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What can I do to improve my batching system’s operating efficiency?

How to choose the right ingredient-batching system for your application

Due to their relatively low upfront costs, batching systems are a common production set-up in many industries. Manufacturers see themselves confronted with various technology options on the market and want to choose the most efficient solution for their individual situation. Operational efficiency of batching systems is a function of several factors including resolution and accuracy of the weighing device and batching technology, overall time required for the batching operation, and overall space availability for the batch weigh system.

Typically, ingredient-batching systems can be categorized into three different technology options: gain-in-weight batching using scale weighing operations, gain-in-weight batching using volumetric feeders, and loss-in-weight batching using gravimetric loss-in-weight feeders.

Gain-in-weight batching using scale weighing operations

Gain-in-weight batching using scale weighing operations

A scale hopper is a receiving hopper suspended on load cells. This system uses a gain-in-weight (GIW) batching method in which the material resides in the scale hopper until the precise weight, combination of materials, or both is achieved. This type of scale weighing system can typically achieve weigh accuracies of ±0.5 percent of the full scale capacity, including material and hopper weight. Once the desired weight has been achieved, a valve at the bottom of the hopper opens and the material is discharged to the process below. This system is ideal for higher volumes of material, such as major ingredients, when precise ingredient accuracy isn't as critical. In this system, ensuring optimal efficiency means making sure that the material is free-flowing and moisture-free, which prevents buildup in the pneumatic line, valve, or hopper. In some cases, vibrators can be used at the end of the batch process to help release the material from the scale hopper, but if the material packs easily, external vibration can also cause the material to pack on the hopper walls and not release the proper batch amount.

Gain-in-Weight (GIW) Batching Principle

Gain-in-weight batching using volumetric feed devices.

GIW batching can also be achieved when volumetric metering devices sequentially feed multiple ingredients into a collection hopper mounted on load cells. Using bulk-and-dribble feeding ensures higher accuracy. Once all the ingredients have been delivered, the batch is complete and the mixture is delivered to the process below. One advantage to this method is that several feeding devices can be used for different ingredients. However, each feeder operates sequentially, resulting in a longer overall batching time if you have multiple ingredients. Another advantage to this method is that it provides greater batch accuracies than GIW batching using scale weighing because of the greater control over ingredient delivery to the weigh hopper.

Gain-in-Weight (GIW) Batching Principle

Loss-in-Weight (LIW) Batching Principle - english

Loss-in-weight batching using gravimetric devices.

If you require high accuracy for the individual ingredients, low overall batching time, or both, then loss-in-weight (LIW) batching will be more efficient. In this method, gravimetric feeders operating in batch mode simultaneously feed multiple ingredients into a collection hopper. Each of the feeders is on load cells or scales, and the material lost from the feeder is weighed. Since all of the ingredients are being delivered simultaneously, the overall batch time is greatly reduced. Additionally, the system's highly accurate load cells specifically sized for the individual ingredient batch weights increase batch accuracy. This method is often used for more expensive microingredients. However, it should be noted that this system could also be more costly, because each feeder requires individual weighing devices.

Loss-in-Weight (LIW) Batching Principle

Combination systems

Many times, a combination of the GIW and LIW batching can be used to make the overall batching operation more cost-effective. GIW batching techniques are used for the macroingredients, and separate LIW feeders are used for the microingredients, whose batch weights may be too small to be detected by the GIW scale hoppers.

How do I choose?
Each of these technologies have inherent advantages and limitations. In order to choose the most efficient system, it is important to review the critical criteria required for the system as a function of batch time, accuracy required, amount of time allowed for quick changeover/cleaning and of course, overall cost.

Optimization of batch accuracy will also be a function of the load cell resolution available. For example, in GIW batching, when discharging into a hopper or receiver on load cells, the accuracy is a function of the full scale load of receiving vessel plus product. In other words, a system designed to add both macro and micro ingredients in the same vessel may not be able to detect accurately the smaller amounts. Therefore, many times, in order to make the overall batching operation more cost effective, a combination of the GIW and LIW batching is used. GIW batching techniques are used for the macro ingredients, and separate LIW feeders are used for the micros whose batch weights may be too small to be detected by the GIW scale hoppers.

Once the correct type of batching technology is chosen, several other design options can be integrated into the system to make it more efficient. These include easy access and easy clean support devices and frames, quick disconnect systems, and even wash in place features in order to allow for quick product changeover and cleanability. It is important to discuss all of these options with the batching system manufacturer, in order to ensure the most efficient overall batching operation.

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