Do you have any of these concerns with your current measurement solutions?
"Our clarity measurement is very noisy. What is causing the noise?"
The #1 culprit of noisy signals with optical measurement is air bubbles in the flowing stream. Air can be a real problem in some process systems - typical sources of air entrainment are upstream cavitating pumps and mixers/agitators. Eliminating entrained air it can be really difficult, if not impossible, so it’s well worth looking at your sensor installation and seeing if there is anything you can do to help alleviate the problem
Is your sensor Installed in a horizontal pipe? If so, is it installed in the side of the pipe with a horizontal plane for the measurement? Installing a sensor top down or bottom up in a pipe can be problematic. Air bubbles rise and tend to run along the top of a pipe. Having your NIR sensor there will definitely create some issues. In the bottom, any heavier materials will sink and run along the bottom of a pipe, again, creating noise in the measurement plus there is also a risk of deposition on the sensor window that will eventually blind the instrument. Ideally, the sensor will be installed in a vertical pipe (flowing upwards). When installed in this way, bubbles and particulate tend to become more evenly distributed across the flowing fluid in the pipe and the measurement is more “homogenous.”
Sometimes it’s not possible to change the installation position. The design of the sensor can help in this case. Is the optical window on your sensor flat? Flat windows, because they are set into the sensor body slightly, tend to collect bubbles on their surface and cause erratic readings. Try a sensor with a ball shaped window (like the Exner EXspect 271) instead. The shape of the window causes bubbles to roll off of the measurement surface. This, in conjunction with signal filtering, can create an acceptable and reliable reading.
"Our clarity probe reads pretty much zero all the time and isn’t very sensitive to small changes."
Making low level turbidity measurements can be very challenging for low-cost turbidity probes. There are higher cost instruments available that will do a pretty good job for you, but these are typically flow through devices and not generally suitable for installation in tanks and vessels. For low-cost solutions, you have two options: 1) a backscatter probe and 2) a long path transmission/absorbance probe. Backscatter probes lose sensitivity at very low levels but have the ability to measure up to fairly high levels of turbidity, while long path absorbance probes are sensitive at low levels but will over-range pretty quickly as turbidity increases. If your plant typically reads low level, an absorbance technology probe will probably solve your issue. If turbidity in your plant changes over quite a wide range, you may find that you have to fit two probes, one of each technology type and switch from one to the other as clarity changes up and down.
"How do I make my clarity probe insensitive to color?"
Clarity probes that use broadband light sources will be very sensitive to color changes in the process stream. This can be a real problem for things like flavored milk drinks, even milk from different farms, as color changes will cause different levels of light absorbance and change the response of the instrument. Always choose a clarity/turbidity probe that uses an NIR light source as this is completely insensitive to color change.
"We run an SIP cycle in our plant to make sure process lines are sanitary but as a result, we get a lot of failed turbidity sensors."
The specifications of some turbidity sensors claim to be able to withstand high temperature. While this may be true for short periods, the reality is that many do not withstand the repeated, prolonged temperature cycles such as those seen in SIP operations and sensor failures are common. Always read the fine print to make sure the instrument you are installing is capable of repeated exposure to high temperatures – they should state in their specifications something like … 140°C for 2 hours max.
For longer term steaming, an alternative is to install probes that can be retracted from the pipe while high temperature operations are taking place. 12mm absorbance probes can be fitted into automatically operated retractable housings and withdrawn before steam is introduced into the process lines. Automatic cleaning systems can be used to clean and sterilize the turbidity probe with sanitizing solutions while the probe is retracted, ensuring it is ready to reinsert once steaming is complete.
"We calibrate our turbidity systems using liquid standards but often get different values when repeating the procedure."
Calibrating turbidity and clarity instruments with liquids is not a simple task. The main problem is that turbid solutions constantly settle, so readings are always on the move during the calibration routine. Furthermore, different technicians may handle solutions differently and that too creates variation. Agitating to re-suspend particulate and pouring into and out of test cups and beakers can further introduce air bubbles that create errors. Calibrating and validating turbidity probes can be best carried out using hard media filters such as those found in the Exner EXCap calibration sets. Filters are available for both absorbance and backscatter instruments and provide a quick and repeatable way of ensuring your probe is working correctly and to specification.
SMALL PIPE INSTALLATION
"I want to install a turbidity sensor into a 1” process line but I’m being advised not to as there will be interference from light reflection from the opposite pipe wall. What is the smallest pipe I can fit a sensor into?"
Backscatter instruments can be severely affected by stray light reflection from pipe walls if the sensor is too close to them. This is a real issue for turbidity sensors with flat windows. Turbidity sensors with a curved or ball type window are far more resilient in small pipes because of the way the light is passed into and out of the stream. The light enters the spherical window pipe at an angle because of refraction and is focused at a very small point on the ball’s surface. The angle of entry into the flowing stream causes the excitation light beam to disappear on down the pipe rather than be reflected off the back wall and into the sensor. Exner EXspect sensors use a ball window and can be installed in pipes as small as 1” diameter.
"I tried installing a turbidity sensor in an existing port on my pipe, but the measurement face ended up being about ½” back from the pipe wall. Is this a problem?"
In general, it’s not good practice to have any sensor set back at any distance from internal pipe wall as the reading it gives may not be representative of the flowing fluid. In the case of turbidity sensors, such a “dead leg”, depending upon orientation, can also collect air or sediment from the stream, creating additional measurement error (not to mention cleanability issues). Ports with dimensions that allow a sensor to reach the internal pipe wall should always be used. If not available, a new one should be installed or a spool piece with correct mounting fitted inline to ensure the measurement performs properly.
SOUTH FORK INSTRUMENTS PROVIDES SUPERIOR QUALITY NIR SENSORS FOR APPLICATIONS OF ALL SCALES AND DIFFICULTIES.
Too often, manufacturers and processors tolerate the high costs—replacement equipment and lost production—resulting from sensors which are fragile and short-lived in the demanding environments of their plants. Often these sensors come with a promise that they will provide reliable measurement and enable significant savings for their end users.
South Fork Instruments specializes in providing sensors which are designed specifically for continuous processing in food, beverage and dairy applications using SIP and CIP, where measurement robustness is a key requirement. Sensors from South Fork Instruments meet the demands of your applications, allowing you to better optimize and automate your processes, reduce overhead costs and increase profitability.
If you are seeking measurement solutions that need highly reliable turbidity and clarity sensors with the surface quality necessary for pharmaceutical applications, and meeting the hygiene requirements of food/beverage processors, South Fork Instruments can deliver exactly what you need.
WHAT ARE NIR PROCESS SENSORS?
NIR process sensors utilize light in the near-infrared (NIR) to determine the clarity of a flowing liquid stream by measuring the amount of particulate or solids present. NIR sensors provide a trending signal following the amount of particulate/solids in the flowing stream, making them very useful in many processing applications. NIR sensors are used in a wide range of applications, from small-scale laboratory research to full scale pharmaceutical, chemical, food, and beverage production processes.
Typical industrial applications for NIR probes include:
NIR sensors are ideally suited for closed systems that are CIP'ed where they provide valuable input into cleaning effectiveness. A major overhead in industries such as pharmaceutical, personal care, food and beverage is the measurement of cleaning efficiency. In order to comply with FDA and USDA regulations, any clean-in-place systems implemented must work well enough to ensure contamination-free manufacturing of certain commodities. Accordingly, there is often a natural tendency for operators to extend cleaning cycles for far longer than is actually necessary.
How can you optimize a cleaning method so that it takes no more time than necessary, and complies with government regulations and requirements? One way is to continually take samples from the line to see how cleaning is progressing. As time progresses, the cleaning solution in the line will become clearer as soil levels fall. Eventually, soil level will reach a minimum indicating that the cleaning cycle is complete.
In a closed system, things are not always so simple and you often can’t just open a valve to take a sample for measurement. Cleaning solutions can be hazardous to health, and you also need to avoid the possibility of contaminants getting into the system and making things worse.
Hence the usefulness of NIR process sensors. These handy devices are mounted directly in the piping of a closed system, continuously monitoring the solids concentration or turbidity of the flowing stream within. During product processing, they can provide valuable quality and consistency information. Once processing is complete, they can be used to spot the arrival of the interface between the product and the clean liquid being used to push the end of the batch through the system. Once a cleaning cycle is underway, signals from these devices provide a downward trend as cleaning progresses, allowing operations personnel to determine when the correct level of cleanliness has been reached and the plant can once again be used for revenue generating processes.
The installation of NIR process sensors can help demonstrate adherence to regulations, reduce product loss, replace manual sampling and the risks it carries and increase plant utilization and efficiency. As a general rule of thumb, most NIR process sensors pay for themselves in saved water volume and water treatment costs very quickly after installation.
In-line filters are used to clarify liquids in many processes. For instance, brewers use haze filters to remove the cloudy appearance of beer while sparkling beverage manufacturers use filters to clarify feed water.
Installing an NIR sensor downstream of a filter will provide real-time feedback about the clarity of the stream and ensure you know your filter system is working properly and efficiently. Sensor signals can be used to indicate when filters should be changed, taking the guesswork out of filter maintenance while saving you money as every filter can be used to its capacity – no more throwing away of partially used filters! Sensor outputs can also be used to automate filter bed regeneration – another efficiency improvement.
Separator Monitoring Systems in Brewing
Final beer clarity is a very important facet of product quality. While some beers are sold as "hazy", or may become hazy due to secondary fermentation in the bottle, there are also many beers that are required to be clear and free of haze. Controlling the amount of haze in beer before final bottling ensures consumer satisfaction.
In brewing, separators are used, amongst other things, to remove yeast, reduce turbidity and clarify green beer before conditioning. The speed at which liquid is fed into a separator can have a marked effect on the turbidity of the outflow. In general, slow feed rates will create a clearer outflow and vice versa but when clarifying a batch of beer, the influent turbidity can vary from initial feed to final feed. Knowing the inflow and outflow turbidity of a separator allows control of the separator feed rate to produce desired outflow clarity
Installing NIR sensors in the inlet and outlet piping of a separator provides real time trend information that can be used by a connected control system to vary the influent flow rate to achieve the best efficiency and most consistent outflow quality. The inlet turbidity measurement is used to monitor the initial load being put on the separator and allows for feed rate adjustment while the outlet monitor will provide real time indication of when the solids collected in the separator needs to be discharged. Furthermore, the inlet sensor can be used to divert flow away from the separator should it become too turbid - conditions seen at the beginning and end of a fermenter discharge cycle - to prevent separator overload and allow for continued operation of the plant.
No matter the application or industry, South Fork Instruments can develop a superior optical sensor-based measurement solution.
We have provided NIR optical sensor solutions to clients in such industries as food and beverage, chemical processing, pharmaceutical manufacturing, and biotechnology, and can assist you in developing and effective and efficient means of fulfilling your measurement needs.