Using weighing systems to optimize batch accuracy
One of the key components of any batching operation is consistency, and weighing plays a pivotal role in ensuring consistent product development, as well as accurate customer billing and inventory records. Electronic weight sensors paired with a multifaceted indicator can help manufacturers improve batch accuracy through weight-based process control, as well as track ingredient use, maintain co...
By Mark Hudzinski, Avery Weigh-Tronix
One of the key components of any batching operation is consistency, and weighing plays a pivotal role in ensuring consistent product development, as well as accurate customer billing and inventory records. Electronic weight sensors paired with a multifaceted indicator can help manufacturers improve batch accuracy through weight-based process control, as well as track ingredient use, maintain consistent product recipes and generate invoices with legal-for-trade accuracy.
Achieving accuracy in batch applications
The importance of batch consistency is demonstrated across each industry in which batching is commonly used. In aggregate applications, the proper mix of ingredients is required to develop asphalt or concrete in identical batches. This ensures each batch will mix seamlessly with the prior ones, yielding a consistent surface. Chemical applications require precise ingredient usage to ensure the desired chemical reactions occur within each batch developed. Food processing depends heavily on batch consistency to maintain the taste, texture, color and nutritional value of food products.
Estimating the volume of ingredients in a recipe can affect the quality, effectiveness and the consistency of the final product. In the long run, this could be very costly. However, using a weighing system to carefully analyze each ingredient ensures precise measurements and, in some cases, improve batch recipe quality, consistency and repeatability.
Weight sensor operation
In addition to ensuring accurate weight in batch applications, electronic weight sensors can offer several advantages when properly applied. They are easily installed directly beneath the structural support for a hopper, tank or bin, which converts the container into a dependable bulk weighing solution. The sensors consume minimal floor space, leaving the space underneath the container and between support structures free for use.
An electronic weight sensor is a type of load cell that leverages certain physical properties to improve weighing system performance and simplify signal conditioning and operation. Because some of these sensors typically use a beam, they are insensitive to side loading and result in a significant amount of deflection.
For example, a cantilevered beam-type sensor with strain gauges mounted on top and bottom effectively eliminates the moment arm in weighing or force measurement. In other words, the relationship of the strain to the bending moment due to the applied load at that point yields an accurate linear signal directly proportional to the weight or force at that point.
If four strain gauges are applied to the cantilevered beam, the results are an inherent amplification factor and simplified connection of electronics to the sensor %%MDASSML%% an arrangement that yields a balanced Wheatstone bridge. This type of design also enables the subtracting of moments, which results in a sensor that is insensitive to end- and torsion-loading, and is not affected by moment arm variations.
Weight indicators, system applications
The second part of a successful batch weighing solution is the weight indicator, which can be a simple onsite or remote weight display or a unit that can essentially serve as a PLC programmed to manage a full batching operation. For applications where the batching process is managed manually, simple indicators can store data about the types of materials being weighed and current batch criteria, as well as collect and display data from designated tanks, bins or hoppers.
To handle more complex batching recipes automatically, a programmable %%MDASSML%% or smart %%MDASSML%% indicator can collect, store and display multiple weight measurements while taking control of batch processes. The indicator may be programmed to send collected weight data over a network from one or more tanks to a PLC, which controls the rest of the batch process. The indicator can also be programmed to perform specific tasks in response to specific weight measurements. For example, the indicator may monitor two bins located at the end of conveyor belts and, once those bins are filled, send a signal that stops the conveyor and another that advises operators that a bin change is needed.
The indicator can help improve inventory management by storing data about ingredient usage. It can also monitor recipes, tracking each ingredient as it is added and shutting off the feeder at the appropriate time to ensure product consistency and quality.
In another type of application, an indicator can be used with a two-speed valve for improved batch process control. The indicator’s first setpoint can signal when a batch has reached 90% completion based on weight. A fully open valve feeds materials into the batch at full speed until this setpoint is met, at which point the indicator sends a signal to partially close the valve. For the remainder of the batch, the valve disperses product at a slower speed, making it easier for the indicator to accurately identify the precise moment the batch reaches 100% then sends a signal for the valve to close completely. Because filling speed and the amount of product dispensed at once has been reduced, the risk of freefall error is minimized.
Electronic weight sensors ensure accurate weighing in batching applications and consume very minimal floor space.
Indicators can collect, store and display multiple weight measurements as well as working with PLCs and other equipment to precisely control batch processes.
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