measuring life of the probe is extended, and the probe is protected from potential handling damage.

At the very least, a manual extractor can provide a safe and efficient means to pull the probe out of the process.

Exner Process Equipment manufactures a wide range of automatic and manual probe retractors that can be used in process conditions both benign and aggressive.

Typically installed directly on process vessels or into piping, the Exner EXtract series use either a pneumatic or manual rotary action actuator to insert the sensor into the process medium and retract it back into an integral cleaning chamber within the assembly. When retracted, the mechanism isolates the probe from the process fluid. In manual retractors, a safety interlock engages at each end of its travel to prevent further movement without depression of an “insert” or “retract” button on the housing. On automatic units, there are pneumatic and optional electrical feedback switches to indicate position. Whether automatic or manual, the insertion mechanism cannot be operated when no sensor is installed, and it is impossible to uninstall any probe while in the inserted position.

All EXtract housings have inlet/outlet fittings for cleaning and rinsing of the installed sensor when retracted from the process. Calibration solutions can also be introduced to the housing while the probe is retracted, allowing for in situ calibration and standardization of the sensor, all without interrupting process flow.

Advantages of Exner Extract Retractable Housings

Greater reliability and confidence in the measurement
Protects technicians from process material contact, with no need for additional PPE
Dramatically reduces maintenance time
Prolongs sensor life
Manual or automatic operation versions
Operate without process line shut down
Integrated process scraper cleans probe as it is retracted
Manual unit has position locking system with indicators
No way to uninstall probe when inserted into process
Automatic safety lock while sensor is removed
Optional electrical position feedback switches
Operates safely under high process pressures
Immersion lengths up to 107mm
Suitable for use in hazardous areas
Wide variety of process connections
Up to 16 bar / 230 psi and 140°C / 285°F

The formation of foam within bioreactors has been an industry-wide issue for decades. The foaming tendency of the nutrient media used to cultivate bacteria, algae or animal cells in the production of antibiotics, vaccines, steroids and other products can create problematic operational issues. Furthermore, the drive to achieve higher viable cell densities for greater product yields has increased process oxygen demand. To support this higher oxygen demand, agitation and aeration rates have also increased, leading to even more foam generation.

Foaming has several undesirable consequences: cell entrapment within the foam, cell damage caused by the bubbles within the foam bursting, reduction of gas transfer rates from the headspace, and over-pressuring of the bioreactor due to clogged vent filters, to name but a few.

It is common to control foam formation within reactor vessels with antifoam additive chemicals. Antifoam chemicals work by reducing the surface tension of the liquid films that form the bubbles within the foam, causing them to more rapidly break down and dissipate. However, there are potential adverse effects—such as toxic effects on metabolism, lowering of cell gas uptake, and reduction of yield—from the addition of antifoam chemicals. At laboratory scale, these effects can be detrimental to drug discovery programs. At production scale, aside from the cost of the chemicals themselves (which can be significant), they can negatively impact the cost per unit of product. Therefore, it is vital that the addition of these chemicals be minimized as much as possible.

Traditional approaches to controlling foam and optimizing bioreactor conditions result in overdosing of antifoam chemicals.

It is generally understood that reliable monitoring of the presence of foam is key to reducing the amount of antifoam additive used.

Many bioreactor manufacturers offer foam detection sensors, as well as optional associated antifoam addition control systems. However, not all foam detection systems are equal, and manufacturers’ standard systems are often not reliable enough for long periods of unattended processing.

Problems with foam detection systems are typically related to coating and fouling of sensors, and the resulting generation of false positives. Because of this difficulty in automating foam control, it’s common to find that the process of antifoam addition is a manual function—a technician sees foam forming and adds chemical to knock it back. The foam detector in the reactor vessel is relegated to being used as a backup to visual observation. When antifoam chemicals are manually added in this manner, overdosing is not uncommon. In addition, different technicians may interpret the quantity of additive needed differently, leading to repeatability concerns with batches and experiments.

To mitigate repeatability issues, antifoam addition can be mandated and systematized in batch instructions, with the chemical being added at set intervals or times during a batch, regardless of whether it is needed or not. These instructions can err on the side of caution, again leading to an overdose condition.

There is a wide variety of foam detection and measurement instrumentation available.

Instrumentation deployed for foam detection are usually single-point, switch-type devices that trigger when a foam layer reaches them. Sensitivity high enough to detect light foam products is an essential requirement. In bioreactors, the fouling and coating of foam detection probes is very common, so it is equally important to differentiate between sensor fouling/coating versus foam rising inside the bioreactor. Typical measurement techniques utilized are based upon conductivity, ultrasonics, and impedance.

Conductivity Switch

Conductivity switches consist of a single probe that is installed above the level of the liquid in the bioreactor. There is an active electrode at its tip, and its shaft is covered with an isolating material such as PTFE to isolate it from the rest of the bioreactor structure. The instrument is set to sense when the tip of the probe changes from being in air to being very close to or in a foam layer. Unfortunately, conductivity switches are notorious for false positives due to the process medium fouling of the probe, creating a conductive bridge between the active electrode and ground circuits. A false-positive condition like this can cause a de-foaming additive dosing pump to continuously dispense until the false detection event is recognized. In extreme cases, false positives like these can lead to the entire process batch being ruined.

Ultrasonic Gap Switch

Ultrasonic gap switches operate by sending an acoustic signal across a gap formed by a Y-shaped sensor. Within the sensor are two piezoelectric crystals, one transmitting and the other receiving. The transmitted signal is produced at a magnitude that is too low to travel across the gap when in air or gas. But when a liquid phase fills the gap, the acoustic signal can travel through the liquid phase to the receiving crystal. This change in signal level is used to indicate the presence of foam.

Unfortunately, because foam is mostly composed of trapped gas, it is not as good a medium for acoustic signal conductivity as liquid is, so the detection threshold level in these devices has to be set at the most sensitive level in order to see foam. This can give rise to false positives when no foam is present, often from media splashing around in the vessel. Furthermore, after a foaming event, material left on the sensor surfaces can cause attenuation of the acoustic signal, preventing switching when the foam level reaches the sensor. In this state, foam can pass the control point, fouling filters and possibly damaging other equipment and instrumentation.

Impedance IMA Foam Detection Probes

Impedance devices work in a similar way to conductivity devices, except that rather than monitoring for a change in dielectric, they operate by passing a small alternating current through the foam being detected, and this is used to measure impedance. The impedance of the material being sensed is used to determine when foam is present.

Foam detection systems based upon impedance are available with IMA (intelligent multi-action) measurement circuits that can detect and mitigate fouling/coating on the sensor, preventing false positives and ensuring reliable measurement where other techniques fail. Systems fitted with this type of probe can be operated unattended in a fully automatic mode and will use only the amount of antifoam additive necessary to keep foam at bay within the vessel.

The benefits of this approach are obvious and significant, which is why we almost always advise the incorporation of Hycontrol Suresense+ sensors—which pioneer the use of IMA measurement circuits—into any foam detection and control solution.

Because SureSense+ systems are designed to be resistant to fouling and buildup, and a single unit can incorporate data from up to three sensing points in one or more vessels, the result is a foam control system that can automated to a far greater degree than approaches based on other methodologies, while eliminating the most significant problems associated with foam control.

Finding the balance between too little and too much foam management.

Studies have shown that the dosing of antifoam chemicals has both positive and negative effects on fermentation and cell culture processes. On the positive side, dispersion of foam increases transfer rates of headspace gases into the media, prevents blockage of vent filters and ensures other equipment such as gas concentration instruments can operate unimpaired. On the other hand, excessive use of antifoam chemicals has been demonstrated to negatively impact cell growth and therefore protein product yields in upstream bioprocessing.

It is a fine balance between too much antifoam additive and not enough. Automated systems using reliable sensing technology can help maintain the balance between high product yield and reduction of foam to prevent issues while the bioreactor is in operation.

Below are some specific questions we often receive from clients in the biopharmaceutical industry, and how the use of automatic foam control methods can remedy these issues.

How can bioreactor processing yields be increased?

Foaming in a bioreactor during processing is a normal occurrence, but can cause serious problems, such as reducing cell growth by lowering the surface area contact between the growth media and the bioreactor headspace, lowering oxygen transfer rates. On the other hand, when antifoam chemicals are used in large amounts, they can also reduce batch production rates due to interaction with the cells in the process.

The best approach is to reduce the amount of antifoaming chemicals added to the process by installing a foam detection probe that will trigger the dispensing of antifoam chemical only when needed. This will prevent the level of antifoam chemicals present from reaching concentrations that reduce cell interaction, while also preventing foam from interfering with cell growth.

The bioreactor filter becomes clogged with foam, causing the pressure relief valve (PRV) to vent. How can this be prevented?

Excessive foam build-up can clog filters and create vessel over-pressures outside of acceptable limits. To prevent foam from reaching the vent filter(s), install a reliable foam detection system that allows for real-time monitoring and action against foam buildup in the bioreactor. This will protect against product loss, prevent filter clogging, and ensure the PRV does not operate with the attendant mess this can cause.

Are there bioreactor probes that don’t give false positive readings when they are coated or fouled?

Reliable foam control requires reliable foam detection. False positives result in overuse of antifoam chemicals leading to increased cost and potential reductions in yield.

Most bioreactor probes are simple devices that, once fouled with process media, can create these false positive readings. However, Hycontrol SureSense+ probes feature a unique sensing method that allows them to control for coating and fouling, and continue to provide reliable foam detection even when completely covered with process material.