Photometers & Turbidimeters

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%.

The dairy industry makes widespread use of clean-in-place (CIP) systems in plants that process milk and produce yogurt, ice cream, and other milk-based products. CIP systems have revolutionized food production, making it easier and less costly to clean and sterilize manufacturing systems. These systems avoid the need for dismantling, and allow for the capture and reuse of water, detergents, and disinfectants.

But there is still a great deal of room for improvement. Dairy manufacturing facilities are still losing thousands or even tens of thousands of dollars per month from unnecessary product shrinkage, and the excessive consumption of water and cleaning agents.

Clean-in-place systems typically use a combination of timed cycles and turbidity sensors for system cleaning—a process which is often unnecessarily inefficient.

First generation CIP systems relied on timed cycles to ensure the cleanliness of product processing systems. Using predetermined intervals, the system was first rinsed out, then flooded with hot water mixed with detergents and disinfectants circulated through the system, followed by a clean water rinse cycle. However, the efficiency of CIP cycles relies heavily on accurate interface detection within the pipe. In systems where detection is either manual or relies solely upon time, loss of product and water can be costly, and product quality can be compromised.

Installing one or more turbidity sensors in the process pipe system greatly improves the efficiency of each cleaning cycle.

When a CIP cycle starts, there is still product in the line and the initial water rinse is used to push it through the system. A turbidity monitor allowed operators and/or automatic control systems to detect the arrival of the rinse water, signaling the end of the “batch” and helping avoid dilution of product in the pipeline by indicating a divert of the oncoming rinse water to a drain. The rinsing process continued until turbidity dropped to a specified point, indicating that most of the product was removed from the line. The drain was then closed and water containing cleaning agents introduced into the system and recirculated for a predetermined time to complete the wash out of the system pipelines. Finally, the cleaning solution was removed from the system by re-introducing clean water to do a final rinse, again relying on a change in turbidity reading to identify the arrival of the clean water to trigger the closing of valves. Clean water, retained in the lines until production resumed, was pushed out by raw product fed into the system. This water, being totally clean, was diverted to a holding tank for future use until the turbidity sensor ‘saw’ the product arriving, signaling the start of the new batch.

The goal of all of this was to get away from old, strictly time-based cycles, and instead act based upon the actual conditions existing in the pipelines. This had a direct impact on product quality, as product contamination/dilution was reduced, and overall consumer satisfaction in the market heightened.

This approach also helped reduced operating costs as well. Water and product were saved, less energy used for heating water and speed of the operation generally increased. Lastly, wastewater discharge volume was lessened, lowering the load on wastewater treatment and reducing sewer system costs.

The implementation of sensor-based CIP systems has saved dairy product plants vast amounts of money, sometimes hundreds of thousands of dollars annually. But there’s still room for improvement. Existing turbidity monitor designs on the market can be unreliable, resulting in ruined product, excess water and cleaning solution usage, higher energy costs, and increased waste discharge. Small investments in improving turbidity measurement and reliability in existing plants can result in fast returns for the bottom line.

Existing turbidimeters are often fooled by bubbles and tricks of light in process fluids, fouling measurements.

Traditional turbidimeters are installed into process pipelines so that their sensors emit light out through a flat window into the process stream. The light is then reflected by particulates, back through the process stream and flat window sensor, to the eye of the sensor.

This approach has long been considered to work well enough, as it represents a vast improvement over strictly time-regulated CIP processes. But there’s an inherent flaw with turbidimeters using this design: they often have an optical focus point that is somewhere in the middle of the pipe.

This light is essentially diffracted out into the pipe. As the light travels through the process fluid, it can encounter bubbles, non-homogeneous mixtures, pipe wall reflections, and other disturbances. In fact, bubbles often collect and linger directly on the window surface, as a low-pressure zone forms over the window when fluid is flowing past it. Bubbles collecting on the window in this way disrupt the light beam and impact the resulting measurement. Turbidity indications affected in this way can be noisy and erratic, producing false positives or negatives that the control system and/or operators act upon.

The consequences of this should be obvious: noisy and inaccurate measurements result in the interfaces between product and water/cleaning agent not being detected correctly. Product is contaminated. Water is wasted. More wastewater is discharged. Money is lost. Furthermore, operators lose faith in the instrument and ignore it, reverting instead to manual control of CIP cycles and defeating the object of installing the monitor in the first place.

Exner has introduced a new sensor package in their EXspect 271 turbidity sensor, eliminating this serious measurement flaw, making it perfect for measuring turbidity in milk products.

The EXspect 271 features a unique, patented ball lens over the sensor, which directly interfaces with the process fluid. The surface of the spherical lens is designed to repel bubbles and other disturbances.

The second significant different is the point of focus. Instead of the optical focus point being somewhere in the center of the pipeline, the EXspect 271’s focal point is exactly at the interface point between the process fluid and the surface of the ball lens.

Thus, only the turbidity of the fluid itself is measured—the measurement is not marred by bubbles collecting on the surface of the lens, reflections from the interior of the pipe, or other disturbances.

Because the light beam is focused on the surface of the lens, another key issue is solved—light absorbance. As mentioned previously, competing products focus light on the center of the pipeline. This means that the light encounters a very ‘thick’ cross-section of fluid, and the light beam loses energy as photons are scattered by the fluid. Less of the light beam is reflected, producing a weaker signal from the turbidimeter, indicating that the process fluid is cleaner than is really the case.

The Exner turbidimeter does not have an appreciable light path through the liquid, and thus doesn’t suffer from this issue. The curved shape of the lens also resolves the issue of generating a low-pressure zone, so bubbles and other debris do not ‘stick’ to the lens.

This new turbidimeter design represents a significant step forward for CIP operations producing milk-based products. To learn more about how the Exner EXspect 271 can improve the cost efficiency of your operations, contact South Fork Instruments today.

Assessing a beer—whether as a finished product or at various points in the brewing process—is largely a matter of measuring visual and flavor-based cues. Does it taste right? What color is it? Is it clear? If it’s hazy, is the level of haze such that it signifies a production problem?

Haze is of key concern in beer brewing, as many mass-produced beers are known for their clarity and brightness.

The presence of haze is typical in many traditional beers, such as Hefeweizens and other wheat beers. In addition, hazy IPAs have become increasingly trendy in recent years.

But many brewers and macro-brewers produce bright, filtered beers that are sold in very large volumes throughout vast distribution areas. For these products, ensuring consistency and product recognizability is crucial to maximizing the visual impact of the product, as well as consumer satisfaction.

Measuring Beer Haze with a Turbidimeter — Beer brewing at the macro scale poses serious challenges in ensuring product consistency and quality, including the appropriate level (or lack) of beer haze.

One of the most common forms of haze is “chill haze.” This results from proteins and polyphenols (micronutrients found in vegetables, fruits, and cereals) bonding together to form large particles which reflect light and are thus visible. Chill haze gets its name from the fact that these particles dissolve when the temperature of the beer rises above 68 degrees Fahrenheit (20 C).

As long as the particulates are soluble at warmer temperatures, chill haze does not pose a problem. However, if chill haze is left unremedied for long enough, or the particulates oxidize, they will form larger particles which are no longer soluble. The result is a beer which is permanently hazy.

More seriously, haze can be an early sign of an infected beer, compromising the taste of the product.

Visual aesthetics are not the only concern when it comes to haze. Haze can be a sign of a beer batch infected with Brettanomyces (wild yeast), Lactobacillus, Acetobacter aceti, or other unwanted organisms. While most forms of infection don’t pose a health concern, infection can still result in a product with significant off-taste.

For brewers that produce beer in extremely large quantities—or smaller brewers that wish to scale up their production—relying on visual inspection to evaluate beer haze is not feasible. This is especially true when brewing occurs in multiple locations, where the subjectivity of multiple brewmasters inevitably results in inconsistent product.

Turbidimeters offer an objective, automated means of measuring beer haze and ensuring consistency across multiple batches, or in beer produced in multiple locations.

While “haze” is the term most often used to describe the foggy quality of a beer, more generally the opacity of a fluid is defined in terms of “turbidity.”

Turbidity is the measure of the quantity of particles suspended in a fluid. As the number of particles in a fluid increase, they begin to scatter light passing through. This is interpreted by the eye as cloudiness or haziness.

In many day-to-day situations, we unconsciously evaluate the turbidity of fluids we interact with. The water that comes out of your tap typically has very low turbidity—it’s clear—and you don’t think twice about drinking it. But if you were to one day run the tap and found that you had a glassful of cloudy water, you likely be instinctively repulsed by it.

This is because we associate clarity (low turbidity) with purity, and a lack of clarity (high turbidity) with contamination. While turbid water may simply have high mineral content, turbidity can also be a sign of something more sinister, such as bacterial growth.

Haze and turbidity are most often controlled or removed from fluids—including beer—via filtration.

Old school homebrewers may crack an egg in their beer—the egg white is placed in the brew, and as it sinks the albumin acts as a mobile filter—or use some other another fining additive to remove haze from their beer. At a large scale, macro brewers pump beer through large filtration setups to get that desirable polished clarity before going on to storage and/or packaging for sale.

Large scale filtration often uses plate and frame equipment with a filter media. Diatomaceous earth is a classic type of filter media—often encountered in swimming pool equipment—although there are other materials, such as perlite. In more recent times, filtration cartridges have become more popular.

Plate and frame filters consist of vertical plates covered with a filter cloth. In between these plates are frames that alternately are hollow or contain filter media. Beer is pumped into the frames filled with filter media, where the solids that cause haze are trapped. Clear beer flows through the media and cloths into the hollow plates, and out through collection tubes.

But what happens if a cloth fails and allows unfiltered beer to flow through into the clear stream? This can be a costly problem, as the beer may be spoiled or require reprocessing to bring it to specification. Sight glasses on the clear outflowing liquid have traditionally been used to spot when the beer is no longer clear, but these require the constant attention of an operator to ensure all is going well. Furthermore, using a sight glass is a subjective measure. It’s easy to see when a gross failure in the filter has happened. But smaller problems can be easily missed until late in the process.

Turbidimeters offer an objective, quantifiable means of measuring turbidity in beer and other fluids.

Enter turbidimeters. A turbidimeter is essentially an electronic eyeball that stares continuously at the flowing stream and reports the amount of particulate it sees. The output from the turbidimeter is fed into the overall control system in operation and can trigger a warning or alarm when the particulate level surpasses a predetermined setpoint, alerting the operator to attend to the problem. Sophisticated systems will also stop the flow of beer or divert the flow back to its holding tank while the issue is taken care of.

Some care has to be taken when applying turbidimeters to a beer haze application. A turbidimeter must have enough sensitivity to see low levels or particulate in the beer while being stable in operation, resilient to optical fouling, and insensitive to color change. The ideal instrument is a 90° scatter device, for sensitivity, with an NIR light source for color independence, and a scatter to attenuation ratio measurement technique for window fouling tolerance. This approach will deliver readings that correlate well with offline methods. Forward scatter and backscatter instruments can also be used to measure beer haze, but will deliver results that differ from those of standard offline instruments.

Natural gas supplied to consumers is almost entirely composed of methane, a C1 hydrocarbon. But when natural gas is first recovered from a well, about 60 to 90 percent of it is methane. Mixed in are a variety of C2 through C6+ hydrocarbons—methane, ethane, propane, butane, pentane, etc.—along with contaminants such as water, sulfur compounds, and carbon dioxide.

The recovery of secondary hydrocarbon products significantly boosts the economic value of natural gas processing.

The process of separating raw natural gas into its component products involves several steps. First, acid gases such as carbon dioxide (CO₂) and hydrogen sulfide (H₂S) are removed—often referred to as ‘sweetening’ the gas—and water is removed as well. The resulting sweet, dry gas is processed in either a refrigeration or cryogenic separation plant, which liquifies C2+ hydrocarbons to separate them from the methane.

The recovery of this mixture of hydrocarbons brings significant additional economic value to gas processing operations, as it contains products that can be used as direct energy sources, in addition to raw components useful to various petrochemical processes. The purified methane is distributed via natural gas pipeline, while the remaining C2+ hydrocarbon products are transported via pipeline for further processing at refineries and other facilities. This hydrocarbon mixture is commonly referred to natural gas liquid (NGL).

Monitoring of the NGL stream—typically via photometric analysis—ensures that necessary costs are imposed on those responsible for the input of impure material.

The composition of NGL varies widely from one gas field to another, but all contain similar components. Of prime importance to the receiver at the end of the NGL pipeline is the quality of the fluid. A stream that contains a great deal of impurities can damage refining equipment and be costly to clean up.

Contracts between supplier and receiver often contain clauses that allow receivers to charge suppliers for costs incurred due to low quality streams. As many pipelines are shared, it is important to constantly monitor the inputs to pipelines to ensure that costs are properly apportioned if impure material is received.

A key quality indicator of NGL is color. The presence of common impurities, such as sulfur-bearing compounds and corrosion byproducts results in a yellowing of the NGL. This yellowing is often very subtle and almost imperceptible to the naked eye. But even very slight discoloration can be indicative of contamination significant enough to cause extremely costly problems downstream.

In years past, measurement of NGL discoloration was often achieved by manually comparing extracted samples (“grab sampling”) to the standard Saybolt color scale. However, this was an inexact, error prone, and potentially dangerous process. Today, measurement of NGL discoloration can easily be achieved, safely and in real-time, with an in-line photometric analyzer.

The Kemtrak DCP007 photometric analyzer is perfectly suited for continuous, in-line color analysis of NGL.

The Kemtrak DCP007 photometer is a fiber optic-based unit that is specifically configured to meet the needs of a given application. Using an all-in-one-place electronic design, the optical bench and electronics are contained in a single compact enclosure for maximum ease of installation.

Light is generated using non-drifting LED sources, and connected to application-optimized sample flow cells using ruggedized industrial fiber optic cables. Flow cells meet the sample demands of a high-pressure liquid hydrocarbon. Electrical compliance is not an issue, as there is no at-line electrical connections or sensors.

The sample cell can be installed directly in the process line, though it is typically installed in a side stream to aid maintenance and contractual verification requirements. A hard media verification system can be included as an optional extra. Kemtrak flow cells require very simple sample handling systems, only needing a stable flow running through the flow cell to ensure the measurement is a true representation of the actual process flow. Particulates and turbidity in the sample are not an issue, and are compensated for using a reference wavelength.

Kemtrak has an extremely impressive track record, with thousands of photometric analyzers installed around the world for a variety of applications. The Kemtrak DCP007 is now found in a variety of gas and liquid applications, in part because of design features tailored to meet the challenging conditions posed. The DCP007 has no moving parts within the analyzer, utilizing a dual-channel approach to compensate for entrained particulates and solid matter. It also features LED light sources that are individually controlled for stable, unwavering output and consistency.

South Fork Instruments has a great deal of expertise in developing in-line solutions for analyzing a variety of process fluids. We can review your needs and determine whether the DCP007 is suitable for your application, or whether an alternative approach would deliver superior performance for in-line color and/or concentration monitoring.

SFI are pleased to announce the release of a range of hygienic single use flow cells for use with the Kemtrak DCP007 UV Absorbance Analyzer. The single use cells are available in a range of different line sizes and with a variety of optical path lengths to suit all applications from small scale discovery to full scale production. Manufactured from high quality medical grade polysulfone, cells are color coded for optical path length and sterilizable either through autoclaving or irradiation. A zero dead volume in the cells ensures sharp peak detection for fractionation control and filtration applications.

Four sizes of cell are available from ¼” to 1” and all have ready-to-attach hose barb connections. A robust, space saving cell holder with quick insertion/release mechanism precisely positions the cell in the optical light path for reliable measurement performance Cells can be delivered with optical path lengths from 10mm to 0.5mm, giving overall measurement range capability of 4.5 to 90 OD when used with a DCP007 UV analyzer.

The Kemtrak DCP007 is an industrial in-line UV fiber optic photometer designed to accurately measure UV absorbance of fluids in filtration and separation systems using long life solid state LED light sources and precision fiber optics to provide drift and noise-free deep UV measurement at very high precision.

The Single Use UV Absorbance system will be on show at Interphex on South Fork Instruments booth #1338.

South Fork Instruments, Inc. is the master distributor for Kemtrak AB in the USA.

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South Fork Instruments, Inc.

Auburn, CA
925 461 5059
[email protected]

Media contact:
John Daly
925-783-5185