The moisture content in a product can have serious effects on its final quality. Controlling and adjusting the moisture content throughout the process can eliminate many common manufacturing issues. While laboratory and other manual methods have been used for years, new automated moisture measurement and control systems can play an important role in improving product quality monitoring, increasing plant efficiency, and lowering energy costs.
Moisture measurement technologies and benefits
Moisture levels present in raw materials and finished products play a critical role in manufacturing quality and consistency. They also have a bearing on costs – water weight is heavy and manufacturers can lose millions of dollars when moisture levels are too high. Those buying and shipping out materials with too much water weight are shouldering needless costs.
There are several available methods for moisture measurement in industrial manufacturing settings, including visual inspection; manual testing; oven weight loss; and moisture sensors. Manufacturers who rely on simple “guesstimates” based on sight or feel determined in a visual inspection cannot provide the necessary consistency or quality. Conducting manual testing by taking samples and bringing them to a laboratory for analysis adds considerable time to the entire process chain. Another possibility is the traditional oven weight loss moisture method, also known as the drying oven method or loss-on-drying (LOD) method. This method measures the moisture content of a sample by weighing it before and after heating it in an oven.[1] While useful, this technique may end up burning off more than just moisture; it can burn off protein inside food or melt PVC inside a pellet.
A more robust technology is the use of moisture sensors. One example is MoistTech’s moisture sensor technology, a non-destructive method of measuring and controlling moisture content. Based on near-infrared (NIR) technology that enables moisture measurement without coming into contact with the product, the moisture sensing technology avoids wasted product, gives instant, accurate and repeatable results and uses a simple light source for measurement, allowing for longer use of equipment. The sensors have been used on a wide variety of applications, including adhesives, chemicals, coating, converting, food, forest products, hemp/cannabis, minerals, paper, plastics, renewable energy, textiles, tobacco, and web.
Under the hood of near-infrared (NIR) technology
Insensitive to material variations such as particle size, material height and color, the MoistTech NIR technology provides continuous, reliable readings with zero maintenance. There is a one-time calibration with a non-drift optical design allowing operational personnel to confidently make immediate process adjustments based on real-time measurements.
Online sensors are mounted in different locations depending upon the application, including on a belt, screw conveyor, chute, roller, chain, drag and elevator conveyors, cyclones, bins, before/after dryer, webs, pipelines, and pneumatic conveyors. Sensors are installed about 4-16 inches from the product using a bracket on the back or top of the sensor. Sensor units are standalone and require no software or external output device. Display options are available but are not required for operation.
In addition to moisture, the sensors can measure coating weight, sheet and film thickness, oil, protein, temperature and other elements that absorb NIR. Accuracy and repeatability is in the +/- 0.01%-0.1% range, depending on the application.
A variety of online units are available, including models that can withstand wash-downs, dusty/dirty environments, aggressive process applications, extreme heat, and explosion-prone areas. Specific models have been designed for black applications such as coal and Sinter. Offline or laboratory units include those specifically designed for tobacco processing; those featuring sampling dishes for rapid moisture determination in 3 seconds or less; as well as the first-ever moisture unit where samples can be measured from the bottom up through sealed jars. They are available with three self-powered 4-20mA outputs, Serial RS232/485 and Ethernet TCP/IP. Additional options include Ethernet IP, Profinet and Profibus.
Benefits of using moisture sensors for moisture control
There are several key advantages of using moisture control for manufacturing processes:
Improved product quality monitoring – Depending on the application, moisture plays a critical role in the process with raw materials. Moisture sensors allow operators to be more proactive in assessing any situation, which can save considerably on costs. Take potato chips for example. A a run of potato chips that gets down to the end of the process line with too much moisture risks wasting tons of products that could have been saved if operators had been able to detect the moisture issue and intervened earlier in the process.
Increased plant efficiency – Moisture measurements taken by hand and brought to the laboratory can take anywhere from 10 minutes to a couple of hours to get lab results. Moisture measurement eliminates this downtime, as well as human error that may be involved in manual testing.
Lower energy costs and less wasted product – Dryer ovens use a large amount of energy and result in very high costs. For wood, paper or oven/food applications, manufacturers can lower energy costs significantly by optimizing dryer/oven settings and knowing exactly what temperature is needed for their application.
Precise dryer or oven control – Especially for wood applications, optimizing dryer settings results in instant savings for the user, allowing them to immediately pay for moisture measurement equipment. They save tenfold in time wasted from rework as well as saving money.
Low cost and high accuracy – By eliminating manual testing, manufacturers can recover their return on investment (ROI) quickly from energy savings, as well as decreasing downtime and wasted product. For example, MoistTech has developed a proprietary ROI calculator that lets manufacturers plug in their application-specific data to quickly see how much money they could save compared to manual testing. The calculator collects information on the number of products/tests run per day, the length of time the tests take, labor and overhead costs, and rejected/wasted material, and comes up with savings (per day and per year) from using moisture measurement equipment, calculating the ROI for the specific application. See the accompanying graphic showing how the ROI calculator was used by one company.
Low to zero maintenance – Sensors use a plug-and-play operation which can be mounted on a production line and ready to go in minutes, with no need for on-site setup and a user-friendly interface.
Process optimization – Operators can tie the moisture sensor into other equipment, and more efficiently control the big picture with a programmable logic controller (PLC). Removing time constraints, the sensors can automate that job, making it more efficient with less room for error.
Moisture measurement helps companies from bakeries to plastics
MoistTech moisture measurement technology is being used all over North America, for applications ranging from plastics to bakeries to potato flakes – and beyond.
At one plastics manufacturing facility, operators need to check moisture in plastics; if the moisture content is too high, the material will degrade during processing and will produce brittle parts. After switching from another measurement device and LOD methods to MoistTech moisture measurement technology, the company reports production is sped up because operators no longer need to wait several minutes to determine if the material is ready for production.
A medium-density fiberboard (MDF) manufacturer in Oregon had a moisture gauge installed on their forming line that was continually failing due to high temperature and other issues, causing production delays. The cost to replace the gauge was between $25-$30,000 and the cost to repair it was $15-$20,000, with excessive repair time. The company went through replacing and/or repairing the gauge several times, before opting for a MoistTech moisture gauge with a vortex cooling panel. The new gauge has been running without any heat problems and is correlating with lab test results within 0.1 percent.
Another example comes from an application that dehydrates cooked mashed potatoes into “flakes,” which are toted for further processing into finished flavored potato product. The company was taking samples at timed intervals and testing them in a lab with NIR equipment, but by the time the samples were taken and the data received, adjustments to the process were delayed, making it difficult to control the product to specifications. They installed a MoistTech sensor over four flat belt conveyors that transfer the potato flake from one location to another. Now the sensors are monitoring the moisture and adjusting the speed of the drum dryer by changing the frequency of the motor VFD compared to the moisture set point to a satisfactory accuracy.
A final example is a family bakery that needed to monitor surface moisture on baked goods. They were using organoleptic testing and estimated they were losing from .5-1 percent of the product each month. After installing the MoistTech sensor above the cooling line, the company achieved significant savings and moisture control.
Moisture control and quality
Moisture control in manufacturing is an important issue with a significant effect on quality and costs. Changing regulations and standards require monitoring and recording of moisture content for quality. In addition, global supply chain disruptions require tighter quality control and finding ways to ensure no waste/low waste. Using moisture measurement technology is an important way of meeting these goals.
[1] Oven weight loss moisture method, Google AI overview, retrieved 6/7/2024.