Maximizing Accuracy in Material Weighing Systems

Material weighing systems that are used to measure large quantities of materials are referred to as bulk material weighing systems and are most often found in industrial settings. Some are also used in agriculture-related industries such as grain processing and animal feed manufacturing. The materials being weighed can be dry or liquid materials. Dry materials are either in powder or granular form. The use of the term “bulk” signifies the material is in large volume or mass. These bulk materials are shipped in large quantities, often in trucks, large plastic containers, pallets of small bags, or in large FIBC (flexible intermediate bulk container) bulk bags.

These weighing systems can vary from very simple mechanical scales to advanced electronic systems that are integrated with sophisticated control technologies and include significant data management. The primary goal of these systems is to accurately measure the quantity of material, which is an essential function for a variety of applications including ingredient batching, blending, and quality control. Knowledge of the materials, containers, material flow, feeding/pumping, and many other functions is necessary to understand the design and characteristics of these weighing systems.

Several factors can impact the accuracy of these material weighing systems. Understanding and addressing these is crucial for optimizing performance:

Scale

1. Minimum Weighment: The smallest quantity a scale can accurately measure needs to be consistent with the minimum weighment you expect to make with the scale. If the minimum weighment of the scale system is greater than your minimum required weighment, the scale system may not provide accurate results meeting your expectations.
   
2. Scale Capacity: This is the maximum weight that a scale can handle. Do not select a scale whose capacity is less than the maximum expected weighment(s) of your required material(s). If your weighment exceeds scale capacity this could introduce inaccuracies due to overloading.
   
3. Accuracy Required and Resolution: The higher the accuracy you require, the more precise the scale will need to be.  This may involve more frequent calibration and maintenance (see below). Resolution is the smallest increment the scale can measure/detect/resolve and display.  Higher resolution scales can typically provide more precise and detailed measurements of small changes in weight.
   
4. Load Cell Quality: The quality and condition of load cells (the components that measure force/weight) directly impact scale accuracy. Wear and tear, or defects in load cells can affect measurement accuracy and consistency (precision).
   
5. Scale Type: While most scales used for material weighing use load-cell technology, the scale type or configuration can vary depending on the application and varying degrees of accuracy.

Calibration and Maintenance

1. Calibration: Regular calibration is essential to ensure the accuracy of weighing systems. Calibration involves comparing the system’s measurements against known standards and adjusting it as needed. It’s important to follow the manufacturer’s recommendations for calibration frequency and procedures. Calibration systems are available that automatically calibrate scales to reduce human error and ensure consistent accuracy.
   
2. Maintenance: Routine preventative maintenance should be carefully scheduled and performed to eliminate issues that can affect accuracy, such as mechanical wear, sensor drift, or software malfunctions. Scheduled inspections and servicing can identify and resolve potential problems before they impact performance. A preventative maintenance strategy is best.

Environmental Conditions

1. Temperature: Temperature fluctuations can cause the expansion or contraction of materials and equipment, affecting weighing system accuracy. Temperature-compensated weighing systems can help mitigate this issue by adjusting measurements based on temperature changes. As a part of the automated weighing system, temperature sensors can be built-in to continuously monitor ambient temperature and allow the system to run compensation algorithms to correct for thermal expansion/contraction of materials and components.
   
2. Humidity: High humidity can impact the weight of hygroscopic materials, which absorb moisture from the air. This can create material flow problems, sticking materials, and calibration and maintenance issues. Using controlled environments can help maintain consistency in weighing.
   
3. Vibration: Vibrations from nearby machinery or traffic can disrupt accurate measurements. Installing weighing systems on stable, vibration-free platforms or using isolation mounts can reduce these effects. Using vibration isolation mounts or pads to minimize the impact of external vibrations is another good approach, along with regular scheduled calibration and maintenance of the weighing scale system.
   

Material Properties

1. Bulk Density: The bulk density of materials can affect the choice of scale, the volume it may hold based on the weighments required, etc. This material characteristic is generally associated with dry powder or granular materials. It can impact how the materials settle and flow into the weighing system. Understanding the bulk density of the materials, selecting the best scale apparatus, and adjusting the weighing system accordingly can improve the accuracy and consistency of measurement. The density and viscosity of liquids, like bulk density, significantly influence their flow behavior, volume measurement, and the dynamics of incoming and outgoing flows in tanks.
   
2. Flow Characteristics: Materials with poor flow characteristics, such as those that are clumpy or sticky, can cause inconsistent measurements. Implementing appropriate feeding mechanisms or using additives to improve flow can enhance accuracy. Dry bulk materials will exhibit varying properties of cohesion (material particle attraction to one another) and adhesion (attraction of particles to other materials such as scale hopper and tank walls). Flow characteristics need to be known and understood for maximum weighing system performance and scale system selection.

To ensure the highest level of accuracy in dry and liquid material weighing systems, consider the following as best practices:

Select the Right Material Weighing System

Choosing the appropriate weighing system for your application is critical. Consult with experts in material weighing and control for your industry and manufacturing process. Factors to consider include:

1. Capacity: Ensure the system can handle the maximum load required for your processes.
   
2. Accuracy and Resolution: Higher accuracy and resolution systems provide more precise measurements, which is essential for applications requiring tight tolerances. They also can come with a higher cost. Refer to other discussions above regarding accuracy and resolution.
   
3. Scale Type: Depending on your needs, you may choose from belt scales, loss-in-weight feeders, tanks on load-cells, scale hoppers, platform bench-type scales, floor scales, inline conveyor scales or other types.  Often your application and use of material weighing systems in your process will dictate the type of scale.

Implement Proper Installation

Correct installation is crucial for maintaining accuracy and consistency over time. Key considerations include:

1. Leveling: Ensure the material weighing system is installed level. This will prevent inaccuracies caused by uneven surfaces and is critical to the long-term performance of your system.
   
2. Foundation: Use a stable foundation or mounting system to reduce the impact of vibrations and other external factors. If in a high-vibration area, consider installation elsewhere or use methods to isolate the material weighing system from the vibrations.
   
3. Alignment: Proper alignment of components, such as load cells and weigh hoppers, ensures accurate measurements.

Utilize Advanced Technologies

Leveraging advanced technologies can significantly improve accuracy:

1. Load Cells: Modern load cells with high precision and stability are essential for accurate measurements. Regularly check and calibrate load cells to ensure optimal performance.
   
2. Automation: Integrating automated systems for calibration, maintenance, and data collection can enhance accuracy and reduce human error.
   
3. Software: Advanced software solutions offer features such as real-time monitoring, data logging, and preventative maintenance, helping to maintain and improve system accuracy.

The field of bulk material weighing is evolving with advancements in technology. Key trends to watch include:

1. Real-Time Data Integration: Data collection exists today. Systems utilizing material weighing collect and can store significant amounts of data, such as by using the SQL or SQL Express programming language to manage and manipulate databases by providing a standard way to interact with databases, and is ideal for applications where significant material weighing exists (such as ingredient batching systems). Integrating this data with your ERP can be done today.
   
2. Machine Learning: Combining data collection and integration to your ERP with Machine learning algorithms applied in your ERP you will be able to optimize your processes, including material weighing, inventory management and more by predicting and making changes to your process, such as correcting potential errors, based on historical data.
   
3. Enhanced Materials Handling: Innovations in materials handling, such as automated handling systems, advanced feeders and conveyor systems, pumping systems for liquids, can contribute to more accurate and efficient bulk weighing.

Maximizing accuracy in bulk material weighing systems is crucial for achieving operational excellence and ensuring product quality. By understanding the factors that affect accuracy, implementing best practices, utilizing advanced technologies, and staying informed about future trends, you can enhance the performance and reliability of your weighing systems. Regular calibration, proper installation, and ongoing maintenance are key to maintaining high accuracy levels and achieving optimal results in your bulk material handling processes.

If you need further assistance or wish to explore advanced solutions for your material weighing requirements, don’t hesitate to reach out to industry experts or consult with specialists who can provide tailored recommendations for your specific requirements.

With over 50 years of expertise in custom engineering material weighing, ingredient batching, liquid handling, process control, and other bulk material handling solutions, Sterling Systems & Controls proudly has the experience to assist you in bulk material weighing. Contact us today to discuss how our knowledge and experience can align with your goals and how you can continue your journey toward manufacturing excellence!