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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.

Foam arises in many industrial processes. It can be produced, for example, biologically (due to anaerobic digestion or brewing), during wastewater cleanup, or while cleaning and preparing starchy vegetables. While it can be an essential part of the production process, it is more often an unwanted side effect.

Effective foam control is essential in biopharmaceutical processing, especially in bioreactors used to produce antibiotics, vaccines, steroids and other lifesaving drugs. This is because excessive foam buildup can lead to batch failure, with costs that may run into the thousands of dollars.

In the preparation of agricultural products such as potatoes, sugar beets and dairy products, foam is caused predominantly by the presence of surface-active substances such as proteins, fatty acids and sugars. The control and abatement of foam is essential in preventing overflows, blocked filters, contamination, and damage to pumps and other equipment, all of which require expensive and time-consuming cleanup.

How does foam form in industrial and manufacturing environments?

Foam is an unstable, two-phase medium consisting of gas pockets trapped in a network of thin liquid films—essentially a pile of bubbles! To produce a foam layer, there must be aeration (through agitation/mixing, stirring, sparging) and surface-active components (surfactants) in the liquid that reduce surface tension. In addition, foam must form faster than or at the same rate as its breakdown. In a column of foam, liquid continuously drains downwards, creating a density gradient with lighter, larger bubbles at the top and smaller, heavier bubbles at the bottom. Eventually, the foam at the top of the column collapses as the films become too thin to support the bubbles.

Why is it necessary to control foam?

Foam is a problem because it can alter natural liquid flow in systems and block process interactions, such as oxygen transfer from air. To prevent foam buildup in industrial processes, antifoam additives such as silicone oil are often used, but the amount of additive used can be difficult to control, and overdosing can be very costly and counterproductive. Additives work by reducing surface tension of the liquid films within the foam, causing them to more rapidly break down and dissipate. However, the additives themselves can have some unwanted side effects, such as reducing the mass gas transfer rates in bioprocessing into the process medium, contaminating the end product, and even creating environmental concerns, so it is essential that excess use is avoided.

What are the most common methods for controlling foam, and their advantages and shortcomings?

In many processes where foam must be kept at bay, it is common to have a constant additive feed. While effective as a method of preventing foam, it assumes that the process will always produce foam, even when it doesn’t. Where this process isn’t automated, additive is added by “the bucket,” or pumps are activated manually when foam becomes an issue. However, this relies heavily on someone noticing the problem and keeping tabs on it until it is resolved. Human nature being what it is, there is often a tendency to “overdose” or pumps turned on are left on because the operator is called to attend to other things. Whether this strategy is automated or implemented manually, it is clear that the high cost of de-foaming additives makes this method an expensive solution to foaming issues.

For the more enlightened who implement automatic dosing systems that detect foam and dispense additives only when required, the potential for cost savings is large. Probes are commercially available which can be easily retrofitted to provide continuous feedback of foam condition. An increasing number of companies are adopting this easy and effective approach to mitigate foaming issues. From simple switches to systems with built-in controllers that directly operate antifoam additive pumps or open vacuum breaker valves to break down foam as it forms, automatic systems can make a significant difference in the way a plant is operated and maintained.

What financial costs are associated with foam control?

Let’s be clear, foam can cause a variety of expensive and time-consuming problems. Aside from the actual cost of the additives themselves, environmental pollution, potential product contamination, loss of product, and downtime and cleanup costs resulting from spill-overs from process vessels can add up to a hefty bill.

In addition, excess foam can create secondary costs by limiting product throughput, and even result in damage to equipment such as pumps, filters and valves. Whichever way you look at it, the implementation of effective foam control has a good chance of paying back both CAPEX and OPEX very quickly.

Why should businesses consider newer methods of foam control?

Companies worldwide spend billions of dollars each year dealing with foam issues and the resulting impact on their businesses. Consideration must also be given to the potential long-term detrimental effects of disposal and dispersal of de-foaming chemicals on our health and the environment.

There is clear evidence that considerable savings can be made by actively controlling the addition of antifoaming chemicals, and with the availability of products specifically designed for reliable foam detection and control—such as those from Hycontrol—there is no need for companies to continue with existing manual methods and outdated control systems.

Bitumen is one of the heaviest and most viscous products produced in refineries. It is created from “vacuum bottoms,” the asphalt-like residue extracted from the bottom of vacuum distillation columns.

Bitumen is a long chain hydrocarbon molecule and appears to be solid at ambient temperatures. However, bitumen is really a highly viscous liquid and does “flow,” though only very slowly. Heating bitumen causes it to soften and eventually become a runny liquid at high temperature. This property of bitumen, near solid at ambient temperature, but liquid at higher temperature, together with its adhesive and waterproofing qualities, is the reason why bitumen is so useful in construction. Most bituminous coated materials are workable when mixed and applied hot, but on cooling become solid. While bitumen is best known for its extensive use as a binding agent in road asphalt, it is also used in the roofing and carpet industries, as well as for making sheets of corrugated papier-mâché water repellant. Many of its uses require unique hardness properties, so there are many different grades of bitumen produced. Different grades are made at refineries by blowing oxygen through bitumen to make it harder when cold.

The measurement of bitumen flow is notoriously difficult because of high process temperatures and viscosity conditions. Conventional meters are challenged with this measurement and failure is a common problem. Rheonik ET and HT Coriolis mass flow meters are ideally suited for the task:

High temperature ratings to 350°C/662°F
No moving parts to wear
Built-in trace heating jacket options
High intrinsic accuracy and measurement stability, even at larger sizes

Steam purging for cleaning purposes will not damage meter internals, nor will over-temperature conditions. Wildly changing fluid properties caused by small variances in temperature are automatically compensated for. The use of Rheonik Coriolis mass flow meters significantly increases measurement reliability while dramatically reducing the maintenance costs often associated with other meter technologies, such as differential pressure devices and mechanical meters. Product quality and consistency are consequently improved, leading to less waste and rework, and greater plant productivity.

Rheonik meters can be used throughout bitumen process operations for a wide variety of applications:

General process metering
Batching
Blending
Coating
Packaging
Truck and railcar loading.

All Rheonik meters are suitable for hazardous area installation and operation and are simple to implement and use.

The Kemtrak NBP007 measures the amount of suspended solids in a sample using backscattered light. While the use of backscattered light is typically applied to measuring suspended solids, the technique is equally applicable to emulsions, suspensions, dispersions and foams. The suspended phase may be either solids (e.g. calcium carbonate) or two immiscible liquid phases, such as oil in water or gas in a liquid (i.e. foam).

The measurement of backscattered light is also a measurement of turbidity. However, one must be aware of significant differences between backscattered light (180°) and other turbidity measurement technologies such as attenuated light measurement (light passing directly through the sample at 0°), forward-scattered light (typically 10-15°), and side-scattered light (at 90°).

Attenuated, forward, and side-scatter turbidity measurement techniques require light to enter into a sample, be scattered by particulates suspended in that sample and then emitted from the cell where the intensity of light can be measured by one or more photodetectors. As light must pass through the sample before being emitted, it is essential the optical density (i.e. concentration of particulates in the sample) is not too high or no light will be emitted. Such techniques are therefore typically used for low and very low sample concentrations or turbidities (<1% total suspended solids down to 0.0005% or 0.01-4000 FNU/NTU).

Backscatter differs in that the sample is illuminated at the window’s surface, and the light scattered back is measured. Light does not have to pass through the sample before measurement. As the concentration of the sample varies, the amount of light scattered back to the detector will vary, making this measurement technique suitable to measure just about any level of solids, even all the way up to 100%. The lower limit or measurement resolution of backscatter is typically around 0.001% suspended solids or 10 FNU/NTU. Backscattered light measurement can provide a wide dynamic range of measurement for applications where suspended solids levels can vary dramatically.

It should be noted that scattered light measurement is a function of concentration, particle size, and—to a lesser extent—refractive index and color. If you intend to measure concentration using any scattered light measurement technology, then it is essential that particle size is consistent. Samples where the refractive index of the suspended particles and continuous phase are similar will not scatter light—light will pass straight through the sample—and should be avoided (e.g. sweetened condensed milk). In the NBP007, measurement is made in the near infrared (NIR, 850nm and higher) and sample color therefore generally has no influence. However, if the sample is known to be highly colored, the influence of the color should always be checked in advance.

Applying Backscatter Measurements to Real-Life Applications

There are a plethora of applications where an accurate measurement of solids concentration is a real advantage. But measurement in many of these applications has historically been performed with instruments that do not have the dynamic range necessary for the job. A prime example is the measurement of spent yeast slurry in breweries. In large scale breweries, spent yeast is sold for animal feed, providing a revenue stream for the brewery while disposing of a large amount of biomass—a win-win for both the brewery and the processor taking the spent yeast.

However, there is a cost associated with transporting spent yeast in trucks, so it is important that the concentration of yeast in the slurry is high enough for the economics to work out. On the other side, too high a concentration can cause pumping and pipe transport difficulties. A reasonable target for solids concentration is around 50%.

A well-known brewery had implemented spent yeast solids concentration measurement using attenuated light probes. These probes, reading in an arbitrary CU unit, worked to some degree at low levels of solids concentration, but exhibited a nonlinear response to higher levels and quickly became blinded over 20% solids. Furthermore, when they were reading, they exhibited continuous drift. This resulted in several batches of spent yeast leaving the brewery with low solids concentration, and charge backs from the processor. Technicians in the plant tried to remedy the issue and operators attempted to work within the limitations of the system. But eventually, the measurements were abandoned, and the operators reverted to manual measurements when transferring spent yeast.

A Kemtrak NBP007 12mm OD backscatter probe was installed in the same Tuchenhagen VariVent “ball” as the transmission probe using an Exner EXstatic port adapter to improve the measurement and resolve the back charge issues the plant was experiencing. Using the native BU (backscatter unit) readout, the NBP007 provided a linear response to solids concentration changes across the entire range with no baseline drift. The unit was then correlated to actual solids concentration and set up in the DCS system as a live solids concentration measurement. Several years later, it continues to provide accurate and reliable readings of solids concentration, and is used to prompt the addition or removal of water from the spent yeast slurry circulating in the spent yeast loop. Savings to the brewery are estimated to be in the hundreds of thousands of dollars over the time it has been in operation, compared to the costs associated with the previous methods, and additional NBP007s have been installed in the plant where high solids levels are experienced.

A unique benefit of the Kemtrak backscatter (or reflectance) probes is that they will not go blind at any concentration of suspended solids. The output of the Kemtrak NBP007 will continue to increase with sample concentration, ensuring a reliable measurement at any concentration. The NBP007-L (low range) analyzer is recommended for process concentrations up to 10% total solids, while the NBP007-H (high range) analyzer should be used for accurate monitoring of suspended solids exceeding 10%.