Reverse Roll Coaters have a metering and applicator roll. Often there are 3 or 4 roll configurations. Coating is applied through the gap between the metering and applicator roll where the nip pressure and gap control the specific coat weight. The applicator roll runs in reverse direction of the web transferring the coating onto the web. Reverse Roll Coaters are capable of producing highly polished surfaces and are more expensive than some other coaters such as slot-die that can’t always achieve that level of polishing. If a Converter operates a Reverse Roll Coater a Cross Direction Web Profile System is a good investment to maintain uniform coat weight on high end products. The Guardian Cross Direction Web Profile System meets the application needs for film, foil and paper coat weight and moisture measurements on Reverse Roll and other coaters.
Sand Moisture Control is important in the manufacturing and processing stages. Giant sand piles may sit exposed to the weather rain or shine impacting the moisture content of the whole pile and external versus internal moisture profiles. It rained for 3 days and yesterday it was hot bright sunshine, then the exterior is dryer than the interior. Near Infrared Moisture Transmitters provide an immediate measurement of sand moisture on the belt. The transmitter is mounted between 8 and 18” (200 – 450 mm) above the product with an air purge of 3 – 10 psig to keep the sight lens clean. Large digital display, proportional analog output (4 – 20mA) and Ethernet communications are available.
Sand is sold by weight and specification, meaning that there is range of acceptable moisture level in the sand upon delivery. If the sand moisture exceeds that moisture level it can be rejected or purchased at a significant discount. If the sand moisture is lower than that specification the supplier is leaving money on the table by not adding water to increase the weight while still being in specification.
Sand moisture can be controlled by dryer temperature, throughput and re-moisturizing. Dryer Temperature adjustment may be used if a known incoming run of sand is high in moisture. As a practical process control option dryers have too slow a response time for minor variations that still need to be optimized to maximize efficiency (profit). Dryer throughput is the best control parameter as it can increase or slow throughput through the dryer based on moisture. When raw product is over dried or oven has over dried a moisture spray station may be triggered by the PLC. Moisture is money for Sand Suppliers. An upper level in-specification sand moisture allows End User to optimize for specific application and maximize profits for supplier.
Lamination is essentially marrying two or more layers of materials together to obtain superior performance characteristics for specific product applications. Near IR Transmitters are well established to measure moisture and coating thickness in the lamination process. Cross Direction Web Profilers greatly assist in producing an even in-specification profile of adhesive thickness. The resulting composite may be designed as a superior moisture or odor barrier, to highlight/protect appearance or gloss, reduce sound transmission, to increase strength or structural stability and many other applications.
Auto windscreens (windshields) laminate two pieces of glass with a layer of PVB (polyvinylbutyral) or other suitable polymer to prevent or minimize sharp glass shards from showering on driver and passengers on impact by wrapping the glass surfaces with the polymer. Near IR can measure the film moisture and thickness.
Converting industries such as Tag, Tape & Labels, Packaging & Release Liners, Textiles and others operate Near IR to measure the adhesive coat weight applied and the moisture after unit operations such as dryers, re-moisturizers and final windup for QC and Process Control. For converting applications a two roll laminator is often employed with one roll made of neoprene or other suitable rubber and the other roll made of steel or chrome plated. The rubber roll applies pressure to the adhesive but also allows for compensation of caliper variations. Nip roll pressure and skew assist in optimizing the process.
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Calibration Procedure for New Products
This procedure is outlined for snack foods that may or may not be ground in the lab for analysis or powder and bulk solid or similar applications. Double-Blind Samples are recommended for calibration and validation. This allows the sensitivity or span (linear regression slope) to be accurately determined in the laboratory to speed up the calibration of on-line transmitter when it’s difficult to create a range of process moisture samples on-line.
Step 1: Collect sufficient product for about four or five samples of 200 grams each.
Step 2: Measure 100 grams +/- 2 grams and place into a sealed Bag or container.
This will be sample 1.
Step 3: Measure 100 grams and spray about 2 grams of water on the sample. Mix
the sample and place into a sealed bag or container. This will be sample 2.
Step 4: Measure 100 grams and spray about 4 grams of water on the sample. Mix
the sample and place into a sealed bag or container. This will be sample 3.
Step 5: Measure 100 grams and place in an oven with a temperature of 100 degrees C.
Leave this sample in the oven for 10 minutes*. Remove from the oven and
Place into a sealed Bag or Container. This will be Sample 4.
Note: If a fifth sample is used repeat Step 5, but keep in oven for 20 minutes*.
Step 6: Leave these samples in the Sealed Bag or Container for at least four hours to equlibrate.
Step 7: Take Sample 1 and place under the MCT. Record the moisture measurement.
Step 8: Do the Normal Lab analysis for this sample. A Confection Oven or
Vacuum Oven is recommended.
Step 9: Repeat Steps 7 and 8 for the remaining samples. When all the samples are
Analyzed, we can begin the MCT Calibration Routine. This can either be performed
via the MCT Operator Interface panel or by using the PSC Viewer Suite software. Entering the Lab vs. MCT Near Infrared Transmitter Data allows for a linear regression to be performed and the new Span/Sensitivity (Linear Regression Slope) and Zero/Offset (Linear Regression Y- Intercept) to automatically be generated for correct calibration.
Step 10: Confirm calibration by collecting sample on-line within target set point values and only make a zero or offset adjustment based on double-blind lab sample. Congratulations!
* Theseare variable.
Some products may need more or less water. Some products may take more or less time. Please contact PSC to discuss any questions or to request our assistance.
Most companies outline sample collection procedures in a Best Practices write up. Consistency in sample collection and sample processing is the most important variable for good sample analysis.
Samples should be collected and immediately taken to the laboratory or packaged for shipment to an outside lab in a sealed moisture barrier container or bag. If sending samples to an outside lab an additional moisture barrier tape should be applied around container lid. If samples are delivered to an in-house lab the procedure must outline for lab personnel the time to grind or process sample prior to measurement.
Calibration samples should be done individually meaning that sample one is ground, weighed, placed in oven for specified time interval at specified temperature for that product and weighed again for moisture determination. At that point the next sample is processed. Grinding all samples initially introduces an opportunity for increased variation while they await analysis unless all samples can be placed in the same oven immediately.
Consistency is the key to this process. If the first shift collects samples and the lab analyzes these samples when received, results are good. If another shift or operator collects the samples in a different manner or lets them sit for a while before bringing to the lab, or the lab lets samples accumulate before processing, variations can occur. Consistency is important for successful calibration.
Alternatively, samples can be created in the lab and allowed to equilibrate. These samples can be used for calibration. A final double- blind target set point sample should be analyzed and averaged to determine any offset (zero) adjustment on-line.
Other parameters such as fat and oil are subject to stratification and a well-mixed double-blind sample analysis is even more important for these constituents during calibration.
Pressure Sensitive Tape Council Meeting Orlando Florida
A Sticky Affair!
Pressure Sensitive Tape Council is a highly technical conference featuring world class presentations on current and emerging technologies that benefit the tape manufacturing process. PSTC also has a very collegial feel with technical people who know situations change and friendships remain. Our Near Infrared Calibration Procedures Poster was featured in the afternoon session.
We appreciate and thank you for our time together at PSTC May 2016!
Powder & Bulk Solids Show in Chicago was a success! First day was a bit slow but second day was high traffic and lots of contact with existing customers with new projects and new customers seeking solutions to their moisture problems.
Interestingly, many of the new inquiries were for Flake Applications which are easy applications for our Near Infrared Technology. Also much interest in our Snorkel Sampler for hopper, vertical and gravity conveyor applications.
Jun and Lucia presented our products and enjoyed the Windy City!
Double-blind refers to the same collected sample being divided into two samples and analyzed “blind” meaning that lab technician or off site lab does not know that within the samples being analyzed that several are duplicate samples.
When calibrating an analyzer the results can never exceed the laboratory accuracy and sample collection method. Variances can be due to sample collection, head space in sample container, temperature and duration and type of lab method and other variables. All can be minimized in a simple specific procedure outline for the product.
Moisture samples should be collected in a polypropylene or other suitable container with a moisture barrier lid. Container should be full with minimal air head space. Crush samples if possible to increase sample density.
Determine the appropriate sample size 200 – 450g, temperature and duration for weigh dry weigh lab determination of control samples. Many labs feature automated weigh dry weigh analyzers that predict sample moisture. The higher the temperature of the convection oven the quicker the extrapolate result, and usually a less accurate result. While this speeds sample turn around and increases throughput its contribution to variance must be considered. Hence, double-blind sample averaging minimizes this variation and improve calibration.
For example, using a weigh-dry-weigh gravimetric procedure with an oven temperature of 115?C for 6 minutes will yield a different result than running the sample at 80?C two or three hours. There also may appear to be “crisping” or “sample browning” at the higher temperature that adversely impacts accuracy. Again, this is in regards to calibration samples and not necessarily day to day production lab tests that require rapid turn around and high throughput.
Let’s view results for samples tested at 80?C, 115?C and those sent to an outside sample as double-blinds. Outside labs can be subject to the same variation as in-house labs and double-blind samples reveal the accuracy of their results too. The chart below shows the benefit of using double-blind samples for calibration and any subsequent validation to improve accuracy.
Process Sensors is seeking to expand representation and service of our product line in some parts of Central and South America. Our areas of interest are outlined below. Process Sensors offers a complete line of Near IR and RF gauges for industrial manufacturers who need to measure moisture, oil/fat, additives, Cross Direction Web Profiles and other systems. Systems are for process, at-line and lab applications.
Costa Rica y Nicaragua: We are interested in representation, preferably with an office in centrally located San Jose, Costa Rica.
Panama: We seek representation with a company that has demonstrated success in process industries.
Ecuador: We seek representation with an industrial manufacturer’s rep, preferably based in Quito.
Venezuela: We seek representation for applications that have sufficient Return on Investment to attract consideration for both domestic and multi-national companies seeking to grow market share.
Please contact us at email@example.com